Accelerated nature-based mitigation can re-open the window to 1.5°C

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Sanjayan, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6164097/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Cutting carbon emissions in half every decade through 2050 1 has become a benchmark for global 2 , national and corporate target-setting that delivers the Paris goal of limiting global warming to 1.5°C above pre-industrial levels. However, with a rapidly shrinking remaining carbon budget 3 , here we show that halving fossil emissions every decade alongside scaling negative emissions technologies (NETs) to balance remaining fossil CO 2 emissions by 2050, is no longer enough to avoid significant and lengthy overshoot past 1.5°C, unless improvements in ecosystem stewardship are also accelerated beyond levels currently assumed in most 1.5°C-aligned climate scenarios. We further show that a decadal acceleration of natural climate solutions, reaching net-zero emissions from agriculture, forestry and land use by 2030 and -7 gigatons CO 2 e per year of net removals by 2050, is both consistent with sectoral (or “bottom-up”) estimates of cost-effective potential and can keep the window to 1.5°C decisively open, if delivered alongside decadal halvings of fossil-fuel emissions and scaling of NETs. This “Carbon Law for Nature” mitigation pathway can feasibly be achieved through a transformation of humanity’s land and coastal stewardship: protecting remaining intact ecosystems, climate-smart management of agricultural and forestry lands, restoring natural ecosystems where appropriate, and reducing excess demand for land-intensive products. Crucially, following this pathway also minimizes the magnitude and length of time of temperature overshoot, reducing both the chronic impacts of climate change 4 and the risk of exceeding tipping points in the earth system 5 . Earth and environmental sciences/Environmental social sciences/Climate-change mitigation Earth and environmental sciences/Environmental social sciences/Climate-change policy Earth and environmental sciences/Climate sciences/Climate change/Climate-change mitigation Figures Figure 1 Figure 2 Figure 3 Main Text The window for a safe climate landing – an average increase in global temperature of no more than 1.5°C – is still open but closing rapidly 6 . This was the central message of the last major report of the Intergovernmental Panel on Climate Change (IPCC). It made clear that climbing through that window requires building a three-rung “decarbonization ladder” that rapidly turns around human emissions of planet warming CO 2 : (1) phasing out fossil fuels from the global energy system; (2) scaling negative emissions technologies (NETs) – industrial carbon dioxide removal (CDR) solutions such as direct air capture or enhanced mineralization that remove CO 2 from the air and store it – from now through 2050 and beyond 3 ; and (3) flipping humanity’s relationship with nature from a greenhouse gas source to a sink by protecting natural ecosystems to reduce CO 2 emissions, managing existing working lands to both reduce emissions and increase nature-based CDR, and restoring natural ecosystems (e.g., reforestation) for additional nature-based CDR. The central principle of this three-rung ladder was introduced by Rockström et al . 1 (2017) as the “Carbon Law” – inspired by "Moore's Law" of an exponential rate of digital technology innovation – demonstrating that the 1.5°C aligned IPCC mitigation pathways translated (approximately) to cutting global carbon emissions by half each decade to reach a net-zero world economy by 2050. The Carbon Law has driven climate action towards both urgency and realism, and has since been included in business plans ( e.g. , Unilever) and national policy goals ( e.g. , the US and Europe). The simple heuristic of “cutting emissions in half by 2030” has become a primary frame for climate action. It was the headline message of the press release of the IPCC AR6 Working Group III, the most up-to-date and comprehensive assessment of what humanity must do to mitigate climate change 2 . Yet today we risk losing the climate fight through delay, with the window for a safe landing currently only 175 GtCO 2 of “remaining carbon budget” (RCB) from January 1, 2024 onward for a 66% chance of staying below 1.5°C (see Methods). Simply put, this indicates that even delivering on the first two rungs – halving fossil emissions each decade, alongside exponentially scaling NETs – will not likely avoid a period of temperature overshoot above 1.5°C for the majority of this century. Any period of overshoot would exacerbate the chronic climatic and extreme weather events that have already increased sharply as we have approached the 1.5°C threshold 7,3 . In 2024 the global mean near-surface temperature anomaly reached 1.55°C ± 0.13°C 8 . The already devastating impacts of these events on communities and economies around the world will accelerate 4,9 ; yet we emphasize a greater concern: overshoot beyond 1.5°C also increases the risk of triggering one or more climate-driven tipping points in the Earth system 10 , perhaps by as much as 72% over non-overshoot scenarios with the same long-term equilibrium temperature 11 , potentially leading to abrupt, non-linear and cascading impacts across climate-ecological-social systems 12 . Reducing the magnitude and length of time of overshoot, therefore, is critical to avoid both the chronic impacts of climate change, as well as abrupt system shifts 5,11,13 and permit a safe climate landing. But is additional mitigation that can minimize overshoot available? We are currently far behind on the first rung 14 – phasing out fossil fuels from the global energy system – so expecting it to contribute more than a decadal halving is unrealistic. The second rung – scaling NETs – relies on still largely unproven technologies, so piling additional reliance on techno-solutions beyond 5 GtCO 2 per year in 2050 would seem similarly unwise 15 . Recent evidence, however, suggests that the third rung of the decarbonization ladder – specifically the mitigation potential available within the AFOLU (agriculture, forestry, and other land use) sector – has been underestimated for several reasons: It is poorly represented in the set of integrated assessment models and model scenario sets that provide the predominant scientific framing of “possible” economy-wide emissions pathways (e.g., those in AR6 WGIII Chapter 3) 16 , as these models are not yet capable of characterizing the full range of AFOLU mitigation potential 17 , nor are they consistent in their representation between models, making inter-model comparisons difficult. The process of improving representation of the AFOLU sector in the IPCC AR cycle is slow, for example with model scenarios used in AR6 WGIII Chapter 3 – and thus the range of potential land use mitigation pathways – locked in before the authors of WGIII Chapter 7 incorporated sectoral models in their estimate of the likely range of AFOLU sector mitigation potential. Future-thinking and scenario-construction in the land and waters sector is overly constrained 18 and mostly limited to existing practices 19 even at the higher end of estimates (for example excluding oceans stewardship and other known albeit uncertain solutions 20 ), as opposed to the energy sector where future mitigation from unproven or prototype technologies is widely accepted as necessary and their contribution in the future simply assumed 21 . Here we provide a pragmatic new assessment of the third rung of the ladder – an urgent and massive transformation of humanity’s relationship with nature, to exponentially reduce AFOLU sector emissions and increase negative emissions, based on an analysis of the most recent sectoral or “bottom-up” estimates available in the literature. This translates to what we call the “Carbon Law for Nature,” which fills a critical gap left by delay in reaching the Carbon Law fossil-fuel phase-out pace, and thereby completes the transformation pathway required to re-open the window for limiting global warming to 1.5°C. We show that the Carbon Law for Nature entails a flip from current net AFOLU emissions of +10 GtCO 2 e per year to net zero emissions by 2030, -5 GtCO 2 e per year of net sequestration by 2040, and -7 GtCO 2 e per year net sequestration by 2050. We provide a science-based narrative that lays out high level milestones for achieving it. We use the MAGICC7 reduced-complexity climate model 22 to demonstrate that delivering on the Carbon Law for Nature, together with other aspects of the Carbon Law (phasing out fossil fuels and scaling NETs) and non-CO 2 industrial emissions in line with AR6 1.5°C-compatible scenarios 16 , can re-open the window to 1.5°C, while minimizing both the magnitude and length of overshoot (Figure 1). A nature transition from source to sink is not optional The latest data from the Global Carbon Project 23 indicate that fossil fuel emissions on their own will soon exceed the RCB for a 66% chance to limit warning to 1.5°C: even successful decadal halving of fossil fuel emissions would result in 376 GtCO 2 of cumulative emissions from 2024-2050 (see Figure 2). And while NETs are critical if we are to hold warming below 1.5°C through 2100 and beyond, even an ambitious NETs pathway delivering 57 GtCO 2 of cumulative sequestrations through 2050 (as assumed in the Carbon Law) is too little to avoid overshoot and the risk of crossing Earth system tipping points. However, the actions we can take to deliver this “nature transition” – termed Natural Climate Solutions (NCS) when aimed principally at delivering climate mitigation outcomes 24 – can provide a notably large amount of cost-effective climate mitigation 19 , sufficient in fact to deliver atmospheric CO 2 drawdown and reach global net zero CO 2 by 2040 (Figure 2B). AFOLU Emissions: a Tangled Web of Sources, Sinks, and non-CO 2 Emissions The mitigation opportunity from NCS, allowing AFOLU emissions to reach net zero dramatically sooner than fossil fuel emissions – by 2030 instead of 2050 – and then flip to become a significant and decades-long net carbon sink, is bigger than it initially appears and significantly larger than its representation in the IAMs. This is because historical AFOLU emissions estimates hide a larger story of human land use disruptions as both a source and a sink simultaneously 25 . Ecosystems are being converted and degraded from higher-carbon to lower-carbon status in some places, while elsewhere nature is recovering due to economic shifts and low-productivity land abandonment, as well as intentional restoration actions. This source-sink dynamic is driven by a complex human land use system connecting food consumption and production, timber production and use, land clearing for forestry, agriculture, and grazing – as well as urbanization, mining, and land use for energy production. It is also entwined with the biosphere’s “natural” stress responses to elevated atmospheric CO 2 , temperature, and nitrogen deposition. To fully leverage the AFOLU mitigation opportunity and deliver on the Carbon Law for Nature, it is necessary to rapidly scale up NCS that protect, restore, and improve management of forests, wetlands, grasslands, agricultural lands, and coastal zones to mitigate climate change on both sides of the AFOLU equation: rapidly decreasing emissions from land conversion, the destruction of nature, and agricultural practices, while exponentially scaling up sequestration of carbon into both managed and natural ecosystem sinks. Figure 3 demonstrates separate emissions reduction and increased storage trajectories that can deliver the Carbon Law for Nature through an ambitious acceleration of AFOLU mitigation consistent with recent sectoral estimates of cost-effective potential 19 (see Methods). Annual non-CO 2 AFOLU emissions decrease from 5.5 GtCO 2 e per year now to 4 GtCO 2 e per year in 2050. Net CO 2 AFOLU emissions drop from their current 4.5 GtCO 2 to -5 GtCO 2 in 2030 and to -11 GtCO 2 in 2050. We further divide this net CO 2 AFOLU pathway into pathways for gross AFOLU sequestrations and gross AFOLU emissions, to emphasize the scale of changes needed across the sector. Gross annual AFOLU sequestration increases by 10 GtCO 2 from -9 GtCO 2 per year now (consisting of about -2 GtCO 2 of reforestation, plus -7 GtCO 2 of regrowth from forestry and shifting cultivation cycles) 26 to -19 GtCO 2 per year by 2050 – a bit more than doubling. Gross annual AFOLU CO 2 emissions are cut by 5.5 GtCO 2 from 13.5 GtCO 2 per year now to 8 GtCO 2 per year in 2050, with remaining gross emissions largely from forestry and shifting cultivation which are balanced out by forest regrowth after harvests and shifting cultivation cycles (see Delivering the Carbon Law for Nature section below and Methods). Crucially, these AFOLU emissions and sequestration pathways from scaling NCS are distinct from the biosphere sink, with increasingly well-resolved and reconciled global estimates of each 28 (see Extended Data Fig. 1). The biosphere sink is comprised of two broad components – the land sink and the ocean sink, which together absorb more than 50% of anthropogenic CO 2 emissions every year – and are continuing to do so despite increasing inter-annual variability 23 . The land sink of approximately 12 GtCO 2 per year 23 represents a response to the changing atmosphere by living vegetation globally, which is carefully separated out from estimates of anthropogenic AFOLU emissions 23 . The Carbon Law for Nature pathway only includes the anthropogenic side of the equation: it flips the AFOLU sector from a net carbon source (humanity’s depletion of carbon stored in the lands and coasts we manage) to a net carbon sink (restoring carbon in those same places). Strengthening Earth Resilience Yet our dependence on NCS for climate stability runs deeper than their AFOLU-sector mitigation potential alone: continuing to mismanage nature also risks weakening or even losing the 50% “climate subsidy” provided by the biosphere every year 29 . Our results demonstrate that delivering on the Carbon Law for Nature pathway would directly support the stability of the Earth System by keeping temperature overshoot to only a fraction (0.07–0.13°C) over 1.5°C and by minimizing the period exceeding this limit (Figure 1). In fact, following this pathway would halve the amount of time in overshoot in comparison to the current AFOLU trajectories in the SSP119 scenario set (the only set that returns mean global temperature to 1.5°C after overshoot) from almost 70 years to 30 – thereby reducing the risk of exceeding Earth System tipping points 30 , including those elements that comprise much of the biosphere land sink. Furthermore, NCS implemented at the scale required by the Carbon Law for Nature will also add back lost resilience to the biosphere’s buffering capacity, particularly for those tipping elements most closely connected to the land sector, such as the Amazon, that are at risk of tipping due to the potential breach of temperature and precipitation thresholds, but also due to human-driven deforestation and degradation 31,32 . Delivering the Carbon Law for Nature Of course, none of this is easy, and the world is far from turning the corner on anthropogenic emissions from nature. The total GHG flux from AFOLU increased an average of 1.6% per year from 2010-2019 17 , and commodity-driven deforestation (one of the largest drivers of gross AFOLU emissions) has been stubbornly persistent, with more than 4 million hectares of loss every year of the last decade 33 – even in the face of the 2014 New York Declaration on Forests (NYDF) global commitment to bring it to zero by 2020. But as more and more studies show – including the Working Group III Report on Mitigation of Climate Change from the IPCC AR6 Cycle published in 2022 17 (though, notably, not in the model ensembles used by Working Group I in simulations for its 2021 Report, estimating the remaining carbon budget) – a transformation of our relationship with nature can be achieved cost-effectively (Methods), and with enormous co-benefits beyond climate regulation 6 . Below we present a science-based narrative for how to operationalize the Carbon Law for Nature and re-open the 1.5°C window, based on four broad and overlapping land use objectives and the NCS necessary to deliver them. This builds on the definition 24 and still developing foundation and operational principles 34 for NCS which include equity and sustainability of biodiversity, food, and wood production; the NCS mitigation hierarchy proposed by Cook-Patton et al. 35 ; and the NCS acceleration curves of Wolosin et al. 36 . 1. Intact Nature is Rapidly Protected: ~3 GtCO 2 e per year by 2030 In the realm of NCS, “protection” refers to management actions that avoid emissions from conversion of forests, grasslands, or wetlands, or from changing wetland hydrology 24 . The area of protected land globally has increased steadily in the last 30 years through expansion of existing protected areas, community-based conservation, and Indigenous land designations, and is likely to receive a major boost through the Convention on Biological Diversity (CBD)’s globally agreed goal to protect 30% of the world’s land and oceans by 2030 (30x30). Currently however, 52% of Earth’s “irrecoverable carbon” (carbon stored in ecosystems that is quickly released when disturbed and cannot be recovered for decades) remains outside of protected areas and Indigenous lands 37 , and many of these critical carbon stores continue to be released by human activities. To follow the Carbon Law for Nature, recent regional progress slowing tropical deforestation 38 must expand and accelerate. We must rapidly cut forest conversion, peat drainage, and mangrove loss by half within 7 years to avoid 3 GtCO 2 e per year of emissions from current levels and save 20 million hectares or more of forests and wetlands from destruction by 2030. Protecting natural ecosystems – or what we here call “intact nature” – at this unprecedented rate will require: Eliminating large-scale clearing of primary and secondary natural forests for permanent agriculture and commodity production within a decade; Official recognition of the rights of Indigenous peoples and local communities to more than two billion hectares of land by 2030; and Expansion of protected and conserved areas, prioritizing areas with high stores of threatened irrecoverable carbon, alongside biodiversity, in nations’ ongoing efforts to reach 30x30. 2. Managed Nature Flips from Source to Sink: nearly 5 GtCO 2 e per year by 2030 Notably, managing existing working lands, which make up at least half of the Earth’s 13.4 billion hectares of ice-free land, using readily deployable climate-smart approaches represents the largest NCS opportunity (45%). Agricultural practices are currently a large source of hard-to-abate non-CO 2 emissions – about 5 GtCO 2 e per year of methane and nitrous oxide combined. But significantly degraded soils, over-grazing, low-diversity cropping, and tree-poor agricultural landscapes have created opportunities for restoration and more sustainable agricultural practices to remove and reliably store carbon in agricultural lands while also maintaining productivity 39,40 . Working forests (those managed at least partly for timber production) are currently a small net global source, managed in ways that both emit more than necessary in harvest cycles and capture less than possible during recovery cycles 41,42 . Transformation of “managed nature” in line with the Carbon Law for Nature will require: Eliminating about $300 billion per year of harmful agriculture and forestry subsidies by 2030 43 and investing instead in incentives for innovative regenerative production models; Rapidly increasing the area of farms, ranches, and working forests implementing climate-smart management practices to reach 20% of the world’s working lands by 2030 and 30% by 2050; Shifting global forestry from a nearly 1 GtCO 2 per year net source now (consisting of about 5 GtCO 2 per year of gross emissions from the decomposition of slash and the decay of wood products, and about 4 GtCO 2 per year of gross removals from regrowth after wood harvesting 23 ) to net zero by 2030 and a nearly 1 GtCO 2 per year net sink by 2050, which can be delivered with known methods that increase wood fiber production 44,45 ; Removing nearly 3 GtCO 2 of carbon from the atmosphere per year by 2030 and 4.5 GtCO 2 per year by 2050 into farmlands and grazing lands through techniques such as no-till agriculture, rotational grazing, and agroforestry; and Flipping agricultural lands and practices – including both carbon and non-carbon sources and sinks – from a 5 GtCO 2 e per year net source now to net zero in 2040 and a 1 GtCO 2 e per year net sink by 2050, with carbon sequestration from regenerative agriculture more than offsetting remaining methane and nitrous oxide emissions. 