Fern Spike Fueled Wildfires During the End-Triassic Mass Extinction

Volcanic Origins and the ‘Fern Spike’

The end-Triassic mass extinction remains one of the most violent periods in Earth’s history. According to a blog post by the U.K.’s Natural History Museum, the crisis began approximately 201 million years ago when the region now known as the Atlantic Ocean experienced massive volcanic eruptions. These events released vast quantities of carbon dioxide and sulfur dioxide, driving rapid climate change, rising sea levels, and increased ocean acidity.

While volcanic activity is traditionally cited as the primary driver of the extinction, researchers are now looking at the role of flora. As global temperatures and carbon dioxide levels climbed, tree-dominated forests began to die off. In their place, ferns rapidly colonized the landscape, particularly in areas of modern Northwest Europe. This phenomenon, known as a “fern spike,” is documented in sedimentary drill cores where researchers observed layers that were progressively, extremely dark brown, according to Bas van de Schootbrugge, an Earth scientist at Utrecht University and senior author of the study.

How Ferns Fueled a ‘Hellish World’

The proliferation of ferns did more than change the scenery; it fundamentally altered the planet’s fire regime. Once these ferns dried out, they created thick, flammable mats that served as ideal fuel for wildfires. This created a feedback loop of destruction that lasted between 40,000 and 300,000 years.

The hypothesis that these wildfires were widespread is supported by evidence found within paleontological records. The research team analyzed sedimentary drill cores from across Europe, finding high concentrations of charcoal and hydrocarbons—specifically polycyclic aromatic hydrocarbons (PAHs)—that correspond directly with the fern spike interval. According to van de Schootbrugge, the consistency of these dark, charred layers across four different core sites, despite their varying geological histories, confirms that the wildfires were a systemic event rather than a localized occurrence.

Analyzing the Paleo-Fire Record

To confirm that the darkened material in the cores was the result of external burning rather than geological pressure or temperature changes, the researchers conducted an extensive analysis of pollen and spores. The team generated 15,000 measurements from samples taken before, during, and after the extinction interval.

The data showed that the darkened sections did not vary significantly based on the type of plant present, which the researchers identified as a strong indication that it was the result of an outside force. While ferns are often associated with resilience—capable of bouncing back from their underground root systems even after their leaves are burned—their ability to thrive in extreme environments made them the perfect, consistent fuel source for the centuries-long fire regime that compounded the mass extinction.

Interconnected Systems and Modern Lessons

The research suggests that the end-Triassic mass extinction was not caused by a single source, but by a complex, interconnected series of events. While the volcanic activity acted as the initial trigger, the transition to a fern-dominated landscape created a dangerous, self-sustaining cycle of fire.

The study highlights how Earth’s systems are inextricably linked, with biological responses to climate change potentially accelerating environmental collapse. As van de Schootbrugge noted in the study’s findings, the event serves as a stark reminder of how unexpected biological collaborations can lead to drastic outcomes—a dynamic that researchers emphasize remains highly relevant to understanding global climate systems today.