Sky islands are isolated mountain ranges found across many disconnected regions worldwide (the Madrean Archipelago, East African and other ranges across the Afrotropical, Australasian, Indomalayan, Nearctic, Neotropical and Palearctic realms), each with its own extent; this atlas's own cited Wikipedia article lists numerous examples by realm and gives individual elevation figures but no aggregate area measurement anywhere in the text, since the concept describes a pattern of isolation rather than one bounded region.
What would resolve this An authoritative global inventory listing every recognized sky island range with its own area, summed under one consistent definition of what counts as a sky island.
OpenBiogeographySky Island (Wikipedia)