3. Restoration of Intact Nature Increases to Accelerate Removals: ~2 GtCO 2 per year by 2030 Restoration of natural forests, wetlands, and grasslands on previously converted and degraded working lands, where they historically occurred, is the third necessary solution for delivering on the Carbon Law for Nature. The amount of carbon being stored every year in ecosystems through human land use change is already increasing in many parts of the world – much of it in wealthier countries through sequestration in forests that have been regrowing for decades on previously cleared agricultural land 46 . But there are also significant ongoing active restoration interventions that are already delivering anthropogenic carbon dioxide removal (e.g., in China and Brazil), and there is the political will and opportunity to expand restoration even further, including in new areas of the world, as part of the global nature transition (e.g., the Bonn Challenge, AFR100, and the Mangrove Breakthrough). Restoration actions must accelerate and spread rapidly, driven by financial and policy incentives, wider adoption of natural regeneration techniques 47 , increased seed and nursery capacity, and reduced demand for marginally productive grazing land 39 . The carbon benefits of this would nonetheless build steadily over time – reaching more than 2 GtCO 2 per year in 2030, accelerating to nearly 6 GtCO 2 per year by 2050. To deliver mitigation at this scale, an emerging global restoration sector must: Restore nearly 200 to 350 million hectares of natural forests and wetlands by 2050 including 15 million hectares of peatlands by 2030; Restore 400 thousand hectares of mangroves by 2030; and Increasingly leverage private sector rather than public-sector finance to become economically self-sustaining. 4. Easing the Global Land Squeeze by Reducing Land Demand: ~2 GtCO 2 e per year by 2050 Land is vital for many, sometimes competing, purposes, but none more so than for providing food to a growing global population. Our ability to deliver NCS at the scale demanded by the Carbon Law for Nature is thus tightly linked to food systems, through the physical, economic, environmental, and social “space” demanded by the food choices made around the world and the amount of food that is lost and wasted from farm to fork 48 . Done right, however, this does not require trading food security for carbon storage and sequestration; recent research suggests that the hidden human health and environmental costs of the existing global food system is on the order of 15 trillion USD per year – and that a transition to healthy and sustainable foods for all would generate approximately 10 trillion USD in economic benefits, including contributions to stabilize the climate 39 . Actions to shift the demand for land-hungry products and reduce food loss and waste that can help deliver this food system transition and ease the global land squeeze include: Decarbonizing the electricity and transportation sectors without relying on food crops or other land-intensive bioenergy crops 49 ; Shifting towards the EAT-Lancet commission’s recommended “planetary health diet”, with decreased over-consumption of animal-sourced foods in some (usually wealthy) countries alongside improved diets in regions where undernutrition is high 50 ; Shifting livestock production towards more regenerative soil carbon-positive models, significantly reducing the global land area used for livestock production by the 2040s, and no longer feeding livestock crops that humans can eat by 2050; Reducing food loss and waste by 25% by 2030 and 50% by 2050; Increasing demand for lower-emissions and regenerative agricultural practices, so they become the default option for new generations of farmers by the 2040s; Continuing to innovate and invest in increasing agricultural productivity, particularly in areas with large yield gaps, at or above historical rates through this decade 51 ; and Continuing to innovate and invest in technologies that dramatically reduce the land required for food production, such as lab grown meats. Conclusion Our results demonstrate that “re-opening” the window to 1.5°C at this juncture is now only realistically within reach if we choose to fully leverage the third rung of the decarbonization ladder. While rapid progress transitioning away from fossil fuels remains critical, even decadal emissions halvings, alongside an unprecedented scaling up of NETs, will no longer be enough to deliver the 1.5°C Paris goal. This means we must exponentially scale NCS implementation through a transformation of our relationship with nature to begin atmospheric CO 2 drawdown by 2040, cut peak temperatures by 0.07-0.13°C, and reduce the time exceeding 1.5°C by at least 3 decades. We further show that: 1) overshoot past 1.5°C is now likely inevitable, even with full delivery of the Carbon Law and Carbon Law for Nature pathways; 2) following the Carbon Law for Nature is achievable and would ramp up the “third rung” of the decarbonization ladder more than currently modeled, to get us back down to 1.5°C and thereby reduce chronic climate impacts; and 3) following the Carbon Law for Nature reduces the risks of exceeding earth system tipping points through minimizing and shortening the period of overshoot and by increasing the resilience of the land-based components of the biosphere sink (hereon the biosphere land sink). Careful consideration of the long-term durability of carbon stored in nature is therefore critical. This must include both the expected rise in climate-driven disturbances that cause emissions and the acceleration in carbon sequestration driven by CO 2 fertilization and other factors. Together, these trends contribute to the non-anthropogenic response of the biosphere land sink to global change. Additionally, the contribution of human activities in the AFOLU sector can also affect the durability of storage. Recent critiques that raise concerns about the durability of carbon sequestration in nature – whether in the biosphere land sink (i.e., its non-anthropogenic response to global change) or in the AFOLU sector (i.e., from NCS investments or policy interventions addressing our lands and forests) – have suffered from misinterpretations of existing science, creating confusion and misguided narratives. We note several specific errors that should be addressed to facilitate a constructive, science-driven discourse around the durability of natural carbon stocks: a) A focus on point estimates or limited time periods that ignore long-term trends 52 , including regrowth, interannual variability, and links to El Nino / La Nina cycles 23 ; b) Extrapolation from specific ecosystems or places 53 to make categorical statements that ignore global trends 23 and the spatial heterogeneity in both underlying processes and climate change itself; c) Failure to specify or correctly characterize temperature-dependence as a factor driving the relative risk of a biosphere land sink reversal, sometimes conflating the disruptive effects of high-emissions scenarios (>2 0 C) with lower-emissions pathways 52,54-57 , or failing to acknowledge the positive role that the sector could play, particularly in the near term, when significant action in the AFOLU sector could keep the climate on track for low overshoot 1.5°C scenarios before the end of the century; d) Failure to differentiate gross versus net accounting in AFOLU fluxes, leading to false interpretations that a weakened or flipped net biosphere land sink, which includes anthropogenic AFOLU emissions, indicates a weakened or flipped biosphere land sink, which excludes AFOLU emissions; e) Misinterpretation of evidence that suggests a potentially diminished net biosphere land sink, as a reversal in the biosphere land sink, which would indicate a net source on an annual basis. Furthermore, the concerns about the durability of NCS implemented in the AFOLU sector are also often exaggerated. Achieving the scale of NCS solutions needed, if effectively designed, inherently addresses durability concerns. Larger scales of NCS implementation inherently reduce the likelihood of reversals, since both natural and anthropogenic disturbance events operate at smaller scales than the biomes across which NCS must be implemented. Even in the face of an increasing risk of reversal for any individual NCS investment (such as a reforestation project) or a geographically constrained AFOLU mitigation intervention (such as a national or jurisdictional land use policy), the expected stability of a strong and positive biosphere land sink within the envelope of target warming scenarios (i.e., 1.5-2°C) suggests that a spatially diversified portfolio of NCS investments in the AFOLU sector is highly likely to result in a stable CO 2 sink over decades if not centuries. This large scale durability is strengthened if we prioritize places for conservation and restoration that are resilient to, or even benefit from, climate change. For example, we should focus reforestation where forests are most likely to remain healthy in a future climate, and we should prioritize protecting high carbon ecosystems that are similarly resilient. Unfortunately, media reporting not subject to peer review can inadvertently string together several of these misinterpretations, from “cherry-picking” data to confusing carbon stocks with carbon fluxes, compounding each other and creating a misleading narrative that confuses decision-makers (e.g. a recent article in the Guardian in October 2024 58 titled “ Trees and land absorbed almost no CO 2 last year. Is Nature’s carbon sink failing? ”). Scrutiny across targets and actions underpinning all three rungs of the decarbonization ladder is critical, but needs to be applied consistently and carefully due to the complexities involved. We further acknowledge that the first two rungs, fossil mitigation and NETs, are not on track to deliver what is needed: · We are not making progress on the Carbon Law for fossil fuels, which needs to be delivered at a rate of more than 7% global CO 2 emission reductions per year, whereas, over the past 10 years from 2014 to 2023, it has grown by 0.6% per year from 35.5 to 37.8 GtCO 2 per year 23 ; · Methane and nitrous oxide emissions must decline in pace with 1.5°C scenarios, yet they are still increasing at around the same rate as fossil fuels – 0.6 to 0.7% per year from 2014 to 2023 59 ; · The NETs scaling pathway requires a global price on carbon exceeding 500 USD/ton CO 2 with current technologies, while also relying on yet-to-be delivered innovations 60 . We argue, however, that these challenges only increase the need for shorter-term wins and carbon sequestration options beyond technology-based solutions, not least because NCS have a much higher likelihood of scalable success in the near term than NETs 61 . Moreover, every fraction of a degree counts, and every year of overshoot increases risk. Delivered in parallel with the first two rungs of the decarbonization ladder, the Carbon Law for Nature reopens the window to 1.5°C, while providing a transformational opportunity for innovation and investment in the AFOLU sector, generating benefits that will spill over into our remaining natural lands, and helping maintain the estimated US$44 trillion in economic value generation that is moderately or highly dependent on nature (including underpinning an estimated 395 million jobs by 2030) 62 , alongside a greater chance of delivering the SDGs 63 . At a minimum, however, it keeps us closer to the safe operating space for planetary boundaries, including biosphere integrity, freshwater security, and biogeochemical flows, 64 while reducing atmospheric GHGs in the near term and providing time (without being an excuse for inaction) to accelerate other solutions and – if needed – replace the mitigation from any localized reversals of land-based sequestration. Yet NCS remain severely underfunded. The kind of investment flooding into fossil mitigation (e.g., the United States’ Inflation Reduction Act of 2022, which allocated $369 billion to clean energy and the estimated US$2 trillion of investment globally in 2024 in clean energy technologies and infrastructure 65 ), is not yet happening for climate finance to AFOLU, which receives only about 3% of global climate finance 66 . Even without sufficient funding, many of the necessary pieces are already in place, with leadership continuing to emerge among policy makers and the private sector to accelerate climate action, transform food systems, reduce deforestation, protect natural ecosystems, and address unequal impacts. In sum, the ‘nature transition’ is – and must be recognized as – equal and complementary to the ‘energy transition’ and energized, leveraged and financed accordingly. There is no other option for delivering a safe climate landing. Declarations Data Availability Statement The authors declare that all other data supporting the findings of this study are available within the paper and its supplementary information files. Acknowledgments Funding Anonymous Donor through the California Community Grant Foundation (MSW, DH, BG, TB) Author contributions: Conceptualization: MSW, JR, DH, BG Methodology: MSW, TB, DH Quantitative analysis: MSW, TB Writing – original draft: MSW Writing – review & editing: MSW, JR, MS, CF, DH, TB, BG Competing Interests Authors declare that they have no competing interests. References Rockström, J. et al. A roadmap for rapid decarbonization. Science 355 , 1269-1271 (2017). IPCC. The evidence is clear: the time for action is now. We can halve emissions by 2030 , (2022). Lee, H. et al. IPCC, 2023: Climate Change 2023: Synthesis Report, Summary for Policymakers. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland. (2023). Pörtner, H.-O. & Belling, D. 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Methods The Remaining CO 2 Budget (RCB), Fossil Emissions, and Negative Emissions Technologies A nearly linear relationship between cumulative CO 2 emissions and global surface temperature increase allows the calculation of a remaining carbon budget (RCB) equivalent to a particular temperature target given total emissions to date, with uncertainty accounted for by selecting a probability of hitting that target. The RCBs for a 50% and 66% chance respectively of keeping temperature increase to 1.5°C have been shrinking from 500 GtCO 2 and 400 GtCO 2 emissions remaining starting Jan 1, 2020 as reported in IPCC AR6 WGI 57 . Global CO 2 emissions in the four years from 2020—2023 have spent down ~ 160 GtCO 2 of that RCB 26 , while updated models and estimates of the transient climate response to cumulative emissions suggest further contraction of the RCB 67 . Starting Jan 1, 2024, that leaves humanity with only about 275 GtCO 2 and 175 GtCO 2 of RCB respectively for a 50% and 66% chance of limiting temperature increase to 1.5°C, with significant uncertainty 26 . These RCBs assume an evolution of nonCO 2 GHG emissions and other climate forcers consistent with the necessary CO 2 pathway, which generally reach net zero levels a decade or two later than CO 2 (see below). Business-as-usual fossil fuel CO 2 emissions alone are on track to deplete this budget in less than a decade. At 10 GtC per year (36.7 GtCO 2 per year) in 2023 26 , a linear trajectory at the recent decade’s ~ 200 MtCO 2 per year average rate of increase through the International Energy Agency’s expected fossil fuel consumption peak in 2030 would result in exceeding the 1.5°C 66% budget during 2028, and the 1.5°C 50% budget during 2031. Keeping 1.5°C within reach requires an immediate and rapid realignment with the Carbon Law 1 of three rungs of a decarbonization ladder. To assess the scale of mitigation required from nature – one of the three critical rungs – we compare the 1.5°C RCBs to the net emissions resulting from Carbon Law fossil fuel and negative emissions technologies (NETs) pathways. We assume flat fossil fuel CO 2 emissions of 36 GtCO 2 per year from 2020–2023, followed by Carbon Law decadal halvings: linear declines to half that level in 2030, half again in 2040, and half again in 2050, resulting in total fossil emissions of 376 GtCO 2 from 2024 through 2050. Our use of 36 GtCO 2 per year to represent recent fossil CO 2 emissions is based on the Global Carbon Budget 26 estimates of E FOS which subtracts cement carbonation from fossil emissions. We choose to exclude the 2020 anomaly, exclude the 2023 initial estimate of 36.7 GtCO2, and round down to 36 from observed 2019, 2021, and 2022 values of 36.3 GtCO2 per year. NETs – such as direct air capture and other industrial CO 2 sequestrations above and beyond any CCS used to deliver the Carbon Law for fossil fuels – follow the pathway of Rockström et al. 1 , reaching 0.5 GtCO 2 per year by 2030, 2.5 GtCO 2 per year by 2040, and 5 GtCO 2 per year (and 57 GtCO 2 cumulative) by 2050. This NETs pathway is consistent with 2020–2100 non-AFOLU CDR quantities in the C1, C2, and C3 scenarios of the AR6 scenarios database (AR6 WGIII Ch3 table 3.5 and section 3.4.7), reaching midway between the medium and upper bounds of economically feasible 2050 geological CDR potential (3–7 GtCO2/yr) estimated by Fuss et al. 15 . Together, the 319 GtCO 2 of net emissions from fossil fuels and NETs from 2024–2050 exceed the 175 GtCO 2 66% RCB for 1.5°C by 144 GtCO 2 and the 275 GtCO 2 50% RCB for 1.5°C by 44 GtCO 2 (Extended Data Table 1.a). AFOLU Emissions While the carbon emissions and sequestration dynamics of fossil fuel use and negative emissions technology deployment are relatively simple, those of land and nature are not: they are diffuse, have complex temporal and spatial dynamics, and are not easily divided into anthropogenic and non-anthropogenic processes. This complexity results in striking differences in estimates of land fluxes between national greenhouse gas inventories, global estimates of anthropogenic fluxes from bookkeeping models, and global land sink estimates from inverse modeling approaches and dynamic global vegetation models. These differences have been significantly untangled in recent years 28 . For estimates of baseline anthropogenic emissions from agriculture, forestry, and other land uses (AFOLU), we rely on the land use emissions methodologies of IPCC AR6 WGI Chap. 5 57 , updated by more recent sources that apply the same methodologies 26,67 . Given high year-to-year variability of AFOLU emissions, we use decadal averages for the most recently available decade (2013–2022 for CO 2 26 and 2012–2021 for nonCO 2 gases 67 ) as the best estimates of “recent” or “current” emissions (Extended Data Table 2). We then round these estimates to the nearest half gigaton; and assume AFOLU emissions in 2023 at this period-average level (Extended Data Table 2). Over the decade 2013–2022, forestry and other land uses were a global net source of about 4.5 GtCO 2 per year. This estimate of global anthropogenic net CO 2 emissions from AFOLU was updated significantly 67 between the release of the IPCC AR6 WGIII 17 and more recent estimates 26 . This net number, estimated by averaging three bookkeeping models of anthropogenic FOLU emissions, is the sum of component fluxes segmented by Friedlingstein