Accounting for albedo to identify climate positive tree cover restoration

Abstract Restoring tree cover is a prominent natural climate solution1–3, but can decrease albedo and lead to global warming in some places4–10. Existing assessments of the mitigation potential from restoring tree cover 2,3,11,12 poorly account for albedo due to a lack of spatial data. Here we produce a global 500-m map that incorporates albedo and maximum carbon storage to quantify the net climate impact (CO2e) of restoring tree cover. We find that albedo offsets some of the carbon storage benefit across most of the globe. Contrary to prior work, albedo is not of greatest concern in boreal forests. Rather, arid biomes have a greater proportion of net negative climate areas (e.g., 61% in temperate savanna versus 10% in boreal forests). Accounting for albedo across previously published opportunity maps reduces total maximum CO2e by up to 37%. However, the magnitude of the offset varies substantially across the landscape, highlighting the importance of spatially refined estimates. Encouragingly, on-the-ground projects to restore tree cover are concentrated in climate-positive areas, but the majority (64%) still face a minimum 10% albedo offset. Thus, strategically deploying restoration of tree cover for maximum climate benefit requires accounting for albedo, and the maps herein facilitate this.