International Union for Conservation of Nature Extinction Analysis

Accounts of all 785 species listed as "extinct" were downloaded from the International Union for Conservation of Nature database (www. iucnredlist.org) in November 2007. Those species comprising the terres trial vertebrate groups (birds, mammals, reptiles, and amphibians; 258 species) and plants (87 species) were considered further. Species accounts were used to classify each species as being from a mainland or an island. Only species restricted to islands were listed as ''island'' species. Included in these tallies are three marine mammals, which we listed as ''mainland'' for the purposes of these analyses. Species accounts were also used to tally the factors listed as having contributed to species extinction. To do so, both the annotated list of contributing factors, and the text description were examined for each species. We classified extinction factors into three categories: predation, competition, and other factors. Predation includes pair-wise species interactions that are positive for one species and negative for the other; this included any of the following: human hunting (including any form of direct human exploitation of a species), carnivorous predation, herbivorous predation, parasitism, and infectious disease. ''Competition'' included interactions where species competed for resources. All other factors, such as habitat loss and pollution, were considered to be ''other factors.'' Tallies were compiled for species listed as (i) only being impacted by predation, (ii) impacted by predation together with other factors, and (iii) impacted by competition together with other factors. In no case was competition listed as the sole factor causing a species extinction. These same tallies were repeated for the subset of extinct species listed as having been impacted by an ''alien,'' i.e., nonnative or exotic, species.

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