Aspiration to action: Opportunities to align freshwater ecosystems with climate actions

Aspiration to action: Opportunities to align freshwater ecosystems with climate actions | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Analysis Aspiration to action: Opportunities to align freshwater ecosystems with climate actions Mahya Hashemi, Kashif Shaad, Vivian Griffey, Ibrahim Mohammed, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6626566/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 29 Jan, 2026 Read the published version in Nature Water → Version 1 posted You are reading this latest preprint version Abstract Freshwater ecosystems play a vital role in regulating the water cycle, supporting biodiversity, and enhancing resilience to hydrological and ecological pressures, yet they remain largely overlooked in global climate policies. Most national climate commitments lack clear, spatially defined targets for protecting and restoring these critical systems. To address this gap, we developed a global map of high-value freshwater ecosystems based on 30-meter land cover data, hydrological networks, and global floodplain models, and identified country-level pathways for climate adaptation and mitigation through nature-based solutions. Here we show that these ecosystems cover over 51 million square kilometers globally, highlighting major opportunities to reduce flood risk, protect freshwater resources, and strengthen ecological resilience through targeted protection and restoration. Our analysis indicates that restoring degraded croplands and short vegetation within these areas could sequester between 1.07 and 3.41 gigatonnes of carbon dioxide each year, across 355 to 484 million hectares, depending on the restoration scenario. Nearly half of this mitigation potential lies within the 49 countries committed to the Freshwater Challenge. These results provide a practical foundation for integrating freshwater ecosystems into national climate strategies and further demonstrate how place-based interventions can align global climate goals with regional freshwater protection targets, advancing efforts to adapt to and mitigate climate change. Scientific community and society/Water resources Earth and environmental sciences/Environmental sciences Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Main Freshwater ecosystems play a fundamental role in regulating hydrological cycles, supporting biodiversity, and maintaining climate stability 1 . They provide essential services such as clean water supply, food production, flood regulation, and carbon sequestration. Yet they are among the most threatened ecosystems globally. Since 1900, wetland extent has declined globally by nearly 70%, only 37% of rivers longer than 1,000 kilometers remain free-flowing over their entire length, and more than 50% of the world’s rivers and streams face high risks of pollution 2,3 . Freshwater vertebrate populations have also suffered an 84% decline between 1970 and 2016 4 . Climate change intensifies these issues, leading to extreme rainfall variability, droughts, and heatwaves 5 . Today, water-related disasters account for 90% of all natural disasters and are becoming increasingly frequent and severe 6 . By 2050, extreme droughts could impact five times more land globally, 5.7 billion people may face water scarcity, and 1.6 billion could be at flood risk 7 . These growing challenges have exposed gaps in reliable access to clean water, flood regulation, and food production for millions of people 2,8 . Despite their critical role in biodiversity, climate resilience, and water security, freshwater ecosystems have long lacked a systematic and unified global approach to restoration and conservation. The country-led Freshwater Challenge (FWC) was launched at the 2023 UN Water Conference to help close this gap. The FWC aims to restore 300,000 kilometers of rivers and 350 million hectares of wetlands by 2030, aligning with global targets such as the Kunming-Montreal Global Biodiversity Framework’s 30x30 goal . The initiative positions freshwater ecosystems at the heart of global environmental commitments and emphasizes that restoration efforts must be integrated with broader climate strategies, including those under the United Nations Framework Convention on Climate Change (UNFCCC) 9 . However, achieving this integration remains challenging, particularly in countries of the Global South. While 49 countries and the European Union have joined the Freshwater Challenge, many still need to demonstrate meaningful progress in aligning freshwater restoration efforts with their Nationally Determined Contributions (NDCs) (country-specific climate action plans, outlining targets and measures for reducing greenhouse gas emissions and adapting to climate impacts), and National Adaptation Plans (NAPs). Freshwater ecosystems remain u nderrepresented in national climate strategies and biodiversity strategies, with references to rivers and wetlands often lacking spatial detail and actionable commitments 10 . Even where political will exists, countries frequently lack robust methodologies and spatial datasets to define coherent, measurable restoration targets that can be effectively linked to climate adaptation under NAPs. While the carbon dynamics of freshwater systems are increasingly well understood 11,12 , including their roles in both greenhouse gas storage and emissions, carbon markets have historically focused on terrestrial forests. Although riparian and headwater forests are technically part of terrestrial ecosystems, they provide essential ecological services that support freshwater function. These freshwater-adjacent landscapes offer both carbon sequestration potential and hydrological benefits, yet they remain a largely untapped opportunity within integrated nature-based climate solutions. To support the identification and mapping of High-Value Freshwater Ecosystems (HVFEs), we adapted a spatially explicit framework to guide the prioritization of protection and restoration actions. This approach enables the formulation of geographically specific, policy-relevant targets and informs national climate strategies such as NDCs and NAPs. The framework emphasizes ecological integrity by prioritizing natural regeneration in forest biomes and avoiding ecologically unsuitable afforestation or wetland conversion 13,14 . By applying this framework, we assess the global carbon sequestration potential of restoring degraded lands near freshwater systems, highlighting the dual adaptation and mitigation benefits of integrated, ecosystem-based strategies. 2. Assessing Global Distribution of High-Value Freshwater Ecosystems We adapted the High Conservation Value (HCV) framework to define HVFEs, aiming to support a more strategic and actionable approach for identifying freshwater ecosystems in need of conservation (including both protection and restoration). HVFEs extend beyond conventional freshwater definitions by integrating freshwater and adjacent terrestrial ecosystems that collectively support the regulation of hydrological and carbon cycles within watersheds. These ecosystems include headwater catchments, surface water bodies (e.g., rivers, lakes, and reservoirs), riparian corridors, inundated wetlands, and geomorphic floodplains (areas shaped by long-term river activity and landform development, rather than by short-term flood frequency). Together, they exert a disproportionate influence on global water flow, filtration, and storage, as well as nutrient and carbon dynamics. Moreover, they serve as vital refugia for aquatic and terrestrial biodiversity. Existing freshwater classifications often overlook the full extent of the terrestrial interface—particularly riparian and floodplain systems—that sustains freshwater ecosystem services. Thus, identifying HVFEs allows for a more comprehensive and ecologically meaningful delineation of priority areas for conservation and restoration, critical for achieving targets under initiatives like the FWC. We developed a high-resolution global map of HVFEs to support actionable conservation strategies. The map, produced at 30-meter resolution, captures freshwater-related features under two delineation scenarios (minimum and maximum), reflecting a range of conservation approaches based on ecosystem service capacity. This delineation draws on foundational global datasets, including University of Maryland (UMD) land cover 15 , MERIT 90-meter hydrography data 16 , and global floodplain layers 17 , to ensure consistency and spatial precision across diverse landscapes. The minimum scenario includes surface water bodies, wetlands, headwater regions, fixed-width riparian corridors along low-order and high-order streams. It also includes riparian buffers surrounding lakes and reservoirs. This conservative delineation focuses on preserving water quality, reducing erosion, and maintaining aquatic habitats. The maximum delineation scenario builds upon this foundation by incorporating geomorphic floodplains and wetland corridors, extending delineation further into broader hydrological zones. This scenario emphasizes flood mitigation, sediment retention, and long-term water storage capacity, recognizing the full hydrological and ecological role of floodplains and their relevance to the functioning of the entire river network. In doing so, it expands beyond the minimum scenario, with floodplains overlapping and masking riparian corridors and headwater regions included in the minimum footprint, as defined by the hierarchical masking rules (Supplementary Methods B). The global map in Fig. 1 reveals that HVFEs, under the maximum delineation scenario, span approximately 51.6 million km² globally. The highest concentrations of HVFEs are found in countries with extensive river networks and wetlands. The Russian Federation holds the largest area (8.68 million km²), followed by Canada (4.80 million km²), the United States of America (3.99 million km²), China (3.67 million km²), and Australia (3.35 million km²). Other major contributors include Brazil (2.92 million km²), Argentina (1.39 million km²), India (1.38 million km²), and Kazakhstan (1.25 million km²). Notably, the 49 countries that are members of the FWC collectively account for 22.9 million km ² , or approximately 44% of the global HVFEs extent under the maximum scenario (without floodplain). If Russia and China were to join the initiative, this share would rise by an additional 12.3 million km², increasing the total coverage to approximately 68% of all HVFEs. These figures underscore both the global relevance of the HVFEs framework and the significant opportunity to enhance global conservation efforts through expanded participation in the FWC. Under the minimum scenario, HVFEs cover 40.9 million km², meaning the 10.7 million km² difference between scenarios highlights the importance of including geomorphic floodplains and wetland corridors in conservation planning. However, this difference is not entirely attributable to floodplains alone, as partial overlap exists between floodplain zones and riparian or wetland areas captured in the minimum scenario (Fig. 1). A detailed breakdown of HVFEs components under each delineation scenario is provided in Supplementary Table 1. To support local adaptation and ensure the global HVFEs map is useful across diverse geographies, we validated the mapping approach in the Contiguous United States (CONUS), which offered the only available riparian reference data, along with ecological variability (e.g., climate, vegetation, and hydrology). In addition to this empirical validation, the foundational datasets underlying the HVFEs framework— including University of Maryland (UMD) land cover 15 , MERIT 90-meter hydrography data 16 , and global floodplain layers 17 —have each undergone independent validation, further supporting the robustness of the approach (see Supplementary Methods A and D). 