Threatened biotas: "hot spots" in tropical forests

Abstract

The mass-extinction episode underway is largely centered 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 characterized 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% of remaining primary forests, they harbor over 34,000 endemic plant species (27% of all plant species in tropical forests and 13% 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% of their forest cover as soon as the end of the century or shortly thereafter, causing the extinction of almost 7% of Earth's plant species and at least a similar proportion of animal species, this occurring in only 0.2% of Earth's land surface. By concentrating on such areas where needs are greatest and where the pay-off from safeguard measures would also be greatest, conservationists can engage in a more systematized response to the challenge of large-scale extinctions impending in tropical forests.