Saturday, 19 January 2008

Ecosystems took 30 million years to recovery from the Permo-Triassic Mass Extinction

Most people are familiar with the extinction that killed the dinosaurs but another series of extinctions, at the end of the Permian, about 250 million years ago, were far worse, killing off over 90% of life on earth, including insects, plants, marine animals, amphibians and reptiles. A new study, published by myself and Michael Benton in the Proceedings of the Royal Society B, indicates that it took ecosystems 30 million years to recovery from this devastating event.

The Permian extinctions occurred in three waves, the largest being at the boundary between the Permian and Triassic periods, 252 million years ago; an event that was exacerbated by two earlier extinctions. This was the most devastating ecological event of all time, thought to be caused by large scale volcanism in Russia which produced the ‘Siberian Traps’, covering over 200,000 square kilometers (77,000 square miles) in lava. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, which are opportunistic organisms filling in the empty ecospace left behind by the extinction, insinuated themselves into almost every corner of the sparsely populated landscape.

Previous work indicates that life on Earth bounced back quickly after the Permian extinctions, but this was mostly in the form of disaster taxa, such as the hardy Lystrosaurus, a barrel-chested herbivorous animal, about the size of a pig. However, this new research indicates that specialized animals forming complex ecosystems, with high biodiversity, complex food webs and a variety of niches took much longer to recover. It is thought that this long recovery was due to the successive waves of extinction, which never gave life a chance to recover as well as prolonged environmental stress which continued into the Early Triassic.

It would not be until the great diversity of the Late Triassic, which included dinosaurs, pterosaurs, crocodiles, archosaurs, amphibians and mammals, some 30 million years after the big event, that diversity in terrestrial communities was restored.