The roles of climate mitigation, sustainable land use and area-based conservation in curbing future biodiversity loss

Biodiversity loss is a pressing global challenge. Protected Areas (PAs) are crucial measures to curb species and ecosystem declines, yet their long-term ecological effectiveness amid future climate and land use changes remains uncertain. Here, we assess future biodiversity changes under different climate, land use, and PA expansion scenarios for 13908 terrestrial vertebrate species. Three PA scenarios (no explicit PA, current 17% coverage, and a 30% target) are investigated alongside two climate and socioeconomic scenarios; the “sustainability” (SSP1-RCP2.6) and the “inequality” scenario (SSP4-RCP6.0). The results show that sustainable land use is the biggest lever in preventing future biodiversity decline, with a projected avoided species richness loss of 7.9-8.6% by 2080, compared to avoided loss of PA expansion (0.9-4.5%). PAs provide an additional but smaller contribution to avoided species richness loss, particularly under the “inequality” scenario, showing the need for PA expansion under unsustainable climate and land use policies. Birds and mammals benefit most from PA expansion. We conclude that expanding PAs supports biodiversity but integrating them with broader climate and land use policies is crucial.