Addressing critiques refines global estimates of reforestation potential for climate change mitigation

Background

Reforestation is a key natural climate solution for carbon dioxide removal, offering large-scale and cost-effective mitigation potential. However, previous global maps estimating reforestation opportunities have faced major critiques concerning definitions, data quality, and safeguards. Many overestimated forest potential by including non-forest ecosystems such as savannas and fire-adapted biomes, ignored socioeconomic constraints like land tenure and food security, or used outdated data. These limitations created uncertainty about the true extent and distribution of reforestation opportunities. To address these gaps, this research refines global reforestation potential using updated datasets, conservative forest definitions, and multiple sustainability safeguards.

Goals and Methods

This study aims to produce credible, policy-relevant global estimates of reforestation potential that integrate ecological, social, and methodological concerns. The authors reviewed 89 reforestation maps from 2011–2022 to identify recurring weaknesses. They then created new global maps using high-resolution datasets and applied multi-layered exclusions for existing forests, croplands, peatlands, and frequently burned areas to identify feasible reforestation zones. Eight scenarios were developed, representing different objectives such as climate mitigation, ecosystem services, and social safeguards. Additional overlays—land tenure security, biodiversity importance, and conflict risk—helped contextualize opportunities. Mitigation potential was over a 30-year regrowth period, incorporating albedo effects and spatial additionality (forest loss-to-gain ratios).

Conclusions and Takeaways

By addressing prior critiques, this study revises global reforestation potential to 195 million hectares (Mha)—a 71–92% reduction from earlier estimates—equivalent to 2,225 TgCO₂e per year, about 5% of annual global emissions. Despite this reduction, reforestation remains the largest natural carbon removal pathway. The authors emphasize avoiding ecologically unsuitable regions and prioritizing lands with secure tenure and low conflict risk. Limited overlap among objectives such as carbon storage and biodiversity highlights the need for context-specific strategies. The study advocates for transparent, conservative, and reproducible mapping to inform equitable and realistic climate policies, emphasizing that global estimates should complement localized, socially informed analyses.