The storage effect is a coexistence mechanism proposed in the ecological theory of species coexistence, which tries to explain how such a wide variety of similar species are able to coexist within the same ecological community or guild. The storage effect was originally proposed in the 1980s[1] to explain coexistence in diverse communities of coral reef fish, however it has since been generalized to cover a variety of ecological communities.[2][3][4] The theory proposes one way for multiple species to coexist: in a changing environment, no species can be the best under all conditions.[5] Instead, each species must have a unique response to varying environmental conditions, and a way of buffering against the effects of bad years.[5] The storage effect gets its name because each population "stores" the gains in good years or microhabitats (patches) to help it survive population losses in bad years or patches.[1] One strength of this theory is that, unlike most coexistence mechanisms, the storage effect can be measured and quantified, with units of per-capita growth rate (offspring per adult per generation).[5]
The storage effect can be caused by both temporal and spatial variation. The temporal storage effect (often referred to as simply "the storage effect") occurs when species benefit from changes in year-to-year environmental patterns,[1] while the spatial storage effect occurs when species benefit from variation in microhabitats across a landscape.[6]