et al. 26 into about 13.5 GtCO 2 per year of gross emissions sources in some places (deforestation of ~ 7 GtCO 2 per year, including both permanent and shifting cultivation of ~ 4.2 and ~ 2.8 GtCO 2 per year respectively; plus other land use transitions of ~ 0.5 GtCO 2 per year; peat drainage and fires of ~ 1 GtCO 2 per year; plus forestry-based decomposition of slash and wood products of ~ 5 GtCO 2 per year) plus about 9 GtCO 2 per year of gross sinks elsewhere (forest regrowth of ~ 4.7 GtCO 2 per year, including both reforestation and regrowth from shifting cultivation of about ~ 2 and ~ 2.7 GtCO 2 per year respectively; plus about 4 GtCO 2 per year of regrowth after forest management harvests). These sources and sinks quantify the carbon imbalances between land and atmosphere driven by anthropogenic processes – or what we call “managed nature”. The extent to which these different processes are “mitigatable” – and at what costs and in what time frame – is discussed below. But it is worth noting that two of these processes – forestry and shifting cultivation – are largely balanced between sources and sinks with better-constrained estimates for net emissions than for gross sources and sinks, and with sinks that are lagged responses to the corresponding sources on the scale of decades. While managed nature’s imbalances are contributing to global anthropogenic CO 2 emissions, the biosphere’s responses to the loading of CO 2 in the atmosphere are also leading to further imbalances. Land and oceans are each absorbing significant portions of anthropogenic CO 2 emissions every year, through increased growth rates of plants and through ocean acidification respectively. These biosphere sinks are signs of an earth out of balance – but for now, they are critical buffers against rising atmospheric CO 2 concentrations. The absorptive response of the biosphere land sink, as partitioned from the ocean sink and from CO 2 emissions that remain in the atmosphere, was ~ 12.3 GtCO 2 per year for 2013-2022 26 . Recent efforts to harmonize land use emissions estimates across global models and national inventories 28 help illustrate our use of the terms “managed nature” and “biosphere response”, and the underlying sources of data that inform these estimates (Extended Data Fig. 1 ). The complexities of the carbon cycle aside, the AFOLU sector is also a major source of nonCO 2 GHG emissions. Agriculture emits over 5 GtCO 2 e per year of methane and nitrous oxide emissions, while human-set fires and the draining of organic soils adds less than 0.5 GtCO 2 e per year of FOLU methane and nitrous oxide emissions. We estimate theses 2012–2021 decadal average nonCO 2 emissions from AFOLU by applying the proportion of global methane and nitrous oxide emissions attributed to AFOLU in IPCC AR6 WGIII Table 7.1 17 to recent estimates of global decadal average methane and nitrous oxide emissions 67 . We include nonCO 2 AFOLU emissions in the Carbon Law for Nature pathway – and accept the resulting slight misnomer – because systemic transformation of global land use will drive simultaneous shifts in emissions of all three gases, and more practically because emerging sectoral mitigation roadmaps 39,51 and science-based target-setting approaches 68 include all gases in their proposed pathways. In total, historical gross AFOLU GHG emissions are estimated as 19 GtCO 2 e per year, about half of which is offset by 9 GtCO 2 per year gross FOLU sink, to yield baseline global net AFOLU GHG emissions of 10 GtCO 2 e per year, consisting of 4.5 GtCO 2 per year net emissions from CO 2 and 5.5 GtCO 2 e per year of nonCO 2 sources (Extended Data Table 2). Because the RCB concept only includes CO 2 emissions explicitly, but assumes an evolution of nonCO 2 GHG emissions consistent with a given CO 2 pathway, we must also assess any all-gases AFOLU pathway against these assumed 1.5°C-compatible nonCO 2 pathways – and potentially adjust our comparisons to the RCB as needed. We estimate from Riahi et al. 16 that the suite of AR6 1.5°C-compatible scenarios show average declines in nonCO 2 AFOLU emissions from 2019 levels of nearly 10% to about 5 GtCO 2 e per year by 2030 and of just over 25% to about 4.4 GtCO 2 e per year by 2050, suggesting cumulative 2024–2050 nonCO 2 AFOLU emissions of about 131 GtCO 2 e and mitigation of about 18 GtCO 2 e (Extended Data Table 1.b). We can account for some substitutability of mitigation across CO 2 and nonCO 2 mitigation (as leveled by AR6 100-year Global Warming Potentials) by adjusting the cumulative net CO 2 -only emissions of any AFOLU all-gases emissions pathway to the difference between this 131 GtCO 2 e and the pathway’s nonCO 2 emissions (as we do in Extended Data Table 1). For AFOLU pathways with similar levels of cumulative nonCO 2 emissions to the 1.5°C-compatible scenarios, we can simply compare cumulative AFOLU CO 2 emissions to the RCB directly. There is no reasonable low-overshoot path to keeping 1.5°C within reach if AFOLU emissions were to continue at their current level through 2050. Period total net AFOLU emissions would be 270 GtCO 2 e, consisting of 122 GtCO 2 of net CO 2 emissions plus another 149 GtCO 2 e of nonCO 2 emissions (Extended Data Table 1.c). Adding 18 GtCO 2 e of excess nonCO 2 emissions (in the flat “BAU” pathway compared to the 1.5°C nonCO 2 pathways) to AFOLU CO 2 -only net emissions of 122 GtCO 2 results in an RCB-comparable net AFOLU emissions of 139 GtCO 2 . Added to fossil fuel emissions that follow carbon law halvings and NETs that scale as assumed above, AFOLU emissions at current levels would yield a fossil fuel, NETs, and AFOLU total net RCB comparable emissions of 458 GtCO 2 from 2024–2050, exceeding the 175 and 275 GtCO 2 RCBs for 66% and 50% chances at 1.5°C by 283 and 183 GtCO 2 of overshoot respectively (Extended Data Table 1.c). The Carbon Law for Nature pathway flips nature to a cumulative all-gases net sink of 59 GtCO 2 e. This can be delivered by AFOLU nonCO 2 emissions following a mitigation pathway just slightly more ambitious than the 1.5°C-compatible scenarios (but consistent with other sectoral roadmaps, see below) totaling 121 GtCO 2 e, plus a pathway for AFOLU net CO 2 totaling a 180 GtCO 2 cumulative sink (Extended Data Table 1.d). After adjustment to account for nonCO 2 mitigation beyond that assumed in the AR6 1.5°C-compatible scenarios, this net AFOLU sink adds to the fossil fuel emissions and NETs sinks through 2050 to deliver an RCB-comparable net cumulative emissions of just 130 GtCO 2 – well below our 1.5°C RCBs. With the Carbon Law for Nature, the three rungs of our decarbonization ladder allow us to more than reach the window for a 66% chance of 1.5°C, with a 45 GtCO 2 buffer (Extended Data Table 1.d). AFOLU Mitigation: Carbon Law for Nature Compared to Sectoral Potential Estimates To assess the feasibility of the Carbon Law for Nature pathway, we look to sectoral estimates of cost-effective (< $ 100/ton) land-based mitigation potential from Roe et al. 19 as our primary source. These estimates are well-aligned with those of the IPCC AR6 WGIII sectoral estimates 17 , with totals of 13.8 GtCO 2 e average per year from 2020–2050 (or 414 GtCO 2 e total) (compared to 13.6 GtCO 2 e average per year) and with a technical potential more than double that. Integrated assessment model estimates are only ~ 58% of the sectoral estimates, with differences driven primarily by more extensive coverage across mitigation measures in the sectoral estimates. We use the higher sectoral estimates as our primary source data, recognizing that a) the median sectoral estimate falls well within the IAM uncertainty bounds; b) many existing 36 and emerging nature-based solutions such as blue carbon 69 and liana removal 45 have yet to be included in IAMs; and c) protecting, managing and restoring nature provides significant value beyond climate stabilization, including maintaining the earth system within other planetary boundaries 70 , which suggests a pragmatic but conservative strategy should be to over- rather than under-invest in nature as a climate solution. Alternative AFOLU mitigation pathways, including some based on subsets of IAM scenarios, are compared below to these sectoral estimates. A baseline standardization is necessary to compare the Carbon Law for Nature pathway, which sets decadal AFOLU benchmarks relative to recent baseline emissions levels, to the sectoral mitigation estimates synthesized in Roe et al. 19 , which are a mix of historical and modeled baselines. We standardize estimates for each mitigation pathway representing more than 2% of the total to a flat historical baseline, by subtracting the period average change in modeled baseline emissions or sequestrations from the 2020–2050 average sectoral mitigation estimates (see Data File S1). The most significant adjustments are needed for agricultural nonCO 2 emissions and food systems demand-side mitigation levers, given an expected significant increase in food systems nonCO 2 emissions of 0.4–0.9 GtCO 2 e by 2030 and 0.9–2.3 GtCO 2 e by 2050 (ranges represent the BAU estimates of combined N 2 O and CH 4 emissions by (Ref 39 ) and (Ref 71 )). Standardizing the baselines reduces the mitigation estimates from a combined 2.5 GtCO 2 e of average annual mitigation from an increasing baseline to 0.7–1.6 GtCO 2 e per year from a standardized flat baseline, with the range representing uncertainty in the underlying sources’ baselines. Estimated mitigation from avoided deforestation and from reforestation also change significantly after baseline standardization, given that two sources averaged in Roe et al. 19 have very different baselines. One of the two 42 has almost no discernable trend in baseline forest fluxes summed across deforestation, reforestation, and forest management, while the other 72 models a baseline (no carbon price) scenario with steadily increasing emissions from deforestation alongside similarly increasing sequestrations from reforestation. Averaging across standardized versions of these two sources yields deforestation mitigation potential estimates at 2.5 GtCO 2 per year average (compared to from 3.6 GtCO 2 per year average before standardization), and a nearly equal increase in reforestation potential from 1.2 GtCO 2 per year average before to 2 GtCO 2 per year average after baseline standardization. Even after these changes, the annual average cost-effective sectoral AFOLU mitigation levels estimated by Roe et al. 19 are sufficient to keep 1.5°C within reach as part of our decarbonization ladder, even if delivered over just the 27 years from 2024–2050 (Extended Data Table 1.e). Adjusted cost-effective AFOLU mitigation from a flat historical baseline is about 12.1 (11.6 to 12.5) GtCO 2 e per year average, or about 326 GtCO 2 e over 27 years. Of this adjusted cumulative total, about 17 (8.5 to 25.5) GtCO 2 e is from nonCO 2 emissions reductions, in line with the 18 GtCO 2 e of nonCO 2 AFOLU mitigation in the 1.5°C-compatible scenarios, allowing us to compare cumulative CO 2 -only emissions to the RCB without any further adjustment. The cumulative net CO 2 sink of about 187 GtCO 2 , subtracted from period total CO 2 emissions of 319 GtCO 2 from fossil fuels and NETs, results in 133 GtCO 2 of cumulative net emissions – 142 and 42 GtCO 2 respectively below the 50% and 66% RCBs for 1.5°C (Extended Data Table 1.e). This shows that the Carbon Law for Nature pathway delivers a comparable annual average level of AFOLU mitigation over the period from 2024–2050 (Extended Data Table 1.e) as the cost-effective sectoral estimates of mitigation potential from IPCC AR6, and thus is likely to be achievable at cost-effective levels of investment. Accelerating AFOLU Mitigation Potential to Deliver the Carbon Law for Nature To construct a vision for accelerating NCS actions to deliver on the Carbon Law for Nature, to break down the mitigation opportunity into policy-relevant categories, and to identify decadal milestones across a range of solutions, we create an explicit set of illustrative annual mitigation curves from 2024 through 2050. The scale of mitigation delivered by these “Protect, Manage, and Restore” curves is based largely on the adjusted sectoral mitigation estimates of Roe et al. 19 described above (see Extended Data Fig. 2 and Data File S1), with the timing of mitigation through 2050 grounded in the “NCS hierarchy” 35 , a framework which suggests a prioritization of NCS investments of protection, improved management, and then restoration, recognizing their different characteristic time horizons, cost-effectiveness, biodiversity values, flux densities, and requirements for land use change. We construct these pathways to deliver cumulative mitigation from 2024–2050 approximately equal to 27 years at the adjusted annual average mitigation estimated above (Extended Data Table 1.f), with a few adjustments to improve alignment with secondary sources and new data. These adjustments include an increase of ~ 0.5 GtCO 2 per year in the cost-effective mitigation potential of improved forest management to account for newly estimated potential from removal of overabundant lianas 45 ; and a decrease of 1.3 GtCO 2 per year in the cost effective mitigation potential from carbon sequestration into agricultural lands, to account for more constrained estimates in Nabuurs et al. 17 than in Roe et al. 19 . We also provide breakdowns of mitigation into policy-relevant categories: reduced nonCO 2 emissions, reduced CO 2 emissions, and increased CO 2 sinks, to align with land-use flux estimates from global models and bookkeeping models; protection of natural ecosystems, management of working lands, restoration of natural ecosystems, and demand-side levers to reduce land demand, to align with categories of NCS intervention; and agriculture vs forestry and other land uses, to align with national greenhouse gas inventories (see Data File S1). Because our NCS mitigation curves start at zero in 2023, and we aim to deliver the same cumulative period mitigation with a monotonically increasing function, it is mathematically required that annual mitigation in 2050 exceed the annual average level. While our curves thus rise above the annual average in later years, they always remain below the technical mitigation potential in every category (see Data File S1). The total mitigation from these pathways closely track the Carbon Law for Nature (see Extended Data Fig. 3 ). About 5.1 GtCO 2 e per year average of AFOLU mitigation potential is on the emissions reduction side of the equation. This is dominated by 2.9 GtCO 2 from protecting forests, peatlands and mangroves from conversion, plus another 0.7 GtCO 2 from protecting peat soil carbon stocks from additional oxidation in drained peatlands by restoring water tables, and about 0.5 GtCO 2 from protecting the carbon stocks in working forests through more strategic forestry. About 1 GtCO 2 e per year of nonCO 2 emissions mitigation opportunity comes from a transformation of our food-systems to reduce food loss and waste and towards healthier, lower-emissions diets. About 7 GtCO 2 per year of AFOLU mitigation potential is from nature-based carbon removals, through actions that intentionally sequester additional carbon into natural and working lands. About half of this increased carbon sink is from forests: about 2.75 GtCO 2 from reforestation, plus another 0.8 GtCO 2 from forest management in working forests. The other half of cost-effective natural carbon removals comes from agricultural lands: about 3.4 GtCO 2 of cost-effective supply-side CO 2 sequestration potential from crop and grazing land soil carbon sequestration and agroforestry. Of course, there is uncertainty in the mitigation potential estimates for any given NCS, and the science is evolving rapidly, including identification of new low-cost NCS that have not yet been included in syntheses such as liana removal. It is also the case that some NCS which are included in our mitigation curves will likely fail to materialize at the levels currently expected. These uncertainties in the ultimate portfolio of successful NCS do not undermine the argument that the Carbon Law for Nature is both necessary and possible – they merely show the need for continued innovation and investment in developing and deploying the pipeline and portfolio of NCS. In this way, the AFOLU sector is no different from the energy sector; for example, the International Energy Agency explicitly recognizes that “in 2050, almost half the reductions come from technologies that are currently at the demonstration or prototype phase” 60 . AFOLU Mitigation Potential and Pathways: Secondary Sources and Alignment We now turn to alternative estimates of AFOLU mitigation potential and modeled 1.5°C scenarios through 2050 to assess their alignment with the Carbon Law for Nature and the protect-manage-restore acceleration curves, and to identify areas of significant uncertainty and difference. The first comparison is of nonCO 2 emissions pathways. Biomass burning and draining of peatlands emits nitrous oxide and methane in addition to CO 2 , but these FOLU nonCO 2 sources are less than about 10% of AFOLU nonCO 2 sources, and a negligibly small proportion of cost-effective AFOLU mitigation. Agricultural sources on the other hand are large (~ 5 GtCO 2 e per year) and expected to grow significantly in the next three decades without climate policy interventions. That expected growth makes this category challenging to align across sources. The simplified Carbon Law for Nature segmentation in (main text Fig. 3 ) maps out a decrease in AFOLU nonCO 2 emissions from 5.5 GtCO 2 e per year in 2023 to 4.75 GtCO 2 e per year in 2030 and 4 GtCO 2 e per year in 2050, a pathway that results in 121 GtCO 2 e of cumulative agricultural nonCO 2 emissions from 2024 through 2050–10 GtCO 2 e less than the 1.5°C-compatible scenarios in AR6 16 . This pathway is conservative compared to the mitigation envisioned by food-systems models of 1.5°C-compatible scenarios. The UN Food and Agriculture Organization suggests a 1.5°C-compatible food system future 51 with deeper reductions in nonCO 2 agricultural emissions, with targets of halving 2020 levels of nitrous oxide emissions by 2040 and halving methane emissions by 2045. These cuts would drop agricultural nonCO 2 emissions below 3 GtCO 2 e per year by 2045, compared to our 4 GtCO 2 e per year in 2050. A linear rate of change that delivers the FAO targets and stabilizes them at half through 2050 would result in cumulative nonCO 2 emissions from 2024–2050 of about 104 GtCO 2 e, 17 GtCO 2 e lower emissions than our curves deliver. The Food System Economics Commission (FSEC) 39 also suggests much deeper cuts of nonCO 2 agriculture emissions than we use, reaching 0.5 GtCO 2 e of nitrous oxide and 1 GtCO 2 e of methane by 2050, corresponding to cumulative 2024–2050 nonCO 2 emissions of just under 100 GtCO2e. In contrast to nonCO 2 emissions, our mitigation curves envision significantly more carbon sequestration into agricultural lands than the FAO’s food systems Roadmap or the FSEC Report, even after adjusting downward from 4.8 GtCO 2 per year average from 2020–2050 in Roe et al. 19 to 3.4 GtCO 2 per year average from 2020–2050 to match Nabuurs et al. 17 . The FAO roadmap includes a milestone of 10 GtCO 2 of additional carbon sequestered into cropland and pasture soils from 2025–2050, which is only 0.4 GtCO 2 per year 51 . This conservative estimate included half of cost-effective soil carbon sequestration opportunities in grasslands identified by the authors, but no other carbon sequestration opportunities in crop and grazing lands. The FSEC Report discusses soil carbon and agroforestry as sequestration levers but does not provide estimates of agricultural sequestrations separate from forestry and other land use. Both sources rely extensively on integrated assessment model scenarios – which do not include estimates of sequestration of carbon into croplands and grazing lands – to construct their mitigation pathways, so their underrepresentation of carbon sequestration into agricultural