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Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines

  1. Rodolfo Dirzob
  1. aInstituto de Ecología, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
  2. bDepartment of Biology, Stanford University, Stanford, CA 94305
  1. Contributed by Paul R. Ehrlich, May 23, 2017 (sent for review March 28, 2017; reviewed by Thomas E. Lovejoy and Peter H. Raven)

  1. Fig. 2.

    Global distribution of terrestrial vertebrate species according to IUCN (28). (Left) Global distribution of species richness as indicated by number of species in each 10,000-km2 quadrat. (Center) Absolute number of decreasing species per quadrat. (Right) Percentage of species that are suffering population losses in relation to total species richness per quadrat. The maps highlight that regions of known high species richness harbor large absolute numbers of species experiencing high levels of decline and population loss (particularly evident in the Amazon, the central African region, and south/southeast Asia), whereas the proportion of decreasing species per quadrat shows a strong high-latitude and Saharan Africa signal. In addition, there are several centers of population decline in both absolute and relative terms (Borneo, for example).

  2. Fig. 3.

    Latitudinal distribution of species richness (Left), decreasing species (Center), and the percentage of species (Right) that are suffering population losses in relation to total species richness, in each 10,000-km2 quadrat. Patterns of species richness in relation to latitude are similar in all vertebrates, although there are more species per quadrat in birds and mammals and, as expected, a scarcity of reptiles and amphibians at high latitudes. The patterns of number of species with decreasing populations indicate that regions with high species richness also have high numbers of decreasing species, but the percentage of decreasing species in relation to species richness shows contrasting patterns between mammals and birds compared with reptiles and amphibians. In mammals and birds, the percentage of decreasing species is relatively similar in regions with low and high species richness. In contrast, there are proportionally more decreasing species of reptiles and amphibians in regions with low species richness.

  3. Fig. 4.

    The percentage of decreasing species classified by IUCN as “endangered” (including “critically endangered,” “endangered,” “vulnerable,” and “near-threatened”) or “low concern” (including “low concern” and “data-deficient”) in terrestrial vertebrates. This figure emphasizes that even species that have not yet been classified as endangered (roughly 30% in the case of all vertebrates) are declining. This situation is exacerbated in the case of birds, for which close to 55% of the decreasing species are still classified as “low concern.”

  4. Fig. 5.

    The percentage of species of land mammals from five major continents/subcontinents and the entire globe undergoing different degrees (in percentage) of decline in the period ~1900–2015. Considering the sampled species globally, 56% of them have lost more than 60% of their range, a pattern that is generally consistent in Africa, Asia, Australia, and Europe, whereas in South America and North America, 35–40% of the species have experienced range contractions of only 20% or less. (See text for details.)

  5. Fig. 6.

    Percentage of local population extinction in 177 species of mammals in 1° × 1° quadrats, as an indication of the severity of the mass extinction crises. The maps were generated by comparing historic and current geographic ranges (49) (SI Appendix, SI Methods). Note that large regions in all continents have lost 50% or more of the populations of the evaluated mammals. Because of the small sample size, biased to large mammal species, this figure can only be used to visualize likely trends in population losses.

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