3. Identifying Freshwater-Related Ecosystems Adaptation Strategies Despite their essential role in climate regulation, biodiversity support, and water security, freshwater ecosystems remain underrepresented in most NDCs 19 and NAPs. References to water often focus on general hazards such as droughts and floods, without spatially explicit targets or actionable strategies. While there is growing recognition of the synergies between adaptation and mitigation—particularly across water, land, and biodiversity sectors 20 —key freshwater systems such as headwaters, riparian corridors, and geomorphic floodplains continue to be overlooked relative to coastal ecosystems like mangroves 10 . Realizing the full potential of NDCs and NAPs will require spatial frameworks and decision-support tools that directly align climate goals with freshwater ecosystem functions. We propose using the HVFE framework to translate these ambitions into informed, holistic nature-based actions. This framework enables countries to identify spatially defined pathways that integrate freshwater interventions with known climate adaptation and mitigation benefits, positioning freshwater ecosystems as foundational assets for climate action. Figure 2 presents a set of measures across HVFE categories and highlights the key ecosystem services each supports. These actions fall into two main categories— Protection and Restoration —based on the multiple benefits freshwater ecosystems offer, including safeguarding water resources, supporting biodiversity, and building resilient livelihoods 21 . Under Protection , countries can regulate environmental flows, restrict harmful resource extraction (e.g., fishing, mining), and designate freshwater protected areas or Other Effective Area-Based Conservation Measures (OECMs). For example, Nepal , with over 36% of its land in headwater regions and a high projected flood risk by 2050 22 (Aqueduct score: 3.8 on a 0–5 scale, see Supplementary Table 2), faces significant climate threats. Proactive management—such as safeguarding upstream ecosystems, enforcing flow regulations, and strengthening zoning in headwater catchments—can help protect downstream communities and maintain ecosystem function. Under Restoration , actions may include reconnecting rivers with floodplains, restoring riparian forests, and rehabilitating degraded vegetation in headwater regions to improve green cover and reduce erosion. Countries such as Mozambique , Pakistan , and Malawi present high-impact opportunities for restoration. For instance, Mozambique , with a flood risk score of 4.1( on a 0–5 scale) and 6.2 million hectares of cropland expansion into tree cover, wetlands, and other natural land covers between 2000–2020 ( Fig. 3 ), can prioritize restoration in degraded floodplains and upper watersheds to enhance water retention and reduce erosion. Similarly, Pakistan , with 21% of its land classified as geomorphic floodplains and a flood risk score of 3.25 , represents a strong candidate for riparian buffer restoration to improve flood resilience in vulnerable basins. Given that around 20% of Malawi’s landscape consists of riparian corridors and floodplains—and with one of the highest projected flood risk scores by 2050 (4.1 on a 0–5 scale)—the country presents a strong opportunity for floodplain reconnection and riparian forest restoration. By guiding countries in selecting geographically tailored and ecologically appropriate interventions, the HVFE framework supports the design of integrated, ecosystem-based strategies that simultaneously advance adaptation, mitigation, and biodiversity goals. 4. Using HVFE Mapping to Prioritize Strategies The land cover composition and cropland transformation across four HVFE classes in 13 countries show that countries like Brazil, Colombia, Democratic Republic of Congo, and Mozambique have experienced the most extensive cropland expansion in HVFEs between 2000 and 2020 (Figure3). Notably, 25% of cropland in the Democratic Republic of Congo replaced tree cover, while 27% in Mozambique originated from both tree cover and wetlands—indicating significant freshwater ecosystem degradation. These types of patterns reveal critical restoration opportunities, particularly where cropland or short vegetation overlaps with HVFEs. Reforestation or wetland recovery in such areas can enhance water infiltration, reduce erosion, and improve water quality—offering measurable adaptation outcomes 23 . These spatial insights can be useful for countries to translate freshwater restoration ambitions into actionable, place-based ecosystem interventions. To further illustrate on the region-specific pathways of action, we analyzed the detailed breakdown of HVFE types and their restoration potential across six case study countries (Table1): Nepal, Pakistan, Mozambique, Democratic Republic of Congo, Brazil, and Peru. These examples span different HVFE types (e.g., headwaters, floodplains, stream buffers) and climate risks and the isolation of the crop land change relative to the HVFE classes, which elucidates more straightforward restoration targets and allows clearer recommendations for both protection and restoration strategies under the HVFE framework (see Supplementary Figure 1 for HVEF maps). Table 1. Distribution of HVFE Categories and Restoration Potential in Six selected FWC Countries. Country Total HVFE Area (ha, % of country) Headwater (ha, % of HVFE) Floodplain (ha, % of HVFE) High-Order Stream Buffer (ha, % of HVFE) Low-Order Stream Buffer (ha, % of HVFE) Restoration Opportunity (ha) % of FWC Goal Brazil 291,991,506 32.6% 2,357,981 8.1% 57,675,677 19.8% 1,542,4967 5.3% 114,630,036 39.3% 104,509,638 29.7 Pakistan 32,342,041 37.0% 5,961,769 18.4% 186,092,3957.5% 1,312,758 4.1% 4,110,006 12.7% 32,064,772 9.1 Peru 60,338,198 46.6% 21,873,575 36.3% 7,325,185 12.1% 2,387,516 4.0% 16,332,939 27.1% 20,029,908 5.7 Democratic Republic of the Congo 81,824,353 35% 6,066,312 7.4% 14,196,578 17.4% 3,563,049 4.4% 33,487,428 40.9% 18,115,205 5.1 Mozambique 25,911,122 32.7% 1,293,732 5.0% 8,295,580 32% 1,115,629 4.3% 11,042,160 42.6% 12,778,794 3.6 Nepal 8,562,265 58.2% 5,305,164 62% 886,650 10.4% 371,098 4.3% 1,816,804 21.2% 4,488,788 1.3 Restoration opportunity refers to areas within HVFE-adjacent terrestrial ecosystems currently under cropland, urban land, or dense/sparse short vegetation. “% of FWC Goal” indicates each country's potential contribution toward the global Freshwater Challenge target of restoring 300,000 kilometers of degraded rivers (focusing on riparian corridors) and 350 million hectares of degraded wetlands by 2030. In Nepal, headwater regions remain largely intact (Table 1), offering an opportunity for proactive protection through zoning regulations, water source protection, and integration into OECMs. These approaches align with the country’s National Water Resources Policy (2020), which promotes watershed management and river basin planning for sustainable water resource use 24 , and ongoing initiatives focused on spring and watershed restoration in upland areas 25 . Furthermore, Nepal has formally recognized OECMs—including community-managed forests and sacred sites—as part of its broader strategy to conserve biodiversity and ecosystem services beyond traditional protected areas 26 . Maintaining these upstream buffers is critical for reducing downstream flood risk in the Terai region, where communities face some of the country’s highest flood-related vulnerabilities 27 . In Pakistan, extensive cropland encroachment into floodplains has reduced flood-buffering capacity, especially in the Indus Basin 28 . Restoration through riparian reforestation and floodplain reconnection to the rivers could mitigate these risks. Similarly, in Mozambique, nearly 70% of cropland expansion between 2000 and 2020 replaced tree covers, wetlands, and other natural land covers—primarily within floodplains and low-order stream buffers (Fig. 3). With high projected flood risk in regions like Sofala Province, hydrologic reconnection and land-use zoning are essential to prevent further loss 29 . In the Democratic Republic of Congo, riparian corridors still retain substantial tree cover and natural vegetation, supporting both freshwater storage and diverse fish populations that are crucial for local livelihoods and climate resilience 30,31 . Prioritizing protection and sustainable management in these areas can help maintain rainfall recycling and the health of aquatic ecosystems. Notably, with 25% of recent cropland expansion replacing tree cover, these same areas could be prioritized for restoration efforts aimed at reversing freshwater ecosystem degradation. Peru is another example where headwater regions along low-order streams still retain substantial forest cover, while areas of short vegetation offer opportunities for restoration. However, cropland expansion is increasingly encroaching on riparian corridors and floodplains. Early intervention through conservation easements and Indigenous-led land management can help safeguard ecosystem function in the Andes–Amazon transition zone 32,33 . In Brazil, on the other hand, riparian corridors and floodplains have experienced significant conversion—over 114,000 km²—from wetlands and forests to cropland, threatening the functionality of these critical ecosystems 34 . Restoring riparian buffers and enforcing the Forest Code are critical for ensuring water regulation and strengthening climate resilience ADDIN ZOTERO_ITEM CSL_CITATION{"citationID":"TCL7o0LO","properties":{"formattedCitation":"\\super35\\nosupersub{}","plainCitation":"35","noteIndex":0},"citationItems":[{"id":215,"uris":["http://zotero.org/users/16566647/items/DUIZ5MMF"],"itemData":{"id":215,"type":"article-journal","abstract":"Brazil'scontroversial new Forest Code grants amnesty to illegal deforesters, butcreates new mechanisms for forest conservation.\n , \n \n Roughly 53% of Brazil's nativevegetation occurs on private properties. Native forests and savannahs on theselands store 105 ± 21 GtCO\n 2\n e (billion tonsof CO\n 2\n equivalents) and play a vitalrole in maintaining a broad range of ecosystem services (\n \n 1\n \n ). Sound management of theseprivate landscapes is critical if global efforts to mitigate climate change areto succeed. Recent approval of controversial revisions to Brazil's Forest Code(FC)—the central piece of legislation regulating land use and management onprivate properties—may therefore have global consequences. Here, we quantifychanges resulting from the FC revisions in terms of environmental obligationsand rights granted to land-owners. We then discuss conservation opportunitiesarising from new policy mechanisms in the FC and challenges for itsimplementation.","container-title":"Science","DOI":"10.1126/science.1246663","ISSN":"0036-8075,1095-9203","issue":"6182","journalAbbreviation":"Science","language":"en","page":"363-364","source":"DOI.org(Crossref)","title":"Cracking Brazil's ForestCode","volume":"344","author":[{"family":"Soares-Filho","given":"Britaldo"},{"family":"Rajão","given":"Raoni"},{"family":"Macedo","given":"Marcia"},{"family":"Carneiro","given":"Arnaldo"},{"family":"Costa","given":"William"},{"family":"Coe","given":"Michael"},{"family":"Rodrigues","given":"Hermann"},{"family":"Alencar","given":"Ane"}],"issued":{"date-parts":[["2014",4,25]]}}}],"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"} 35 . In Peru, headwater regions along low-order streams still retain substantial forest cover, while areas of short vegetation offer opportunities for restoration. However, cropland expansion is increasingly encroaching on riparian corridors and floodplains. Early intervention through conservation easements and Indigenous-led land management can help safeguard ecosystem function in the Andes–Amazon transition zone. Altogether, these case studies demonstrate how HVFE maps can help align restoration, protection and improved management of freshwater ecosystems with climate adaptation needs at the national level. By linking HVFE conditions with spatial risk layers (e.g., flood risk maps, water stress layers, and drought vulnerability zones), countries can identify high-impact interventions, refine NDC/NAP strategies, attract climate finance, and monitor adaptation outcomes. Notably, many of these adaptation measures also offer mitigation co-benefits. Restoring HVFE can not only contribute to improved climate resilience but also increase carbon sinks. Next steps could include developing implementation roadmaps, strengthening local capacity, and integrating HVFE-based targets into national investment and monitoring systems, as highlighted in recent implementation and investment planning frameworks for ecosystem restoration and resilience . 5. Assessing Climate Mitigation Benefits To strengthen integration of freshwater-related ecosystem restoration targets (such as those to be developed by the state-members in FWC) and carbon mitigation commitments in NDCs, we have mapped the mitigation potential globally of reforesting degraded terrestrial ecosystems within HVFE delineation (of Section 2) in areas where forests would be the natural cover. Reforestation within HVFEs could provide 1.07–3.41 GtCO₂/year of mitigation across 355–484 million hectares, depending on the scenario used (maximum and minimum delineation with associated tree cover thresholds; see Methods d,e). The mitigation potential of the minimum scenario is approximately equivalent to that of global peatland restoration, while the maximum restoration scenario is slightly over half the potential of reducing global deforestation 36 . Fig. 4 compares the total carbon removal potential for the top 50 countries, based on the reforestation of areas where HVFEs are currently in croplands or short vegetation indicating abandoned agriculture or grazing land, within forest biomes under the minimum and maximum restoration scenarios. Large countries dominate the top five in terms of total mitigation potential – Brazil, China, India, the United States, and Mexico – contributing 48% of the global total under all scenarios. However, when adjusting for country size by evaluating carbon removal per hectare, we find a hotspot of mitigation potential in West and Central Africa, with the highest-ranking countries being the Republic of Congo, Liberia, Ghana, Nigeria, and Côte d’Ivoire. These countries achieve average carbon removal rates of 9.7 MgCO₂/ha/yr (minimum scenario) and 17.9 MgCO₂/ha/yr (maximum scenario), nearly double the average of all other countries. Among the 49 FWC member states, reforestation of degraded HVFE-adjacent terrestrial ecosystems could deliver 0.43–1.28 GtCO₂/yr of mitigation across 128–155 million hectares of forest areas—representing nearly half of both the global mitigation potential and the total area restored under each scenario. This would also contribute significantly to the FWC target of restoring 300,000 Kilometers of rivers by 2030. This spatially explicit assessment highlights how prioritizing both total and area-adjusted mitigation potential can align freshwater