July 19, 2006

Pimm numbers

Of the 10000 named bird species, we know that about 129 have gone extinct since the year 1500. Many others went extinct before scientists could describe them. In a new paper Stuart Pimm, Peter Raven, Alan Peterson, Çağan H. Şekercioğlu, and Paul R. Ehrlich estimate just how many. They make a clever analysis of the dates of scientific description and the dates of extinction of bird species and, after adding various other corrections, they estimate that about 500 bird species have gone extinct since the year 1500. Most of these species were oceanic island endemics. They further predict that at least another 1000 species will go extinct during the 21st century due to habitat loss in continents.

"What our study does, for the first time, is provide a well-justified and careful estimate of how much faster bird species are going extinct now than they did before humans began altering their environments," said Pimm in a press release. But, although the paper meticulously examines recent extinction rates, it does not carefully address the rates before human impacts. The benchmark extinction rate they use (one species per million per year, which would predict five bird extinctions since the year 1500) derives mainly from estimates of average durations of species, mosty marine invertebrates, that left abundant and geographically widespread fossils. I would like to know the average natural durations of island bird endemics.

No comments:

Post a Comment