For years, scientists have wondered if humans could cause the extinction of enough species to significantly affect life on Earth. But a new paper co-authored by a Duke paleobiologist shows that the magnitude of extinction doesn't matter-any extinction we cause will affect the Earth for millions of years to come.
The paper, which appears in the March 9 issue of Nature, asserts that the global ecosystem takes 10 million years to fully recover from any recordable extinction.
The finding has opened the eyes of scientists and non-scientists worldwide because it challenges the widely held belief that the earth recovers more slowly from multi-species extinctions. "The really exciting implication is it doesn't matter how big the extinction is," said Anne Weil, a research associate in the department of biological anthropology and anatomy and one of the paper's two authors.
Since size does not matter, any extinction caused by humans will have reverberations in the ecosystem for millions of years to come.
James Kirchner of the University of California-Berkeley, who co-wrote the paper with Weil, attributed their findings to the fresh approach that he and Weil brought to their analysis. "By focusing on major mass extinctions and recoveries from them, paleontologists had simply not asked the question of how fast the biosphere recovers from small extinctions," he said.
Weil explained that she and Kirchner, an associate professor of geology and geophysics, came to their conclusion after applying a complex mathematical algorithm to a widely available data set from which many different conclusions have been reached. The algorithm, which is used mainly in astrophysics, compensated for the statistical difficulties scientists had encountered while running analyses on the data.
Weil said the algorithm allowed her and Kirchner to come to their startling conclusion. "Origination rates-the rates at which new species evolve-are highly correlated with extinction rates 10 million years before, and that goes for high as well as low points of extinction," she said.
To explain the significance of the findings, Weil used an example that compared species to cars in a parking lot. When a species goes extinct, it is "as if a car pulled out of a space, and a guy came along with a jackhammer and destroyed the space," she said.
By the time the spaces are repaved and repainted, the parking lot is much different from before. The same applies for the biosphere. "The new ecosystem is never the same as the old ecosystem," Weil said.
Kirchner encouraged people to keep in mind the findings of the paper when considering the consequences of actions that could lead to further extinctions. "I hope that this work and other work that biologists are doing will encourage people to think very carefully about choices they make," he said.
The discovery has caused a stir around the world. Newspapers from England, France, and Brazil have run articles about the research, and The New York Times has already published one story and is planning to run another.
For Weil, the elation that accompanied the July discovery has faded. "I have another paper in the computer that I am very excited about," she said.
The new paper, also co-authored with Kirchner, uses the same algorithms that led to the findings of the first paper. "The results of it corroborate the results of the first paper," she said.
As much success as she has had lately, Weil says she is tiring of what she calls "computer jack work."
"It's not why I went into paleobiology," she said. "I went into it because part of my job is to go camping two or three months out of the year."
Jaime Levy contributed to this story.
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