Disproportionate low-elevation forest loss in over 65% of the world’s mountains calls for targeted conservation

Forest loss is a leading threat to global biodiversity. For many mountains worldwide, forest loss appears to occur disproportionately at lower elevations. This pattern—if confirmed—means widespread loss and scarcity of lower-elevation forest habitat, with profound biodiversity implications within and beyond these elevations. However, there remains no global assessment of this pattern based on robustly mapped forest loss, crucially by disentangling forest loss from the natural absence of forest. We fill this gap and demonstrate disproportionate forest loss at lower elevations for >65% of all 769 mountains in the world’s forested ecoregions that we assessed. We find a clear lack of lower-elevation forest—most of which remains unprotected—and associated warmer and drier climatic conditions, explainable by high human impacts and low precipitation at these elevations. Our findings call for targeted forest protection and restoration at lower elevations for mountains worldwide, including integrated mountain-scale conservation planning for entire elevational gradients.