Afforestation and Reforestation Have Varying Biodiversity Impacts Across and Within Biomes

Background

Afforestation and reforestation (AR) are widely promoted as nature-based solutions (NbS) for carbon dioxide removal and climate mitigation. Global initiatives aim to expand forest cover significantly to meet climate targets. However, AR can produce unintended biodiversity impacts, particularly when implemented in ecosystems such as grasslands or savannas, where native species are not adapted to forest conditions. The ecological outcomes of AR vary across biomes and species, highlighting the need for spatially explicit, biodiversity-sensitive planning frameworks.

Goals and Methods

This study develops a global framework to assess the trade-offs between carbon sequestration and biodiversity under AR. Using the AIM-BIO species distribution model, the research evaluates habitat suitability for more than 1500 species across multiple taxonomic groups. Species responses to forest expansion are classified as favorable or unfavorable. A Zonation-based spatial prioritization approach generates habitat suitability indices, which are combined with carbon sequestration potential under future climate scenarios. The analysis spans multiple time horizons and global terrestrial biomes.

Conclusions and Takeaways

This study finds that AR impacts on biodiversity vary significantly across and within biomes. Tropical forests often offer synergies between carbon storage and biodiversity, while grasslands and savannas face higher ecological risks. The results emphasize that poorly planned AR can harm biodiversity despite climate benefits. Practitioners should adopt biome-specific strategies and prioritize restoration over indiscriminate tree planting. This framework provides a decision-support tool to align climate mitigation with biodiversity conservation. Future research should refine spatial prioritization and integrate socioeconomic considerations into AR planning.