Threatened biotas: "Hot spots" in tropical forests

Summary

The mass-extinction episode underway is largely centred on tropical forests, insofar as they contain at least half of all Earth's species and they are being depleted faster than any other biome. But species distributions and depletion patterns are anything but uniform throughout the biome. This paper identifies 10 areas that, a) are characterised by exceptional concentrations of species with high levels of endemism and b) are experiencing unusually rapid rates of depletion. While these "hotspot" areas comprise less than 3.5 percent of remaining primary forests, they harbour over 34 000 endemic plant species (27 percent of all plant species in tropical forests and 13 percent of all plant species worldwide). They also feature 700 000 endemic animal species and possibly several times more. Unfortunately, they appear likely to lose 90 percent of their forest cover as soon as the end of the century or shortly thereafter, causing the extinction of almost 7 percent of Earth's plant species and at least a similar proportion of animal species, this occurring in only 0.2 percent of Earth's land surface. By concentrating on such areas where needs are greatestand where the pay-off from safeguard measures would also be greatest, conservationists can engage in a more systematised response to the challenge of largescale extinctions impending in tropical forests.