Global assessments of mountain forest loss in the early 21st century

Mountains are diverse and ecologically fragile areas that serve as critical refuges of biodiversity and water towers for lowland population centres. They are often perceived as facing limited deforestation given their complex and rugged terrain. In this context, loss of mountain forest imposes a distinct and pronounced set of impacts, and knowing the locations, trends, magnitude, and drivers of mountain forest loss is essential to appropriately guide conservation strategies and priorities. Here, we combine state-of-the-art datasets of global forest change and mountain topography to provide the first global assessment of the spatiotemporal patterns and drivers of mountain forest loss. We find mountain forest loss has accelerated significantly during 2001-2018, with the most recent loss being 2.7 times greater than that in the early 2000s. The greatest losses and acceleration of montane forest loss are in the tropics, largely overlapping the areas with high biodiversity. Specifically, the five countries with the largest mountain forest loss in mountain biodiversity hotspots are Indonesia, Malaysia, Madagascar, Vietnam, and Colombia. Mountain forest loss in these regions was primarily driven by deforestation for commodities and shifting agriculture. In addition, we find that even in protected areas, forest loss is increasing significantly. Our high-resolution analyses of mountain forest loss capture localized dynamics to produce far more accurate estimates of loss, which have the potential to improve biophysical climate impact models and global carbon budgets.