lands is not surprising. While alignment issues and differences in coverage make comparisons of AFOLU pathways difficult for subcomponents, there are multiple touchpoints for the full mitigation pathway for both CO 2 only and for all gases. Our sectoral CO 2 pathway is significantly more ambitious than the 1.5°C compatible scenarios in AR6: we aim for about 4.75 GtCO 2 net CO 2 sink by 2030 and 11 GtCO 2 net sink by 2050, while the AR6 C1 scenarios deliver net zero in 2030 and about 2–3 GtCO 2 net sink by 2050. A more constrained set of 1.5°C compatible scenarios – limited to exclude “silver bullet” levels of mitigation from any one mitigation lever – includes scenarios with net AFOLU CO 2 sinks in 2050 of 2.5 to 8.6 GtCO 2 per year 73 . For the full suite of gases, we note that the global scientific consensus sectoral estimates of cost-effective AFOLU mitigation from Nabuurs et al. 17 are very well-aligned with Roe et al. 19 ; the Carbon Law for Nature pathways match these sources. Our all-gases AFOLU mitigation pathway is only slightly more ambitious than the pathway envisioned by the FSEC: we aim to deliver global AFOLU net zero by 2030 compared to the FSEC pathway’s 2035 sectoral net zero year, while we aim for 7 GtCO 2 e of net global sequestration in 2050 compared to their 6.7 GtCO 2 e of net global sequestration mid-century 39 . In summary, our Carbon Law for Nature and mitigation curves to deliver it are in line with bottom-up estimates of cost-effective mitigation potential, but drive significantly more mitigation out of the AFOLU sector than most model-based scenarios. Treatment of bioenergy and BECCS likely explains some of this difference; our inclusion of significant soil carbon sequestration in agricultural lands and agroforestry sequestration, which are largely excluded from IAMs, drives some of the difference; and our target rate of acceleration for AFOLU mitigation – reaching period-average levels of cost-effective (< $ 100/ton) mitigation by about 2034, and going well beyond these $ 100/ton levels by 2050 – largely explain the rest. Global Surface Temperature Trajectories We use the MAGICCv7.5.3 reduced-complexity model with default configuration 22 to compare future global surface temperature trajectories under four alternative emissions pathways: “SSP1-19”, representing the average emissions of the CMIP6 model ensemble in the SSP1-19 scenario set; “SSP1-26”, similarly; “CLfN-SSP1-19”, which substitutes the level of mitigation in the CLfN AFOLU mitigation pathway for the SSP119 AFOLU CO 2 pathways; and “CLfN-SSP1-26”, with a similar substitution. Several adjustments to the Carbon Law for Nature pathway are needed to remove discontinuities and make appropriate comparisons to the SSP scenario sets. The first adjustment addresses differences in the starting year of mitigation: the SSP scenario sets begin reducing emissions in 2020, while the CLfN pathway’s first year of mitigation is 2024. The CLfN pathways are thus adjusted down to the levels of the comparison SSP scenarios for 2020 through 2025 (see Extended Data Fig. 5). The second small adjustment is to “count” excess nonCO 2 mitigation – beyond the average nonCO 2 mitigation of the comparision SSP scenario sets – as CO 2 mitigation instead. This adjustment allows us to avoid a significant difference in the assumed baseline nonCO 2 AFOLU emissions, by using the SSP pathways for the MAGICC runs. We converted the nonCO 2 gases methane (CH 4 ) and nitrous oxide (N 2 O) to CO 2 equivalents using the GWP100 conversion factors from the latest IPCC report. Lastly, to provide a rough estimate of the CLfN’s impact on the period of overshoot, we assume a simple linear reduction in the AFOLU net CO 2 sequestration from a maximum of -11 GtCO2 per year in 2050, to zero in 2100. This is a conservative assumption, because some NCS actions like reforestation would continue to sequester carbon well beyond 2100, and because it assumes no new innovations that would allow humanity to continue to drive carbon into the biosphere. Methods References Forster, P. M. et al. Indicators of Global Climate Change 2022: annual update of large-scale indicators of the state of the climate system and human influence. Earth System Science Data 15 , 2295-2327 (2023). Anderson, C., Bicalho, T., Wallace, E., Letts, T. & Stevenson, M. Forest, Land and Agriculture Science-Based Target-Setting Guidance. (2022). Howard, J. et al. Blue carbon pathways for climate mitigation: Known, emerging and unlikely. Marine Policy 156 , 105788 (2023). Rockström, J. et al. Safe and just Earth system boundaries. Nature 619 , 102-111 (2023). EPA, U. Global Non-CO2 Greenhouse Gas Emission Projections & Mitigation 2015-2050. 67-71 (2019). Busch, J. et al. Potential for low-cost carbon dioxide removal through tropical reforestation. Nature Climate Change 9, 463-466 (2019). Warszawski, L. et al. All options, not silver bullets, needed to limit global warming to 1.5 C: A scenario appraisal. Environmental Research Letters 16 , 064037 (2021). Additional Declarations There is NO Competing Interest. Supplementary Files TheCarbonLawforNatureSupplementaryDataS1toS403052025.xlsx Supplementary Table 1-4 ExtendedDataInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6164097","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":436086820,"identity":"fb53938d-daa3-4d66-a2e0-ec2c2d3bc68f","order_by":0,"name":"Michael Wolosin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYHACxgMMDBIM/CBmQgGResBaJBtAWgyI18LAYAAhiVCuOyP5wIEPfyzyjM+vTvzwwIBBnl/sAH4tZjfSEg7ObJMoNrvxdrME0GGGM2cnENByO8fgMG+DROK2G2c3gLQkGNwmRgvPH4nEzTPObv5BghY2icQN/L3biLTl/jOwXxJn3ODdZpFgIEGEX84cPvjgw5+6xP7+s5tv/qiwkeeXJqAFASTAKiWIVQ4C/AdIUT0KRsEoGAUjCQAAGpBKm6oHdHcAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-8163-6606","institution":"Conservation International","correspondingAuthor":true,"prefix":"","firstName":"Michael","middleName":"","lastName":"Wolosin","suffix":""},{"id":436086821,"identity":"fb9e6e9c-fa19-4436-9214-cd9dae21cbf4","order_by":1,"name":"Johan Rockström","email":"","orcid":"https://orcid.org/0000-0001-8988-2983","institution":"Potsdam Institute for Climate Impact Research","correspondingAuthor":false,"prefix":"","firstName":"Johan","middleName":"","lastName":"Rockström","suffix":""},{"id":436086822,"identity":"7e081723-e2bb-4eaa-9613-0d31f6cfdd99","order_by":2,"name":"Christiana Figueres","email":"","orcid":"","institution":"Global Optimism","correspondingAuthor":false,"prefix":"","firstName":"Christiana","middleName":"","lastName":"Figueres","suffix":""},{"id":436086823,"identity":"1cdf7b0a-0b2d-40a7-8950-d7c96fe9faf9","order_by":3,"name":"M. Sanjayan","email":"","orcid":"","institution":"Conservation International","correspondingAuthor":false,"prefix":"","firstName":"M.","middleName":"","lastName":"Sanjayan","suffix":""},{"id":436086824,"identity":"56e202ce-0ba1-4066-a7fc-567c1bdf33ee","order_by":4,"name":"Tim Beringer","email":"","orcid":"","institution":"Potsdam Institute for Climate Impact Research","correspondingAuthor":false,"prefix":"","firstName":"Tim","middleName":"","lastName":"Beringer","suffix":""},{"id":436086825,"identity":"870f55f5-ea14-4f2e-98dc-d544409c7c2f","order_by":5,"name":"Bronson Griscom","email":"","orcid":"https://orcid.org/0000-0002-8496-7213","institution":"Center for Natural Climate Solutions, Conservation International","correspondingAuthor":false,"prefix":"","firstName":"Bronson","middleName":"","lastName":"Griscom","suffix":""},{"id":436086826,"identity":"76dc3796-09ef-48aa-8547-253c8238bc3e","order_by":6,"name":"David Hole","email":"","orcid":"https://orcid.org/0000-0001-9117-2956","institution":"Conservation International","correspondingAuthor":false,"prefix":"","firstName":"David","middleName":"","lastName":"Hole","suffix":""}],"badges":[],"createdAt":"2025-03-05 15:50:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6164097/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6164097/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81119353,"identity":"399d0a92-632b-490d-8693-421606018516","added_by":"auto","created_at":"2025-04-22 12:31:03","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":135362,"visible":true,"origin":"","legend":"\u003cp\u003eSimulations of global surface temperature trajectories under the 1.5°C-compatible AR6 scenarios with standard AFOLU trajectories compared to the same scenarios with “Carbon Law for Nature” AFOLU trajectories,\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6164097/v1/1af89c66fff6d0e30ef28543.png"},{"id":81118458,"identity":"eb2b7a4d-cf9e-4fd7-b832-d813044586a4","added_by":"auto","created_at":"2025-04-22 12:23:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":167106,"visible":true,"origin":"","legend":"\u003cp\u003eThe three rungs of the decarbonization ladder to deliver the Paris 1.5°C Goal. \u003cstrong\u003e(A)\u003c/strong\u003e Annual net anthropogenic emissions and removals, including carbon law halving of fossil fuel CO\u003csub\u003e2\u003c/sub\u003e emissions (black), long-term growth of CO\u003csub\u003e2\u003c/sub\u003e removals through NETs (grey), and flipping net AFOLU GHG emissions from source (orange) to sink (green) by 2030. The net AFOLU pathway includes both CO\u003csub\u003e2\u003c/sub\u003e emissions and removals (orange and green), as well as AFOLU non-CO\u003csub\u003e2\u003c/sub\u003e emissions. \u003cstrong\u003e(B)\u003c/strong\u003e Cumulative net anthropogenic CO\u003csub\u003e2\u003c/sub\u003e-only emissions and removals from January 1, 2024, at 5-year intervals compared to the 66% probability 1.5°C RCB, showing a period of overshoot from 2031 to 2046. Cumulative AFOLU non-CO\u003csub\u003e2\u003c/sub\u003e emissions from the Carbon Law for Nature are not shown here, as they are essentially the same in the Carbon Law for Nature pathway as for the IPCC runs that provide RCB estimates and thus may be excluded from the RCB comparison (Methods).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6164097/v1/b83847dd9a299e9a3c7e32cc.png"},{"id":81118460,"identity":"4dfe2695-0d8d-49ef-a151-83063e0e5ae9","added_by":"auto","created_at":"2025-04-22 12:23:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":134148,"visible":true,"origin":"","legend":"\u003cp\u003eThe Carbon Law for Nature pathway for Net AFOLU GHGs (dashed line), and a representative set of sub-pathways to deliver it from reductions in AFOLU non-CO\u003csub\u003e2\u003c/sub\u003e emissions (pink), alongside reductions in Gross AFOLU CO\u003csub\u003e2\u003c/sub\u003e emissions (orange) and increases in gross AFOLU CO\u003csub\u003e2\u003c/sub\u003e removals (dark green) which sum to net AFOLU CO\u003csub\u003e2\u003c/sub\u003e emissions pathway (dotted line). A significant proportion of AFOLU gross CO\u003csub\u003e2\u003c/sub\u003e emissions and removals (grey dotted lines) are from cycles of tree cutting and regrowth from shifting cultivation and managed forestry. None of the biosphere land sink (light green, with the future pathway roughly represented as constant at the last decade’s average 12.3 GtCO\u003csub\u003e2\u003c/sub\u003e per year) is included in these AFOLU pathways. Historical estimates from Friedlingstein \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e26\u003c/sup\u003e and Crippa \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e27\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6164097/v1/1bb9153bedd442235ec86673.png"},{"id":81120352,"identity":"650dff5d-2e79-4f1e-8db6-7c172a59e542","added_by":"auto","created_at":"2025-04-22 12:39:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1549804,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6164097/v1/5429c081-2f7b-4e25-b0a9-61439be3d996.pdf"},{"id":81118462,"identity":"c5052ea9-fd72-44df-b24c-7e3d2c1103e5","added_by":"auto","created_at":"2025-04-22 12:23:03","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3856742,"visible":true,"origin":"","legend":"Supplementary Table 1-4","description":"","filename":"TheCarbonLawforNatureSupplementaryDataS1toS403052025.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6164097/v1/78decc82428acb4165ad2da8.xlsx"},{"id":81118461,"identity":"d054aaa5-2e02-4850-83c6-0ea1d8ca7e73","added_by":"auto","created_at":"2025-04-22 12:23:03","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1014626,"visible":true,"origin":"","legend":"","description":"","filename":"ExtendedDataInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6164097/v1/f937dae67ff6a1bef0f64cb5.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Accelerated nature-based mitigation can re-open the window to 1.5°C","fulltext":[{"header":"Main Text","content":"\u003cp\u003eThe window for a safe climate landing \u0026ndash; an average increase in global temperature of no more than 1.5\u0026deg;C \u0026ndash; is still open but closing rapidly\u003csup\u003e6\u003c/sup\u003e. This was the central message of the last major report of the Intergovernmental Panel on Climate Change (IPCC). It made clear that climbing through that window requires building a three-rung \u0026ldquo;decarbonization ladder\u0026rdquo; that rapidly turns around human emissions of planet warming CO\u003csub\u003e2\u003c/sub\u003e: (1) phasing out fossil fuels from the global energy system; (2) scaling negative emissions technologies (NETs) \u0026ndash; industrial carbon dioxide removal (CDR) solutions such as direct air capture or enhanced mineralization that remove CO\u003csub\u003e2\u003c/sub\u003e from the air and store it \u0026ndash; from now through 2050 and beyond\u003csup\u003e3\u003c/sup\u003e; and (3) flipping humanity\u0026rsquo;s relationship with nature from a greenhouse gas source to a sink by protecting natural ecosystems to reduce CO\u003csub\u003e2\u003c/sub\u003e emissions, managing existing working lands to both reduce emissions and increase nature-based CDR, and restoring natural ecosystems (e.g., reforestation) for additional nature-based CDR.\u003c/p\u003e\n\u003cp\u003eThe central principle of this three-rung ladder was introduced by Rockstr\u0026ouml;m \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e1\u003c/sup\u003e (2017) as the \u0026ldquo;Carbon Law\u0026rdquo; \u0026ndash; inspired by \u0026quot;Moore\u0026apos;s Law\u0026quot; of an exponential rate of digital technology innovation \u0026ndash; demonstrating that the 1.5\u0026deg;C aligned IPCC mitigation pathways translated (approximately) to cutting global carbon emissions by half each decade to reach a net-zero world economy by 2050. The Carbon Law has driven climate action towards both urgency and realism, and has since been included in business plans (\u003cem\u003ee.g.\u003c/em\u003e, Unilever) and national policy goals (\u003cem\u003ee.g.\u003c/em\u003e, the US and Europe). The simple heuristic of \u0026ldquo;cutting emissions in half by 2030\u0026rdquo; has become a primary frame for climate action. It was the headline message of the press release of the IPCC AR6 Working Group III, the most up-to-date and comprehensive assessment of what humanity must do to mitigate climate change\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eYet today we risk losing the climate fight through delay, with the window for a safe landing currently only 175 GtCO\u003csub\u003e2\u003c/sub\u003e of \u0026ldquo;remaining carbon budget\u0026rdquo; (RCB) from January 1, 2024 onward for a 66% chance of staying below 1.5\u0026deg;C (see Methods). Simply put, this indicates that even delivering on the first two rungs \u0026ndash; halving fossil emissions each decade, alongside exponentially scaling NETs \u0026ndash; will not likely avoid a period of temperature overshoot above 1.5\u0026deg;C for the majority of this century. Any period of overshoot would exacerbate the chronic climatic and extreme weather events that have already increased sharply as we have approached the 1.5\u0026deg;C threshold\u003csup\u003e7,3\u003c/sup\u003e. In 2024 the global mean near-surface temperature anomaly reached 1.55\u0026deg;C \u0026plusmn; 0.13\u0026deg;C\u003csup\u003e8\u003c/sup\u003e. The already devastating impacts of these events on communities and economies around the world will accelerate\u003csup\u003e4,9\u003c/sup\u003e; yet we emphasize a greater concern: overshoot beyond 1.5\u0026deg;C also increases the risk of triggering one or more climate-driven tipping points in the Earth system\u003csup\u003e10\u003c/sup\u003e, perhaps by as much as 72% over non-overshoot scenarios with the same long-term equilibrium temperature\u003csup\u003e11\u003c/sup\u003e, potentially leading to abrupt, non-linear and cascading impacts across climate-ecological-social systems\u003csup\u003e12\u003c/sup\u003e. Reducing the magnitude and length of time of overshoot, therefore, is critical to avoid both the chronic impacts of climate change, as well as abrupt system shifts\u003csup\u003e5,11,13\u003c/sup\u003e and permit a safe climate landing.\u003c/p\u003e\n\u003cp\u003eBut is additional mitigation that can minimize overshoot available? We are currently far behind on the first rung\u003csup\u003e14\u003c/sup\u003e \u0026ndash; phasing out fossil fuels from the global energy system \u0026ndash; so expecting it to contribute \u003cem\u003emore\u003c/em\u003e than a decadal halving is unrealistic. The second rung \u0026ndash; scaling NETs \u0026ndash; relies on still largely unproven technologies, so piling additional reliance on techno-solutions beyond 5 GtCO\u003csub\u003e2\u003c/sub\u003e per year in 2050 would seem similarly unwise\u003csup\u003e15\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRecent evidence, however, suggests that the third rung of the decarbonization ladder \u0026ndash; specifically the mitigation potential available within the AFOLU (agriculture, forestry, and other land use) sector \u0026ndash; has been underestimated for several reasons:\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eIt is poorly represented in the set of integrated assessment models and model scenario sets that provide the predominant scientific framing of \u0026ldquo;possible\u0026rdquo; economy-wide emissions pathways (e.g., those in AR6 WGIII Chapter 3)\u003csup\u003e16\u003c/sup\u003e, as these models are not yet capable of characterizing the full range of AFOLU mitigation potential\u003csup\u003e17\u003c/sup\u003e, nor are they consistent in their representation between models, making inter-model comparisons difficult.\u003c/li\u003e\n \u003cli\u003eThe process of improving representation of the AFOLU sector in the IPCC AR cycle is slow, for example with model scenarios used in AR6 WGIII Chapter 3 \u0026ndash; and thus the range of potential land use mitigation pathways \u0026ndash; locked in before the authors of WGIII Chapter 7 incorporated sectoral models in their estimate of the likely range of AFOLU sector mitigation potential.