Sky island

A sky island is an isolated mountain or highland that rises out of lowlands whose environment is radically different, such as a forested peak standing above a surrounding desert. The term first described mountains on the Mexican Plateau and was later stretched to any similarly cut-off, high-elevation forest. Separation by physical distance from other ranges is the defining element, and it has biological consequences: endemic species, altitudinal migration and relict populations are all typical. Some sky islands act as refuges for cool-climate species left stranded as the climate warmed after the last glacial period, while on others isolated populations drift toward becoming new species, much as on oceanic islands. The idea draws on island biogeography and matters to conservation biology, and it can be applied to mountains, highlands and massifs worldwide.