Landscape-scale benefits of protected areas for tropical biodiversity

The United Nations recently agreed to major expansions of global protected areas (PAs) to slow biodiversity declines. But while reserves often reduce habitat loss, their efficacy at preserving animal diversity is unclear, as is their influence on biodiversity in surrounding unprotected areas. Unregulated hunting can empty PAs of larger animals, illegal tree felling can degrade habitat quality, and parks can simply displace disturbances such as logging and hunting to unprotected areas of the landscape (‘leakage’). Alternatively, well-functioning PAs could enhance animal diversity within reserves as well as in nearby unprotected sites (‘spillover’). Here we test if PAs across mega-diverse Southeast Asia contribute to vertebrate conservation inside and outside their boundaries. Reserves increased all facets of bird diversity. Large reserves also had substantially enhanced mammal diversity in the adjacent unprotected landscape. Rather than PAs generating leakage that deteriorated ecological conditions elsewhere, our results are consistent with PAs inducing spillover that benefits biodiversity in surrounding areas. These findings support the 2030 United Nations goals of achieving 30% PA coverage by demonstrating that protected areas are associated with higher vertebrate diversity both inside their boundaries and in the broader landscape.