The great, late comedian George Carlin had a line in his act where he would rail against “save the whales” environmentalists by pointing out that 90 percent of species that ever lived are extinct. “We didn’t kill them all,” he would say in a mocking voice, and it’d get a big laugh.
I dunno, though, George. This new study seems to show that even if we didn’t kill them all, we were no slouches either. It shows that humans have increased the natural rate of extinction 1,000 times, even worse than the 100 times previously thought.
“This reinforces the urgency to conserve what is left and to try to reduce our impacts,” said lead author Jurriaan de Vos, a Brown University postdoctoral researcher. “It was very, very different before humans entered the scene.”
The research compares the rate of extinction to 60 million years before the arrival of humans on the scene, to after the arrival of humans to come to its troubling conclusion. The team used evidence from the phylogenies, or evolutionary family trees, of various plant and animal species to study how species diversified and work out a model of extinction rates.
“The diversification rate is the speciation rate minus the extinction rate,” said co-author Lucas Joppa, a scientist at Microsoft Research in Redmond, Wash. “The total number of species on earth has not been declining in recent geological history. It is either constant or increasing. Therefore, the average rate at which groups grew in their numbers of species must have been similar to or higher than the rate at which other groups lost species through extinction.”
The upshot is that although humans have made efforts to conserve some species, population growth, land use, and other activities have been even more destructive that they appeared.
“We’ve known for 20 years that current rates of species extinctions are exceptionally high,” said senior author Stuart Pimm, Duke University professor and president of the conservation nonprofit organization SavingSpecies. “This new study comes up with a better estimate of the normal background rate — how fast species would go extinct were it not for human actions. It’s lower than we thought, meaning that the current extinction crisis is much worse by comparison.”
So getting back to Carlin’s act, the reason he dismissed extinctions was because he didn’t care. At least on stage, he presented himself as a nihilist, sure humanity was in its final self-destructive death throes anyway. So, are we? Do you care?
[Source: Brown University via Science Daily]
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