Quantifying the Extent of North American Mammal Extinction Relative to the Pre-Anthropogenic Baseline

• DOI: 10.1371/journal.pone.0008331
• Publication Date: 2009-12-15T22:48:47Z
• Authors: Marc A. Carrasco; Anthony D. Barnosky; Russell W. Graham
• Keywords: Mammal; Extinction (optical mineralogy); Biota; Baseline (sea)

Earth has experienced five major extinction events in the past 450 million years. Many scientists suggest we are now witnessing a sixth, driven by human impacts. However, it been difficult to quantify real extent of current episode, either for given taxonomic group at continental scale or worldwide biota, largely because comparisons pre-anthropogenic and anthropogenic biodiversity baselines have unavailable. Here, compute those mammals temperate North America, using sampling-standardized rich fossil record reconstruct species-area relationships series time slices ranging from 30 500 years ago. We show that shortly after humans first arrived mammalian diversity dropped become least 15%–42% too low compared “normal” baseline had existed millions While Holocene reduction American mammal long recognized qualitatively, our results provide quantitative measure clarifies how significant actually was. If mass extinctions defined as loss 75% species on global scale, data already progressed one-fifth more than halfway (depending biogeographic province) towards benchmark, even before industrialized society began affect them. Data currently not available make similar estimates other continents, but qualitative declines also widely South Eurasia, Australia. Extending methodology these areas, well taxa where possible, would reasonable way assess magnitude extinction, impact threatened species, efficacy conservation efforts into future.