Home to 25 of the world’s 34 biodiversity hotspots and 1.2 billion people, mountain ecosystems are warming faster than lowland regions — pushing species uphill at a pace five times faster than half a century ago.
Mountains cover roughly 27% of Earth's land surface and encompass an outsized share of global biodiversity: 25 of the world's 34 recognized biodiversity hotspots and 30% of all Key Biodiversity Areas are found in mountain regions, which also supply water and support the livelihoods of an estimated 1.2 billion people.
High mountain regions are warming faster than lower elevations in a well-documented pattern known as elevation-dependent warming, with declining frost days, retreating glaciers, and shorter snow-cover seasons recorded across multiple mountain ranges.
Source: Oxford Research Encyclopedia of Climate Science; multiple regional studies, 2025Lower-elevation species are colonizing mountain summit habitats at an accelerating rate — approximately five times faster than observed half a century ago — as warming allows species to survive at altitudes previously too cold, squeezing high-altitude specialists into an ever-shrinking band of suitable habitat near the summit.
Mountain species have limited options when their climate zone shifts upslope — once a species reaches the summit, there is nowhere higher to go. This makes mountain ecosystems a particularly stark illustration of climate change's "nowhere left to run" dynamic for range-restricted species.
Long-term, high-resolution monitoring of species range shifts exists mainly for well-studied ranges such as the Alps and parts of the Rockies; equivalent long-term data is sparser for many biodiversity-rich tropical mountain ranges, including parts of the Andes and the Himalayas.