An Early Mass Extinction Event Cooked Our Planet and Erased Most Life

252 million years ago, volcanic eruptions in modern-day Siberia spewed 100 trillion metric tons of carbon dioxide (CO2) into the atmosphere over the span of a million years. This natural disaster, called the “Great Dying,” killed most animals on the planet. New research shows that it also dramatically changed Earth’s ecosystems.

An international team of researchers used climate models and plant fossils to link the Great Dying with an 18-degree Fahrenheit rise (10 degrees Celsius) in average global temperatures. Their work, detailed in a study published Tuesday in the journal Frontiers in Earth Science, provides insight on how humanity’s carbon dioxide emissions might dramatically change the planet.

The researchers focused on five time periods encompassing parts of the Permian and Triassic periods: the Permian’s Wuchiapingian and Changhsingian, and the Triassic’s Induan, Olenekian, and Anisian. The Great Dying marks the transition from the Permian to the Triassic period, so it’s often referred to as the Permian-Triassic mass extinction, or the Permian-Triassic Boundary. If “Triassic” sounds familiar, that’s because it’s the period that saw the rise of the dinosaurs, whose ancestors survived the Great Dying.

“Life on Earth had to adjust to repeated changes in climate and the carbon cycle for several million years after the Permian-Triassic Boundary,” lead author Maura Brunetti, a researcher in the University of Geneva’s Group of Applied Physics Institute for Environmental Sciences, said in a Frontiers statement.

Brunetti and her colleagues estimated the changes within six different biomes (distinct ecological habitats) across the aforementioned time periods by analyzing plant fossils and computer model simulations under different temperature and CO2 level scenarios, and then cross-referenced their results. The biomes included tropical everwet biomes (hot and humid), seasonal tropical or temperate biomes (fluctuating conditions), and desert biomes (dry).

Broadly, the researchers revealed that the Permian period was cold, the Induan was unclear (more research is needed), and the Olenekian and Anisian were much hotter. “This transition from the colder climatic state to the hotter state is marked by an increase of approximately 10⁰C [18 degrees Fahrenheit] in the mean global surface air temperature,” Brunetti explained. This is consistent with the huge amounts of CO2 the volcanic eruptions launched into the atmosphere—the higher levels of CO2, the warmer and wetter the planet.

Unsurprisingly, the researchers found that the biomes changed significantly during this transition. “Tropical everwet and summerwet biomes emerged in the tropics, replacing predominantly desertic landscapes,” Brunetti continued. “Meanwhile, the warm-cool temperate biome shifted towards polar regions, leading to the complete disappearance of tundra ecosystems.” Simply put, deserts near the equator turned tropical and cold tundra landscapes closer to the pole were replaced by more temperate forests.

This “shift in vegetation cover can be linked to tipping mechanisms,” or irreversible shifts, between stable climate periods, creating a potential framework to “understand tipping behavior in the climate system in response to the present-day CO2 increase,” Brunetti added. “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.”

While the researchers caution that more research is needed to confirm their results, the study can be interpreted as a stark warning: in the very long run, continued human emissions of CO2 could change the planet more dramatically than the Great Dying.