Southern white rhinoceros at the San Diego Zoo Safari Park in March 2013.

Photo: Ken Bohn / Copyright:  San Diego Zoo Safari Park

Southern white rhinoceros at the San Diego Zoo Safari Park in March 2013.

Science


The Earth appears to be in the early stages of the Sixth Extinction, the latest in a series of mass biodiversity losses that have punctuated the history of life on the planet, according to a paper published in Science this week.

The defining characteristic of the current round — the latest since the dinosaurs disappeared about 65 million years ago — seems to be driven mostly by the actions of humankind. We’re steadily encroaching on the habitat of millions of species while fundamentally altering the environment.

More than 320 terrestrial vertebrates have become extinct since 1500, according to the researchers at Stanford University. Surviving species have declined in abundance by about 25 percent, particularly devastating the ranks of large animals like elephants, rhinoceroses and polar bears.

And it’s only likely to get worse. The U.N. Intergovernmental Panel on Climate Change report in 2007 predicts that an increase of 3.5 degrees Celsius, within the range of scientistic forecasts for 2100, could wipe out 40 to 70 percent of the species assessed so far.

I interviewed New Yorker writer Elizabeth Kolbert on this topic earlier this year, following the publication of her grim but important book, “The Sixth Extinction: An Unnatural History.”

“Right now, in the amazing moment that to us counts as the present, we are deciding, without quite meaning to, which evolutionary pathways will remain open and which will forever be closed,” Kolbert wrote. “No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy.”



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