Extinction debt: origins, developments, and applications of a biogeographical trope

The concept of the extinction debt has two components: a direct timelag between an environmental perturbation and the consequent extinction of a species and the idea that among species going extinct the strong competitors/weak colonizers go extinct first. Although the term was first used in 1994 in the context of metapopulation models, its roots go back to general systems theory and the theory of island biogeography. It has been qualified and elaborated since 1994, mostly in terms of the effects of spatial pattern on the outcomes. The strongest critiques of the concept emphasize that the direct trade-off between competition and colonization abilities is not simple. The original application was to remnant habitat patches, but it could be applied to spatially heterogeneous habitats that are subject to climate change or invasive species. As a guide to conservation practice, extinction debt remains a general cautionary principle rather than a specific prescription, but the raising of awareness is nevertheless significant.