National Science Foundation | 2011 Mar 02
Are We in the Middle of a Sixth Mass Extinction?Steep decline of many animal species warns that Earth is on the brink
With the steep decline in populations of many animal species, scientists have warned that Earth is on the brink of a mass extinction like those that have occurred just five times during the past 540 million years.
Each of these "Big Five" saw three-quarters or more of all animal species go extinct.
In results of a study published in this week's issue of journal Nature, researchers report on an assessment of where mammals and other species stand today in terms of possible extinction compared with the past 540 million years.
They find cause for hope--and alarm. ...
Science NOW | Ann Gibbons | 2011 Mar 02
Has the Earth’s sixth mass extinction already arrived? - AD Barnosky et alEarth's creatures are on the brink of a sixth mass extinction, comparable to the one that wiped out the dinosaurs. That's the conclusion of a new study, which calculates that three-quarters of today's animal species could vanish within 300 years. "This is really gloom-and-doom stuff," says the study's lead author, paleobiologist Anthony Barnosky of the University of California, Berkeley. "But the good news is we haven't come so far down the road that it's inevitable."
Species naturally come and go over long periods of time. But what sets a mass extinction apart is that three-quarters of all species vanish quickly. Earth has already endured five mass extinctions, including the asteroid that wiped out dinosaurs and other creatures 65 million years ago. Conservationists have warned for years that we are in the midst of a sixth, human-caused extinction, with species from frogs to birds to tigers threatened by climate change, disease, loss of habitat, and competition for resources with nonnative species. But how does this new mass extinction compare with the other five? ...
- Nature 471(7336) 51 (03 Mar 2011) DOI: 10.1038/nature09678