Analysis of pollen and spores from the end-Triassic mass extinction event (ETME) suggests that intense prehistoric climate change-fuelled wildfires raged across Europe, burning fern savannahs, extinguishing forests, and drastically changing the ecosystem.
Researchers from the University of Nottingham's School of Biosciences and Department of Chemical & Environmental Engineering were part of an international team led Utrecht University in the Netherlands, investigating the ETME. Their results, published today in Nature Geoscience, suggest that the intense wildfires covering large swathes of the continent spanning thousands of miles from Luxemburg to Greenland.
The research team collected samples from across the ETME area from drill cores in Germany, Luxemburg, Denmark and the United Kingdom and found that they exhibit a remarkable darkening of pollen and spores that is at odds with simple thermal maturation. To test the underlying cause of this darkening the team conducted controlled combustion experiments on spores from the modern clubmoss plants, and these results indicate that darkening was likely be caused by fires with higher combustion temperatures resulting in darker spores. Further analyses by the team supports this interpretation with the recovery of micro-charcoal and pyrolytic polycyclic aromatic hydrocarbons (PAHs) from these rocks providing evidence of frequent and widespread wildfire activity across Europe during the ETME.
Dr Bas van de Schootbrugge from Utrecht University, a senior author on the paper, said, "Ferns are truly remarkable plants that have withstood many crises throughout Earth history, and some species can adapt to some of the most extreme environments today. They can be considered to be true disaster species."
Understanding how the world changed in the past reveals fundamental processes that could happen again. Our scenario for the ETME has similarities with studies on modern wildfires where as a result of high temperatures, changes in climatic water deficits and changes in vegetation types lead to increased fire risks and fire severity.
Some ferns can rapidly spread across disturbed landscapes, and wildfires can stimulate the ferns to spread even further and faster. While ferns would burn themselves, they can rapidly grow back from underground root systems, outcompeting other plants in the process. This effect likely played an important role in the duration of the fern spike interval that is estimated to have lasted from 40,000 years to perhaps as long as 300,000 years.
Dr Van de Schootbrugge added: "When the ferns dry-out, the thick matts act as the ideal fuel to trigger massive wildfires. Weeding and pioneering ferns formed widespread fern savannahs, with some species functioning as fire ladders while smothering other vegetation. Ferns responded to and delivered the fuel that fanned the flames, triggering repeated massive wildfires. A truly hellish world."The lesson we can learn from this, is that the combination of climate change, deforestation, and the spread of opportunistic species can provide all the ingredients for a perfect storm."
