Equilibrium theory of island biogeography

The Theory of Island Biogeography perceives the number of species found in a habitat patch to be a function of immigration and extinction (Scannlan, 1981). Where immigration rate is inversely proportional to the distance of a patch (island) from its source regions and extinction rate is thought to decline with increasing area of an island.

The 'Theory' was originally applied to oceanic islands but was thought to be equally applicable to terrestrial habitat islands (patches of habitat surrounded by less favourable habitat). This approach has been used to understand effects of habitat fragmentation.