Accelerating global mountain forest loss threatens biodiversity hotspots

The frontier of forest loss has encroached into mountains in some regions. However, the global distribution of forest loss in mountain areas, which are home to >85% of the world’s birds, mammals, and amphibians, is uncertain. Here we combine multiple datasets, including global forest change and selected species distributions, to examine spatiotemporal patterns, drivers, and impacts of mountain forest loss. We find 78 Mha of montane forest was lost during 2001–2018 and annual loss accelerated significantly, with recent losses being 2.7-fold greater than those at the beginning of the century. Key drivers of mountain forest loss include commercial forestry, agriculture, and wildfire. Areas with the greatest forest loss overlap with important tropical biodiversity hotspots. Our results indicate protected areas within mountain biodiversity hotspots experienced lower loss rates than their surroundings. Increasing the area of protection in mountains should be central to preserving montane forests and biodiversity in the future.