protection with global climate goals. The mitigation potential we identify within HVFEs (1.07–3.41 GtCO₂/yr) accounts for 2.7–8.5% of current global emissions (~40 GtCO₂ in 2021) according to the Global Carbon Budget 37 . Given that the suggested carbon budget to limit warming to 1.5 °C is estimated at just 380 GtCO₂ from 2023 onward, restoring areas adjacent to HVFEs could play a meaningful role in meeting emissions reduction targets. Notably, the upper end of our scenario (3.41 GtCO₂/yr) exceeds the estimated annual reduction of 1.4 GtCO₂ needed to reach net zero by 2050 37 —underscoring the critical role that freshwater-adjacent ecosystem restoration can play in climate mitigation, biodiversity conservation, and water security. Climate mitigation commitments in NDCs can be conditional on external financing, unconditional, or a mix of both. Among them, unconditional absolute reduction commitments —defined as firm emission cuts below a historical reference level, irrespective of economic or population growth—are considered the most ambitious. In contrast, Business-as-Usual (BAU) reduction commitments refer to emission targets relative to projected future growth trends, which may still permit annual emissions increases and are thus seen as less stringent. Among the 32 countries with unconditional absolute emissions reduction targets, five FWC member states contribute approximately 92% of the total mitigation potential estimated within this subset (Fig. 5), regardless of restoration scenario (0.27 GtCO2/yr minimum and 0.77 GtCO2/yr maximum. Mitigation potential from the reforestation of degraded HVFE-adjacent terrestrial ecosystems is highest in countries with gold-standard NDCs and is concentrated in these five nations. In contrast, countries with less stringent NDCs show a more diffuse and modest potential. These five countries thus represent a strategic opportunity to advance their climate goals through targeted restoration of HVFE-adjacent terrestrial ecosystems. In order of decreasing potential, these are Brazil, the United States, Canada, Australia, and the United Kingdom. By contrast, Business-as-Usual (BAU) reduction commitments, which are based on projected emissions growth, may still allow for year-on-year emissions increases and are therefore regarded as less ambitious. FWC countries with BAU-based targets contribute 42-44% (scenario dependent) of the mitigation potential among all nations with such targets (FWC n = 22; all n = 71). Compared to the maximum restoration scenario, the minimum scenario yields consistently lower climate mitigation potential across all NDC types (Supplementary Figure 2). The decline is particularly pronounced for FWC countries with Absolute and BAU Reduction commitments, underscoring how national-level contributions are highly sensitive to the assumed extent of HVFE-adjacent reforestation. Although our analysis focused on forest restoration adjacent to HVFEs, we did not quantify the mitigation potential of wetland restoration—an area that could also offer significant opportunities for nature-based climate solutions. Wetlands were excluded from this study due to the current lack of globally applicable carbon accumulation models for wetland restoration. A recent global analysis estimated that approximately 3.4 million km² (21%) of inland wetlands have been lost since 1700, primarily due to conversion to cropland and rice fields 39 . Using the UMD Land Cover Change dataset, we estimated that only ~0.16 million km² of this loss occurred between 2000 and 2020 through conversion of wetlands to cropland, suggesting that the majority of wetland loss occurred prior to the 21st century. Complementing our forest-based estimates, future efforts should evaluate the carbon sequestration potential and broader co-benefits of restoring degraded wetlands within HVFEs, particularly in regions where historical wetland loss has been extensive. 6. Conclusion To meet the global demand for unified climate mitigation, freshwater ecosystems and their biological and hydrological functions—ranging from water supply and flood regulation to fish production and food security—must no longer be overlooked. Our global map, combined with metrics on ecosystem condition and mitigation potential, offers a critical foundation for systematically identifying, prioritizing, financing, and implementing conservation, adaptation, and restoration actions. In this way, by integrating freshwater and adjacent terrestrial ecosystems into national planning processes, we provide quantifiable benefits including not only carbon sequestration, but of improved ecosystem management, for a more coordinated global response and cascade of restoration benefits. Importantly, this helps bridge the disconnect between freshwater action plans and plans addressing the climate and biodiversity crises. As global mapping methodologies are refined and informed by local ground-truthing, our ability to characterize ecosystems at the land-water interface—including wetlands, riparian zones, low-order streams, and headwater catchments—will continue to improve. Notably, our results show that restoring degraded areas adjacent to freshwater ecosystems could deliver up to 3.4 GtCO₂ per year—equivalent to over 8% of global emissions—highlighting the powerful role that integrated restoration can play in advancing climate goals. By highlighting overlaps among these three global imperatives, our analysis aims to help harmonize global and local narratives—an essential step toward adapting to and mitigating the impacts of climate change. 7. Methods We assessed global forest restoration potential near freshwater ecosystems using a geospatial workflow built on the best-available, openly accessible global datasets (Supplementary Table 3). A schematic overview of the mapped HVFE features—including freshwater systems and adjacent terrestrial zones—along with detailed definitions, is provided in Supplementary Methods A. All features were classified and mapped at ~30-meter spatial resolution, consistent with the land cover dataset used to evaluate restoration potential in this study. a) Global Delineation of HVFEs The global HVFE layer consists of seven ecosystem classes, two of which—surface water and regularly flooded wetlands—represent core freshwater ecosystems. These were derived from the global land cover change dataset developed by Potapov et al. 15 , based on Landsat imagery spanning from 2000 to 2020. This dataset was selected for its capacity to capture both seasonal and interannual dynamics of surface water bodies, as well as its detailed land cover classifications, which are critical for identifying forest restoration opportunities and estimating carbon accumulation potential. To reduce the uncertainty associated with transient surface water and wetland features in a static global map, we combined extents from both endpoints (2000 and 2020), thus representing long-term freshwater presence. Accurate delineation of wetlands at a global scale remains challenging due to limited in-situ validation data. As a result, the mapped freshwater classes in this product primarily reflect the presence of water at or near the surface and serve as proxies to identify adjacent terrestrial ecosystems that influence freshwater function. The remaining five HVFE classes represent terrestrial ecosystems closely linked to freshwater systems, serving as critical areas for restoration and protection to sustain local and downstream freshwater benefits. The integration of these seven classes into two composite layers (with and without the inclusion of floodplains) and the associated overlap logic are detailed in Supplementary Methods B. b) Headwater Catchments To delineate headwater catchments, we identified first-order sub-catchments with hydrologically active terrain. We utilized the MERIT Hydro sub-catchment dataset (90-meter resolution) 16 , which was downscaled to 30-meter for consistency with the HVFE map. First-order sub-catchments were extracted by overlaying the MERIT Hydro stream network (Strahler order = 1) and applying a minimum slope threshold of 0.1 (~5.7°) to exclude flat, low-energy areas. This approach prioritizes regions likely to contribute significantly to streamflow and freshwater regulation at the watershed scale. c) Fixed-Width Corridors and Floodplains Due to the absence of a globally consistent riparian mapping dataset, we delineated riparian corridors using a combination of fixed-width buffers and geomorphic floodplains to approximate zones suitable for restoration along streams, lakes, and regularly flooded wetlands. Fixed-width buffers were applied to surface water features identified in the land cover dataset. Because these features may not represent a continuous hydrological network, we merged them using centerlines from the MERIT Hydro stream network to create a connected riverine system. Buffer widths were selected to reflect common policy or conservation standards, with justification for each width provided in Supplementary Methods. Validation of riparian buffers was conducted in the CONUS using the USFS riparian dataset ADDIN ZOTERO_ITEM CSL_CITATION{"citationID":"JYUh9SRs","properties":{"formattedCitation":"\\super40\\nosupersub{}","plainCitation":"40","noteIndex":0},"citationItems":[{"id":119,"uris":["http://zotero.org/users/16566647/items/32H3IBVR"],"itemData":{"id":119,"type":"article-journal","note":"publisher:Forest Service Research Data Archive","title":"US ForestService national riparian areas base map for the conterminous United States in2019","author":[{"family":"Abood","given":"SinanA"},{"family":"Spencer","given":"Linda"},{"family":"Wieczorek","given":"Michael"}],"issued":{"date-parts":[["2022"]]}}}],"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"} 40 (see Supplementary Methods D), which provides 10-meter resolution reference data for comparison. Unlike fixed-width buffers, floodplains are variable-width zones that follow the terrain and hydrological conditions associated with rivers and streams. We used the GFPLAIN90 dataset 41 to map geomorphic floodplains globally. Developed using the GFPLAIN v1.0 algorithm 17 and the MERIT Hydro terrain model, GFPLAIN90 offers a high-resolution (90-meter) representation of floodplain extents, using a minimum contributing area threshold of 20 km² to define stream networks. This dataset was selected for its scalability across diverse landscapes and hydrologic regimes. d) Restoration Potential in Freshwater-Adjacent Terrestrial Ecosystems We calculated area available for restoration only within a targeted subset of the HVFE delineation described above, based on biome, HVFE class, delineation scenario, and land use/land cover. These criteria are in place to avoid afforestation. We only considered areas within forest biomes, as defined by RESOLVE 2017 vector dataset 42 , to be available for reforestation. Within forest biomes, we used three HVFE classes included in both the minimum and maximum delineation scenarios: headwater regions, fixed-width buffers around low-order streams, and fixed-width buffers around surface water bodies and high-order streams. In the maximum scenario, we additionally incorporated geomorphic floodplains, bringing the total to four HVFE classes used in the analysis. Finally, within these geographic criteria, we considered degraded or deforested areas as available for restoration, i.e. croplands and short vegetation classes from Potapov et al. 43 . e) Carbon Removals from Restoration We estimated carbon removals from restoring croplands and short vegetation using carbon accumulation rates from the first 30 years of natural forest regeneration, as mapped globally by Cook-Patton et al. 44 . This study modelled aboveground carbon accumulation rates globally at ~1km 2 (at the equator) resolution using 13,000+ field observations and a suite of environmental variables to predict rates of carbon accumulation per hectare per year up to 30 years. We adjusted the carbon accumulation rates for the headwater regions and fixed-width buffer around low-order streams in the minimum scenario (without floodplain) by multiplying them by the maximum optimal tree cover percentage in agricultural lands, as estimated by Sprenkle-Hyppolite et al. 45 . This adjustment was applied specifically to the minimum scenario to reflect minimal impact on agricultural production. These values were derived through an expert-elicitation process, identifying maximum tree cover thresholds for 53 regional cropping and grazing systems that safeguard agricultural yields 45 . Following this adjustment to the carbon accumulation rates, we calculated summary statistics using Google Earth Engine (see Code Availability). Country-level and global totals were derived by multiplying the modified carbon accumulation layer by pixel area, converting the units from Mg C ha -1 yr -1 to Mg C pixel -1 yr -1 . This enabled a straightforward summation of pixel values to estimate national and global carbon accumulation. Although the analysis was conducted in units of carbon, results are reported in terms of carbon dioxide by applying a molecular weight conversion factor of 44/12 (CO₂/C). Declarations Data Availability The global HVFEs maps, delineated under both minimum and maximum scenarios at 30-meter resolution, are available on Zenodo (https://doi.org/10.5281/zenodo.15338535). Code Availability The Python code used to generate the global HVFEs map and to produce country-level freshwater and carbon estimates is accessible at https://github.com/MahyaSad/Global-High-Value-Freshwater-Ecosystem. Code development was conducted primarily in Python (v3.9.15; https://www.python.org/) for HVFEs mapping, freshwater analysis, and figure generation. Carbon estimation was performed using Google Earth Engine (https://earthengine.google.com/). Acknowledgements This work was supported in part by the NASA Applied Sciences Program, Conservation International, and Khalifa University Award number 001092-00001. Any opinions, findings, conclusions or recommendations expressed in this work are those of the author(s) and do not necessarily reflect the views of NASA, Conservation International, or Khalifa University. We would like to thank Robin Abell, Derek Vollmer, and Ian Harrison for their feedback on early concepts leading to development of this work. Author contributions Mahya G.Z Hashemi, Kashif Shaad, Ibrahim Nourein Mohammed, John D. Bolten, Maíra Ometto Bezerra, Vivian Griffey, and Starry Sprenkle-Hyppolite conceptualized the study. Mahya G.Z Hashemi developed the HVFE’s maps. Mahya G.Z Hashemi, Kashif Shaad, and Vivian Griffey designed and carried out the statistical analyses. Mahya G.Z Hashemi, Kashif Shaad and Vivian Griffey designed the visual materials and co-wrote the paper. All authors reviewed, edited and contributed to the discussion. References Lynch, A. J. et al. People need freshwater biodiversity. WIREs Water 10 , e1633 (2023). Damania, R., Desbureaux, S., Rodella, A.