Species-Area Math

Species-Area Math

There is a fairly simple formula (known as the species-area relationship) for calculating the number of species an isolated area should have:

where S is the number of species on the island or isolated patch, and C and Z are constants that depend on the type of ecosystem (tropical vs. temperate, dry vs. moist, etc.) and the type of species involved (birds, insects, etc.). Z values range from 0.15 to 0.35, while C varies depending on the diversity of the group (insects will have a much higher C value than birds).

This model is also used to estimate how many species go extinct when habitat is lost. Since the relationship is logarithmic and not linear, a 10% reduction on habitat does not result in a 10% extinction of species. The rough estimates are for a 50% reduction of habitat a 10% loss of species and for a 90% reduction of habitat, a 50% loss of species. Thus if only 10% of the planet's natural habitat left intact, we can expect half of the world's species to go extinct.