Evrim Yazgin
Cosmos science journalist
Modelling of changes in vegetation during Earth’s most severe mass extinction event at the end of the Permian period could help explain how our planet’s biomes will change under conditions of another mass extinction amid current global warming.
Known as the “Great Dying”, the end-Permian mass extinction saw the disappearance of about 90% of marine species and 70% of land-based vertebrates.
Overall, 57% of all biological families and 80–95% of species went extinct during the Great Dying about 252 million years ago. The mass extinction marked the beginning of the Mesozoic era – the “Age of Dinosaurs”.
What can the plants that survived the Great Dying tell us about rapid global warming?
Geologists studying the end-Permian extinction believe that the Great Dying was caused by volcanic eruptions in modern-day Siberia which released 100 trillion metric tons of carbon dioxide into the atmosphere over 1 million years.
This process would have led to an accelerated greenhouse effect. Earth’s biosphere took several million years to recover.
New research published in the journal Frontiers in Earth Science models the effect of the mass extinction on plants to show global temperatures rose by 10°C 252 million years ago. Tundra habitats were lost and the polar regions turned temperate.
“Our study links land plant macrofossil assemblages and numerical simulations describing possible climates from the late Permian to the early Triassic,” says lead author Maura Brunetti of the University of Geneva, Switzerland.
“We show that a shift from a cold climatic state to one with a mean surface air temperature approximately 10°C higher is consistent with changes in plant biomes.”
The scientists studied 5 stages on either side of the Permian-Triassic Boundary: the Permian Wuchiapingian and Changhsingian, the early Triassic Induan and Olenekian, and the middle Triassic Anisian.
Early parts of the Permian were relatively cold. Global temperatures were much hotter in the Triassic.
Plant fossil data suggested that there were 6 major biomes that changed over the course of the Permian-Triassic extinction.
In cold temperature states, tropical latitudes had desert, while at higher latitudes cold-temperate vegetation and tundra appear. Hot states feature temperate vegetation at polar latitudes and desert at equatorial latitudes. The more CO2 is present, the warmer and wetter biomes are.
“The shift in vegetation cover can be linked to tipping mechanisms between climatic steady states, providing a potential framework for understanding the transition between Permian and Triassic,” adds Brunetti.
“This framework can be used to understand tipping behaviour in the climate system in response to the present-day CO2 increase. If this increase continues at the same rate, we will reach the level of emissions that caused the Permian-Triassic mass extinction in around 2,700 years – a much faster timescale than the Permian-Triassic Boundary emissions.”
Brunetti notes that a clearer understanding of the biome shifts during the Permian-Triassic extinction requires further research, refined models and a more comprehensive fossil record.
“The comparison between simulated biomes and the dataset is influenced by uncertainties, arising from paleogeographic reconstructions and the classification of fossil assemblages into biomes,” cautions Brunetti. “Furthermore, our climate modelling setup relies on offline coupling between models – the vegetation model uses the final outputs of the climatic model for biome reconstruction. This could be enhanced using a dynamic vegetation model.”