\u003c/li\u003e\n \u003cli\u003eFuture-thinking and scenario-construction in the land and waters sector is overly constrained\u003csup\u003e18\u003c/sup\u003e and mostly limited to existing practices\u003csup\u003e19\u003c/sup\u003e even at the higher end of estimates (for example excluding oceans stewardship and other known albeit uncertain solutions\u003csup\u003e20\u003c/sup\u003e), as opposed to the energy sector where future mitigation from unproven or prototype technologies is widely accepted as necessary and their contribution in the future simply assumed\u003csup\u003e21\u003c/sup\u003e. \u0026nbsp;\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eHere we provide a pragmatic new assessment of the third rung of the ladder \u0026ndash; an urgent and massive transformation of humanity\u0026rsquo;s relationship with nature, to exponentially reduce AFOLU sector emissions and increase negative emissions, based on an analysis of the most recent sectoral or \u0026ldquo;bottom-up\u0026rdquo; estimates available in the literature. This translates to what we call the \u0026ldquo;Carbon Law for Nature,\u0026rdquo; which fills a critical gap left by delay in reaching the Carbon Law fossil-fuel phase-out pace, and thereby completes the transformation pathway required to re-open the window for limiting global warming to 1.5\u0026deg;C. We show that the Carbon Law for Nature entails a flip from current net AFOLU emissions of +10 GtCO\u003csub\u003e2\u003c/sub\u003ee per year to net zero emissions by 2030, -5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of net sequestration by 2040, and -7 GtCO\u003csub\u003e2\u003c/sub\u003ee per year net sequestration by 2050. We provide a science-based narrative that lays out high level milestones for achieving it. We use the MAGICC7 reduced-complexity climate model\u003csup\u003e22\u003c/sup\u003e to demonstrate that delivering on the Carbon Law for Nature, together with other aspects of the Carbon Law (phasing out fossil fuels and scaling NETs) and non-CO\u003csub\u003e2\u003c/sub\u003e industrial emissions in line with AR6 1.5\u0026deg;C-compatible scenarios\u003csup\u003e16\u003c/sup\u003e, can re-open the window to 1.5\u0026deg;C, while minimizing both the magnitude and length of overshoot (Figure 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA nature transition from source to sink is not optional\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe latest data from the Global Carbon Project\u003csup\u003e23\u003c/sup\u003e indicate that fossil fuel emissions on their own will soon exceed the RCB for a 66% chance to limit warning to 1.5\u0026deg;C: even successful decadal halving of fossil fuel emissions would result in 376 GtCO\u003csub\u003e2\u003c/sub\u003e of cumulative emissions from 2024-2050 (see Figure 2). And while NETs are critical if we are to hold warming below 1.5\u0026deg;C through 2100 and beyond, even an ambitious NETs pathway delivering 57 GtCO\u003csub\u003e2\u003c/sub\u003e of cumulative sequestrations through 2050 (as assumed in the Carbon Law) is too little to avoid overshoot and the risk of crossing Earth system tipping points.\u003c/p\u003e\n\u003cp\u003eHowever, the actions we can take to deliver this \u0026ldquo;nature transition\u0026rdquo; \u0026ndash; termed Natural Climate Solutions (NCS) when aimed principally at delivering climate mitigation outcomes\u003csup\u003e24\u003c/sup\u003e \u0026ndash; can provide a notably large amount of cost-effective climate mitigation\u003csup\u003e19\u003c/sup\u003e, sufficient in fact to deliver atmospheric CO\u003csub\u003e2\u003c/sub\u003e drawdown and reach global net zero CO\u003csub\u003e2\u003c/sub\u003e by 2040 (Figure 2B).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAFOLU Emissions: a Tangled Web of Sources, Sinks, and non-CO\u003csub\u003e2\u003c/sub\u003e Emissions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe mitigation opportunity from NCS, allowing AFOLU emissions to reach net zero dramatically sooner than fossil fuel emissions \u0026ndash; by 2030 instead of 2050 \u0026ndash; and then flip to become a significant and decades-long net carbon sink, is bigger than it initially appears and significantly larger than its representation in the IAMs. This is because historical AFOLU emissions estimates hide a larger story of human land use disruptions as both a source \u003cem\u003eand\u0026nbsp;\u003c/em\u003ea sink simultaneously\u003csup\u003e25\u003c/sup\u003e. Ecosystems are being converted and degraded from higher-carbon to lower-carbon status in some places, while elsewhere nature is recovering due to economic shifts and low-productivity land abandonment, as well as intentional restoration actions. This source-sink dynamic is driven by a complex human land use system connecting food consumption and production, timber production and use, land clearing for forestry, agriculture, and grazing \u0026ndash; as well as urbanization, mining, and land use for energy production. It is also entwined with the biosphere\u0026rsquo;s \u0026ldquo;natural\u0026rdquo; stress responses to elevated atmospheric CO\u003csub\u003e2\u003c/sub\u003e, temperature, and nitrogen deposition.\u003c/p\u003e\n\u003cp\u003eTo fully leverage the AFOLU mitigation opportunity and deliver on the Carbon Law for Nature, it is necessary to rapidly scale up NCS that protect, restore, and improve management of forests, wetlands, grasslands, agricultural lands, and coastal zones to mitigate climate change on both sides of the AFOLU equation: rapidly decreasing emissions from land conversion, the destruction of nature, and agricultural practices, while exponentially scaling up sequestration of carbon into both managed and natural ecosystem sinks.\u003c/p\u003e\n\u003cp\u003eFigure 3 demonstrates separate emissions reduction and increased storage trajectories that can deliver the Carbon Law for Nature through an ambitious acceleration of AFOLU mitigation consistent with recent sectoral estimates of cost-effective potential\u003csup\u003e19\u003c/sup\u003e (see Methods). Annual non-CO\u003csub\u003e2\u003c/sub\u003e AFOLU emissions decrease from 5.5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year now to 4 GtCO\u003csub\u003e2\u003c/sub\u003ee per year in 2050. Net CO\u003csub\u003e2\u003c/sub\u003e AFOLU emissions drop from their current 4.5 GtCO\u003csub\u003e2\u003c/sub\u003e to -5 GtCO\u003csub\u003e2\u003c/sub\u003e in 2030 and to -11 GtCO\u003csub\u003e2\u003c/sub\u003e in 2050. We further divide this net CO\u003csub\u003e2\u003c/sub\u003e AFOLU pathway into pathways for gross AFOLU sequestrations and gross AFOLU emissions, to emphasize the scale of changes needed across the sector. Gross annual AFOLU sequestration increases by 10 GtCO\u003csub\u003e2\u003c/sub\u003e from -9 GtCO\u003csub\u003e2\u003c/sub\u003e per year now (consisting of about -2 GtCO\u003csub\u003e2\u003c/sub\u003e of reforestation, plus -7 GtCO\u003csub\u003e2\u003c/sub\u003e of regrowth from forestry and shifting cultivation cycles)\u003csup\u003e26\u003c/sup\u003e to -19 GtCO\u003csub\u003e2\u003c/sub\u003e per year by 2050 \u0026ndash; a bit more than doubling. Gross annual AFOLU CO\u003csub\u003e2\u003c/sub\u003e emissions are cut by 5.5 GtCO\u003csub\u003e2\u003c/sub\u003e from 13.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year now to 8 GtCO\u003csub\u003e2\u003c/sub\u003e per year in 2050, with remaining gross emissions largely from forestry and shifting cultivation which are balanced out by forest regrowth after harvests and shifting cultivation cycles (see Delivering the Carbon Law for Nature section below and Methods).\u003c/p\u003e\n\u003cp\u003eCrucially, these AFOLU emissions and sequestration pathways from scaling NCS are distinct from the biosphere sink, with increasingly well-resolved and reconciled global estimates of each\u003csup\u003e28\u003c/sup\u003e (see Extended Data Fig. 1). The biosphere sink is comprised of two broad components \u0026ndash; the land sink and the ocean sink, which together absorb more than 50% of anthropogenic CO\u003csub\u003e2\u003c/sub\u003e emissions every year \u0026ndash; and are continuing to do so despite increasing inter-annual variability\u003csup\u003e23\u003c/sup\u003e. The land sink of approximately 12 GtCO\u003csub\u003e2\u003c/sub\u003e per year\u003csup\u003e23\u003c/sup\u003e represents a response to the changing atmosphere by living vegetation globally, which is carefully separated out from estimates of anthropogenic AFOLU emissions\u003csup\u003e23\u003c/sup\u003e. The Carbon Law for Nature pathway \u003cem\u003eonly\u003c/em\u003e includes the anthropogenic side of the equation: it flips the AFOLU sector from a net carbon source (humanity\u0026rsquo;s depletion of carbon stored in the lands and coasts we manage) to a net carbon sink (restoring carbon in those same places).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStrengthening Earth Resilience\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYet our dependence on NCS for climate stability runs deeper than their AFOLU-sector mitigation potential alone: continuing to mismanage nature also risks weakening or even losing the 50% \u0026ldquo;climate subsidy\u0026rdquo; provided by the biosphere every year\u003csup\u003e29\u003c/sup\u003e. Our results demonstrate that delivering on the Carbon Law for Nature pathway would directly support the stability of the Earth System by keeping temperature overshoot to only a fraction (0.07\u0026ndash;0.13\u0026deg;C) over 1.5\u0026deg;C and by minimizing the period exceeding this limit (Figure 1). In fact, following this pathway would halve the amount of time in overshoot in comparison to the current AFOLU trajectories in the SSP119 scenario set (the only set that returns mean global temperature to 1.5\u0026deg;C after overshoot) from almost 70 years to 30 \u0026ndash; thereby reducing the risk of exceeding Earth System tipping points\u003csup\u003e30\u003c/sup\u003e, including those elements that comprise much of the biosphere land sink. Furthermore, NCS implemented at the scale required by the Carbon Law for Nature will also \u003cem\u003eadd back\u003c/em\u003e lost resilience to the biosphere\u0026rsquo;s buffering capacity, particularly for those tipping elements most closely connected to the land sector, such as the Amazon, that are at risk of tipping due to the potential breach of temperature and precipitation thresholds, but also due to human-driven deforestation and degradation\u003csup\u003e31,32\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDelivering the Carbon Law for Nature\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOf course, none of this is easy, and the world is far from turning the corner on anthropogenic emissions from nature. The total GHG flux from AFOLU increased an average of 1.6% per year from 2010-2019\u003csup\u003e17\u003c/sup\u003e, and commodity-driven deforestation (one of the largest drivers of gross AFOLU emissions) has been stubbornly persistent, with more than 4 million hectares of loss every year of the last decade\u003csup\u003e33\u003c/sup\u003e \u0026ndash; even in the face of the 2014 New York Declaration on Forests (NYDF) global commitment to bring it to zero by 2020.\u003c/p\u003e\n\u003cp\u003eBut as more and more studies show \u0026ndash; including the Working Group III Report on Mitigation of Climate Change from the IPCC AR6 Cycle published in 2022\u003csup\u003e17\u003c/sup\u003e (though, notably, not in the model ensembles used by Working Group I in simulations for its 2021 Report, estimating the remaining carbon budget) \u0026ndash; a transformation of our relationship with nature \u003cem\u003ecan\u003c/em\u003e be achieved cost-effectively (Methods), and with enormous co-benefits beyond climate regulation\u003csup\u003e6\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eBelow we present a science-based narrative for how to operationalize the Carbon Law for Nature and re-open the 1.5\u0026deg;C window, based on four broad and overlapping land use objectives and the NCS necessary to deliver them. This builds on the definition\u003csup\u003e24\u003c/sup\u003e and still developing foundation and operational principles\u003csup\u003e34\u003c/sup\u003e for NCS which include equity and sustainability of biodiversity, food, and wood production; the NCS mitigation hierarchy proposed by Cook-Patton \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e35\u003c/sup\u003e; and the NCS acceleration curves of Wolosin \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e36\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e1. Intact Nature is Rapidly Protected: ~3 GtCO\u003csub\u003e2\u003c/sub\u003ee per year by 2030\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn the realm of NCS, \u0026ldquo;protection\u0026rdquo; refers to management actions that avoid emissions from conversion of forests, grasslands, or wetlands, or from changing wetland hydrology\u003csup\u003e24\u003c/sup\u003e. The area of protected land globally has increased steadily in the last 30 years through expansion of existing protected areas, community-based conservation, and Indigenous land designations, and is likely to receive a major boost through the Convention on Biological Diversity (CBD)\u0026rsquo;s globally agreed goal to protect 30% of the world\u0026rsquo;s land and oceans by 2030 (30x30). Currently however, 52% of Earth\u0026rsquo;s \u0026ldquo;irrecoverable carbon\u0026rdquo; (carbon stored in ecosystems that is quickly released when disturbed and cannot be recovered for decades) remains outside of protected areas and Indigenous lands\u003csup\u003e37\u003c/sup\u003e, and many of these critical carbon stores continue to be released by human activities.\u003c/p\u003e\n\u003cp\u003eTo follow the Carbon Law for Nature, recent regional progress slowing tropical deforestation\u003csup\u003e38\u003c/sup\u003e must expand and accelerate. We must rapidly cut forest conversion, peat drainage, and mangrove loss by half within 7 years to avoid 3 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of emissions from current levels and save 20 million hectares or more of forests and wetlands from destruction by 2030.\u003c/p\u003e\n\u003cp\u003eProtecting natural ecosystems \u0026ndash; or what we here call \u0026ldquo;intact nature\u0026rdquo; \u0026ndash; at this unprecedented rate will require:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eEliminating large-scale clearing of primary and secondary natural forests for permanent agriculture and commodity production within a decade;\u003c/li\u003e\n \u003cli\u003eOfficial recognition of the rights of Indigenous peoples and local communities to more than two billion hectares of land by 2030; and\u003c/li\u003e\n \u003cli\u003eExpansion of protected and conserved areas, prioritizing areas with high stores of threatened irrecoverable carbon, alongside biodiversity, in nations\u0026rsquo; ongoing efforts to reach 30x30.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e2. Managed Nature Flips from Source to Sink: nearly 5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year by 2030\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNotably, managing \u003cem\u003eexisting\u003c/em\u003e working lands, which make up at least half of the Earth\u0026rsquo;s 13.4 billion hectares of ice-free land, using readily deployable climate-smart approaches represents the largest NCS opportunity (45%). Agricultural practices are currently a large source of hard-to-abate non-CO\u003csub\u003e2\u003c/sub\u003e emissions \u0026ndash; about 5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of methane and nitrous oxide combined. But significantly degraded soils, over-grazing, low-diversity cropping, and tree-poor agricultural landscapes have created opportunities for restoration and more sustainable agricultural practices to remove and reliably store carbon in agricultural lands while also maintaining productivity\u003csup\u003e39,40\u003c/sup\u003e. Working forests (those managed at least partly for timber production) are currently a small net global source, managed in ways that both emit more than necessary in harvest cycles and capture less than possible during recovery cycles\u003csup\u003e41,42\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eTransformation of \u0026ldquo;managed nature\u0026rdquo; in line with the Carbon Law for Nature will require:\u003c/p\u003e\n\u003cul class=\"decimal_type\"\u003e\n \u003cli\u003eEliminating about $300 billion per year of harmful agriculture and forestry subsidies by 2030\u003csup\u003e43\u003c/sup\u003e and investing instead in incentives for innovative regenerative production models;\u003c/li\u003e\n \u003cli\u003eRapidly increasing the area of farms, ranches, and working forests implementing climate-smart management practices to reach 20% of the world\u0026rsquo;s working lands by 2030 and 30% by 2050;\u003c/li\u003e\n \u003cli\u003eShifting global forestry from a nearly 1 GtCO\u003csub\u003e2\u003c/sub\u003e per year net source now (consisting of about 5 GtCO\u003csub\u003e2\u003c/sub\u003e per year of gross emissions from the decomposition of slash and the decay of wood products, and about 4 GtCO\u003csub\u003e2\u003c/sub\u003e per year of gross removals from regrowth after wood harvesting\u003csup\u003e23\u003c/sup\u003e) to net zero by 2030 and a nearly 1 GtCO\u003csub\u003e2\u003c/sub\u003e per year net sink by 2050, which can be delivered with known methods that increase wood fiber production\u003csup\u003e44,45\u003c/sup\u003e;\u003c/li\u003e\n \u003cli\u003eRemoving nearly 3 GtCO\u003csub\u003e2\u003c/sub\u003e of carbon from the atmosphere per year by 2030 and 4.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year by 2050 into farmlands and grazing lands through techniques such as no-till agriculture, rotational grazing, and agroforestry; and\u003c/li\u003e\n \u003cli\u003eFlipping agricultural lands and practices \u0026ndash; including both carbon and non-carbon sources and sinks \u0026ndash; from a 5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year net source now to net zero in 2040 and a 1 GtCO\u003csub\u003e2\u003c/sub\u003ee per year net sink by 2050, with carbon sequestration from regenerative agriculture more than offsetting remaining methane and nitrous oxide emissions.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e3. Restoration of Intact Nature Increases to Accelerate Removals: ~2 GtCO\u003csub\u003e2\u003c/sub\u003e per year by 2030\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRestoration of natural forests, wetlands, and grasslands on previously converted and degraded working lands, where they historically occurred, is the third necessary solution for delivering on the Carbon Law for Nature. The amount of carbon being stored every year in ecosystems through human land use change is already increasing in many parts of the world \u0026ndash; much of it in wealthier countries through sequestration in forests that have been regrowing for decades on previously cleared agricultural land\u003csup\u003e46\u003c/sup\u003e. But there are also significant ongoing active restoration interventions that are already delivering anthropogenic carbon dioxide removal (e.g., in China and Brazil), and there is the political will and opportunity to expand restoration even further, including in new areas of the world, as part of the global nature transition (e.g., the Bonn Challenge, AFR100, and the Mangrove Breakthrough).\u003c/p\u003e\n\u003cp\u003eRestoration actions must accelerate and spread rapidly, driven by financial and policy incentives, wider adoption of natural regeneration techniques\u003csup\u003e47\u003c/sup\u003e, increased seed and nursery capacity, and reduced demand for marginally productive grazing land\u003csup\u003e39\u003c/sup\u003e. The carbon benefits of this would nonetheless build steadily over time \u0026ndash; reaching more than 2 GtCO\u003csub\u003e2\u003c/sub\u003e per year in 2030, accelerating to nearly 6 GtCO\u003csub\u003e2\u003c/sub\u003e per year by 2050. To deliver mitigation at this scale, an emerging global restoration sector must:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eRestore nearly 200 to 350 million hectares of natural forests and wetlands by 2050 including 15 million hectares of peatlands by 2030;\u003c/li\u003e\n \u003cli\u003eRestore 400 thousand hectares of mangroves by 2030; and\u003c/li\u003e\n \u003cli\u003eIncreasingly leverage private sector rather than public-sector finance to become economically self-sustaining.