Land availability and policy commitments limit global climate mitigation from forestation

Background

This research examines the global potential of forestation (both afforestation and reforestation) as a climate mitigation strategy through carbon sequestration in biomass and soil. Forests offer vital ecosystem services and carbon storage functions, yet widespread deforestation and degradation persist, particularly in tropical and boreal regions. Previous studies have produced inconsistent global estimates of forestation’s mitigation potential, primarily due to uncertainty in soil carbon dynamics and overestimation of available land. Many assessments also neglected biophysical and ecological constraints such as albedo-induced warming, water stress, and biodiversity loss. Consequently, the true contribution of forestation to achieving global carbon neutrality goals under the Paris Agreement remains unclear, highlighting the need for an integrated, evidence-based global assessment.

Goals and Methods

This study aims to refine global estimates of forestation’s carbon mitigation potential by jointly assessing soil and biomass carbon dynamics, accounting for realistic land availability, and considering national policy commitments. The authors developed a machine learning model (mSOC) using 1,595 paired soil observations across diverse forest types to quantify soil organic carbon changes after forestation. Combined with existing biomass carbon data, global carbon sequestration rates were mapped for 2021–2050. Land availability was assessed using a newly developed dataset (“Qin24”), which excludes areas with biodiversity, water, or albedo conflicts. The study also compared “potential,” “committed,” and “achievable” forestation areas to analyze the gap between global biophysical supply and policy-driven demand.

Conclusions and Takeaways

The findings of this study reveal that the realistic global land availability for forestation is only approximately 389 million hectares, capable of sequestering 39.9 petagrams (Pg) of carbon by 2050, which is far below earlier projections. When restricted to lands within existing policy commitments, the achievable sequestration drops to 12.5 Pg C, with 95% of this potential located in low- and middle-income countries. The study emphasizes that rapid, ambitious, and well-coordinated forestation actions could substantially enhance global mitigation outcomes. However, success depends on equitable financing, stronger policy commitments, and alignment of national pledges with ecological and social realities. The authors conclude that forestation can be an important natural climate solution, but land constraints and uneven political will limit its global impact; protecting existing forests remains equally crucial for meeting net-zero goals.