Synergies and trade-offs between tree cover expansion efforts within and outside forests to achieve climate, biodiversity and human well-being outcomes

This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. Increasing tree cover is hailed as a leading climate mitigation strategy, yet there is increasing evidence that there may be trade-offs between trees in different parts of the landscape. Existing science, policy, and practice on natural climate solutions (NCS) assumes that trees outside of forests, for example on farms, homesteads, or in urban areas, are synergistic with forest conservation: if people have more access to trees outside forests, the thinking goes, they will use fewer trees in the forest, leading to forest conservation. However, recent evidence shows that trees inside and outside forests often serve different purposes and produce different ecological, social or economic outcomes. As a result, in many contexts trees outside of forests do not necessarily substitute for trees inside of forests, and in some circumstances, an increase in trees outside of forests could even contribute to forest loss. In this perspective, we review the existing evidence on dynamics and trade-offs of trees inside and outside forests to describe pathways that lead to trade-offs and synergies and identify critical research gaps that, if addressed, can inform the implementation of ecosystem restoration and climate mitigation programs and policies. These diverse pathways are not widely recognized in science, policy, or practice, leading to potentially unproductive policy investments and leaving significant research gaps that we identify in this paper. Additionally, there is a risk that tree planting programs that are not cognizant of potential trade-offs may have negative repercussions for forest conservation, biodiversity, carbon storage, and rural livelihoods. Recognizing pathways that lead to negative outcomes, and identifying research gaps that could anticipate or prevent such negative outcomes will help scientists, policymakers and practitioners move forward with more effective NCS. https://doi.org/10.32942/X2H089 Biodiversity, Environmental Studies, Nature and Society Relations, Other Forestry and Forest Sciences, Physical and Environmental Geography, Remote Sensing afforestation, trees outside forests, forest, tree planting, forest restoration, tree plantingforest restoration Published: 2026-03-23 04:38 CC-By Attribution-NonCommercial-NoDerivatives 4.0 International Conflict of interest statement: None Data and Code Availability Statement: Visualizations were created using data in the public domain Language: English