Ancient Wildfires: Researchers Examine Evolution Of Forest Fires

Even though plants first emerged on Earth 400 million years ago, it was not until approximately 80 million years later that wildfires began ripping through forests and grasslands like they do today in California, a new study revealed.

So, if there was plenty of foliage, what prevented raging wildfires during this time? Researchers from University of Royal Holloway London discovered that there simply was not enough oxygen in the atmosphere, according to a news release. It turns out that widespread forest fires were not present until around 360 million years ago, in the latest Devonian Period, when oxygen levels rose to above 17 percent. Today, the atmospheric oxygen is approximately 21 percent, the release noted.

Fire is just a process of combustion, where oxygen in the air chemically reacts with some sort of fuel. In the case of wildfires, the fuel would be plants, and the reaction would be driven by heat, or high atmospheric temperatures.

For their study, researchers examined ancient charcoal that washed into an ocean that originally covered present day North America. This revealed that widespread fires were very rare until the Early Mississippian; extensive charcoal suggests well-established fire systems, researchers explained in their study.

"What surprised us was that many of these early extensive fires were surface fires burning the undergrowth, as we can see the anatomy of the plants being burned through scanning electron microscope studies of larger pieces of the fossil charcoal," Andrew C. Scott, one of the study researchers and a professor in the Department of Earth Sciences at Royal Holloway, explained in the release. "This may be because plants were small and were limited in their distribution but over the following 50 million years they diversified and spread across the globe and some of the plants were trees and could have provided a good fuel to burn."

This study helps researchers understand the evolution of regular forest fires and how they would have impacted the growth of both plants and animals during this time.

"Extensive forest fires soon followed, however and we see widespread charcoal deposits throughout the Lower Carboniferous (Mississippian) Period 358-323 million years ago," Scott concluded in the release.

Their study was recently published in the American Journal of Science.

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