This map shows the orientation of the Earth's land masses in the supercontinent Pangea, about 250 million years ago, at the time of the greatest mass extinction in the planet's history.
Photograph by: handout photo, Ron Blakey, Northern Arizona University
A Canadian-led team of scientists may have solved the biggest whodunit in Earth history in a study showing that the all-time greatest mass extinction on the planet - which wiped out about 90% of all species 250 million years ago - appears to have been linked to rising levels of ocean acidity.
Researchers have long believed that massive volcanic eruptions in present-day Siberia - or possibly a huge meteorite strike - triggered the so-called PermianTriassic extinction. But the precise mechanism of death for so many species remains a subject of debate, with some scientists convinced it was a resulting lack of oxygen in the Earth's oceans or a greenhouse-gas nightmare that nearly ended all plant and animal life.
But the Canadian study, headed by St. Francis Xavier University climate scientist Alvaro Montenegro, points to ocean acidification as a possible "main culprit" in the harrowing, prehistoric die-off.
And the Nova Scotia researcher told Postmedia News that the finding should serve as a warning about present-day increases in ocean acidification. Though still far lower than that experienced in the ancient mass extinction, rising acidity has been documented by researchers around the world and is linked to the effects of climate change.
Using a series of computer simulations to recreate conditions on the planet at the time, Montenegro and his five colleagues from Canada and Australia found it unlikely that oxygen-starved oceans led to the mass extinction.
Instead, their models pointed to a new prime suspect: spiking acid levels in the world's marine environments.
Runaway ocean acidification "would definitely have a very serious biological impact on ocean calcifiers," said Montenegro, referring to creatures that manufacture their own bodily structures from minerals found in ocean water.
Among the species that vanished from the rock record around the time of the P-T extinction were most of the ammonites - large, snail-shaped marine creatures that are known today from the beautifully iridescent, multi-coloured fossils of their spiral shells, found in places such as southern Alberta. The relatively few ammonite species that survived the mass extinction 250 million years ago were later killed off by the meteorite-linked extinction at the end of the dinosaur age 65 million years ago.