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Figure 3.3. Species Extinction Rates(Adapted from C4 Fig 4.22) "Distant past" refers to average extinction rates as calculated from the fossil record. "Recent past" refers to extinction rates calculated from known extinctions of species (lower estimate) or known extinctions plus "possibly extinct" species (upper bound). A species is considered to be "possibly extinct" if it is believed to be extinct by experts but extensive surveys have not yet been undertaken to confirm its disappearance. "Future" extinctions are model-derived estimates using a variety of techniques, including species-area models, rates at which species are shifting to increasingly more threatened categories, extinction probabilities associated with the IUCN categories of threat, impacts of projected habitat loss on species currently threatened with habitat loss, and correlation of species loss with energy consumption. The time frame and species groups involved differ among the "future" estimates, but in general refer to either future loss of species based on the level of threat that exists today or current and future loss of species as a result of habitat changes taking place roughly from 1970 to 2050. Estimates based on the fossil record are low certainty. The lower-bound estimates for known extinctions are high certainty, while the upper-bound estimates are medium certainty; lower-bound estimates for modeled extinctions are low certainty, and upper-bound estimates are speculative.  Source: Millennium Ecosystem Assessment |
