October 31, 2020

I, Science

The science magazine of Imperial College

It’s not how you fail, it’s how you bounce back.  And while the end-Permian mass extinction may have been nature’s greatest failure, new evidence shows its recovery was even more impressive than we thought.

Two hundred and fifty million years ago, life nearly died.  96% of marine species were lost, 70% of land vertebrates perished, and even insects, who have not been wiped out en-masse since, took a 50% hit.

No-one’s quite sure what caused the crisis at the Permian-Triassic boundary.  Theories of meteor strikes jostle with volcanic eruptions, methane emissions, loss of oxygen from the oceans and shifting tectonic plates.  Some see impact craters inAustralia and Antarctica as undeniable proof of an extraterrestrial killer.  Others view huge outpourings of lava in Siberia with suspicion.

Whatever authored this catastrophe, it scoured the sea bed almost clean of animal life all over the world.   Until recently, scientists believed that it took five million years for ecosystems to recover.  Now though, with new discoveries in China, they think it may have been a fraction of that time.

Originally the long delay was thought to be from the extinction’s enduring effects, or from new factors creating fresh adversity and further extinctions that prevented life from repairing.

But work by researchers from China, Australia and the UK shows that communities on the ocean floor began to flourish just one million years after the Permian-Triassic event.  By searching for life in sediments from the Yangtze and Nanpanjiang Basin in South China, the team led by Dr Haijun Song had challenged theories of extinctions in the early Triassic.

Not all species recovered at the same rate though.  Song’s results, published in Geology journal, show that algae and small creatures called forams were the first to shake off ill effects, while corals came much later.  The pacing of each species’ recovery seems to tie in with what’s known about the rate that they evolve.  So those able to adapt into the new niches quickest saw the fastest turn around.

The discovery suggests that recovery from mass extinction is much faster and more complex than we originally thought.   And with authoritative voices claiming that we’re going through a mass extinction right now, we need more research into these past events, so we can understand who lives, who dies, who recovers and, most importantly, why.