Global variation in the costs and ecological benefits of tropical natural regeneration

Natural regeneration is a cost-effective alternative to manual tree planting for restoring degraded and converted tropical forests, which contributes to climate mitigation and biodiversity recovery. However, global variation in its costs and benefits remain poorly quantified, limiting the ability of restoration programmes to strategically leverage its full potential. Here, we assess variation in costs and ecological benefits for the 9.85 million km² with biophysical potential for natural forest regeneration across the tropics. If completely regenerated, this additional forested area could accumulate approximately 1.01 Gt C per year and expand the available distribution of threatened species by 12.89% over 30 years. We show that Indonesia, Malaysia, Thailand, Vietnam and Laos have the largest areas with potential for high carbon and biodiversity benefits at low costs, which we refer to as ‘holistic hotspots’ for natural regeneration. We find that patterns for cost-effective potential for natural regeneration areas with either high carbon or biodiversity benefits differ from those of holistic hotspots. These tradeoffs in achieving both benefits reduce the area of holistic hotspots to only 3.21% of the entire study region. The cost-benefit maps we provide can enable decision-makers to improve their spatial planning and investing approaches to achieve their forest restoration goals.