Understanding biodiversity loss requires global perspective

The Bulletin of the Atomic Scientists reports on the state of biodiversity in the world:

More than 1,500 animals and plant species are federally listed as endangered or threatened. The protections afforded by listing have saved species such as the bald eagle and California condor from extinction, but only 30 species have been delisted during the past four decades because of recovery. Focusing on success stories, which represent less than 2 percent of the total species listed, gives a misleading picture of American biodiversity. Ten species on the US federal list (not yet counting the eastern cougar) have gone extinct in the meantime, and many more are candidates for listing.

The situation is much worse in many other parts of the world. A paper just published in the journal Science Advances reported that, even by a conservative estimate, the average rate of vertebrate species loss since 1900 is as much as 100 times higher than the natural rate. The authors wrote: “Although biologists cannot say precisely how many species there are, or exactly how many have gone extinct in any time interval, we can confidently conclude that modern extinction rates are exceptionally high, that they are increasing, and that they suggest a mass extinction under way—the sixth of its kind in Earth’s 4.5 billion years of history.”

Counting species is, to be sure, a tricky business. Clear-cutting a virgin forest, for example, can sometimes increase biodiversity at a specific site by creating a different kind of habitat that is hospitable to a greater number of species. But “alpha biodiversity”—the number of species within a local area or habitat—is only one measure of biodiversity.

“Gamma biodiversity”—the total species diversity across many local habitats, within an ecosystem, region, or the entire globe—can give a different picture. The world’s overall forest cover is declining markedly, for example, and while that may be a boon to species that can colonize a clear-cut, it leaves many other plants and animals homeless.

To read more about the changing world and what you can do to prepare, visit: www.greatwavesofchange.org

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