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e4. Easing the Global Land Squeeze by Reducing Land Demand: ~2 GtCO\u003csub\u003e2\u003c/sub\u003ee per year by 2050\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLand is vital for many, sometimes competing, purposes, but none more so than for providing food to a growing global population. Our ability to deliver NCS at the scale demanded by the Carbon Law for Nature is thus tightly linked to food systems, through the physical, economic, environmental, and social \u0026ldquo;space\u0026rdquo; demanded by the food choices made around the world and the amount of food that is lost and wasted from farm to fork\u003csup\u003e48\u003c/sup\u003e. Done right, however, this does not require trading food security for carbon storage and sequestration; recent research suggests that the hidden human health and environmental costs of the existing global food system is on the order of 15 trillion USD per year \u0026ndash; and that a transition to healthy and sustainable foods for all would generate approximately 10 trillion USD in economic benefits, including contributions to stabilize the climate\u003csup\u003e39\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eActions to shift the demand for land-hungry products and reduce food loss and waste that can help deliver this food system transition and ease the global land squeeze include:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eDecarbonizing the electricity and transportation sectors without relying on food crops or other land-intensive bioenergy crops\u003csup\u003e49\u003c/sup\u003e;\u003c/li\u003e\n \u003cli\u003eShifting towards the EAT-Lancet commission\u0026rsquo;s recommended \u0026ldquo;planetary health diet\u0026rdquo;, with decreased over-consumption of animal-sourced foods in some (usually wealthy) countries alongside improved diets in regions where undernutrition is high\u003csup\u003e50\u003c/sup\u003e;\u003c/li\u003e\n \u003cli\u003eShifting livestock production towards more regenerative soil carbon-positive models, significantly reducing the global land area used for livestock production by the 2040s, and no longer feeding livestock crops that humans can eat by 2050;\u003c/li\u003e\n \u003cli\u003eReducing food loss and waste by 25% by 2030 and 50% by 2050;\u003c/li\u003e\n \u003cli\u003eIncreasing demand for lower-emissions and regenerative agricultural practices, so they become the default option for new generations of farmers by the 2040s;\u003c/li\u003e\n \u003cli\u003eContinuing to innovate and invest in increasing agricultural productivity, particularly in areas with large yield gaps, at or above historical rates through this decade\u003csup\u003e51\u003c/sup\u003e; and\u003c/li\u003e\n \u003cli\u003eContinuing to innovate and invest in technologies that dramatically reduce the land required for food production, such as lab grown meats.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOur results demonstrate that \u0026ldquo;re-opening\u0026rdquo; the window to 1.5\u0026deg;C at this juncture is now only realistically within reach if we choose to fully leverage the third rung of the decarbonization ladder. While rapid progress transitioning away from fossil fuels remains critical, even decadal emissions halvings, alongside an unprecedented scaling up of NETs, will no longer be enough to deliver the 1.5\u0026deg;C Paris goal. This means we must exponentially scale NCS implementation through a transformation of our relationship with nature to begin atmospheric CO\u003csub\u003e2\u003c/sub\u003e drawdown by 2040, cut peak temperatures by 0.07-0.13\u0026deg;C, and reduce the time exceeding 1.5\u0026deg;C by at least 3 decades.\u003c/p\u003e\n\u003cp\u003eWe further show that: 1) overshoot past 1.5\u0026deg;C is now likely inevitable, \u003cem\u003eeven with\u003c/em\u003e full delivery of the Carbon Law and Carbon Law for Nature pathways; 2) following the Carbon Law for Nature is achievable and would ramp up the \u0026ldquo;third rung\u0026rdquo; of the decarbonization ladder more than currently modeled, to get us back down to 1.5\u0026deg;C and thereby reduce chronic climate impacts; and 3) following the Carbon Law for Nature reduces the risks of exceeding earth system tipping points through minimizing and shortening the period of overshoot and by increasing the resilience of the land-based components of the biosphere sink (hereon the biosphere land sink).\u003c/p\u003e\n\u003cp\u003eCareful consideration of the long-term durability of carbon stored in nature is therefore critical. This must include both the expected rise in climate-driven disturbances that cause emissions \u003cem\u003eand\u003c/em\u003e the acceleration in carbon sequestration driven by CO\u003csub\u003e2\u003c/sub\u003e fertilization and other factors. Together, these trends contribute to the non-anthropogenic response of the biosphere land sink to global change. Additionally, the contribution of human activities in the AFOLU sector can also affect the durability of storage.\u003c/p\u003e\n\u003cp\u003eRecent critiques that raise concerns about the durability of carbon sequestration in nature \u0026ndash; whether in the biosphere land sink (i.e., its non-anthropogenic response to global change) or in the AFOLU sector (i.e., from NCS investments or policy interventions addressing our lands and forests) \u0026ndash; have suffered from misinterpretations of existing science, creating confusion and misguided narratives. We note several specific errors that should be addressed to facilitate a constructive, science-driven discourse around the durability of natural carbon stocks:\u003c/p\u003e\n\u003cp\u003ea)\u0026nbsp; \u0026nbsp;A focus on point estimates or limited time periods that ignore long-term trends\u003csup\u003e52\u003c/sup\u003e, including regrowth, interannual variability, and links to El Nino / La Nina cycles\u003csup\u003e23\u003c/sup\u003e;\u003c/p\u003e\n\u003cp\u003eb)\u0026nbsp; \u0026nbsp;Extrapolation from specific ecosystems or places\u003csup\u003e53\u003c/sup\u003e to make categorical statements that ignore global trends\u003csup\u003e23\u003c/sup\u003e and the spatial heterogeneity in both underlying processes and climate change itself;\u003c/p\u003e\n\u003cp\u003ec)\u0026nbsp; \u0026nbsp;Failure to specify or correctly characterize temperature-dependence as a factor driving the relative risk of a biosphere land sink reversal, sometimes conflating the disruptive effects of high-emissions scenarios (\u0026gt;2\u003csup\u003e0\u003c/sup\u003eC) with lower-emissions pathways\u003csup\u003e52,54-57\u003c/sup\u003e, or failing to acknowledge the positive role that the sector could play, particularly in the near term, when significant action in the AFOLU sector could keep the climate on track for low overshoot 1.5\u0026deg;C scenarios before the end of the century;\u003c/p\u003e\n\u003cp\u003ed)\u0026nbsp; \u0026nbsp;Failure to differentiate gross versus net accounting in AFOLU fluxes, leading to false interpretations that a weakened or flipped \u003cem\u003enet\u003c/em\u003e biosphere land sink, which \u003cem\u003eincludes\u003c/em\u003e anthropogenic AFOLU emissions, indicates a weakened or flipped biosphere land sink, which \u003cem\u003eexcludes\u003c/em\u003e AFOLU emissions;\u003c/p\u003e\n\u003cp\u003ee)\u0026nbsp; \u0026nbsp;Misinterpretation of evidence that suggests a potentially \u003cem\u003ediminished\u003c/em\u003e net biosphere land sink, as a \u003cem\u003ereversal\u003c/em\u003e in the biosphere land sink, which would indicate a net source on an annual basis.\u003c/p\u003e\n\u003cp\u003eFurthermore, the concerns about the durability of NCS implemented in the AFOLU sector are also often exaggerated. Achieving the scale of NCS solutions needed, if effectively designed, inherently addresses durability concerns. Larger scales of NCS implementation inherently reduce the likelihood of reversals, since both natural and anthropogenic disturbance events operate at smaller scales than the biomes across which NCS must be implemented. Even in the face of an increasing risk of reversal for any \u003cem\u003eindividual\u003c/em\u003e NCS investment (such as a reforestation project) or a geographically constrained AFOLU mitigation intervention (such as a national or jurisdictional land use policy), the expected stability of a strong and positive biosphere land sink within the envelope of target warming scenarios (i.e., 1.5-2\u0026deg;C) suggests that a spatially diversified \u003cem\u003eportfolio\u003c/em\u003e of NCS investments in the AFOLU sector is highly likely to result in a stable CO\u003csub\u003e2\u003c/sub\u003e sink over decades if not centuries. This large scale durability is strengthened if we prioritize places for conservation and restoration that are resilient to, or even benefit from, climate change. For example, we should focus reforestation where forests are most likely to remain healthy in a future climate, and we should prioritize protecting high carbon ecosystems that are similarly resilient.\u003c/p\u003e\n\u003cp\u003eUnfortunately, media reporting not subject to peer review can inadvertently string together several of these misinterpretations, from \u0026ldquo;cherry-picking\u0026rdquo; data to confusing carbon stocks with carbon fluxes, compounding each other and creating a misleading narrative that confuses decision-makers (e.g. a recent article in the Guardian in October 2024\u003csup\u003e58\u003c/sup\u003e titled \u0026ldquo;\u003cem\u003eTrees and land absorbed almost no CO\u003csub\u003e2\u003c/sub\u003e last year. Is Nature\u0026rsquo;s carbon sink failing?\u003c/em\u003e\u0026rdquo;). Scrutiny across targets and actions underpinning all three rungs of the decarbonization ladder is critical, but needs to be applied consistently and carefully due to the complexities involved.\u003c/p\u003e\n\u003cp\u003eWe further acknowledge that the first two rungs, fossil mitigation and NETs, are not on track to deliver what is needed:\u003c/p\u003e\n\u003cp\u003e\u0026middot;\u0026nbsp; \u0026nbsp;\u0026nbsp;We are not making progress on the Carbon Law for fossil fuels, which needs to be delivered at a rate of more than 7% global CO\u003csub\u003e2\u003c/sub\u003e emission reductions per year, whereas, over the past 10 years from 2014 to 2023, it has grown by 0.6% per year from 35.5 to 37.8 GtCO\u003csub\u003e2\u003c/sub\u003e per year\u003csup\u003e23\u003c/sup\u003e;\u003c/p\u003e\n\u003cp\u003e\u0026middot;\u0026nbsp; \u0026nbsp;\u0026nbsp;Methane and nitrous oxide emissions must decline in pace with 1.5\u0026deg;C scenarios, yet they are still increasing at around the same rate as fossil fuels \u0026ndash; 0.6 to 0.7% per year from 2014 to 2023\u003csup\u003e59\u003c/sup\u003e;\u003c/p\u003e\n\u003cp\u003e\u0026middot;\u0026nbsp; \u0026nbsp;\u0026nbsp;The NETs scaling pathway requires a global price on carbon exceeding 500 USD/ton CO\u003csub\u003e2\u003c/sub\u003e with current technologies, while also relying on yet-to-be delivered innovations\u003csup\u003e60\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eWe argue, however, that these challenges only \u003cem\u003eincrease\u003c/em\u003e the need for shorter-term wins and carbon sequestration options beyond technology-based solutions, not least because NCS have a much higher likelihood of scalable success in the near term than NETs\u003csup\u003e61\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eMoreover, every fraction of a degree counts, and every year of overshoot increases risk. Delivered in parallel with the first two rungs of the decarbonization ladder, the Carbon Law for Nature reopens the window to 1.5\u0026deg;C, while providing a transformational opportunity for innovation and investment in the AFOLU sector, generating benefits that will spill over into our remaining natural lands, and helping maintain the estimated US$44 trillion in economic value generation that is moderately or highly dependent on nature (including underpinning an estimated 395 million jobs by 2030)\u003csup\u003e62\u003c/sup\u003e, alongside a greater chance of delivering the SDGs\u003csup\u003e63\u003c/sup\u003e. At a minimum, however, it keeps us closer to the safe operating space for planetary boundaries, including biosphere integrity, freshwater security, and biogeochemical flows,\u003csup\u003e64\u003c/sup\u003e while reducing atmospheric GHGs in the near term and providing time (without being an excuse for inaction) to accelerate other solutions and \u0026ndash; if needed \u0026ndash; replace the mitigation from any localized reversals of land-based sequestration.\u003c/p\u003e\n\u003cp\u003eYet NCS remain severely underfunded. The kind of investment flooding into fossil mitigation (e.g., the United States\u0026rsquo; Inflation Reduction Act of 2022, which allocated $369 billion to clean energy and the estimated US$2 trillion of investment globally in 2024 in clean energy technologies and infrastructure\u003csup\u003e65\u003c/sup\u003e), is not yet happening for climate finance to AFOLU, which receives only about 3% of global climate finance\u003csup\u003e66\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eEven without sufficient funding, many of the necessary pieces are already in place, with leadership continuing to emerge among policy makers and the private sector to accelerate climate action, transform food systems, reduce deforestation, protect natural ecosystems, and address unequal impacts.\u003c/p\u003e\n\u003cp\u003eIn sum, the \u0026lsquo;nature transition\u0026rsquo; is \u0026ndash; and must be recognized as \u0026ndash; equal and complementary to the \u0026lsquo;energy transition\u0026rsquo; and energized, leveraged and financed accordingly. There is no other option for delivering a safe climate landing.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eData Availability Statement\u003c/p\u003e\n\u003cp\u003eThe authors declare that all other data supporting the findings of this study are available within the paper and its supplementary information files.\u003c/p\u003e\n\u003cp\u003eAcknowledgments\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eAnonymous Donor through the California Community Grant Foundation (MSW, DH, BG, TB)\u003c/p\u003e\n\u003cp\u003eAuthor contributions:\u003c/p\u003e\n\u003cp\u003eConceptualization: MSW, JR, DH, BG\u003c/p\u003e\n\u003cp\u003eMethodology: MSW, TB, DH\u003c/p\u003e\n\u003cp\u003eQuantitative analysis: MSW, TB\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; original draft: MSW\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; review \u0026amp; editing: MSW, JR, MS, CF, DH, TB, BG\u003c/p\u003e\n\u003cp\u003eCompeting Interests\u003c/p\u003e\n\u003cp\u003eAuthors declare that they have no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eRockstr\u0026ouml;m, J.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e A roadmap for rapid decarbonization. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e355\u003c/strong\u003e, 1269-1271 (2017).\u003c/li\u003e\n \u003cli\u003eIPCC. \u003cem\u003eThe evidence is clear: the time for action is now. 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(IEA, Paris, 2024).\u003c/li\u003e\n \u003cli\u003eBuchner, B.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Global Lanscape of Climate Finance 2023. \u003cem\u003eClimate Policy Initiative Report (November), https://www. climatepolicyinitiative. org/publication/global-landscape-of-climatefinance-2023\u003c/em\u003e (2023).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eThe Remaining CO\u003csub\u003e2\u003c/sub\u003e Budget (RCB), Fossil Emissions, and Negative Emissions Technologies\u003c/h2\u003e\n \u003cp\u003eA nearly linear relationship between cumulative CO\u003csub\u003e2\u003c/sub\u003e emissions and global surface temperature increase allows the calculation of a remaining carbon budget (RCB) equivalent to a particular temperature target given total emissions to date, with uncertainty accounted for by selecting a probability of hitting that target. The RCBs for a 50% and 66% chance respectively of keeping temperature increase to 1.5\u0026deg;C have been shrinking from 500 GtCO\u003csub\u003e2\u003c/sub\u003e and 400 GtCO\u003csub\u003e2\u003c/sub\u003e emissions remaining starting Jan 1, 2020 as reported in IPCC AR6 WGI\u003csup\u003e57\u003c/sup\u003e. Global CO\u003csub\u003e2\u003c/sub\u003e emissions in the four years from 2020\u0026mdash;2023 have spent down ~\u0026thinsp;160 GtCO\u003csub\u003e2\u003c/sub\u003e of that RCB\u003csup\u003e26\u003c/sup\u003e, while updated models and estimates of the transient climate response to cumulative emissions suggest further contraction of the RCB\u003csup\u003e67\u003c/sup\u003e. Starting Jan 1, 2024, that leaves humanity with only about 275 GtCO\u003csub\u003e2\u003c/sub\u003e and 175 GtCO\u003csub\u003e2\u003c/sub\u003e of RCB respectively for a 50% and 66% chance of limiting temperature increase to 1.5\u0026deg;C, with significant uncertainty\u003csup\u003e26\u003c/sup\u003e. These RCBs assume an evolution of nonCO\u003csub\u003e2\u003c/sub\u003e GHG emissions and other climate forcers consistent with the necessary CO\u003csub\u003e2\u003c/sub\u003e pathway, which generally reach net zero levels a decade or two later than CO\u003csub\u003e2\u003c/sub\u003e (see below).\u003c/p\u003e\n \u003cp\u003eBusiness-as-usual fossil fuel CO\u003csub\u003e2\u003c/sub\u003e emissions alone are on track to deplete this budget in less than a decade. At 10 GtC per year (36.7 GtCO\u003csub\u003e2\u003c/sub\u003e per year) in 2023\u003csup\u003e26\u003c/sup\u003e, a linear trajectory at the recent decade\u0026rsquo;s\u0026thinsp;~\u0026thinsp;200 MtCO\u003csub\u003e2\u003c/sub\u003e per year average rate of increase through the International Energy Agency\u0026rsquo;s expected fossil fuel consumption peak in 2030 would result in exceeding the 1.5\u0026deg;C 66% budget during 2028, and the 1.5\u0026deg;C 50% budget during 2031.\u003c/p\u003e\n \u003cp\u003eKeeping 1.5\u0026deg;C within reach requires an immediate and rapid realignment with the Carbon Law\u003csup\u003e1\u003c/sup\u003e of three rungs of a decarbonization ladder. To assess the scale of mitigation required from nature \u0026ndash; one of the three critical rungs \u0026ndash; we compare the 1.5\u0026deg;C RCBs to the net emissions resulting from Carbon Law fossil fuel and negative emissions technologies (NETs) pathways. We assume flat fossil fuel CO\u003csub\u003e2\u003c/sub\u003e emissions of 36 GtCO\u003csub\u003e2\u003c/sub\u003e per year from 2020\u0026ndash;2023, followed by Carbon Law decadal halvings: linear declines to half that level in 2030, half again in 2040, and half again in 2050, resulting in total fossil emissions of 376 GtCO\u003csub\u003e2\u003c/sub\u003e from 2024 through 2050. Our use of 36 GtCO\u003csub\u003e2\u003c/sub\u003e per year to represent recent fossil CO\u003csub\u003e2\u003c/sub\u003e emissions is based on the Global Carbon Budget\u003csup\u003e26\u003c/sup\u003e estimates of E\u003csub\u003eFOS\u003c/sub\u003e which subtracts cement carbonation from fossil emissions. We choose to exclude the 2020 anomaly, exclude the 2023 initial estimate of 36.7 GtCO2, and round down to 36 from observed 2019, 2021, and 2022 values of 36.3 GtCO2 per year.\u003c/p\u003e\n \u003cp\u003eNETs \u0026ndash; such as direct air capture and other industrial CO\u003csub\u003e2\u003c/sub\u003e sequestrations above and beyond any CCS used to deliver the Carbon Law for fossil fuels \u0026ndash; follow the pathway of Rockstr\u0026ouml;m \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e, reaching 0.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year by 2030, 2.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year by 2040, and 5 GtCO\u003csub\u003e2\u003c/sub\u003e per year (and 57 GtCO\u003csub\u003e2\u003c/sub\u003e cumulative) by 2050. This NETs pathway is consistent with 2020\u0026ndash;2100 non-AFOLU CDR quantities in the C1, C2, and C3 scenarios of the AR6 scenarios database (AR6 WGIII Ch3 table 3.5 and section 3.4.7), reaching midway between the medium and upper bounds of economically feasible 2050 geological CDR potential (3\u0026ndash;7 GtCO2/yr) estimated by Fuss \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e15\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eTogether, the 319 GtCO\u003csub\u003e2\u003c/sub\u003e of net emissions from fossil fuels and NETs from 2024\u0026ndash;2050 exceed the 175 GtCO\u003csub\u003e2\u003c/sub\u003e 66% RCB for 1.5\u0026deg;C by 144 GtCO\u003csub\u003e2\u003c/sub\u003e and the 275 GtCO\u003csub\u003e2\u003c/sub\u003e 50% RCB for 1.5\u0026deg;C by 44 GtCO\u003csub\u003e2\u003c/sub\u003e (Extended Data Table\u0026nbsp;1.a).