The earth has been through five major mass extinctions, and some scientists believe we are in the midst of the sixth great extinction.
Unlike the others, spurred by huge meteorites and the like, this one belongs to us. As many as 50% of all species could disappear by the middle of next century, according to some projections, primarily because of our encroachment into wilderness and pollution-fueled global warming.
If that happens, it could take a long time to get back to business as usual, from a biological point of view.
New research out of the University of Bristol, published this week in Proceedings of the Royal Society B, estimates that it took 30 million years for life to evolve in such a way that the world again hosted the kind of biodiversity and complex food webs that had characterized it before the greatest extinction the world has ever seen.
The Permian extinction, which happened in three waves beginning about 250 million years ago, saw the destruction of more than 90% of species plants, animals, insects, reptiles and amphibians on land and in the sea. The root cause is believed to have been massive volcanic eruptions in Russia that covered 77,000 square miles with lava and sent enough sulfur and carbon into the atmosphere to alter the climate dramatically.
Our research shows that after a major ecological crisis, recovery takes a very long time," said Sarda Sahney, who wrote the paper with Michael Benton. "So although we have not yet witnessed anything like the level of the extinction that occurred at the end of the Permian, we should nevertheless bear in mind that ecosystems take a very long time to fully recover.
The Permian extinction played out over the course of hundreds of thousands of years. The sixth great extinction could play out over just a few hundred. It would take much longer for the Earth to recover.
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