When Europe Burned for Thousands of Years: How Ferns Helped Fuel an Ancient Climate Catastrophe

Around 201 million years ago, Earth witnessed one of its greatest environmental disasters.
During the end-Triassic mass extinction, enormous volcanic eruptions triggered rapid global warming, destroyed forests across Northwest Europe, and created conditions for relentless wildfires. Surprisingly, scientists now believe that one of the biggest contributors to these ancient fires was not trees, but vast fields of fast-growing ferns.

The End-Triassic Mass Extinction

The end-Triassic mass extinction ranks among the five largest extinction events in Earth’s history. It occurred about 201 million years ago, eliminating numerous species of plants and animals and reshaping life on our planet.

Scientists have linked this catastrophic event to the breakup of the supercontinent Pangaea. Massive volcanic eruptions released nearly 100,000 gigatonnes of carbon dioxide (CO₂) into the atmosphere. As greenhouse gases accumulated, global temperatures increased by approximately 5°C to 10°C.

The hotter climate brought severe droughts, unpredictable rainfall, and widespread forest collapse across much of Northwest Europe.

Ferns Took Over the Landscape

With forests disappearing, a new type of vegetation quickly spread across the damaged landscape. According to a study published in Nature Geoscience, large fern-dominated savannahs replaced the once-thriving forests.

Unlike trees, ferns regenerate rapidly from underground stems called rhizomes. Even after intense fires, these underground structures survive and produce new growth within a short time.

This ability allowed ferns to dominate the landscape, but it also created an unexpected problem. Dense fern vegetation dried easily, becoming highly flammable fuel for recurring wildfires.

Ancient Fire Evidence Hidden in Fossil Spores

Researchers led by geologist Bas van de Schootbrugge from Utrecht University examined sediment cores collected from the United Kingdom, Germany, Luxembourg, and Denmark. One newly drilled core from Britain extended nearly 640 meters, preserving an exceptional geological record.

The scientists analyzed nearly 15,000 fossil pollen grains and fern spores using a technique known as the Palynomorph Darkness Index (PDI). This method measures how dark fossil spores appear under a microscope.

The results showed that fern spores became significantly darker during the extinction event, indicating they had been scorched by wildfire before becoming fossilized.

Researchers also discovered:

• Large quantities of fossil charcoal
• Fire-related chemicals called polycyclic aromatic hydrocarbons (PAHs)
• Evidence of repeated wildfires across multiple European regions

A Self-Sustaining Fire Cycle

The research suggests that ferns were more than simple survivors. They helped maintain an ecological feedback loop that allowed fires to continue for thousands of years.

1. Massive volcanic eruptions warmed the climate.
2. Heat and drought destroyed forests.
3. Fast-growing ferns rapidly covered the land.
4. Dry fern vegetation ignited easily.
5. Wildfires prevented forests from recovering.
6. Ferns regenerated quickly after each fire.
7. The fire cycle repeated again and again.

Researchers estimate this “fern spike” may have lasted anywhere between 40,000 and 300,000 years, making it one of the longest-lasting ecological disruptions known from Earth’s fossil record.

Why Ferns Survived

Many fern species possess underground rhizomes that remain protected even after surface vegetation burns. Once rainfall returns, fresh fronds quickly emerge from these underground stems.

Trees require many years to recover after severe fires, giving ferns a significant ecological advantage during periods of repeated burning.

Lessons for Today

Although these events occurred more than 200 million years ago, they provide valuable insights into how ecosystems respond to climate change.

The study demonstrates that rising temperatures, drought, forest loss, and highly flammable vegetation can create self-reinforcing wildfire cycles that persist for thousands of years.

Lead researcher Bas van de Schootbrugge describes this combination of climate change, deforestation, and rapidly spreading pioneer plants as a “perfect storm” capable of transforming entire ecosystems.