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eAFOLU Emissions\u003c/h2\u003e\n \u003cp\u003eWhile the carbon emissions and sequestration dynamics of fossil fuel use and negative emissions technology deployment are relatively simple, those of land and nature are not: they are diffuse, have complex temporal and spatial dynamics, and are not easily divided into anthropogenic and non-anthropogenic processes. This complexity results in striking differences in estimates of land fluxes between national greenhouse gas inventories, global estimates of anthropogenic fluxes from bookkeeping models, and global land sink estimates from inverse modeling approaches and dynamic global vegetation models. These differences have been significantly untangled in recent years\u003csup\u003e28\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eFor estimates of baseline anthropogenic emissions from agriculture, forestry, and other land uses (AFOLU), we rely on the land use emissions methodologies of IPCC AR6 WGI Chap.\u0026nbsp;5\u003csup\u003e57\u003c/sup\u003e, updated by more recent sources that apply the same methodologies\u003csup\u003e26,67\u003c/sup\u003e. Given high year-to-year variability of AFOLU emissions, we use decadal averages for the most recently available decade (2013\u0026ndash;2022 for CO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e26\u003c/sup\u003e and 2012\u0026ndash;2021 for nonCO\u003csub\u003e2\u003c/sub\u003e gases\u003csup\u003e67\u003c/sup\u003e) as the best estimates of \u0026ldquo;recent\u0026rdquo; or \u0026ldquo;current\u0026rdquo; emissions (Extended Data Table\u0026nbsp;2). We then round these estimates to the nearest half gigaton; and assume AFOLU emissions in 2023 at this period-average level (Extended Data Table\u0026nbsp;2).\u003c/p\u003e\n \u003cp\u003eOver the decade 2013\u0026ndash;2022, forestry and other land uses were a global net source of about 4.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year. This estimate of global anthropogenic net CO\u003csub\u003e2\u003c/sub\u003e emissions from AFOLU was updated significantly\u003csup\u003e67\u003c/sup\u003e between the release of the IPCC AR6 WGIII\u003csup\u003e17\u003c/sup\u003e and more recent estimates\u003csup\u003e26\u003c/sup\u003e. This net number, estimated by averaging three bookkeeping models of anthropogenic FOLU emissions, is the sum of component fluxes segmented by Friedlingstein \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e\u003cem\u003e26\u003c/em\u003e\u003c/sup\u003e into about 13.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year of gross emissions sources in some places (deforestation of ~\u0026thinsp;7 GtCO\u003csub\u003e2\u003c/sub\u003e per year, including both permanent and shifting cultivation of ~\u0026thinsp;4.2 and ~\u0026thinsp;2.8 GtCO\u003csub\u003e2\u003c/sub\u003e per year respectively; plus other land use transitions of ~\u0026thinsp;0.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year; peat drainage and fires of ~\u0026thinsp;1 GtCO\u003csub\u003e2\u003c/sub\u003e per year; plus forestry-based decomposition of slash and wood products of ~\u0026thinsp;5 GtCO\u003csub\u003e2\u003c/sub\u003e per year) plus about 9 GtCO\u003csub\u003e2\u003c/sub\u003e per year of gross sinks elsewhere (forest regrowth of ~\u0026thinsp;4.7 GtCO\u003csub\u003e2\u003c/sub\u003e per year, including both reforestation and regrowth from shifting cultivation of about\u0026thinsp;~\u0026thinsp;2 and ~\u0026thinsp;2.7 GtCO\u003csub\u003e2\u003c/sub\u003e per year respectively; plus about 4 GtCO\u003csub\u003e2\u003c/sub\u003e per year of regrowth after forest management harvests). These sources and sinks quantify the carbon imbalances between land and atmosphere driven by anthropogenic processes \u0026ndash; or what we call \u0026ldquo;managed nature\u0026rdquo;. The extent to which these different processes are \u0026ldquo;mitigatable\u0026rdquo; \u0026ndash; and at what costs and in what time frame \u0026ndash; is discussed below. But it is worth noting that two of these processes \u0026ndash; forestry and shifting cultivation \u0026ndash; are largely balanced between sources and sinks with better-constrained estimates for net emissions than for gross sources and sinks, and with sinks that are lagged responses to the corresponding sources on the scale of decades.\u003c/p\u003e\n \u003cp\u003eWhile managed nature\u0026rsquo;s imbalances are \u003cem\u003econtributing\u003c/em\u003e to global anthropogenic CO\u003csub\u003e2\u003c/sub\u003e emissions, the biosphere\u0026rsquo;s responses to the loading of CO\u003csub\u003e2\u003c/sub\u003e in the atmosphere are also leading to further imbalances. Land and oceans are each absorbing significant portions of anthropogenic CO\u003csub\u003e2\u003c/sub\u003e emissions every year, through increased growth rates of plants and through ocean acidification respectively. These biosphere sinks are signs of an earth out of balance \u0026ndash; but for now, they are critical buffers against rising atmospheric CO\u003csub\u003e2\u003c/sub\u003e concentrations.\u003c/p\u003e\n \u003cp\u003eThe absorptive response of the biosphere land sink, as partitioned from the ocean sink and from CO\u003csub\u003e2\u003c/sub\u003e emissions that remain in the atmosphere, was ~\u0026thinsp;12.3 GtCO\u003csub\u003e2\u003c/sub\u003e per year for 2013-2022\u003csup\u003e26\u003c/sup\u003e. Recent efforts to harmonize land use emissions estimates across global models and national inventories\u003csup\u003e28\u003c/sup\u003e help illustrate our use of the terms \u0026ldquo;managed nature\u0026rdquo; and \u0026ldquo;biosphere response\u0026rdquo;, and the underlying sources of data that inform these estimates (Extended Data Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe complexities of the carbon cycle aside, the AFOLU sector is also a major source of nonCO\u003csub\u003e2\u003c/sub\u003e GHG emissions. Agriculture emits over 5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of methane and nitrous oxide emissions, while human-set fires and the draining of organic soils adds less than 0.5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of FOLU methane and nitrous oxide emissions. We estimate theses 2012\u0026ndash;2021 decadal average nonCO\u003csub\u003e2\u003c/sub\u003e emissions from AFOLU by applying the proportion of global methane and nitrous oxide emissions attributed to AFOLU in IPCC AR6 WGIII Table\u0026nbsp;7.1\u003csup\u003e17\u003c/sup\u003e to recent estimates of global decadal average methane and nitrous oxide emissions\u003csup\u003e67\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eWe include nonCO\u003csub\u003e2\u003c/sub\u003e AFOLU emissions in the Carbon Law for Nature pathway \u0026ndash; and accept the resulting slight misnomer \u0026ndash; because systemic transformation of global land use will drive simultaneous shifts in emissions of all three gases, and more practically because emerging sectoral mitigation roadmaps\u003csup\u003e39,51\u003c/sup\u003e and science-based target-setting approaches\u003csup\u003e68\u003c/sup\u003e include all gases in their proposed pathways.\u003c/p\u003e\n \u003cp\u003eIn total, historical gross AFOLU GHG emissions are estimated as 19 GtCO\u003csub\u003e2\u003c/sub\u003ee per year, about half of which is offset by 9 GtCO\u003csub\u003e2\u003c/sub\u003e per year gross FOLU sink, to yield baseline global net AFOLU GHG emissions of 10 GtCO\u003csub\u003e2\u003c/sub\u003ee per year, consisting of 4.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year net emissions from CO\u003csub\u003e2\u003c/sub\u003e and 5.5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of nonCO\u003csub\u003e2\u003c/sub\u003e sources (Extended Data Table\u0026nbsp;2).\u003c/p\u003e\n \u003cp\u003eBecause the RCB concept only includes CO\u003csub\u003e2\u003c/sub\u003e emissions explicitly, but assumes an evolution of nonCO\u003csub\u003e2\u003c/sub\u003e GHG emissions consistent with a given CO\u003csub\u003e2\u003c/sub\u003e pathway, we must also assess any all-gases AFOLU pathway against these assumed 1.5\u0026deg;C-compatible nonCO\u003csub\u003e2\u003c/sub\u003e pathways \u0026ndash; and potentially adjust our comparisons to the RCB as needed. We estimate from Riahi \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e16\u003c/sup\u003e that the suite of AR6 1.5\u0026deg;C-compatible scenarios show average declines in nonCO\u003csub\u003e2\u003c/sub\u003e AFOLU emissions from 2019 levels of nearly 10% to about 5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year by 2030 and of just over 25% to about 4.4 GtCO\u003csub\u003e2\u003c/sub\u003ee per year by 2050, suggesting cumulative 2024\u0026ndash;2050 nonCO\u003csub\u003e2\u003c/sub\u003e AFOLU emissions of about 131 GtCO\u003csub\u003e2\u003c/sub\u003ee and mitigation of about 18 GtCO\u003csub\u003e2\u003c/sub\u003ee (Extended Data Table\u0026nbsp;1.b). We can account for some substitutability of mitigation across CO\u003csub\u003e2\u003c/sub\u003e and nonCO\u003csub\u003e2\u003c/sub\u003e mitigation (as leveled by AR6 100-year Global Warming Potentials) by adjusting the cumulative net CO\u003csub\u003e2\u003c/sub\u003e-only emissions of any AFOLU all-gases emissions pathway to the difference between this 131 GtCO\u003csub\u003e2\u003c/sub\u003ee and the pathway\u0026rsquo;s nonCO\u003csub\u003e2\u003c/sub\u003e emissions (as we do in Extended Data Table\u0026nbsp;1). For AFOLU pathways with similar levels of cumulative nonCO\u003csub\u003e2\u003c/sub\u003e emissions to the 1.5\u0026deg;C-compatible scenarios, we can simply compare cumulative AFOLU CO\u003csub\u003e2\u003c/sub\u003e emissions to the RCB directly.\u003c/p\u003e\n \u003cp\u003eThere is no reasonable low-overshoot path to keeping 1.5\u0026deg;C within reach if AFOLU emissions were to continue at their current level through 2050. Period total net AFOLU emissions would be 270 GtCO\u003csub\u003e2\u003c/sub\u003ee, consisting of 122 GtCO\u003csub\u003e2\u003c/sub\u003e of net CO\u003csub\u003e2\u003c/sub\u003e emissions plus another 149 GtCO\u003csub\u003e2\u003c/sub\u003ee of nonCO\u003csub\u003e2\u003c/sub\u003e emissions (Extended Data Table\u0026nbsp;1.c). Adding 18 GtCO\u003csub\u003e2\u003c/sub\u003ee of excess nonCO\u003csub\u003e2\u003c/sub\u003e emissions (in the flat \u0026ldquo;BAU\u0026rdquo; pathway compared to the 1.5\u0026deg;C nonCO\u003csub\u003e2\u003c/sub\u003e pathways) to AFOLU CO\u003csub\u003e2\u003c/sub\u003e-only net emissions of 122 GtCO\u003csub\u003e2\u003c/sub\u003e results in an RCB-comparable net AFOLU emissions of 139 GtCO\u003csub\u003e2\u003c/sub\u003e. Added to fossil fuel emissions that follow carbon law halvings and NETs that scale as assumed above, AFOLU emissions at current levels would yield a fossil fuel, NETs, and AFOLU total net RCB comparable emissions of 458 GtCO\u003csub\u003e2\u003c/sub\u003e from 2024\u0026ndash;2050, exceeding the 175 and 275 GtCO\u003csub\u003e2\u003c/sub\u003e RCBs for 66% and 50% chances at 1.5\u0026deg;C by 283 and 183 GtCO\u003csub\u003e2\u003c/sub\u003e of overshoot respectively (Extended Data Table\u0026nbsp;1.c).\u003c/p\u003e\n \u003cp\u003eThe Carbon Law for Nature pathway flips nature to a cumulative all-gases net sink of 59 GtCO\u003csub\u003e2\u003c/sub\u003ee. This can be delivered by AFOLU nonCO\u003csub\u003e2\u003c/sub\u003e emissions following a mitigation pathway just slightly more ambitious than the 1.5\u0026deg;C-compatible scenarios (but consistent with other sectoral roadmaps, see below) totaling 121 GtCO\u003csub\u003e2\u003c/sub\u003ee, plus a pathway for AFOLU net CO\u003csub\u003e2\u003c/sub\u003e totaling a 180 GtCO\u003csub\u003e2\u003c/sub\u003e cumulative sink (Extended Data Table\u0026nbsp;1.d). After adjustment to account for nonCO\u003csub\u003e2\u003c/sub\u003e mitigation beyond that assumed in the AR6 1.5\u0026deg;C-compatible scenarios, this net AFOLU sink adds to the fossil fuel emissions and NETs sinks through 2050 to deliver an RCB-comparable net cumulative emissions of just 130 GtCO\u003csub\u003e2\u003c/sub\u003e \u0026ndash; well below our 1.5\u0026deg;C RCBs. With the Carbon Law for Nature, the three rungs of our decarbonization ladder allow us to more than reach the window for a 66% chance of 1.5\u0026deg;C, with a 45 GtCO\u003csub\u003e2\u003c/sub\u003e buffer (Extended Data Table\u0026nbsp;1.d).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003eAFOLU Mitigation: Carbon Law for Nature Compared to Sectoral Potential Estimates\u003c/h2\u003e\n \u003cp\u003eTo assess the feasibility of the Carbon Law for Nature pathway, we look to sectoral estimates of cost-effective (\u0026lt;\u003cspan\u003e$\u003c/span\u003e100/ton) land-based mitigation potential from Roe \u003cem\u003eet al.\u003c/em\u003e \u003csup\u003e19\u003c/sup\u003e as our primary source. These estimates are well-aligned with those of the IPCC AR6 WGIII sectoral estimates\u003csup\u003e17\u003c/sup\u003e, with totals of 13.8 GtCO\u003csub\u003e2\u003c/sub\u003ee average per year from 2020\u0026ndash;2050 (or 414 GtCO\u003csub\u003e2\u003c/sub\u003ee total) (compared to 13.6 GtCO\u003csub\u003e2\u003c/sub\u003ee average per year) and with a technical potential more than double that. Integrated assessment model estimates are only\u0026thinsp;~\u0026thinsp;58% of the sectoral estimates, with differences driven primarily by more extensive coverage across mitigation measures in the sectoral estimates. We use the higher sectoral estimates as our primary source data, recognizing that a) the median sectoral estimate falls well within the IAM uncertainty bounds; b) many existing\u003csup\u003e36\u003c/sup\u003e and emerging nature-based solutions such as blue carbon\u003csup\u003e69\u003c/sup\u003e and liana removal\u003csup\u003e45\u003c/sup\u003e have yet to be included in IAMs; and c) protecting, managing and restoring nature provides significant value beyond climate stabilization, including maintaining the earth system within other planetary boundaries\u003csup\u003e70\u003c/sup\u003e, which suggests a pragmatic but conservative strategy should be to over- rather than under-invest in nature as a climate solution. Alternative AFOLU mitigation pathways, including some based on subsets of IAM scenarios, are compared below to these sectoral estimates.\u003c/p\u003e\n \u003cp\u003eA baseline standardization is necessary to compare the Carbon Law for Nature pathway, which sets decadal AFOLU benchmarks relative to recent baseline emissions levels, to the sectoral mitigation estimates synthesized in Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e, which are a mix of historical and modeled baselines. We standardize estimates for each mitigation pathway representing more than 2% of the total to a flat historical baseline, by subtracting the period average change in modeled baseline emissions or sequestrations from the 2020\u0026ndash;2050 average sectoral mitigation estimates (see Data File S1).\u003c/p\u003e\n \u003cp\u003eThe most significant adjustments are needed for agricultural nonCO\u003csub\u003e2\u003c/sub\u003e emissions and food systems demand-side mitigation levers, given an expected significant \u003cem\u003eincrease\u003c/em\u003e in food systems nonCO\u003csub\u003e2\u003c/sub\u003e emissions of 0.4\u0026ndash;0.9 GtCO\u003csub\u003e2\u003c/sub\u003ee by 2030 and 0.9\u0026ndash;2.3 GtCO\u003csub\u003e2\u003c/sub\u003ee by 2050 (ranges represent the BAU estimates of combined N\u003csub\u003e2\u003c/sub\u003eO and CH\u003csub\u003e4\u003c/sub\u003e emissions by (Ref \u003csup\u003e39\u003c/sup\u003e) and (Ref \u003csup\u003e71\u003c/sup\u003e)). Standardizing the baselines reduces the mitigation estimates from a combined 2.5 GtCO\u003csub\u003e2\u003c/sub\u003ee of average annual mitigation from an increasing baseline to 0.7\u0026ndash;1.6 GtCO\u003csub\u003e2\u003c/sub\u003ee per year from a standardized flat baseline, with the range representing uncertainty in the underlying sources\u0026rsquo; baselines.\u003c/p\u003e\n \u003cp\u003eEstimated mitigation from avoided deforestation and from reforestation also change significantly after baseline standardization, given that two sources averaged in Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e have very different baselines. One of the two\u003csup\u003e42\u003c/sup\u003e has almost no discernable trend in baseline forest fluxes summed across deforestation, reforestation, and forest management, while the other\u003csup\u003e72\u003c/sup\u003e models a baseline (no carbon price) scenario with steadily increasing emissions from deforestation alongside similarly increasing sequestrations from reforestation. Averaging across standardized versions of these two sources yields deforestation mitigation potential estimates at 2.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year average (compared to from 3.6 GtCO\u003csub\u003e2\u003c/sub\u003e per year average before standardization), and a nearly equal increase in reforestation potential from 1.2 GtCO\u003csub\u003e2\u003c/sub\u003e per year average before to 2 GtCO\u003csub\u003e2\u003c/sub\u003e per year average after baseline standardization.\u003c/p\u003e\n \u003cp\u003eEven after these changes, the annual average cost-effective sectoral AFOLU mitigation levels estimated by Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e are sufficient to keep 1.5\u0026deg;C within reach as part of our decarbonization ladder, even if delivered over just the 27 years from 2024\u0026ndash;2050 (Extended Data Table\u0026nbsp;1.e). Adjusted cost-effective AFOLU mitigation from a flat historical baseline is about 12.1 (11.6 to 12.5) GtCO\u003csub\u003e2\u003c/sub\u003ee per year average, or about 326 GtCO\u003csub\u003e2\u003c/sub\u003ee over 27 years. Of this adjusted cumulative total, about 17 (8.5 to 25.5) GtCO\u003csub\u003e2\u003c/sub\u003ee is from nonCO\u003csub\u003e2\u003c/sub\u003e emissions reductions, in line with the 18 GtCO\u003csub\u003e2\u003c/sub\u003ee of nonCO\u003csub\u003e2\u003c/sub\u003e AFOLU mitigation in the 1.5\u0026deg;C-compatible scenarios, allowing us to compare cumulative CO\u003csub\u003e2\u003c/sub\u003e-only emissions to the RCB without any further adjustment. The cumulative net CO\u003csub\u003e2\u003c/sub\u003e sink of about 187 GtCO\u003csub\u003e2\u003c/sub\u003e, subtracted from period total CO\u003csub\u003e2\u003c/sub\u003e emissions of 319 GtCO\u003csub\u003e2\u003c/sub\u003e from fossil fuels and NETs, results in 133 GtCO\u003csub\u003e2\u003c/sub\u003e of cumulative net emissions \u0026ndash; 142 and 42 GtCO\u003csub\u003e2\u003c/sub\u003e respectively below the 50% and 66% RCBs for 1.5\u0026deg;C (Extended Data Table\u0026nbsp;1.e).\u003c/p\u003e\n \u003cp\u003eThis shows that the Carbon Law for Nature pathway delivers a comparable annual average level of AFOLU mitigation over the period from 2024\u0026ndash;2050 (Extended Data Table\u0026nbsp;1.e) as the cost-effective sectoral estimates of mitigation potential from IPCC AR6, and thus is likely to be achievable at cost-effective levels of investment.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003eAccelerating AFOLU Mitigation Potential to Deliver the Carbon Law for Nature\u003c/h2\u003e\n \u003cp\u003eTo construct a vision for accelerating NCS actions to deliver on the Carbon Law for Nature, to break down the mitigation opportunity into policy-relevant categories, and to identify decadal milestones across a range of solutions, we create an explicit set of illustrative annual mitigation curves from 2024 through 2050. The scale of mitigation delivered by these \u0026ldquo;Protect, Manage, and Restore\u0026rdquo; curves is based largely on the adjusted sectoral mitigation estimates of Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e described above (see Extended Data Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e and Data File S1), with the timing of mitigation through 2050 grounded in the \u0026ldquo;NCS hierarchy\u0026rdquo;\u003csup\u003e35\u003c/sup\u003e, a framework which suggests a prioritization of NCS investments of protection, improved management, and then restoration, recognizing their different characteristic time horizons, cost-effectiveness, biodiversity values, flux densities, and requirements for land use change.