7.2 The Red List

The Red List, produced by the International Union for Conservation of Nature (IUCN), gives the global conservation status of organisms. Species at risk are categorised using standard criteria (Figure 22). Applying these criteria gives each species’ Red List status and the list can be used to quantify the biodiversity on the planet.

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Figure 22 The categories and criteria used to describe the status of endangered species (Source: National Geographic [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] )

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The categories and criteria used to describe the status of endangered species, presented in a table.

Figure 22 The categories and criteria used to describe the status of endangered species (Source: National Geographic)

The IUCN Red List index measures overall trends in extinction risk for groups of species based on observed changes in their Red List status over time. At present, index values have been calculated for only four groups of organism (Figure 23). In order to establish a trend, at least two sets of observations are required, so there is much more work to do.

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(Source: IUCN)

Figure 23 The Red List index of species survival for four groups of animals. The higher the index number, the lower the risk faced by the group.

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The graph illustrates the decline in the IUCN Red List index value for four groups of animals. The horizontal axis is time and the vertical axis is the index value. The higher the value of the index for species survival, the less the risk faced by the group. Corals show the largest decline, with an index of 0.98 in 1997 and 0.81 in 2010. Amphibians have declined from 0.78 in 1980 to 0.76 in 2006. Mammals and birds show slight declines in the index.

Figure 23 The Red List index of species survival for four groups of animals. The higher the index number, the lower the risk faced by the...

As you can be see, with just two measures of the Red List index for each of the four groups, a decline in status is apparent for all of them. This is powerful evidence that there is a rapid decline in biodiversity in some major groups. Does this mean we really are heading towards a sixth extinction event?