Each year 52 vertebrate species move one Red List category closer to extinction
The Red List Index (RLI) measures the risk of extinction, divided into seven categories of extinction risk, as calculated from the IUCN Red List of Threatened Species. An RLI value of 1.0 equates to species not being expected to become extinct in the near future; a RLI value of zero indicates that all species have become ‘Extinct’ (Hoffman and others 2010). The graph shows that for those vertebrate groups where sufficient data are available, the trend is generally negative; i.e., that birds, mammals and amphibians are becoming increasingly threatened. The five principal pressures driving biodiversity loss are habitat change, overexploitation, pollution, invasive alien species and climate change (CBD 2010).
“Almost one-fifth of extant vertebrate species are classified as ‘threatened’, ranging from 13% of birds to 41% of amphibians” (Hoffman and others 2010). On average, 52 species per year moved one category closer to extinction from 1980 to 2008. Amphibians are more threatened than birds and mammals, and are declining at a faster rate. The status of other groups is likely to be similar if not worse; nearly a quarter of plant species are estimated to be threatened with extinction (CBD 2010), and in some plant groups over 60% of species are considered threatened (Hoffman and others 2010). As renowned ecologist Edward O. Wilson puts it: “One small step up the Red List is one giant leap towards extinction”.
The highest numbers of threatened vertebrates can be observed in the tropical regions, with figures disproportionally higher than in other regions (Hoffman and others 2010).
This graphic is part of the publication Keeping Track of Our Changing Environment