Biodiversity hotspots

Sala [6] provides us with a way to say something about what areas of the world are likely to suffer the greatest changes in biodiversity as a result of changes projected through 2100. But we all know that some regions of the world are more diverse than others. Most groups of organisms have far more species in the tropics than they do in the temperate zone or in higher latitudes. As a result, a lot of the focus on the extinction crisis has been associated with loss of tropical rainforests. Because the numbers are so daunting, many conservationists have focused on identifying those places with the highest amount of diversity, ``biodiversity hotspots'' as Norman Myers [3] called them. Myers et al. [4, p. 853] argue that because ``the number of species threatened with extinction far outstrips available conservation resources $\dots$ this places a premium on identifying priorities'', which they propose to do by identifying ``areas featuring exceptional concentrations of endemic species and experiencing exceptional loss of habitat.'' Their analysis suggest that ``as many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to hotspots comprising only 1.4% of the land surface of the Earth'' (Figure 3).

Figure 3: The 25 biodiversity hotspots identified by Myers et al. [4].

Because the definition of ``hotspot'' Myers et al. [4] used included ``exceptional loss of habitat'' and because land use changes are the biggest driver of biodiversity loss [6], it shouldn't be surprising that several of the hotspots correspond with areas identified in the Sala et al. analysis as areas where the greates biodiversity changes are expected, notably the Mediterranean climate regions: the Mediterranean basin itself, the Cape Floristic Province, southwest Australia, central Chile, and the California Floristic Province.