Biodiversity Hotspots Revisited, Conservation International, 2011

The biodiversity hotspots are regions known to hold especially high numbers of species found nowhere else, yet their remaining habitat combined covers a little more than two percent of Earth's land surface. According to the criteria developed by Myers et al. (2000), a hotspot must meet two thresholds in order to qualify: 1) it must have at least 1500 endemic, native vascular plant species, and 2) it must have already lost at least 70% of its primary, native vegetation.

A major finding of this updated analysis is that six previously overlooked areas qualify for hotspot status. These are the Madrean Pine-Oak Woodlands of northern Mexico and the southwestern United States, southern Africa’s Maputaland-Pondoland-Albany region, the Horn of Africa, the Irano-Anatolian region, the Mountains of Central Asia, and Japan. In addition, two hotspots have been subdivided, as data are now sufficient to show that they contain quite distinctive biotas. The original Eastern Arc Mountains and Coastal Forests hotspot has been partitioned, such that the Coastal Forests of Eastern Africa stand alone as a separate hotspot (now extending into southeastern Somalia and southern Mozambique), while the Eastern Arc Mountains have been grouped with the mountains of the Southern Rift, Albertine Rift and Ethiopian Highlands to form the Eastern Afromontane Hotspot. Similarly, the Himalaya and Indo-Burma regions are now listed as separate hotspots, with the former extending further to the west into Pakistan and the northeast Afghanistan than did the Himalayan portion of the original Indo-Burma Hotspot.

The final change revealed in our reassessment of the hotspots is truly terrifying. Less than a decade ago, the islands of eastern Melanesia, while known to be extremely endemic-rich, still held largely intact habitat. Since then, rampant logging and establishment of oil palm plantations have devastated these islands, leaving only 30 percent of their forests remaining, a situation mirroring the fate of Indonesia’s forests a decade ago. In revisiting the boundaries of the hotspots, we have tried to achieve a balance between what is scientifically defensible, and what is practically acceptable. However, in order to accommodate some tropical islands that might otherwise slip through the net of conservation priorities, we have grouped certain islands with their closest-lying hotspots including: Galapagos and Malpelo with Tumbes-Chocó-Magdalena, Juan Fernandez with the Chilean Winter Rainfall-Valdivian Forests, the Azores and Cape Verde Islands with the Mediterranean Basin; and Lord Howe and Norfolk Islands with New Zealand. This is done pragmatically, and with full recognition that the floristic affiliations of these islands with their associated landmasses are often tenuous at best. Finally, delineating hotspots is by no means an exact science. It requires that a line – that might be easily discernible or rather vague on the ground – must be drawn to represent a transition between two habitats. The map of Ecoregions developed by the World Wildlife Fund-U.S. is now the most widely used system for such bioregional classification. In order to facilitate analysis, interoperability, and collaboration, we have therefore gone to considerable lengths to ensure that both the boundaries of the hotspots (and those of the high biodiversity wilderness areas) correspond directly to those of the World Wildlife Fund-U.S. Ecoregions.

For more information:  http://www.conservation.org/where/priority_areas/hotspots/Pages/hotspots_main.aspx