-S., Russ, J. & Zaveri, E. Quality Unknown: The Invisible Water Crisis . (World Bank Publications, 2019). Grill, G. et al. Mapping the world’s free-flowing rivers. Nature 569 , 215–221 (2019). Bending the Curve of Biodiversity Loss . (WWF, Gland, 2020). Calvin, K. et al. IPCC, 2023: Climate Change 2023: Synthesis Report. 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Indigenous groups unveil plan to protect 80% of the Amazon in Peru and Ecuador. Mongabay Environ. News (2021). Monterroso, I., Cronkleton, P., Pinedo, D. & Larson, A. M. Reclaiming Collective Rights: Land and Forest Tenure Reforms in Peru (1960-2016) . vol. 224 (CIFOR, 2017). Biggs, T. W., Santiago, T. M. O., Sills, E. & Caviglia-Harris, J. The Brazilian Forest Code and riparian preservation areas: spatiotemporal analysis and implications for hydrological ecosystem services. Reg. Environ. Change 19 , 2381–2394 (2019). Soares-Filho, B. et al. Cracking Brazil’s Forest Code. Science 344 , 363–364 (2014). Roe, S. et al. Land-based measures to mitigate climate change: Potential and feasibility by country. Glob. Change Biol. 27 , 6025–6058 (2021). Friedlingstein, P. et al. Global Carbon Budget 2022. Earth Syst. Sci. Data 14 , 4811–4900 (2022). Savin, I., King, L. C. & van den Bergh, J. Analysing content of Paris climate pledges with computational linguistics. Nat. Sustain. 8 , 297–306 (2025). Fluet-Chouinard, E. et al. Extensive global wetland loss over the past three centuries. Nature 614 , 281–286 (2023). Abood, S. A., Spencer, L. & Wieczorek, M. US Forest Service national riparian areas base map for the conterminous United States in 2019. (2022). Lane, C. R. et al. Mapping global non-floodplain wetlands. Earth Syst. Sci. Data 15 , 2927–2955 (2023). Dinerstein, E. et al. An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm. BioScience 67 , 534–545 (2017). Potapov, P. et al. Global maps of cropland extent and change show accelerated cropland expansion in the twenty-first century. Nat. Food 3 , 19–28 (2021). Cook-Patton, S. C. et al. Mapping carbon accumulation potential from global natural forest regrowth. Nature 585 , 545–550 (2020). Sprenkle-Hyppolite, S., Griscom, B., Griffey, V., Munshi, E. & Chapman, M. Maximizing tree carbon in croplands and grazing lands while sustaining yields. Carbon Balance Manag. 19 , 23 (2024). Additional Declarations There is NO Competing Interest. Supplementary Files Appendix09052025.docx Supplementary Methods Cite Share Download PDF Status: Published Journal Publication published 29 Jan, 2026 Read the published version in Nature Water → 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6626566","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Analysis","associatedPublications":[],"authors":[{"id":460432327,"identity":"243dafdb-f63c-4d7a-9a1a-540bfc8940b4","order_by":0,"name":"Mahya Hashemi","email":"","orcid":"","institution":"NASA Goddard Space Flight Center","correspondingAuthor":false,"prefix":"","firstName":"Mahya","middleName":"","lastName":"Hashemi","suffix":""},{"id":460432326,"identity":"a31cd40e-c6d1-4181-ac51-6e5ceb4e5850","order_by":1,"name":"Kashif Shaad","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA80lEQVRIiWNgGAWjYBACCQYeIMlmgxBhI1JLGkKAWC2HkQQIAcn+swc//Cg7L88v3f7wcWWbXR0fe+8Bho97anFqkZbIS5bsOXfbcOacM8aGZ9uSJdh4ziUwznh2HKcWOQkeAwnettsJBjdy2CQbzjBLsEnkGDDzHDiGWwv/GeOff9vOAbWkP//ZcKaesBZphhwzad62A0AtCWaMDRWHYVpqcHt/Ro6Ztcy5ZMOZM3KMJRsqjku28ZwxODjjwAGcWiTOnzG++abMTp5fIv3hxwaDan759h7DBx8O1OHUgh0ArThMUBEGINWWUTAKRsEoGMYAACKnUFLRL5E1AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-9954-6323","institution":"Conservation International","correspondingAuthor":true,"prefix":"","firstName":"Kashif","middleName":"","lastName":"Shaad","suffix":""},{"id":460432328,"identity":"1891de3d-1f79-48d9-8cfb-9674f9807fd3","order_by":2,"name":"Vivian Griffey","email":"","orcid":"","institution":"Conservation International","correspondingAuthor":false,"prefix":"","firstName":"Vivian","middleName":"","lastName":"Griffey","suffix":""},{"id":460432329,"identity":"417b684c-af89-4025-be6a-ea34c69043fb","order_by":3,"name":"Ibrahim Mohammed","email":"","orcid":"https://orcid.org/0000-0002-6542-319X","institution":"Khalifa University","correspondingAuthor":false,"prefix":"","firstName":"Ibrahim","middleName":"","lastName":"Mohammed","suffix":""},{"id":460432330,"identity":"962f127e-def8-4475-ba52-c43b48b4fa2a","order_by":4,"name":"John Bolten","email":"","orcid":"","institution":"NASA Goddard Space Flight Center","correspondingAuthor":false,"prefix":"","firstName":"John","middleName":"","lastName":"Bolten","suffix":""},{"id":460432331,"identity":"20a1a5f4-69af-4568-8fde-6f0084e437fc","order_by":5,"name":"Maíra Bezerra","email":"","orcid":"","institution":"Conservation International","correspondingAuthor":false,"prefix":"","firstName":"Maíra","middleName":"","lastName":"Bezerra","suffix":""},{"id":460432332,"identity":"5f2cc8bf-e559-443c-a3ae-97afa293a7a5","order_by":6,"name":"Starry Sprenkle-Hyppolite","email":"","orcid":"","institution":"Conservation International","correspondingAuthor":false,"prefix":"","firstName":"Starry","middleName":"","lastName":"Sprenkle-Hyppolite","suffix":""}],"badges":[],"createdAt":"2025-05-09 08:17:01","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6626566/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6626566/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s44221-025-00573-x","type":"published","date":"2026-01-29T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83432579,"identity":"aee23b6b-fbb5-4b37-8ce4-3b48e36e0e07","added_by":"auto","created_at":"2025-05-26 07:35:11","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":709241,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eGlobal distribution and delineation of High-Value Freshwater Ecosystems (HVFEs). (a) Global map of HVFEs under the maximum delineation scenario, showing surface water bodies (rivers, lakes, and reservoirs), headwater catchments, regularly flooded wetlands, geomorphic floodplains, and fixed-width riparian corridors along low-order and high-order streams. Bubble sizes in the legend represent the global area of each HVFEs component in million km²; (b) Comparison of the maximum and minimum HVFEs delineation scenarios (with and without floodplain); (c) Top 50 countries ranked by the extent of fixed-width riparian corridors around high-order streams and lakes\u003c/em\u003e, \u003cstrong\u003erepresenting the \u003c/strong\u003e\u003cem\u003em\u003c/em\u003e\u003cstrong\u003eaximum possible buffer coverage within the HVFE framework.\u003c/strong\u003e\u003cem\u003e Percentages indicate each country's contribution to the global total, with color coding representing different world regions \u003c/em\u003e\u003csup\u003e18\u003c/sup\u003e\u003cem\u003e.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/972f2c505076c00acc368a8f.png"},{"id":83432581,"identity":"f2c1fca7-d8eb-468c-8d80-09720ca79529","added_by":"auto","created_at":"2025-05-26 07:35:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":337268,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExamples of protection and restoration measures to safeguard freshwater-related ecosystems. Icons created with elements licensed from Canva.com.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/5ef1eda4a6e960075c1c6dd0.png"},{"id":83432435,"identity":"8efbfedd-b655-41c1-9418-5fe52640642f","added_by":"auto","created_at":"2025-05-26 07:27:11","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":197419,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLand cover composition and cropland transformation across HVFE types in 13 FWC countries. This figure shows the land cover distribution across four HVFE classes—Class 1 (headwater regions), Class 2 (fixed-width corridors around first-order streams), Class 3 (corridors around higher-order streams and lakes), and Class 4 (geomorphic floodplains)—based on UMD land cover data from 2000 to 2020. Stacked bars represent current land cover (in billion m²) per HVFE class, including tree cover, short vegetation, dense vegetation, cropland, and urban areas. Inset pie charts represent the cumulative cropland area across all four HVFE classes and the percentage of cropland gained from pre-existing tree cover, wetlands, or other land covers.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/ef1ac5d9abb4387838dc0738.png"},{"id":83432439,"identity":"a72b35ed-78f1-4c4d-8994-6c405e79749b","added_by":"auto","created_at":"2025-05-26 07:27:12","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":370896,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAnnual CO₂ removal potential (Tg CO₂ yr⁻¹) across the top 50 countries under maximum and minimum restoration scenarios.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/00d8308d585394feff40ff05.png"},{"id":83433221,"identity":"7ebd062d-d80f-4561-963b-bc3c6182d781","added_by":"auto","created_at":"2025-05-26 07:43:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":41738,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eComparison of climate mitigation potential (GtCO₂ Yr\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e-1\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e) from the maximum restoration scenario between countries committed and uncommitted to the FWC across NDC types. Three of the eight countries committed to the FWC and with Absolute Reduction NDCs (Norway, Moldova, and Tajikistan) were not included in this figure because their mitigation potential (as defined in this study) is negligible. NDC types included in the” Other” category are GDP Intensity reduction, Actions only, Trajectory target, BAU not specified, Per capita intensity reduction, Cumulative emission target and unspecified. More information on these NDC types can be found in Savin et al.\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e38\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/b318ddc287a998fb5726e196.png"},{"id":101481389,"identity":"9cfa023c-a38c-4e1c-8708-bf42bc617fda","added_by":"auto","created_at":"2026-01-30 08:13:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3428739,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/8474173e-61be-4b72-b0e2-bf46ef9cb255.pdf"},{"id":83432452,"identity":"efea4fe0-a8df-4372-83f0-5212dc0ee4e8","added_by":"auto","created_at":"2025-05-26 07:27:12","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":10043452,"visible":true,"origin":"","legend":"Supplementary Methods","description":"","filename":"Appendix09052025.docx","url":"https://assets-eu.researchsquare.com/files/rs-6626566/v1/a7e722cdeaa7fc377f56f737.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Aspiration to action: Opportunities to align freshwater ecosystems with climate actions","fulltext":[{"header":"1.