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Hotspots in Peril
Habitat destruction is a pervasive threat affecting hotspots and is already causing extinctions in many areas. Accelerating anthropogenic climate change will undoubtedly magnify the effects of habitat destruction and fragmentation. Predatory invasive species have already had a devastating impact on the island hotspots, where species evolved in the absence of animals such as cats and rats. Introduction of exotic plant species into hotspots, particularly those of Mediterranean-type vegetation, is also having massive ecosystem effects. Direct exploitation of species for food, medicine, and the pet trade is a serious threat to all hotspots, particularly in the Guinean Forests of West Africa and several Asian hotspots. Another grave concern is the severe decline of amphibians worldwide, the cause of which remains unknown.
Threatened Species in the Hotspots
Critically Endangered and Extinct Species
Human Population in the Hotspots
The most direct measure of this threat can be derived from assessments of conservation status of species. The IUCN Red List of Threatened Species, compiled by the Species Survival Commission of IUCN-The World Conservation Union, classifies species that have a high probability of extinction in the medium-term future as Critically Endangered, Endangered, or Vulnerable. For mammals, birds, and amphibians, the three groups of species for which assessments of distribution and conservation status have been conducted, we can measure these proportions with a high level of accuracy. The IUCN Global Reptile Assessment is currently underway, and equivalent data for threatened reptile species should be available in a few years time.
Researchers have also found that the hotspots hold more people than expected. But the relationship between people and biodiversity is not simply one where more people lead to greater impacts on biodiversity. Human population density among hotspots varies widely, from four people per km² (in the Succulent Karoo) to as much as 336 people per km² (in Japan). Of course, much of our understanding of human-biodiversity interactions lies not in human density but rather in human activity. A good example of this is the Cerrado, with a population density of only 13 persons per km², but which has suffered considerable habitat loss due to the expansion of commercial agriculture.
Maybe most disconcertingly, hotspots are also notable centers of violent conflict. For example, areas in Mesoamerica, the Caribbean, the Tropical Andes, the Guinean Forests of West Africa, the Eastern Afromontane rifts, the Horn of Africa, the Caucasus, the Irano-Anatolian region, the Mountains of Central Asia, Indo-Burma, Sundaland, Wallacea, the southern Philippines, and the East Melanesian Islands have all been plagued by recent violence. The degree to which these conflicts cause biodiversity loss or are caused by biodiversity loss is unclear, but the correlation is unnerving.
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