At ScienceDaily (Mar. 5, 2011), we are invited to contemplate, “Has Earth’s Sixth Mass Extinction Already Arrived?”,
With the steep decline in populations of many animal species, from frogs and fish to tigers, some scientists have warned that Earth is on the brink of a mass extinction like those that occurred only five times before during the past 540 million years.Each of these ‘Big Five’ saw three-quarters or more of all animal species go extinct.
Is a three-quarters disappeance – as hinted by the University of California, Berkeley, paleobiologists who published a study in Nature, March3, – at all likely to happen, short of a worldwide nuclear holocaust or giant asteroid hit?
Tigers are featured in the article but – and here is one difficulty – tigers are top predators. Surely their possible disappearance in the wild would lead to an increase in the numbers of their prey?
As it happens, further into the column inches, we encounter more hope:
“So far, only 1 to 2 percent of all species have gone extinct in the groups we can look at clearly, so by those numbers, it looks like we are not far down the road to extinction. We still have a lot of Earth’s biota to save,” Barnosky said. “It’s very important to devote resources and legislation toward species conservation if we don’t want to be the species whose activity caused a mass extinction.”Coauthor Charles Marshall, UC Berkeley professor of integrative biology and director of the campus’s Museum of Paleontology, emphasized that the small number of recorded extinctions to date does not mean we are not in a crisis.
“Just because the magnitude is low compared to the biggest mass extinctions we’ve seen in a half a billion years doesn’t mean to say that they aren’t significant,” he said. “Even though the magnitude is fairly low, present rates are higher than during most past mass extinctions.”
Okay, but how are the rates calculated? I suspect it is easier to know how many species are going extinct today than it would be to know how many went extinct in the Cretaceous.
Even the Berkeley paleobiologists seem to recognize that they are conducting a fire drill, at least in countries where major projects are already stopped or rerouted because of damage to wildlife habitats. And about the others, it is striking how little attention gets directed to opinion leaders there. It’s always directed to people like me, who recycle our cartridges and sort our garbage.