Washington: A scientific analysis of millions of years of data has suggested that if the course of human history is any model, then the wheels are already turning on Earth’s sixth mass extinction, thanks to habitat destruction, pollution and now global warming.
According to a report in the San Francisco Chronicle, the study of the fossil and archaeological record over the past 30 million years by UC (University of California) Berkeley and Penn State University researchers shows that between 15 and 42 percent of the mammals in North America disappeared after humans arrived.
That means North American mammals are well on the way - perhaps as much as half way - to a level of extinction comparable to other epic die-offs, like the one that wiped out the dinosaurs.
Anthony Barnosky, a UC Berkeley professor of integrative biology and co-author of the study, said that the most dramatic human-caused impacts on the ecosystem have occurred in the last century.
“We are seeing a lot of geographic range reductions that are of a greater magnitude than we would expect, and we are seeing loss of subspecies and even a few species,” Barnosky said.
“So it looks like we are going into another one of these extinction events,” he added.
The analysis by Barnosky, research associate Marc Carrasco and Penn State’s Russell Graham compares the extinctions of mammals in North America after humans arrived 13,000 years ago to the five mass extinctions on Earth over the past 450 million years.
The least severe of those extinctions wiped out the dinosaurs 68 million years ago and killed off 75 percent of the species on the planet.
Although humans clearly did not have anything to do with the previous extinctions, many scientists are afraid that global warming and other environmental problems caused by the ever-increasing human population could have similarly catastrophic consequences.
“Here we are again, astronomically increasing the number of humans on the face of the globe, plus unusual climate change,” Barnosky said.
“That seems to be a recipe for extinction that we saw in the past, and we are seeing again,” he added.
At least 50 species went extinct in North America soon after humans arrived on the continent 13,000 years ago.
Among the mammals that disappeared were California tapirs, peccaries, lions and cheetahs, llamas, ox, horses, mammoths and mastodons.
First Published: Monday, December 28, 2009, 12:59