Land availability and policy commitments limit global climate mitigation from forestation

Forestation is often promoted as a major climate solution, yet its true mitigation potential remains uncertain. Using global maps of soil‑carbon change, this study shows that most carbon gains occur in topsoil and that realistic land‑availability constraints sharply reduce global sequestration potential. When limiting forestation to land that avoids albedo‑driven warming and protects water and biodiversity, only 389 million hectares remain—sequestering 39.9 Pg C by 2050, far below earlier estimates. Restricting land further to existing policy commitments drops potential to 12.5 Pg C. Achieving greater mitigation will require expanding dedicated forestation areas and stronger national commitments, especially in regions with large untapped potential.