It happened 252 million years ago. As much as ninety five percent of Earth's marine species, and seventy percent of its land species died. With such a large loss in biodiversity, the planet took longer to recover from this Permian Triassic extinction than from any other extinction event. Many scientists wondered how it managed to recover at all.
There Must Have Been Refuges For Survivors, But Where?
During the Permian, the planet was dominated by a single supercontinent called Pangea.
The seas teamed with trilobites, mollusks and nautilus ancestors. Cockroaches, dragonflies, and other arthropods moved among swamp loving lycopod trees, giant ferns and early conifers, while amphibians and lizard like ancestors of dinosaurs and mammals roamed the forests.
Solving The Mystery
There have been several hypotheses posed to explain the mass extinction at the end of the Permian: a catastrophic event or climate change. Maybe it was both. The cause remains a mystery, but the question of an extinction refuge as been, at least partly, solved.
In Greenland and China, Permian Triassic marine rock formations paint a grim picture of low oxygen conditions and few organisms in deep seas. But what about the rest of the Earth? Were there safe havens?
Examining The Evidence
Looking at trace fossils, the burrows and actions of ancient worms and marine arthropods, teams of researchers working the coasts of ancient Alberta, British Columbia and the Canadian arctic made a discovery.
There were plenty of bottom-dwelling marine organisms in the area during the extinction, an indication that oxygen levels were high enough to support life. They believe that worldwide low oxygen levels were responsible for the slow recovery after the extinction, but small habitable areas preserved enough organisms to help re-establish marine life in the Triassic seas.