Permian extinction decimated land species, too
About 252 million years ago, Earth experienced its most devastating extinction in the history of life on our planet. And while scientists have long known that more than 80 percent of ocean-dwelling species disappeared, they have long debated what happened on land.
The Lystrosaurus a relative to mammals, was one of a handful of "disaster taxa" to survive the rubble of the Permian Period, along with the meter-high spore-tree Pleuromeia. Victor Leshyk
Oct. 26, 2011, 10:17 PM UTC / Source: Discovery Channel
By By Emily Sohn
Now, researchers are reporting that land-dwelling species were equally decimated during the extinction, which ended an era called the Permian period. After the massive wave of devastation swept through, just a few "disaster" species remained, including a handful of large four-legged creatures, a new study found.
Recovery, the study also found, was slow. Animals that survived the near-apocalypse remained on the edge of collapse for the next 8 million years, before the food supply stabilized again.
As we enter what appears to be the Earth's sixth major extinction event, the new findings emphasize the value of having a wide range of creatures around, and more warnings of the danger of letting too many species disappear.
"When you talk about diversity loss and recovery, it's not something that rebounds in 10 years. It takes millions of years," said Jessica Whiteside, a paleobiologist at Brown University. "This is basically a warning call about the loss of biodiversity. It's something that takes a substantial amount of time to rebound from."
In a study published last year in the journal Geology, Whiteside found that it took as many as 10 million years for marine species to recover from the Permian-Triassic extinction. To find out what was happening on land during the same period, she and colleague Randall Irmis analyzed close to 8,600 fossils from South Africa and Russia.
When they counted types and numbers of creatures that existed before and after the extinction, they found that nearly 78 percent of terrestrial species disappeared as the Permian period ended. Among the few creatures that remained, they reported in Proceedings of the Royal Society B, was a German-Shepard sized mammal-like animal called Lystrosaurus and a lizard-like creature called Procolophon.
The species that remained faced major challenges. For 8 million years after the extinction event was over, researchers found that there was instability in the ratio of carbon atoms on Earth. That suggests that predator-prey relationships were totally out of whack.
In a healthy ecosystem, the food web looks like a pyramid, with lots of creatures on the bottom rungs being eaten by successively fewer species as you work your way up to the top predators. But after the Permian period ended, there were often just one or two species filling niches that were once occupied by 20 or 30 kinds of animals.
Plants, too, suffered in the same way. And those conditions set up even more species for continued extinctions until the food web finally stabilized again.
Generally, the species that emerge from these periods are the ones that have broader geographic ranges or are less specialized in their needs for food or habitat, according to Arnold Miller, a paleobiologist at the University of Cincinnati.
That kind of insight may help scientists envision which species will dominate the Earth of the future. Our planet is currently experiencing high rates of extinction as a result of global warming, overhunting and habitat destruction.
"One good reason to study and be aware of natural mass extinctions in the past is that they can inform what is going to happen in the present and what might happen in the future," Miller said.
"There is no question that species that have limited ranges today, geographically or environmentally, are more susceptible to extinction and easier to kill," he added. "In the end, we're left with species that are more general and less unique in a lot of respects."
By Emily Sohn