\tMain ","content":"\u003cp\u003eFreshwater ecosystems play a fundamental role in regulating hydrological cycles, supporting biodiversity, and maintaining climate stability\u0026nbsp;\u003csup\u003e1\u003c/sup\u003e. They provide essential services such as clean water supply, food production, flood regulation, and carbon sequestration. Yet they are among the most threatened ecosystems globally. Since 1900, wetland extent has declined globally by nearly 70%, only 37% of rivers longer than 1,000 kilometers remain free-flowing over their entire length, and more than 50% of the world\u0026rsquo;s rivers and streams face high risks of pollution\u0026nbsp;\u003csup\u003e2,3\u003c/sup\u003e. Freshwater vertebrate populations have also suffered an 84% decline between 1970 and 2016\u0026nbsp;\u003csup\u003e4\u003c/sup\u003e. Climate change intensifies these issues, leading to extreme rainfall variability, droughts, and heatwaves\u0026nbsp;\u003csup\u003e5\u003c/sup\u003e. Today, water-related disasters account for 90% of all natural disasters and are becoming increasingly frequent and severe\u003csup\u003e6\u003c/sup\u003e. By 2050, extreme droughts could impact five times more land globally, 5.7 billion people may face water scarcity, and 1.6 billion could be at flood risk\u0026nbsp;\u003csup\u003e7\u003c/sup\u003e. These growing challenges have exposed gaps in reliable access to clean water, flood regulation, and food production for millions of people\u0026nbsp;\u003csup\u003e2,8\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDespite their critical role in biodiversity, climate resilience, and water security, freshwater ecosystems have long lacked a systematic and unified global approach to restoration and conservation. The country-led \u003cstrong\u003eFreshwater Challenge (FWC)\u003c/strong\u003e was launched at the 2023 UN Water Conference to help close this gap. \u0026nbsp;The FWC aims to restore \u003cstrong\u003e300,000 kilometers of rivers\u003c/strong\u003e and \u003cstrong\u003e350 million hectares of wetlands\u003c/strong\u003e by 2030, aligning with global targets such as the \u003cstrong\u003eKunming-Montreal Global Biodiversity Framework\u0026rsquo;s 30x30 goal\u003c/strong\u003e. The initiative positions freshwater ecosystems at the heart of global environmental commitments and emphasizes that restoration efforts must be integrated with broader climate strategies, including those under the \u003cstrong\u003eUnited Nations Framework Convention on Climate Change (UNFCCC)\u003c/strong\u003e\u003csup\u003e9\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eHowever, achieving this integration remains challenging, particularly in countries of the Global South. While 49 countries and the European Union have joined the Freshwater Challenge, many still need to demonstrate meaningful progress in aligning freshwater restoration efforts with their Nationally Determined Contributions (NDCs) (country-specific climate action plans, outlining targets and measures for reducing greenhouse gas emissions and adapting to climate impacts), and National Adaptation Plans (NAPs). Freshwater ecosystems remain u\u003cstrong\u003enderrepresented\u003c/strong\u003e in national climate strategies and biodiversity strategies, with references to rivers and wetlands often lacking spatial detail and actionable commitments\u003csup\u003e10\u003c/sup\u003e. Even where political will exists, countries frequently lack robust methodologies and spatial datasets to define coherent, measurable restoration targets that can be effectively linked to climate adaptation under NAPs. While the carbon dynamics of freshwater systems are increasingly well understood\u003csup\u003e11,12\u003c/sup\u003e, including their roles in both greenhouse gas storage and emissions, carbon markets have historically focused on terrestrial forests. Although riparian and headwater forests are technically part of terrestrial ecosystems, they provide essential ecological services that support freshwater function. These freshwater-adjacent landscapes offer both carbon sequestration potential and hydrological benefits, yet they remain a largely untapped opportunity within integrated nature-based climate solutions.\u003c/p\u003e\n\u003cp\u003eTo support the identification and mapping of High-Value Freshwater Ecosystems (HVFEs), we adapted a spatially explicit framework to guide the prioritization of protection and restoration actions. This approach enables the formulation of geographically specific, policy-relevant targets and informs national climate strategies such as NDCs and NAPs. The framework emphasizes ecological integrity by prioritizing natural regeneration in forest biomes and avoiding \u0026nbsp;ecologically unsuitable afforestation or wetland conversion\u003csup\u003e13,14\u003c/sup\u003e. By applying this framework, we assess the global carbon sequestration potential of restoring degraded lands near freshwater systems, highlighting the dual adaptation and mitigation benefits of integrated, ecosystem-based strategies.\u003c/p\u003e"},{"header":"2. Assessing Global Distribution of High-Value Freshwater Ecosystems ","content":"\u003cp\u003eWe adapted the High Conservation Value (HCV) framework to define HVFEs, aiming to support a more strategic and actionable approach for identifying freshwater ecosystems in need of conservation (including both protection and restoration). HVFEs extend beyond conventional freshwater definitions by integrating freshwater and adjacent terrestrial ecosystems that collectively support the regulation of hydrological and carbon cycles within watersheds. These ecosystems include headwater catchments, surface water bodies (e.g., rivers, lakes, and reservoirs), riparian corridors, inundated wetlands, and geomorphic floodplains (areas shaped by long-term river activity and landform development, rather than by short-term flood frequency). Together, they exert a disproportionate influence on global water flow, filtration, and storage, as well as nutrient and carbon dynamics. Moreover, they serve as vital refugia for aquatic and terrestrial biodiversity. Existing freshwater classifications often overlook the full extent of the terrestrial interface\u0026mdash;particularly riparian and floodplain systems\u0026mdash;that sustains freshwater ecosystem services. Thus, identifying HVFEs allows for a more comprehensive and ecologically meaningful delineation of priority areas for conservation and restoration, critical for achieving targets under initiatives like the FWC.\u003c/p\u003e\n\u003cp\u003eWe developed a high-resolution global map of HVFEs to support actionable conservation strategies. The map, produced at 30-meter resolution, captures freshwater-related features under two delineation scenarios (minimum and maximum), reflecting a range of conservation approaches based on ecosystem service capacity. \u0026nbsp;This delineation draws on foundational global datasets, including University of Maryland (UMD) land cover\u003csup\u003e15\u003c/sup\u003e, MERIT 90-meter hydrography data\u003csup\u003e16\u003c/sup\u003e, and global floodplain layers\u003csup\u003e17\u003c/sup\u003e, to ensure consistency and spatial precision across diverse landscapes.\u003c/p\u003e\n\u003cp\u003eThe minimum scenario includes surface water bodies, wetlands, headwater regions, fixed-width riparian corridors along low-order and high-order streams. It also includes riparian buffers surrounding lakes and reservoirs. This conservative delineation focuses on preserving water quality, reducing erosion, and maintaining aquatic habitats. The maximum delineation scenario builds upon this foundation by incorporating geomorphic floodplains and wetland corridors, extending delineation further into broader hydrological zones. This scenario emphasizes flood mitigation, sediment retention, and long-term water storage capacity, recognizing the full hydrological and ecological role of floodplains and their relevance to the functioning of the entire river network. In doing so, it expands beyond the minimum scenario, with floodplains overlapping and masking riparian corridors and headwater regions included in the minimum footprint, as defined by the hierarchical masking rules (Supplementary Methods B).\u003c/p\u003e\n\u003cp\u003eThe global map in Fig. 1 reveals that HVFEs, under the maximum delineation scenario, span approximately 51.6 million km\u0026sup2; globally. The highest concentrations of HVFEs are found in countries with extensive river networks and wetlands. The Russian Federation holds the largest area (8.68 million km\u0026sup2;), followed by Canada (4.80 million km\u0026sup2;), the United States of America (3.99 million km\u0026sup2;), China (3.67 million km\u0026sup2;), and Australia (3.35 million km\u0026sup2;). Other major contributors include Brazil (2.92 million km\u0026sup2;), Argentina (1.39 million km\u0026sup2;), India (1.38 million km\u0026sup2;), and Kazakhstan (1.25 million km\u0026sup2;). Notably, the 49 countries that are members of the FWC collectively account for 22.9 million km\u003cstrong\u003e\u0026sup2;\u003c/strong\u003e, or approximately 44% of the global HVFEs extent under the maximum scenario (without floodplain). If Russia and China were to join the initiative, this share would rise by an additional 12.3 million km\u0026sup2;, increasing the total coverage to approximately 68% of all HVFEs. These figures underscore both the global relevance of the HVFEs framework and the significant opportunity to enhance global conservation efforts through expanded participation in the FWC. Under the minimum scenario, HVFEs cover 40.9 million km\u0026sup2;, meaning the 10.7 million km\u0026sup2; difference between scenarios highlights the importance of including geomorphic floodplains and wetland corridors in conservation planning. However, this difference is not entirely attributable to floodplains alone, as partial overlap exists between floodplain zones and riparian or wetland areas captured in the minimum scenario (Fig. 1). A detailed breakdown of HVFEs components under each delineation scenario is provided in Supplementary Table 1.\u003c/p\u003e\n\u003cp\u003eTo support local adaptation and ensure the global HVFEs map is useful across diverse geographies, we validated the mapping approach in the Contiguous United States (CONUS), which offered the only available riparian reference data, along with ecological variability (e.g., climate, vegetation, and hydrology). In addition to this empirical validation, the foundational datasets underlying the HVFEs framework\u0026mdash; including University of Maryland (UMD) land cover\u003csup\u003e15\u003c/sup\u003e, MERIT 90-meter hydrography data\u003csup\u003e16\u003c/sup\u003e, and global floodplain layers\u003csup\u003e17\u003c/sup\u003e\u0026mdash;have each undergone independent validation, further supporting the robustness of the approach (see Supplementary Methods A and D).\u003c/p\u003e"},{"header":"3. Identifying Freshwater-Related Ecosystems Adaptation Strategies","content":"\u003cp\u003eDespite their essential role in climate regulation, biodiversity support, and water security, freshwater ecosystems remain underrepresented in most NDCs\u003csup\u003e19\u003c/sup\u003e and NAPs. References to water often focus on general hazards such as droughts and floods, without spatially explicit targets or actionable strategies. While there is growing recognition of the synergies between adaptation and mitigation\u0026mdash;particularly across water, land, and biodiversity sectors\u003csup\u003e20\u003c/sup\u003e\u0026mdash;key freshwater systems such as headwaters, riparian corridors, and geomorphic floodplains continue to be overlooked relative to coastal ecosystems like mangroves\u003csup\u003e10\u003c/sup\u003e. Realizing the full potential of NDCs and NAPs will require spatial frameworks and decision-support tools that directly align climate goals with freshwater ecosystem functions.\u003c/p\u003e\n\u003cp\u003eWe propose using the \u003cstrong\u003eHVFE framework\u003c/strong\u003e to translate these ambitions into informed, holistic nature-based actions. This framework enables countries to identify spatially defined pathways that integrate freshwater interventions with known climate adaptation and mitigation benefits, positioning freshwater ecosystems as foundational assets for climate action. \u003cstrong\u003eFigure 2\u003c/strong\u003e presents a set of measures across HVFE categories and highlights the key ecosystem services each supports. These actions fall into two main categories\u0026mdash;\u003cstrong\u003eProtection\u003c/strong\u003e and \u003cstrong\u003eRestoration\u003c/strong\u003e\u0026mdash;based on the multiple benefits freshwater ecosystems offer, including safeguarding water resources, supporting biodiversity, and building resilient livelihoods\u003csup\u003e21\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eUnder \u003cstrong\u003eProtection\u003c/strong\u003e, countries can regulate environmental flows, restrict harmful resource extraction (e.g., fishing, mining), and designate freshwater protected areas or Other Effective Area-Based Conservation Measures (OECMs). For example, \u003cstrong\u003eNepal\u003c/strong\u003e, with over \u003cstrong\u003e36% of its land in headwater regions\u003c/strong\u003e and a \u003cstrong\u003ehigh projected flood risk by 2050\u003c/strong\u003e\u003csup\u003e22\u003c/sup\u003e (Aqueduct score: \u003cstrong\u003e3.8\u003c/strong\u003e on a 0\u0026ndash;5 scale, see Supplementary Table 2), faces significant climate threats. Proactive management\u0026mdash;such as safeguarding upstream ecosystems, enforcing flow regulations, and strengthening zoning in headwater catchments\u0026mdash;can help protect downstream communities and maintain ecosystem function.\u003c/p\u003e\n\u003cp\u003eUnder \u003cstrong\u003eRestoration\u003c/strong\u003e, actions may include reconnecting rivers with floodplains, restoring riparian forests, and rehabilitating degraded vegetation in headwater regions to improve green cover and reduce erosion. Countries such as \u003cstrong\u003eMozambique\u003c/strong\u003e, \u003cstrong\u003ePakistan\u003c/strong\u003e, and \u003cstrong\u003eMalawi\u003c/strong\u003e present high-impact opportunities for restoration. For instance, \u003cstrong\u003eMozambique\u003c/strong\u003e, with a \u003cstrong\u003eflood risk score of 4.1(\u003c/strong\u003eon a 0\u0026ndash;5 scale)\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eand\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e6.2 million hectares\u003c/strong\u003e of cropland expansion into tree cover, wetlands, and other natural land covers between 2000\u0026ndash;2020 (\u003cstrong\u003eFig. 3\u003c/strong\u003e), can prioritize restoration in degraded floodplains and upper watersheds to enhance water retention and reduce erosion. Similarly, \u003cstrong\u003ePakistan\u003c/strong\u003e, with \u003cstrong\u003e21% of its land classified as geomorphic floodplains\u003c/strong\u003e and a \u003cstrong\u003eflood risk score of 3.25\u003c/strong\u003e, represents a strong candidate for riparian buffer restoration to improve flood resilience in vulnerable basins. Given that around 20% of Malawi\u0026rsquo;s landscape consists of riparian corridors and floodplains\u0026mdash;and with one of the highest projected flood risk scores by 2050 (4.1 on a 0\u0026ndash;5 scale)\u0026mdash;the country presents a strong opportunity for floodplain reconnection and riparian forest restoration.