DEFINE ENDANGERED

When Is a Species Endangered?
Bryan Walsh, October 19, 2009 (Time Magazine)

"The planet is in the middle of an extinction crisis, the sixth great wave in its history. But unlike major extinction events of the past…this time human beings are the cause. Hard numbers are difficult to find, but many scientists believe Earth's species are going extinct at a rate that is up to 1,000 times higher than before human beings came on the scene…

"…[But] human beings have also been working to counteract the effects of their development and growth as well as man-made climate change. Measures like the U.S. Endangered Species Act, habitat-protecting nature reserves and hunting prohibitions are all designed to slow the rate of extinction and preserve dwindling species. But…A team of Australian researchers led by environmental scientist Lochran Traill finds that current conservation policy tends to underestimate the number of individuals needed in a population of endangered species to keep it viable…[W]e need animal populations to number in the thousands for survival — not in the hundreds…"

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"…[T]he smaller a species population becomes, the more vulnerable it is to extinction. Not only are small, dispersed populations more easily wiped out, but also they are more susceptible to inbreeding, which leads to a decrease in genetic diversity and further pushes the species toward extinction. So the goal is to boost species' numbers…50 adults in a population are required to avoid the risks of inbreeding, and 500 are needed to avoid extinction due to sudden environmental change.

"But…[the researchers now think] no fewer than 5,000 adult individuals are needed to keep a species safe from the threat of extinction. Dip below that level, and any sudden change — the loss of a valued habitat, a new disease — could wipe out a species before conservationists would have time to act…"

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"Increasing species numbers, however, may not be possible…The needs of a real conservation effort may require a level of animal protection beyond what is politically possible…Do [conservationists, therefore,] push for the tighter levels of protection that might successfully preserve endangered species or do they accept what is politically feasible?

"…[T]he political realities are sometimes dire. As American environmentalists discovered during former President George W. Bush's Administration, it was difficult enough to preserve existing levels of protection for wildlife, let alone push for tougher standards. Yet…the status quo [may not be] enough… to stop the sixth great extinction wave…[Similarly, do climate scientists] push for the strict carbon-emissions reductions that many studies say are necessary to prevent serious global warming or do they accept weaker but more politically realistic targets? Whether it's conservation or climate change, science must often give way to statecraft."