Mass Extinction #6

The death of the dinosaurs was just a drop in the bucket compared to some of the real mass extinction events out there. And PhysOrg thinks we may be at the beginning of a really big one:

“The modern global mass extinction is a largely unaddressed hazard of climate change and human activities,” said H. Richard Lane, program director in the National Science Foundation’s Division of Earth Sciences, which funded the research. “Its continued progression, as this paper shows, could result in unforeseen – and irreversible – negative consequences to the environment and to humanity.”

The study originated in a graduate seminar Barnosky organized in 2009 to bring biologists and paleontologists together in an attempt to compare the extinction rate seen in the fossil record with today’s extinction record. These are “like comparing apples and oranges,” Barnosky said.

To get around this limitation, Marshall said, “This paper, instead of calculating a single death rate, estimates the range of plausible rates for the mass extinctions from the fossil record and then compares these rates to where we are now.”

[UC Berkeley professor of integrative biology Anthony D.] Barnosky’s team chose mammals as a starting point because they are well studied today and are well represented in the fossil record going back some 65 million years. Biologists estimate that within the past 500 years, at least 80 mammal species have gone extinct out of a starting total of 5,570 species.

The team’s estimate for the average extinction rate for mammals is less than two extinctions every million years, far lower than the current extinction rate for mammals.

“It looks like modern extinction rates resemble mass extinction rates, even after setting a high bar for defining ‘mass extinction,'” Barnosky said.