\u003c/p\u003e\n\u003cp\u003eBy guiding countries in selecting geographically tailored and ecologically appropriate interventions, the HVFE framework supports the design of integrated, ecosystem-based strategies that simultaneously advance adaptation, mitigation, and biodiversity goals.\u003c/p\u003e"},{"header":"4. Using HVFE Mapping to Prioritize Strategies","content":"\u003cp\u003eThe land cover composition and cropland transformation across four HVFE classes in 13 countries show that countries like Brazil, Colombia, Democratic Republic of Congo, and Mozambique have experienced the most extensive cropland expansion in HVFEs between 2000 and 2020 (Figure3). Notably, 25% of cropland in the\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eDemocratic Republic of Congo replaced tree cover, while 27% in Mozambique originated from both tree cover and wetlands\u0026mdash;indicating significant freshwater ecosystem degradation.\u003c/p\u003e\n\u003cp\u003eThese types of patterns reveal critical restoration opportunities, particularly where cropland or short vegetation overlaps with HVFEs. Reforestation or wetland recovery in such areas can enhance water infiltration, reduce erosion, and improve water quality\u0026mdash;offering measurable adaptation outcomes\u003csup\u003e23\u003c/sup\u003e. These spatial insights can be useful for countries to translate freshwater restoration ambitions into actionable, place-based ecosystem interventions.\u003c/p\u003e\n\u003cp\u003eTo further illustrate on the region-specific pathways of action, we analyzed the detailed breakdown of HVFE types and their restoration potential across six case study countries (Table1): Nepal, Pakistan, Mozambique, Democratic Republic of Congo, Brazil, and Peru. These examples span different HVFE types (e.g., headwaters, floodplains, stream buffers) and climate risks and the isolation of the crop land change relative to the HVFE classes, which elucidates more straightforward restoration targets and allows clearer recommendations for both protection and restoration strategies under the HVFE framework (see Supplementary Figure 1 for HVEF maps).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eTable 1.\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cstrong\u003eDistribution of HVFE Categories and Restoration Potential in Six selected FWC Countries.\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable style=\"width: 4.6e+2pt;border: none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eCountry\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTotal HVFE Area (ha, % of country)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eHeadwater (ha, % of HVFE)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eFloodplain (ha, % of HVFE)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eHigh-Order Stream Buffer (ha, % of HVFE)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eLow-Order Stream Buffer (ha, % of HVFE)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eRestoration Opportunity (ha)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e% of FWC Goal\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eBrazil\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e291,991,506 32.6%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2,357,981\u003c/p\u003e\n \u003cp\u003e8.1%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e57,675,677 19.8%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1,542,4967 5.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e114,630,036 39.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e104,509,638\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e29.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003ePakistan\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e32,342,041 37.0%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5,961,769 18.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e186,092,3957.5%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1,312,758\u003c/p\u003e\n \u003cp\u003e4.1%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4,110,006 12.7%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e32,064,772\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e9.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003ePeru\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e60,338,198\u003c/p\u003e\n \u003cp\u003e46.6%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21,873,575\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;36.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e7,325,185 12.1%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2,387,516\u003c/p\u003e\n \u003cp\u003e4.0%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e16,332,939 27.1%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20,029,908\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eDemocratic Republic of the Congo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e81,824,353 35%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e6,066,312 7.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e14,196,578\u003c/p\u003e\n \u003cp\u003e17.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3,563,049\u003c/p\u003e\n \u003cp\u003e4.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e33,487,428 40.9%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e18,115,205\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eMozambique\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e25,911,122 32.7%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1,293,732 5.0%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e8,295,580 32%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1,115,629\u003c/p\u003e\n \u003cp\u003e4.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e11,042,160 42.6%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e12,778,794\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eNepal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e8,562,265 58.2%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5,305,164 62%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e886,650 10.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e371,098 4.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1,816,804 21.2%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4,488,788\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"8\"\u003e\n \u003cp\u003eRestoration opportunity refers to areas within HVFE-adjacent terrestrial ecosystems currently under cropland, urban land, or dense/sparse short vegetation. \u0026ldquo;% of FWC Goal\u0026rdquo; indicates each country\u0026apos;s potential contribution toward the global Freshwater Challenge target of restoring 300,000 kilometers of degraded rivers (focusing on riparian corridors) and 350 million hectares of degraded wetlands by 2030.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eIn Nepal, headwater regions remain largely intact (Table 1), offering an opportunity for proactive protection through zoning regulations, water source protection, and integration into OECMs. These approaches align with the country\u0026rsquo;s National Water Resources Policy (2020), which promotes watershed management and river basin planning for sustainable water resource use\u003csup\u003e24\u003c/sup\u003e, and ongoing initiatives focused on spring and watershed restoration in upland areas\u003csup\u003e25\u003c/sup\u003e. Furthermore, Nepal has formally recognized OECMs\u0026mdash;including community-managed forests and sacred sites\u0026mdash;as part of its broader strategy to conserve biodiversity and ecosystem services beyond traditional protected areas\u003csup\u003e26\u003c/sup\u003e. Maintaining these upstream buffers is critical for reducing downstream flood risk in the Terai region, where communities face some of the country\u0026rsquo;s highest flood-related vulnerabilities\u003csup\u003e27\u003c/sup\u003e. In Pakistan, extensive cropland encroachment into floodplains has reduced flood-buffering capacity, especially in the Indus Basin\u003csup\u003e28\u003c/sup\u003e. Restoration through riparian reforestation and floodplain reconnection to the rivers could mitigate these risks. Similarly, in Mozambique, nearly 70% of cropland expansion between 2000 and 2020 replaced tree covers, wetlands, and other natural land covers\u0026mdash;primarily within floodplains and low-order stream buffers (Fig. 3). With high projected flood risk in regions like Sofala Province, hydrologic reconnection and land-use zoning are essential to prevent further loss\u003csup\u003e29\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eIn the Democratic Republic of Congo, riparian corridors still retain substantial tree cover and natural vegetation, supporting both freshwater storage and diverse fish populations that are crucial for local livelihoods and climate resilience\u003csup\u003e30,31\u003c/sup\u003e. Prioritizing protection and sustainable management in these areas can help maintain rainfall recycling and the health of aquatic ecosystems. Notably, with 25% of recent cropland expansion replacing tree cover, these same areas could be prioritized for restoration efforts aimed at reversing freshwater ecosystem degradation. Peru is another example where headwater regions along low-order streams still retain substantial forest cover, while areas of short vegetation offer opportunities for restoration. However, cropland expansion is increasingly encroaching on riparian corridors and floodplains. Early intervention through conservation easements and Indigenous-led land management can help safeguard ecosystem function in the Andes\u0026ndash;Amazon transition zone\u003csup\u003e32,33\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eIn Brazil, on the other hand, riparian corridors and floodplains have experienced significant conversion\u0026mdash;over 114,000 km\u0026sup2;\u0026mdash;from wetlands and forests to cropland, threatening the functionality of these critical ecosystems\u003csup\u003e34\u003c/sup\u003e. Restoring riparian buffers and enforcing the \u0026nbsp; \u0026nbsp; \u0026nbsp;Forest Code are critical for ensuring water regulation and strengthening climate resilience\u003c!--[if supportFields]\u003e\u003cspanstyle='mso-element:field-begin'\u003e\u003c/span\u003e ADDIN ZOTERO_ITEM CSL_CITATION{\u0026quot;citationID\u0026quot;:\u0026quot;TCL7o0LO\u0026quot;,\u0026quot;properties\u0026quot;:{\u0026quot;formattedCitation\u0026quot;:\u0026quot;\\\\super35\\\\nosupersub{}\u0026quot;,\u0026quot;plainCitation\u0026quot;:\u0026quot;35\u0026quot;,\u0026quot;noteIndex\u0026quot;:0},\u0026quot;citationItems\u0026quot;:[{\u0026quot;id\u0026quot;:215,\u0026quot;uris\u0026quot;:[\u0026quot;http://zotero.org/users/16566647/items/DUIZ5MMF\u0026quot;],\u0026quot;itemData\u0026quot;:{\u0026quot;id\u0026quot;:215,\u0026quot;type\u0026quot;:\u0026quot;article-journal\u0026quot;,\u0026quot;abstract\u0026quot;:\u0026quot;Brazil'scontroversial new Forest Code grants amnesty to illegal deforesters, butcreates new mechanisms for forest conservation.\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;, \\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;Roughly 53% of Brazil's nativevegetation occurs on private properties. Native forests and savannahs on theselands store 105 ± 21 GtCO\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;2\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;e (billion tonsof CO\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;2\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;equivalents) and play a vitalrole in maintaining a broad range of ecosystem services (\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;1\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\\n\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;). Sound management of theseprivate landscapes is critical if global efforts to mitigate climate change areto succeed. Recent approval of controversial revisions to Brazil's Forest Code(FC)—the central piece of legislation regulating land use and management onprivate properties—may therefore have global consequences. Here, we quantifychanges resulting from the FC revisions in terms of environmental obligationsand rights granted to land-owners. We then discuss conservation opportunitiesarising from new policy mechanisms in the FC and challenges for itsimplementation.