Insular biogeography is a field within
biogeography that examines the factors that affect the
species richness of isolated natural communities. The theory was originally developed as
island biogeography, to explain species richness of actual islands, principally oceanic. Under either name it is now used in reference to any ecosystem (present or past) that is isolated due to being surrounded by unlike ecosystems, and has been extended to mountain peaks,
oases, fragmented forest, and even natural habitats isolated by human land development. The field was started in the 1960s by the ecologists
Robert H. MacArthur and
E. O. Wilson, who coined the term
island biogeography in their theory, which attempted to predict the number of species that would exist on a newly created island.