A recent report from the University of Bristol, and published in the Proceedings of the Royal Society B this week, focuses on just what it takes for real recovery to take place after a mass extinction. The study, conducted by Sarda Sahney and Professor Michael Benton focused upon the mass extinction at the end of the Permian era, known as the end-Permian mass extinction.
Taking place some 251 million years ago, the end-Permian was the most devastating ecological event of all time, and the only event that comes close to completely wiping life off the face of this planet. Furthermore, it came after two previous extinction events, lesser in severity, but overall unfortunate.
The previous extinction took place at the beginning and end of the Guadalupian, a period middling the Permian, 270 and 260 million years ago.
The study, entitled “Recovery from the most profound mass extinction of all time,” is a new view of an era of time that has been long short on evidence. Most studies of the time have focused on the marine impact, with very little evidence to be found, apart from two sedimentary basins; the Karoo Basin of South Africa and the South Urals Basin of Russia.
Previous work on the subject had theorized that life bounced back quickly after these extinction events. But the latest study shows that the life that bounced back was disaster taxa; organisms that insinuate themselves in to gaps in the ecological landscape. One leading example of this was Lystrosaurus, which accounted for approximately 90% of terrestrial vertebrates.
Sahney and Benton’s study presents the theory that while life did in fact bounce back, the communities and ecosystems that had flourished prior to the extinction events had not. Complexity is the key here, with the Lystrosaurus proving their point.
Sahney said: “Our research shows that after a major ecological crisis, recovery takes a very long time. 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.”
In fact, according to their study, while tetrapods – four limbed vertebrates – did bounce back, the communal structuring of the species did not recover ecologically or numerically, until some 30 million years later, well into the Triassic era (the late Triassic). This included species such as dinosaurs, pterosaurs, crocodilians, amphibians and mammals.
Professor Benton explained: “Diversity is most commonly assessed by tallying the number of taxa on a global scale, but these studies are subject to the vagaries of sampling. By examining well-preserved and well-studied faunas, the taxonomic and ecological recovery of communities after the Permian extinction event can be examined more accurately, and the problems of geological bias are largely avoided.”
The end-Permian mass extinction, also known as the Permian–Triassic (P–Tr) extinction event and informally as the Great Dying, occurred 251.4 million years ago. Subsequently it became the boundary between the Permian and Triassic geological periods. What caused the event is – as with many geological incidents – uncertain, though several theories present themselves.
One primary theory is often seen as, if not solely responsible, coincidentally responsible, for the Permian-Triassic extinction event. The large-scale volcanism in Russia that eventually formed the Siberian Traps is described as one of the largest volcanic events of the last 500 million years of Earth’s geological history.
The massive eruption occurred about 251 to 250 million years ago, and formed a large igneous province in Siberia. ‘Traps’ refers to the step-like hills that were formed, derived from the Swedish word for stairs, trappa, or sometimes trapp.