\u0026quot;,\u0026quot;container-title\u0026quot;:\u0026quot;Science\u0026quot;,\u0026quot;DOI\u0026quot;:\u0026quot;10.1126/science.1246663\u0026quot;,\u0026quot;ISSN\u0026quot;:\u0026quot;0036-8075,1095-9203\u0026quot;,\u0026quot;issue\u0026quot;:\u0026quot;6182\u0026quot;,\u0026quot;journalAbbreviation\u0026quot;:\u0026quot;Science\u0026quot;,\u0026quot;language\u0026quot;:\u0026quot;en\u0026quot;,\u0026quot;page\u0026quot;:\u0026quot;363-364\u0026quot;,\u0026quot;source\u0026quot;:\u0026quot;DOI.org(Crossref)\u0026quot;,\u0026quot;title\u0026quot;:\u0026quot;Cracking Brazil's ForestCode\u0026quot;,\u0026quot;volume\u0026quot;:\u0026quot;344\u0026quot;,\u0026quot;author\u0026quot;:[{\u0026quot;family\u0026quot;:\u0026quot;Soares-Filho\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Britaldo\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Rajão\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Raoni\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Macedo\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Marcia\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Carneiro\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Arnaldo\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Costa\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;William\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Coe\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Michael\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Rodrigues\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Hermann\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Alencar\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Ane\u0026quot;}],\u0026quot;issued\u0026quot;:{\u0026quot;date-parts\u0026quot;:[[\u0026quot;2014\u0026quot;,4,25]]}}}],\u0026quot;schema\u0026quot;:\u0026quot;https://github.com/citation-style-language/schema/raw/master/csl-citation.json\u0026quot;}\u003cspan style='mso-element:field-separator'\u003e\u003c/span\u003e\u003c![endif]--\u003e\u003csup\u003e35\u003c/sup\u003e. In Peru, headwater regions along low-order streams still retain substantial forest cover, while areas of short vegetation offer opportunities for restoration. However, cropland expansion is increasingly encroaching on riparian corridors and floodplains. Early intervention through conservation easements and Indigenous-led land management can help safeguard ecosystem function in the Andes\u0026ndash;Amazon transition zone.\u003c/p\u003e\n\u003cp\u003eAltogether, these case studies demonstrate how HVFE maps can help align restoration, protection and improved management of freshwater ecosystems with climate adaptation needs at the national level. By linking HVFE conditions with spatial risk layers (e.g., flood risk maps, water stress layers, and drought vulnerability zones), countries can identify high-impact interventions, refine NDC/NAP strategies, attract climate finance, and monitor adaptation outcomes. Notably, many of these adaptation measures also offer mitigation co-benefits. Restoring HVFE can not only contribute to improved climate resilience but also increase carbon sinks.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNext steps could include developing implementation roadmaps, strengthening local capacity, and integrating HVFE-based targets into national investment and monitoring systems, as highlighted in recent implementation and investment planning frameworks for ecosystem restoration and resilience\u003c/strong\u003e\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e"},{"header":"5.\tAssessing Climate Mitigation Benefits ","content":"\u003cp\u003eTo strengthen integration of freshwater-related ecosystem restoration targets (such as those to be developed by the state-members in FWC) and carbon mitigation commitments in NDCs, we have mapped the mitigation potential globally of reforesting degraded terrestrial ecosystems within HVFE delineation (of Section 2) in areas where forests would be the natural cover. Reforestation within HVFEs could provide 1.07\u0026ndash;3.41 GtCO₂/year of mitigation across 355\u0026ndash;484 million hectares, depending on the scenario used (maximum and minimum delineation with associated tree cover thresholds; see Methods d,e). The mitigation potential of the minimum scenario is approximately equivalent to that of global peatland restoration, while the maximum restoration scenario is slightly over half the potential of reducing global deforestation\u003csup\u003e36\u003c/sup\u003e. Fig. 4 compares the total carbon removal potential for the top 50 countries, based on the reforestation of areas where HVFEs are currently in croplands or short vegetation indicating abandoned agriculture or grazing land, within forest biomes under the minimum and maximum restoration scenarios.\u003c/p\u003e\n\u003cp\u003eLarge countries dominate the top five in terms of total mitigation potential \u0026ndash; Brazil, China, India, the United States, and Mexico \u0026ndash; contributing 48% of the global total under all scenarios. However, when adjusting for country size by evaluating carbon removal per hectare, we find a hotspot of mitigation potential in West and Central Africa, with the highest-ranking countries being the Republic of Congo, Liberia, Ghana, Nigeria, and C\u0026ocirc;te d\u0026rsquo;Ivoire. These countries achieve average carbon removal rates of 9.7 MgCO₂/ha/yr (minimum scenario) and 17.9 MgCO₂/ha/yr (maximum scenario), nearly double the average of all other countries. Among the 49 FWC member states, reforestation of degraded HVFE-adjacent terrestrial ecosystems could deliver 0.43\u0026ndash;1.28 GtCO₂/yr of mitigation across 128\u0026ndash;155 million hectares of forest areas\u0026mdash;representing nearly half of both the global mitigation potential and the total area restored under each scenario. This would also contribute significantly to the FWC target of restoring 300,000 Kilometers of rivers by 2030.\u003c/p\u003e\n\u003cp\u003eThis spatially explicit assessment highlights how prioritizing both total and area-adjusted mitigation potential can align freshwater protection with global climate goals. The mitigation potential we identify within HVFEs (1.07\u0026ndash;3.41 GtCO₂/yr) accounts for 2.7\u0026ndash;8.5% of current global emissions (~40 GtCO₂ in 2021) according to the Global Carbon Budget\u003csup\u003e37\u003c/sup\u003e. Given that the suggested carbon budget to limit warming to 1.5 \u0026deg;C is estimated at just 380 GtCO₂ from 2023 onward, restoring areas adjacent to HVFEs could play a meaningful role in meeting emissions reduction targets. Notably, the upper end of our scenario (3.41 GtCO₂/yr) exceeds the estimated annual reduction of 1.4 GtCO₂ needed to reach net zero by 2050\u003csup\u003e37\u003c/sup\u003e\u0026mdash;underscoring the critical role that freshwater-adjacent ecosystem restoration can play in climate mitigation, biodiversity conservation, and water security.\u003c/p\u003e\n\u003cp\u003eClimate mitigation commitments in NDCs can be conditional on external financing, unconditional, or a mix of both. Among them, \u003cstrong\u003eunconditional absolute reduction commitments\u003c/strong\u003e\u0026mdash;defined as firm emission cuts below a historical reference level, irrespective of economic or population growth\u0026mdash;are considered the most ambitious. In contrast, \u003cstrong\u003eBusiness-as-Usual (BAU) reduction commitments\u003c/strong\u003e refer to emission targets relative to projected future growth trends, which may still permit annual emissions increases and are thus seen as less stringent.\u003c/p\u003e\n\u003cp\u003eAmong the 32 countries with unconditional absolute emissions reduction targets, five FWC member states contribute approximately 92% of the total mitigation potential estimated within this subset (Fig. 5), regardless of restoration scenario (0.27 GtCO2/yr minimum and 0.77 GtCO2/yr maximum.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMitigation potential from the reforestation of degraded HVFE-adjacent terrestrial ecosystems is highest in countries with gold-standard NDCs and is concentrated in these five nations. In contrast, countries with less stringent NDCs show a more diffuse and modest potential. These five countries thus represent a strategic opportunity to advance their climate goals through targeted restoration of HVFE-adjacent terrestrial ecosystems.\u003c/p\u003e\n\u003cp\u003eIn order of decreasing potential, these are Brazil, the United States, Canada, Australia, and the United Kingdom. By contrast, Business-as-Usual (BAU) reduction commitments, which are based on projected emissions growth, may still allow for year-on-year emissions increases and are therefore regarded as less ambitious. FWC countries with BAU-based targets contribute 42-44% (scenario dependent) of the mitigation potential among all nations with such targets (FWC\u0026nbsp;n\u0026nbsp;=\u0026nbsp;22; all\u0026nbsp;n\u0026nbsp;=\u0026nbsp;71). Compared to the maximum restoration scenario, the minimum scenario yields consistently lower climate mitigation potential across all NDC types (Supplementary Figure 2). The decline is particularly pronounced for FWC countries with Absolute and BAU Reduction commitments, underscoring how national-level contributions are highly sensitive to the assumed extent of HVFE-adjacent reforestation.\u003c/p\u003e\n\u003cp\u003eAlthough our analysis focused on forest restoration adjacent to HVFEs, we did not quantify the mitigation potential of wetland restoration\u0026mdash;an area that could also offer significant opportunities for nature-based climate solutions. Wetlands were excluded from this study due to the current lack of globally applicable carbon accumulation models for wetland restoration. A recent global analysis estimated that approximately 3.4 million km\u0026sup2; (21%) of inland wetlands have been lost since 1700, primarily due to conversion to cropland and rice fields\u003csup\u003e39\u003c/sup\u003e. Using the UMD Land Cover Change dataset, we estimated that only ~0.16 million km\u0026sup2; of this loss occurred between 2000 and 2020 through conversion of wetlands to cropland, suggesting that the majority of wetland loss occurred prior to the 21st century. Complementing our forest-based estimates, future efforts should evaluate the carbon sequestration potential and broader co-benefits of restoring degraded wetlands within HVFEs, particularly in regions where historical wetland loss has been extensive.\u003c/p\u003e"},{"header":"6.\tConclusion ","content":"\u003cp\u003eTo meet the global demand for unified climate mitigation, freshwater ecosystems and their biological and hydrological functions\u0026mdash;ranging from water supply and flood regulation to fish production and food security\u0026mdash;must no longer be overlooked. Our global map, combined with metrics on ecosystem condition and mitigation potential, offers a critical foundation for systematically identifying, prioritizing, financing, and implementing conservation, adaptation, and restoration actions. In this way, by integrating freshwater and adjacent terrestrial ecosystems into national planning processes, we provide quantifiable benefits including not only carbon sequestration, but of improved ecosystem management, for a more coordinated global response and cascade of restoration benefits. Importantly, this helps bridge the disconnect between freshwater action plans and plans addressing the climate and biodiversity crises. As global mapping methodologies are refined and informed by local ground-truthing, our ability to characterize ecosystems at the land-water interface\u0026mdash;including wetlands, riparian zones, low-order streams, and headwater catchments\u0026mdash;will continue to improve. Notably, our results show that restoring degraded areas adjacent to freshwater ecosystems could deliver up to 3.4 GtCO₂ per year\u0026mdash;equivalent to over 8% of global emissions\u0026mdash;highlighting the powerful role that integrated restoration can play in advancing climate goals. By highlighting overlaps among these three global imperatives, our analysis aims to help harmonize global and local narratives\u0026mdash;an essential step toward adapting to and mitigating the impacts of climate change.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e"},{"header":"7.\tMethods","content":"\u003cp\u003eWe assessed global forest restoration potential near freshwater ecosystems using a geospatial workflow built on the best-available, openly accessible global datasets (Supplementary Table 3). A schematic overview of the mapped HVFE features\u0026mdash;including freshwater systems and adjacent terrestrial zones\u0026mdash;along with detailed definitions, is provided in Supplementary Methods A. All features were classified and mapped at ~30-meter spatial resolution, consistent with the land cover dataset used to evaluate restoration potential in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea) Global Delineation of HVFEs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe global HVFE layer consists of seven ecosystem classes, two of which\u0026mdash;surface water and regularly flooded wetlands\u0026mdash;represent core freshwater ecosystems. These were derived from the global land cover change dataset developed by Potapov et al.\u003csup\u003e15\u003c/sup\u003e, based on Landsat imagery spanning from 2000 to 2020. This dataset was selected for its capacity to capture both seasonal and interannual dynamics of surface water bodies, as well as its detailed land cover classifications, which are critical for identifying forest restoration opportunities and estimating carbon accumulation potential. To reduce the uncertainty associated with transient surface water and wetland features in a static global map, we combined extents from both endpoints (2000 and 2020), thus representing long-term freshwater presence.