November 5, 2012
Global Warming 250 Million Years Ago Triggered Slow Species Recovery
Brett Smith for redOrbit.com - Your Universe Online
After a major extinction event occurred 250 million years ago, many species that survived had a long, slow recovery, which was exacerbated by the effects of global warming, according to a new study presented at the Geological Society of America meeting in North Carolina this week.Ohio State University doctoral student Alexa Sedlacek, in his study, found that rising temperatures, high levels of greenhouse gases and a more acidic ocean, which were the result of heavy volcanic activity, suppressed biodiversity and the proliferation of life for around 5 million years after the event now referred to as the "Great Dying".
"The lesson is, life doesn't just snap back," said Matthew Saltzman, professor of earth sciences at Ohio State and Sedlacek's advisor. "We've long known from the fossil record that there was a long period with very little recovery right after the Great Dying. It's as if life had a 5-million-year hangover. Now we know why."
Based on the analysis of sedimentary rocks dated back to that time period, the two scientists were able to identify atmospheric conditions after the volcanic eruptions of the Great Dying. According to their report, large regions of the landscape were weathered away by greenhouse gases in the atmosphere, resulting in a chemical alteration of Earth's climate and oceans.
"People are understandably interested in the Great Dying because 90 percent of marine species went extinct," Sedlacek said. "But the recovery from that event is equally important, because the survivors determined what kind of life we have on Earth today."
"Extinctions are still happening today," she continued, "and though things were much worse back then, the greenhouse gases that were made by volcanoes are analogous to the man-made greenhouse gases we have today. So our findings have the power to inform us about modern climate change."
The rock samples used in the study were collected by Austrian researchers in a region known as Zal, near the northern Iranian border. After receiving the samples, Sedlacek and Saltzman analyzed them for two forms of strontium, strontium-87 and strontium-86. The ratio of these two isotopes indicates how much bedrock was being weathered away from the Earth's surface during the Great Dying.
The researchers also found that carbon levels during this time period were steadily increasing. Higher levels of carbon would have reacted with water vapor to form acid rains, which eroded the limestone bedrock.
"It was a game-changer, biologically. Fish would have had silt in their gills, coral reefs would have been buried — as far as we can tell, the things that truly thrived in the ocean during that time were microbes," Sedlacek said.
In describing how conditions might have been at the time, the scientists pointed to a recent study which found that ocean temperatures were around 104 degrees Fahrenheit, around the temperature of a typical hot tub.
The Ohio State scientists said that these findings clarify why life took so long to recuperate from the Great Dying — and suggest that life on Earth today could face similar problems in trying to recover from the current climate change.