L I V I N G P L A N E T I N D E X : TA X A While broad trends across ecosystems provide an overview of changes in population numbers, they do not show the relative impacts of human pressures across different species and taxonomic groups. There are almost 10,000 species of bird inhabiting a diverse range of habitats. Their widespread distribution, plus the fact that extensive information has been collected on them, has enabled a robust indicator of bird trends to be produced. The decline of 20 per cent in the bird index (Figure 20) masks a more serious decline of 50 per cent experienced by surveyed populations of tropical and marine birds. Major threats include habitat loss, invasive alien species, overexploitation and pollution. More than 5,400 mammal species have
been described, of which 20 per cent are classified as threatened by the IUCN Red List of Threatened Species. The mammal index has decreased by about 20 per cent over the last decade (Figure 21), with the most serious declines in the tropical realms. Overexploitation is one of the principal threats to this group, extensively targeted by the bushmeat trade, notably in Africa and Southeast Asia. While populations of species are increasing and decreasing in different areas of the globe (see opposite), and the threats resulting from humanity’s growing footprint do not impact all species equally, the overwhelming picture that is seen from averaging these trends is one of global decline in species abundance. Apart from
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12 LIVING PLANET REPORT 2008
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TRENDS IN SAMPLE POPULATIONS OF SELECTED SPECIES The opposite page reveals population trends for 12 terrestrial, marine and freshwater species, illustrating the kinds of data that are used to calculate the Living Planet Index. The examples shown give an insight into trends in animal populations from different locations but do not necessarily represent the picture for the entire species. A positive sign is that some populations are either stable or increasing and these represent conservation successes from which we can learn, such as the reintroduction of the Mauritius kestrel. Unfortunately the number of declining trends among these populations highlights key issues that still need to be addressed. One of the main threats impacting some of the sample populations is habitat degradation, as illustrated by the decline in the black-winged stilt. Another threat is the overexploitation of species either directly – through current hunting as in the case of the hippopotamus in the Democratic Republic of Congo or historical hunting in the case of the diamondback terrapin – or indirectly as the bycatch of certain fishing practices. Examples of the latter include the wandering albatross and the loggerhead turtle.
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Figure 21: Mammal Living Planet Index. This shows an average -19 per cent trend from 1970 to 2005 in 1,161 populations of 355 species.
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Figure 20: Bird Living Planet Index. This shows an average -20 per cent trend between 1970 and 2005 in 2,185 populations of 895 species. Temperate and tropical species have equal weighting to compensate for the much larger temperate data set.
Fig. 21: MAMMAL LIVING PLANET INDEX, 1970–2005
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Fig. 20: BIRD LIVING PLANET INDEX, 1970–2005
representing a regrettable loss in terms of global biodiversity, this trend has implications for human well-being. Humans depend on healthy ecosystems and thriving species populations to ensure the continued provision of ecological services.
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Note: the baseline on all sample species graphs is zero. 1970
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