The dodo went extinct (and other ecological myths)
The scientific consensus is that human impacts are driving species to extinction hundreds to thousands of times faster than expected from the natural background rate. Critics challenge this. Perhaps giving them more credit than they deserve, I examine four concerns. First, that the extinction crisis is not real. It is and high rates of extinction are the rule, not the exception, within well-known taxa. The second criticism dismisses the problem as one restricted just to islands. It is not. Island species have special vulnerabilities, but they are far more locally abundant within their ranges than are continental species with the same range size. There are large numbers of locally rare, continental species with small geographic ranges that are threatened by human impacts. A third criticism notes the few species that became extinct following the clearing of forests from eastern North America in the 19th century, casting doubt upon the relationship between habitat loss and species loss. Analysis of this case history shows that exactly as many species of birds were lost as expected, for the region had very few species to lose. Extensions to species-rich areas such as Southeast Asia and the Atlantic coast of Brazil confirm the expected calibrations with an interesting caveat. Forest losses predict the number of threatened species - those on the verge of extinction - not the number of extinctions. This leads to the final criticism: that there have been too few recent extinctions. The reply is that in these regions the deforestation is more recent and species do not go extinct immediately. Some doomed species can linger for decades - as did the now-extinct species in eastern North America.
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