Mongabay: The Theory of Island Biogeography, coined by Robert MacArthur and E.O. Wilson, helps describe why species are distributed as they are. The larger and closer an island is to another (or to the mainland), the more biodiverse it should be. This can be used to describe actual islands in the ocean, like the Galapagos, or even mountaintops, like the Madrean Sky Islands in southern Arizona and New Mexico.
In human-dominated countryside areas, forests are often fragmented and scattered among a matrix...