Protect young secondary forests for optimum carbon removal

Abstract Meeting global climate commitments and avoiding severe global warming requires drastic reductions in emissions and large-scale removals of atmospheric carbon dioxide1. Forest regrowth offers scalable and cost-effective carbon removal,2,3 but rates vary substantially by location and age of forest stand4,5. Here we generate pixel level (~1-km2) Chapman-Richards growth curves for aboveground carbon accumulation in naturally regrowing forests, based on 109,708 field estimates and 66 environmental covariates. Across the globe and over the first 100 years of growth, maximum carbon removal rates varied 160-fold demonstrating the need for spatially and temporally refined estimates. Tropical and subtropical moist broadleaf forests, and some temperate forest areas, exhibited the highest rates at young stand ages, suggesting that newly regrowing forests in these areas can provide the largest and most timely carbon removal. However, overall removal rates were greatest in ~20 to 40 year old forests. Thus. during the next climate critical decades, protecting secondary forests can provide greater carbon removal per hectare than new regrowth (up to 8-fold more). These data help optimize natural forest regrowth as a carbon removal strategy and improve estimates of secondary forests’ contribution to global carbon cycling.