Secondary forest fragments offer important carbon‐biodiversity co‐benefits

Tropical forests store large amounts of carbon and high biodiversity, but are being degraded at alarming rates. The emerging global Forest and Landscape Restoration (FLR) agenda seeks to limit global climate change by removing carbon dioxide from the atmosphere through the growth of trees. In doing so, it may also protect biodiversity as a free co‐benefit, which is vital given the massive shortfall in funding for biodiversity conservation. We investigated whether natural forest regeneration on abandoned pastureland offers such co‐benefits, focusing for the first time on the recovery of taxonomic, phylogenetic and functional diversity of trees, including the recovery of threatened and endemic species richness, within isolated secondary forest fragments. We focused on the globally threatened Brazilian Atlantic Forest, where commitments have been made to restore one million hectares under FLR. Three decades after land abandonment, regenerating forests had recovered ~20% (72 Mg/ha−1) of the above‐ground carbon stocks of a primary forest, with cattle pasture containing just 3% of stocks relative to primary forests. Over this period, secondary forest recovered ~76% of taxonomic, 84% of phylogenetic and 96% of functional diversity found within primary forests. In addition, secondary forests had on average recovered 65% of threatened and ~30% of endemic species richness of primary Atlantic forest. Finally, we find positive relationships between carbon stock and tree diversity recovery. Our results emphasize that secondary forest fragments offer co‐benefits under FLR and other carbon‐based payments for ecosystem service schemes (e.g. carbon enhancements under REDD +). They also indicate that even isolated patches of secondary forest could help to mitigate climate change and the biodiversity extinction crisis by recovering species of high conservation concern and improving landscape connectivity