Worldwide vertebrate status

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The status of the world's vertebrates and conservation efforts were recently published in an article from Science Magazine. The study looked at various data covering the taxonomy, distribution, population, and threat status for 25,780 species of vertebrates (mammals, birds, amphibians, reptiles, cartilaginous and bony fish). Also included in the analyses were potential threats to the species as well as conservation efforts. Species were categorized using a standard called the Red List set by the International Union for Conservation and Nature (IUCN). Threatened species include those in the Critically Endangered, Endangered, or Vulnerable categories.

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Shown above is Figure 1: "The proportion of vertebrate species in different Red List categories compared with completely (or representatively) assessed invertebrate and plant taxa on the 2010 IUCN Red List (15). EW, Extinct in the Wild; CR, Critically Endangered; EN, Endangered; VU, Vulnerable; NT, Near Threatened; LC, Least Concern; DD, Data Deficient."

According to the article, close to one-fifth of existing vertebrates in mainly tropical regions, are considered threatened. This corresponds to areas with fisheries and deforestation. Using the Red List Index (RLI), the authors found that over the last 20 years or so the status of amphibians deteriorated at an alarming rate of 3.4% per year whereas birds and mammals declined at rates of 0.02% and 0.07%, respectively. Between 1980 and 2008, an average of 52 species moved one step closer to extinction each year.

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Shown above is Figure 3 from the article: "(A) Trends in the Red List Index (RLI) for the world's birds, mammals, and amphibians. (B to D) Observed change in the RLI for each group (black) compared with RLI trends that would be expected if species that underwent an improvement in status due to conservation action had undergone no change (red). The difference is attributable to conservation. An RLI value of 1 equates to all species being Least Concern; an RLI value of 0 equates to all species being Extinct. Improvements in species conservation status lead to increases in the RLI; deteriorations lead to declines. A downward trend in the RLI value means that the net expected rate of species extinctions is increasing. Shading shows 95% confidence intervals. Note: RLI scales for (B), (C), and (D) vary."

In the absence of conservation efforts, biodiversity would have deteriorated at an even faster rate. We cannot relax just yet since the current threat greatly outweighs conservation efforts. Greater efforts are still needed to help stem the decline of global biodiversity.

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