\u003c/p\u003e\n \u003cp\u003eWe construct these pathways to deliver cumulative mitigation from 2024\u0026ndash;2050 approximately equal to 27 years at the adjusted annual average mitigation estimated above (Extended Data Table\u0026nbsp;1.f), with a few adjustments to improve alignment with secondary sources and new data. These adjustments include an increase of ~\u0026thinsp;0.5 GtCO\u003csub\u003e2\u003c/sub\u003e per year in the cost-effective mitigation potential of improved forest management to account for newly estimated potential from removal of overabundant lianas\u003csup\u003e45\u003c/sup\u003e; and a decrease of 1.3 GtCO\u003csub\u003e2\u003c/sub\u003e per year in the cost effective mitigation potential from carbon sequestration into agricultural lands, to account for more constrained estimates in Nabuurs \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e17\u003c/sup\u003e than in Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eWe also provide breakdowns of mitigation into policy-relevant categories: reduced nonCO\u003csub\u003e2\u003c/sub\u003e emissions, reduced CO\u003csub\u003e2\u003c/sub\u003e emissions, and increased CO\u003csub\u003e2\u003c/sub\u003e sinks, to align with land-use flux estimates from global models and bookkeeping models; protection of natural ecosystems, management of working lands, restoration of natural ecosystems, and demand-side levers to reduce land demand, to align with categories of NCS intervention; and agriculture vs forestry and other land uses, to align with national greenhouse gas inventories (see Data File S1).\u003c/p\u003e\n \u003cp\u003eBecause our NCS mitigation curves start at zero in 2023, and we aim to deliver the same cumulative period mitigation with a monotonically increasing function, it is mathematically \u003cem\u003erequired\u003c/em\u003e that annual mitigation in 2050 exceed the annual average level. While our curves thus rise above the annual average in later years, they always remain below the technical mitigation potential in every category (see Data File S1). The total mitigation from these pathways closely track the Carbon Law for Nature (see Extended Data Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eAbout 5.1 GtCO\u003csub\u003e2\u003c/sub\u003ee per year average of AFOLU mitigation potential is on the emissions reduction side of the equation. This is dominated by 2.9 GtCO\u003csub\u003e2\u003c/sub\u003e from protecting forests, peatlands and mangroves from conversion, plus another 0.7 GtCO\u003csub\u003e2\u003c/sub\u003e from protecting peat soil carbon stocks from additional oxidation in drained peatlands by restoring water tables, and about 0.5 GtCO\u003csub\u003e2\u003c/sub\u003e from protecting the carbon stocks in working forests through more strategic forestry. About 1 GtCO\u003csub\u003e2\u003c/sub\u003ee per year of nonCO\u003csub\u003e2\u003c/sub\u003e emissions mitigation opportunity comes from a transformation of our food-systems to reduce food loss and waste and towards healthier, lower-emissions diets.\u003c/p\u003e\n \u003cp\u003eAbout 7 GtCO\u003csub\u003e2\u003c/sub\u003e per year of AFOLU mitigation potential is from nature-based carbon removals, through actions that intentionally sequester additional carbon into natural and working lands. About half of this increased carbon sink is from forests: about 2.75 GtCO\u003csub\u003e2\u003c/sub\u003e from reforestation, plus another 0.8 GtCO\u003csub\u003e2\u003c/sub\u003e from forest management in working forests. The other half of cost-effective natural carbon removals comes from agricultural lands: about 3.4 GtCO\u003csub\u003e2\u003c/sub\u003e of cost-effective supply-side CO\u003csub\u003e2\u003c/sub\u003e sequestration potential from crop and grazing land soil carbon sequestration and agroforestry.\u003c/p\u003e\n \u003cp\u003eOf course, there is uncertainty in the mitigation potential estimates for any given NCS, and the science is evolving rapidly, including identification of new low-cost NCS that have not yet been included in syntheses such as liana removal. It is also the case that some NCS which \u003cem\u003eare\u003c/em\u003e included in our mitigation curves will likely fail to materialize at the levels currently expected. These uncertainties in the ultimate portfolio of successful NCS do not undermine the argument that the Carbon Law for Nature is both necessary and possible \u0026ndash; they merely show the need for continued innovation and investment in developing and deploying the pipeline and portfolio of NCS. In this way, the AFOLU sector is no different from the energy sector; for example, the International Energy Agency explicitly recognizes that \u0026ldquo;in 2050, almost half the reductions come from technologies that are currently at the demonstration or prototype phase\u0026rdquo;\u003csup\u003e60\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003eAFOLU Mitigation Potential and Pathways: Secondary Sources and Alignment\u003c/h2\u003e\n \u003cp\u003eWe now turn to alternative estimates of AFOLU mitigation potential and modeled 1.5\u0026deg;C scenarios through 2050 to assess their alignment with the Carbon Law for Nature and the protect-manage-restore acceleration curves, and to identify areas of significant uncertainty and difference.\u003c/p\u003e\n \u003cp\u003eThe first comparison is of nonCO\u003csub\u003e2\u003c/sub\u003e emissions pathways. Biomass burning and draining of peatlands emits nitrous oxide and methane in addition to CO\u003csub\u003e2\u003c/sub\u003e, but these FOLU nonCO\u003csub\u003e2\u003c/sub\u003e sources are less than about 10% of AFOLU nonCO\u003csub\u003e2\u003c/sub\u003e sources, and a negligibly small proportion of cost-effective AFOLU mitigation. Agricultural sources on the other hand are large (~\u0026thinsp;5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year) and expected to grow significantly in the next three decades without climate policy interventions. That expected growth makes this category challenging to align across sources. The simplified Carbon Law for Nature segmentation in (main text Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) maps out a decrease in AFOLU nonCO\u003csub\u003e2\u003c/sub\u003e emissions from 5.5 GtCO\u003csub\u003e2\u003c/sub\u003ee per year in 2023 to 4.75 GtCO\u003csub\u003e2\u003c/sub\u003ee per year in 2030 and 4 GtCO\u003csub\u003e2\u003c/sub\u003ee per year in 2050, a pathway that results in 121 GtCO\u003csub\u003e2\u003c/sub\u003ee of cumulative agricultural nonCO\u003csub\u003e2\u003c/sub\u003e emissions from 2024 through 2050\u0026ndash;10 GtCO\u003csub\u003e2\u003c/sub\u003ee less than the 1.5\u0026deg;C-compatible scenarios in AR6\u003csup\u003e16\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThis pathway is conservative compared to the mitigation envisioned by food-systems models of 1.5\u0026deg;C-compatible scenarios. The UN Food and Agriculture Organization suggests a 1.5\u0026deg;C-compatible food system future\u003csup\u003e51\u003c/sup\u003e with deeper reductions in nonCO\u003csub\u003e2\u003c/sub\u003e agricultural emissions, with targets of halving 2020 levels of nitrous oxide emissions by 2040 and halving methane emissions by 2045. These cuts would drop agricultural nonCO\u003csub\u003e2\u003c/sub\u003e emissions below 3 GtCO\u003csub\u003e2\u003c/sub\u003ee per year by 2045, compared to our 4 GtCO\u003csub\u003e2\u003c/sub\u003ee per year in 2050. A linear rate of change that delivers the FAO targets and stabilizes them at half through 2050 would result in cumulative nonCO\u003csub\u003e2\u003c/sub\u003e emissions from 2024\u0026ndash;2050 of about 104 GtCO\u003csub\u003e2\u003c/sub\u003ee, 17 GtCO\u003csub\u003e2\u003c/sub\u003ee lower emissions than our curves deliver. The Food System Economics Commission (FSEC)\u003csup\u003e39\u003c/sup\u003e also suggests much deeper cuts of nonCO\u003csub\u003e2\u003c/sub\u003e agriculture emissions than we use, reaching 0.5 GtCO\u003csub\u003e2\u003c/sub\u003ee of nitrous oxide and 1 GtCO\u003csub\u003e2\u003c/sub\u003ee of methane by 2050, corresponding to cumulative 2024\u0026ndash;2050 nonCO\u003csub\u003e2\u003c/sub\u003e emissions of just under 100 GtCO2e.\u003c/p\u003e\n \u003cp\u003eIn contrast to nonCO\u003csub\u003e2\u003c/sub\u003e emissions, our mitigation curves envision significantly more carbon sequestration into agricultural lands than the FAO\u0026rsquo;s food systems Roadmap or the FSEC Report, even after adjusting downward from 4.8 GtCO\u003csub\u003e2\u003c/sub\u003e per year average from 2020\u0026ndash;2050 in Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e to 3.4 GtCO\u003csub\u003e2\u003c/sub\u003e per year average from 2020\u0026ndash;2050 to match Nabuurs \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e17\u003c/sup\u003e. The FAO roadmap includes a milestone of 10 GtCO\u003csub\u003e2\u003c/sub\u003e of additional carbon sequestered into cropland and pasture soils from 2025\u0026ndash;2050, which is only 0.4 GtCO\u003csub\u003e2\u003c/sub\u003e per year\u003csup\u003e51\u003c/sup\u003e. This conservative estimate included half of cost-effective soil carbon sequestration opportunities in grasslands identified by the authors, but no other carbon sequestration opportunities in crop and grazing lands. The FSEC Report discusses soil carbon and agroforestry as sequestration levers but does not provide estimates of agricultural sequestrations separate from forestry and other land use. Both sources rely extensively on integrated assessment model scenarios \u0026ndash; which do not include estimates of sequestration of carbon into croplands and grazing lands \u0026ndash; to construct their mitigation pathways, so their underrepresentation of carbon sequestration into agricultural lands is not surprising.\u003c/p\u003e\n \u003cp\u003eWhile alignment issues and differences in coverage make comparisons of AFOLU pathways difficult for subcomponents, there are multiple touchpoints for the full mitigation pathway for both CO\u003csub\u003e2\u003c/sub\u003e only and for all gases. Our sectoral CO\u003csub\u003e2\u003c/sub\u003e pathway is significantly more ambitious than the 1.5\u0026deg;C compatible scenarios in AR6: we aim for about 4.75 GtCO\u003csub\u003e2\u003c/sub\u003e net CO\u003csub\u003e2\u003c/sub\u003e sink by 2030 and 11 GtCO\u003csub\u003e2\u003c/sub\u003e net sink by 2050, while the AR6 C1 scenarios deliver net zero in 2030 and about 2\u0026ndash;3 GtCO\u003csub\u003e2\u003c/sub\u003e net sink by 2050. A more constrained set of 1.5\u0026deg;C compatible scenarios \u0026ndash; limited to exclude \u0026ldquo;silver bullet\u0026rdquo; levels of mitigation from any one mitigation lever \u0026ndash; includes scenarios with net AFOLU CO\u003csub\u003e2\u003c/sub\u003e sinks in 2050 of 2.5 to 8.6 GtCO\u003csub\u003e2\u003c/sub\u003e per year\u003csup\u003e73\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eFor the full suite of gases, we note that the global scientific consensus sectoral estimates of cost-effective AFOLU mitigation from Nabuurs \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e17\u003c/sup\u003e are very well-aligned with Roe \u003cem\u003eet al.\u003c/em\u003e\u003csup\u003e19\u003c/sup\u003e; the Carbon Law for Nature pathways match these sources. Our all-gases AFOLU mitigation pathway is only slightly more ambitious than the pathway envisioned by the FSEC: we aim to deliver global AFOLU net zero by 2030 compared to the FSEC pathway\u0026rsquo;s 2035 sectoral net zero year, while we aim for 7 GtCO\u003csub\u003e2\u003c/sub\u003ee of net global sequestration in 2050 compared to their 6.7 GtCO\u003csub\u003e2\u003c/sub\u003ee of net global sequestration mid-century\u003csup\u003e39\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eIn summary, our Carbon Law for Nature and mitigation curves to deliver it are in line with bottom-up estimates of cost-effective mitigation potential, but drive significantly more mitigation out of the AFOLU sector than most model-based scenarios. Treatment of bioenergy and BECCS likely explains some of this difference; our inclusion of significant soil carbon sequestration in agricultural lands and agroforestry sequestration, which are largely excluded from IAMs, drives some of the difference; and our target rate of acceleration for AFOLU mitigation \u0026ndash; reaching period-average levels of cost-effective (\u0026lt;\u003cspan\u003e$\u003c/span\u003e100/ton) mitigation by about 2034, and going well beyond these \u003cspan\u003e$\u003c/span\u003e100/ton levels by 2050 \u0026ndash; largely explain the rest.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003eGlobal Surface Temperature Trajectories\u003c/h2\u003e\n \u003cp\u003eWe use the MAGICCv7.5.3 reduced-complexity model with default configuration\u003csup\u003e22\u003c/sup\u003e to compare future global surface temperature trajectories under four alternative emissions pathways: \u0026ldquo;SSP1-19\u0026rdquo;, representing the average emissions of the CMIP6 model ensemble in the SSP1-19 scenario set; \u0026ldquo;SSP1-26\u0026rdquo;, similarly; \u0026ldquo;CLfN-SSP1-19\u0026rdquo;, which substitutes the level of mitigation in the CLfN AFOLU mitigation pathway for the SSP119 AFOLU CO\u003csub\u003e2\u003c/sub\u003e pathways; and \u0026ldquo;CLfN-SSP1-26\u0026rdquo;, with a similar substitution.\u003c/p\u003e\n \u003cp\u003eSeveral adjustments to the Carbon Law for Nature pathway are needed to remove discontinuities and make appropriate comparisons to the SSP scenario sets. The first adjustment addresses differences in the starting year of mitigation: the SSP scenario sets begin reducing emissions in 2020, while the CLfN pathway\u0026rsquo;s first year of mitigation is 2024. The CLfN pathways are thus adjusted down to the levels of the comparison SSP scenarios for 2020 through 2025 (see Extended Data Fig.\u0026nbsp;5). The second small adjustment is to \u0026ldquo;count\u0026rdquo; excess nonCO\u003csub\u003e2\u003c/sub\u003e mitigation \u0026ndash; beyond the average nonCO\u003csub\u003e2\u003c/sub\u003e mitigation of the comparision SSP scenario sets \u0026ndash; as CO\u003csub\u003e2\u003c/sub\u003e mitigation instead. This adjustment allows us to avoid a significant difference in the assumed baseline nonCO\u003csub\u003e2\u003c/sub\u003e AFOLU emissions, by using the SSP pathways for the MAGICC runs. We converted the nonCO\u003csub\u003e2\u003c/sub\u003e gases methane (CH\u003csub\u003e4\u003c/sub\u003e) and nitrous oxide (N\u003csub\u003e2\u003c/sub\u003eO) to CO\u003csub\u003e2\u003c/sub\u003e equivalents using the GWP100 conversion factors from the latest IPCC report.\u003c/p\u003e\n \u003cp\u003eLastly, to provide a rough estimate of the CLfN\u0026rsquo;s impact on the period of overshoot, we assume a simple linear reduction in the AFOLU net CO\u003csub\u003e2\u003c/sub\u003e sequestration from a maximum of -11 GtCO2 per year in 2050, to zero in 2100. This is a conservative assumption, because some NCS actions like reforestation would continue to sequester carbon well beyond 2100, and because it assumes no new innovations that would allow humanity to continue to drive carbon into the biosphere.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch2\u003eMethods References\u003c/h2\u003e\n\u003col start=\"67\"\u003e\n \u003cli\u003eForster, P. M.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Indicators of Global Climate Change 2022: annual update of large-scale indicators of the state of the climate system and human influence. \u003cem\u003eEarth System Science Data\u003c/em\u003e \u003cstrong\u003e15\u003c/strong\u003e, 2295-2327 (2023).\u003c/li\u003e\n \u003cli\u003eAnderson, C., Bicalho, T., Wallace, E., Letts, T. \u0026amp; Stevenson, M. Forest, Land and Agriculture Science-Based Target-Setting Guidance. (2022).\u003c/li\u003e\n \u003cli\u003eHoward, J.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Blue carbon pathways for climate mitigation: Known, emerging and unlikely. \u003cem\u003eMarine Policy\u003c/em\u003e \u003cstrong\u003e156\u003c/strong\u003e, 105788 (2023).\u003c/li\u003e\n \u003cli\u003eRockstr\u0026ouml;m, J.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Safe and just Earth system boundaries. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e619\u003c/strong\u003e, 102-111 (2023).\u003c/li\u003e\n \u003cli\u003eEPA, U. Global Non-CO2 Greenhouse Gas Emission Projections \u0026amp; Mitigation 2015-2050. 67-71 (2019).\u003c/li\u003e\n \u003cli\u003eBusch, J.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e Potential for low-cost carbon dioxide removal through tropical reforestation. \u003cem\u003eNature Climate Change\u003c/em\u003e 9, 463-466 (2019).\u003c/li\u003e\n \u003cli\u003eWarszawski, L.\u003cem\u003e\u0026nbsp;et al.\u003c/em\u003e All options, not silver bullets, needed to limit global warming to 1.5 C: A scenario appraisal. \u003cem\u003eEnvironmental Research Letters\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 064037 (2021).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6164097/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6164097/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCutting carbon emissions in half every decade through 2050\u003csup\u003e1\u003c/sup\u003e has become a benchmark for global\u003csup\u003e2\u003c/sup\u003e, national and corporate target-setting that delivers the Paris goal of limiting global warming to 1.5°C above pre-industrial levels. However, with a rapidly shrinking remaining carbon budget\u003csup\u003e3\u003c/sup\u003e, here we show that halving fossil emissions every decade alongside scaling negative emissions technologies (NETs) to balance remaining fossil CO\u003csub\u003e2\u003c/sub\u003e emissions by 2050, is no longer enough to avoid significant and lengthy overshoot past 1.5°C, unless improvements in ecosystem stewardship are also accelerated beyond levels currently assumed in most 1.5°C-aligned climate scenarios. We further show that a decadal acceleration of natural climate solutions, reaching net-zero emissions from agriculture, forestry and land use by 2030 and -7 gigatons CO\u003csub\u003e2\u003c/sub\u003ee per year of net removals by 2050, is both consistent with sectoral (or “bottom-up”) estimates of cost-effective potential and can keep the window to 1.5°C decisively open, if delivered alongside decadal halvings of fossil-fuel emissions and scaling of NETs. This “Carbon Law for Nature” mitigation pathway can feasibly be achieved through a transformation of humanity’s land and coastal stewardship: protecting remaining intact ecosystems, climate-smart management of agricultural and forestry lands, restoring natural ecosystems where appropriate, and reducing excess demand for land-intensive products. Crucially, following this pathway also minimizes the magnitude and length of time of temperature overshoot, reducing both the chronic impacts of climate change\u003csup\u003e4\u003c/sup\u003e and the risk of exceeding tipping points in the earth system\u003csup\u003e5\u003c/sup\u003e.\u003c/p\u003e","manuscriptTitle":"Accelerated nature-based mitigation can re-open the window to 1.5°C","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-22 12:22:58","doi":"10.21203/rs.3.rs-6164097/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"6deb83ac-0d68-47ab-af57-06ede9b33999","owner":[],"postedDate":"April 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":46426913,"name":"Earth and environmental sciences/Environmental social sciences/Climate-change mitigation"},{"id":46426914,"name":"Earth and environmental sciences/Environmental social sciences/Climate-change policy"},{"id":46426915,"name":"Earth and environmental sciences/Climate sciences/Climate change/Climate-change mitigation"}],"tags":[],"updatedAt":"2025-04-22T12:22:58+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-22 12:22:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6164097","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6164097","identity":"rs-6164097","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}