\u003c/p\u003e\n\u003cp\u003eAccurate delineation of wetlands at a global scale remains challenging due to limited in-situ validation data. As a result, the mapped freshwater classes in this product primarily reflect the presence of water at or near the surface and serve as proxies to identify adjacent terrestrial ecosystems that influence freshwater function. The remaining five HVFE classes represent terrestrial ecosystems closely linked to freshwater systems, serving as critical areas for restoration and protection to sustain local and downstream freshwater benefits. The integration of these seven classes into two composite layers (with and without the inclusion of floodplains) and the associated overlap logic are detailed in Supplementary Methods B.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb) Headwater Catchments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo delineate headwater catchments, we identified first-order sub-catchments with hydrologically active terrain. We utilized the MERIT Hydro sub-catchment dataset (90-meter resolution)\u003csup\u003e16\u003c/sup\u003e, which was downscaled to 30-meter for consistency with the HVFE map. First-order sub-catchments were extracted by overlaying the MERIT Hydro stream network (Strahler order = 1) and applying a minimum slope threshold of 0.1 (~5.7\u0026deg;) to exclude flat, low-energy areas. This approach prioritizes regions likely to contribute significantly to streamflow and freshwater regulation at the watershed scale.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ec) Fixed-Width Corridors and Floodplains\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDue to the absence of a globally consistent riparian mapping dataset, we delineated riparian corridors using a combination of fixed-width buffers and geomorphic floodplains to approximate zones suitable for restoration along streams, lakes, and regularly flooded wetlands. Fixed-width buffers were applied to surface water features identified in the land cover dataset. Because these features may not represent a continuous hydrological network, we merged them using centerlines from the MERIT Hydro stream network to create a connected riverine system. Buffer widths were selected to reflect common policy or conservation standards, with justification for each width provided in Supplementary Methods.\u003c/p\u003e\n\u003cp\u003eValidation of riparian buffers was conducted in the CONUS using the USFS riparian dataset\u003c!--[if supportFields]\u003e\u003cspanstyle='mso-element:field-begin'\u003e\u003c/span\u003e ADDIN ZOTERO_ITEM CSL_CITATION{\u0026quot;citationID\u0026quot;:\u0026quot;JYUh9SRs\u0026quot;,\u0026quot;properties\u0026quot;:{\u0026quot;formattedCitation\u0026quot;:\u0026quot;\\\\super40\\\\nosupersub{}\u0026quot;,\u0026quot;plainCitation\u0026quot;:\u0026quot;40\u0026quot;,\u0026quot;noteIndex\u0026quot;:0},\u0026quot;citationItems\u0026quot;:[{\u0026quot;id\u0026quot;:119,\u0026quot;uris\u0026quot;:[\u0026quot;http://zotero.org/users/16566647/items/32H3IBVR\u0026quot;],\u0026quot;itemData\u0026quot;:{\u0026quot;id\u0026quot;:119,\u0026quot;type\u0026quot;:\u0026quot;article-journal\u0026quot;,\u0026quot;note\u0026quot;:\u0026quot;publisher:Forest Service Research Data Archive\u0026quot;,\u0026quot;title\u0026quot;:\u0026quot;US ForestService national riparian areas base map for the conterminous United States in2019\u0026quot;,\u0026quot;author\u0026quot;:[{\u0026quot;family\u0026quot;:\u0026quot;Abood\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;SinanA\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Spencer\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Linda\u0026quot;},{\u0026quot;family\u0026quot;:\u0026quot;Wieczorek\u0026quot;,\u0026quot;given\u0026quot;:\u0026quot;Michael\u0026quot;}],\u0026quot;issued\u0026quot;:{\u0026quot;date-parts\u0026quot;:[[\u0026quot;2022\u0026quot;]]}}}],\u0026quot;schema\u0026quot;:\u0026quot;https://github.com/citation-style-language/schema/raw/master/csl-citation.json\u0026quot;}\u003cspan style='mso-element:field-separator'\u003e\u003c/span\u003e\u003c![endif]--\u003e\u003csup\u003e40\u003c/sup\u003e (see Supplementary Methods D), which provides 10-meter resolution reference data for comparison.\u003c/p\u003e\n\u003cp\u003eUnlike fixed-width buffers, floodplains are variable-width zones that follow the terrain and hydrological conditions associated with rivers and streams. We used the GFPLAIN90 dataset\u003csup\u003e41\u003c/sup\u003e to map geomorphic floodplains globally. Developed using the GFPLAIN v1.0 algorithm\u003csup\u003e17\u003c/sup\u003e and the MERIT Hydro terrain model, GFPLAIN90 offers a high-resolution (90-meter) representation of floodplain extents, using a minimum contributing area threshold of 20 km\u0026sup2; to define stream networks. This dataset was selected for its scalability across diverse landscapes and hydrologic regimes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ed) Restoration Potential in Freshwater-Adjacent Terrestrial Ecosystems\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe calculated area available for restoration only within a targeted subset of the HVFE delineation described above, based on biome, HVFE class, delineation scenario, and land use/land cover. These criteria are in place to avoid afforestation. We only considered areas within forest biomes, as defined by RESOLVE 2017 vector dataset\u003csup\u003e42\u003c/sup\u003e, to be available for reforestation. Within forest biomes,\u0026nbsp;we used three HVFE classes included in both the minimum and maximum delineation scenarios: headwater regions, fixed-width buffers around low-order streams, and fixed-width buffers around surface water bodies and high-order streams. In the maximum scenario, we additionally incorporated geomorphic floodplains, bringing the total to four HVFE classes used in the analysis. Finally, within these geographic criteria, we considered degraded or deforested areas as available for restoration, i.e. croplands and short vegetation classes from\u0026nbsp;Potapov et al.\u0026nbsp;\u003csup\u003e43\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ee) Carbon Removals from Restoration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe estimated carbon removals from restoring croplands and short vegetation using carbon accumulation rates from the first 30 years of natural forest regeneration, as mapped globally by Cook-Patton et al.\u003csup\u003e44\u003c/sup\u003e. This study modelled aboveground carbon accumulation rates globally at ~1km\u003csup\u003e2\u003c/sup\u003e (at the equator) resolution using 13,000+ field observations and a suite of environmental variables to predict rates of carbon accumulation per hectare per year up to 30 years.\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp;We adjusted the carbon accumulation rates for the headwater regions and fixed-width buffer around low-order streams in the minimum scenario (without floodplain) by multiplying them by the maximum optimal tree cover percentage in agricultural lands, as estimated by\u0026nbsp;Sprenkle-Hyppolite\u0026nbsp;et al.\u003csup\u003e45\u003c/sup\u003e. This adjustment was applied specifically to the minimum scenario to reflect minimal impact on agricultural production. These values were derived through an expert-elicitation process, identifying maximum tree cover thresholds for 53 regional cropping and grazing systems that safeguard agricultural yields\u003csup\u003e45\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eFollowing this adjustment to the carbon accumulation rates, we calculated summary statistics using Google Earth Engine (see Code Availability). Country-level and global totals were derived by multiplying the modified carbon accumulation layer by pixel area, converting the units from Mg C ha\u003csup\u003e-1\u003c/sup\u003e yr\u003csup\u003e-1\u003c/sup\u003e to Mg C pixel\u003csup\u003e-1\u003c/sup\u003e yr\u003csup\u003e-1\u003c/sup\u003e. This enabled a straightforward summation of pixel values to estimate national and global carbon accumulation. Although the analysis was conducted in units of carbon, results are reported in terms of carbon dioxide by applying a molecular weight conversion factor of 44/12 (CO₂/C).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe global HVFEs maps, delineated under both minimum and maximum scenarios at 30-meter resolution, are available on Zenodo (https://doi.org/10.5281/zenodo.15338535).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Python code used to generate the global HVFEs map and to produce country-level freshwater and carbon estimates is accessible at https://github.com/MahyaSad/Global-High-Value-Freshwater-Ecosystem. Code development was conducted primarily in Python (v3.9.15; https://www.python.org/) for HVFEs mapping, freshwater analysis, and figure generation. Carbon estimation was performed using Google Earth Engine (https://earthengine.google.com/).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported in part by the NASA Applied Sciences Program, Conservation International, and Khalifa University Award number 001092-00001. Any opinions, findings, conclusions or recommendations expressed in this work are those of the author(s) and do not necessarily reflect the views of NASA, Conservation International, or Khalifa University. We would like to thank Robin Abell, Derek Vollmer, and Ian Harrison for their feedback on early concepts leading to development of this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMahya G.Z Hashemi, Kashif Shaad, Ibrahim Nourein Mohammed, John D. Bolten, Ma\u0026iacute;ra Ometto Bezerra, Vivian Griffey, and Starry Sprenkle-Hyppolite conceptualized the study. Mahya G.Z Hashemi developed the HVFE\u0026rsquo;s maps. Mahya G.Z Hashemi, Kashif Shaad, and Vivian Griffey designed and carried out the statistical analyses. Mahya G.Z Hashemi, Kashif Shaad and Vivian Griffey designed the visual materials and co-wrote the paper. All authors reviewed, edited and contributed to the discussion.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLynch, A. J. \u003cem\u003eet al.\u003c/em\u003e People need freshwater biodiversity. \u003cem\u003eWIREs Water\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, e1633 (2023).\u003c/li\u003e\n\u003cli\u003eDamania, R., Desbureaux, S., Rodella, A.-S., Russ, J. \u0026amp; Zaveri, E. \u003cem\u003eQuality Unknown: The Invisible Water Crisis\u003c/em\u003e. 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Most national climate commitments lack clear, spatially defined targets for protecting and restoring these critical systems.\u003c/p\u003e \u003cp\u003eTo address this gap, we developed a global map of high-value freshwater ecosystems based on 30-meter land cover data, hydrological networks, and global floodplain models, and identified country-level pathways for climate adaptation and mitigation through nature-based solutions. Here we show that these ecosystems cover over 51\u0026nbsp;million square kilometers globally, highlighting major opportunities to reduce flood risk, protect freshwater resources, and strengthen ecological resilience through targeted protection and restoration. Our analysis indicates that restoring degraded croplands and short vegetation within these areas could sequester between 1.07 and 3.41 gigatonnes of carbon dioxide each year, across 355 to 484\u0026nbsp;million hectares, depending on the restoration scenario. Nearly half of this mitigation potential lies within the 49 countries committed to the Freshwater Challenge.\u003c/p\u003e \u003cp\u003eThese results provide a practical foundation for integrating freshwater ecosystems into national climate strategies and further demonstrate how place-based interventions can align global climate goals with regional freshwater protection targets, advancing efforts to adapt to and mitigate climate change.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Aspiration to action: Opportunities to align freshwater ecosystems with climate actions","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-26 07:27:07","doi":"10.21203/rs.3.rs-6626566/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-water","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"natwater","sideBox":"Learn more about [Nature Water](https://www.nature.com/natwater/)","snPcode":"44221","submissionUrl":"https://mts-natwater.nature.com/cgi-bin/main.plex","title":"Nature Water","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Research","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"1b785231-4174-42c5-a394-b4812e762a59","owner":[],"postedDate":"May 26th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":48908684,"name":"Scientific community and society/Water resources"},{"id":48908685,"name":"Earth and environmental sciences/Environmental sciences"}],"tags":[],"updatedAt":"2026-01-30T08:13:36+00:00","versionOfRecord":{"articleIdentity":"rs-6626566","link":"https://doi.org/10.1038/s44221-025-00573-x","journal":{"identity":"nature-water","isVorOnly":false,"title":"Nature Water"},"publishedOn":"2026-01-29 05:00:00","publishedOnDateReadable":"January 29th, 2026"},"versionCreatedAt":"2025-05-26 07:27:07","video":"","vorDoi":"10.1038/s44221-025-00573-x","vorDoiUrl":"https://doi.org/10.1038/s44221-025-00573-x","workflowStages":[]},"version":"v1","identity":"rs-6626566","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6626566","identity":"rs-6626566","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}