China's mangrove expansion boosts avian diversity.

Over the past half-century, ∼1/3 of global mangroves have been lost. To comply with international conventions, China implemented targeted mangrove restoration policies, but their effects on ecosystem functions against the backdrop of climate change remain unclear. Our study used bird diversity (a key ecological proxy) to examine whether policy-driven mangrove expansion had promoted such functions. Results showed that China's mangrove area increased by 166% over the past three decades (1998-2020). Bird diversity correlated strongly with mangrove area and coverage. The number of threatened species on the IUCN Red List increased by 91%. Climate change promoted the expansion of mangroves. Mechanistically, mangrove expansion improved marine quality, regulated phytoplankton, and synergized with climate change, boosting avian diversity. China's mangrove protection policies have effectively facilitated mangrove restoration, which in turn has enhanced bird diversity by improving marine habitat conditions. Our findings confirm policy effectiveness, validate the restoration feasibility of coastal ecosystems, and inform global coastal restoration.