Many mountain ecosystems are host to higher species richness and levels of endemism than adjacent lowlands. Mountains at lower altitudes can support exceptional biodiversity, due to compression of a wide range of ecosystems into a relatively short distance. Mountains also often provide islands of suitable habitat, isolated from unfavourable surrounding lowlands.

Endemism levels are often high, particularly on mountains at medium elevations in the tropics and warmer temperate zones. For some taxa, mountains have acted as refuges from environmental change or competing species, and they often represent sites of in situ speciation. Mountain species with narrow habitat tolerance, particularly higher elevation forms and those with low dispersal capacity, are at high risk from the environmental effects of climate change. Slope dynamics and livestock grazing are significant drivers of diversity in many alpine regions. Flower-rich alpine meadows are an important cultural heritage that is increasingly threatened as traditional grazing practices decline.