Future climate and land use change will equally impact global terrestrial vertebrate diversity

Aim: Terrestrial biodiversity is impacted by both climate and land use change. Yet, future biodiversity projections have rarely considered these two drivers in combination. In this study, we aim to assess the individual and combined impact of future climate and land use change on global terrestrial vertebrate diversity under a "sustainability" (SSP1-RCP2.6) and an "inequality" (SSP4-RCP6.0) scenario. Location: Global land, excluding Antarctica. Time period: 1995, 2080 Major taxa studied: Amphibians, birds, and mammals. Methods: We combined global climate-driven species distribution model (SDM) projections of 13903 vertebrates (amphibians, birds, and mammals) with future and present land use projections from the Land Use Harmonization 2 (LUH2) project. We refined the SDM outputs by the habitat requirements of each species using a land use filtering approach. We then analyzed future species richness changes globally, per region, and per land use category, and looked at taxon-specific effects. Results: Under both scenarios, decreases in future species richness dominate at low and mid-latitudes, with climate and land use change playing an equally important role. Land use change can be either an alleviating (SSP1-RCP2.6) or an exacerbating (SSP4-RCP6.0) factor of climate-induced biodiversity loss. Sub-Saharan Africa is projected to become a high-risk area for future land use-driven biodiversity loss under the SSP4-RCP6.0. Under SSP1-RCP2.6, forested and non-forested land areas increase, while SSP4-RCP6.0 leads to higher rates of deforestation and pasture expansion. Mammals experience the largest climate-driven losses, affecting 56.4% of land area under SSP4-RCP6.0, while amphibians are particularly vulnerable to land use-driven losses, especially under SSP4-RCP6.0. Main conclusions: Our results suggest that both climate and land use pressures on biodiversity will be highest in lower latitudes, which harbor the highest levels of biodiversity.