A team of scientists from University College Cork (Ireland), the University of Connecticut (USA), and the Natural History Museum of Vienna (Austria) have uncovered how plants responded to catastrophic climate changes 250 million years ago. Their findings, published in GSA Bulletin, reveal the long, drawn-out process of ecosystem recovery following one of the most extreme periods of warming in Earth’s history: the “End-Permian Event.”
UConn Department of Earth Sciences Professor and Department Head Tracy Frank, Professor Chris Fielding, and Associate Professor Michael Hren are co-authors on the paper. Frank and Hren performed a series of geochemical analyses through the sedimentary strata recording the event to help tie down ancient climate conditions, and Fielding provided sedimentological data to constrain ancient environmental conditions.
The End-Permian Extinction, also known as the Great Dying, is the most severe ecological crisis of the past 500 million years.
“It is believed to have entailed a five-fold increase in atmospheric CO2, global temperature rise of up to 10° C or more, ozone depletion, widespread wildfires, and changes in rainfall patterns across the Earth’s surface,” says Fielding.
With more than 80% of ocean species wiped out, the end-Permian event was the worst mass extinction of all time. But the impacts of this event for life on land have been elusive. By examining fossil plants and rocks from eastern Australia’s Sydney Basin, researchers have pieced together a multi-million-year story of resilience, recovery, and the long-term effects of climate change following the Great Dying.
The long, unsteady path to ecosystem recovery
The fossils from these Australian rocks show that conifers, like modern pines, were some of the earliest to colonize the land immediately after the End-Permian catastrophe. However, the recovery back to flourishing forests was not smooth sailing.
The researchers discovered that even higher temperatures during the “Late Smithian Thermal Maximum,” approximately 3 million years after the End-Permian Extinction, caused the collapse of these conifer survivors. In turn, they were replaced by tough, shrubby plants resembling modern clubmosses. This scorching period lasted for about 700,000 years and made life challenging for trees and other large plants.
It wasn’t until a subsequent significant cooling event—the “Smithian-Spathian Event”—that large, but unusual plants called “seed ferns” began to flourish and establish more stable forests. These plants eventually came to dominate Earth’s landscapes for millions of years, paving the way for the lush forests during the Mesozoic “age of dinosaurs.”
“The first post-apocalyptic floras were ‘opportunistic’ in nature, perhaps the equivalent of what in the modern world are called ‘weeds.’ These plants were mostly small, and were sparsely distributed. Larger trees and other more complex plant types took considerable time to become established as surface conditions gradually improved,” says Fielding.
After millions of years, the forest ecosystems of the Mesozoic came to look like those from before the end-Permian collapse. But crucially, the plant species that made up the new forests were completely different. “The term ‘recovery’ can be misleading” says Chris Mays, Leader of the Mass Extinction Group at University College Cork, “forests recover eventually, but extinction is forever.”
What does this mean for us?
By understanding how ancient plant ecosystems weathered extreme climate swings, researchers hope to learn valuable lessons about how modern plants and ecosystems might cope with today’s climate crisis. Ecosystems depend on a fragile balance, with plants as the backbone of land food webs and climate regulation.
“This research highlights how crucial plants are, not just as the base of land food chains, but also as natural carbon sinks that stabilize Earth’s climate,” explains Ph.D. student Marcos Amores, the study’s lead author, who spent time in the UConn Earth Science Department as a visiting scholar. “The disruption of these systems can have impacts lasting hundreds of thousands of years, so protecting today’s ecosystems is more important than ever.”
This deep dive into Earth’s distant past reminds us that plants are unsung heroes of life on Earth—then, now, and in the future.
“The protracted and complex path back to ‘normality’ after the end-Permian crisis tells us that Earth can recover from devastating environmental tipping points, but that recovery may take periods of time beyond the range of human endurance or even existence,” says Fielding.
