Scientists have discovered the world's oldest wildfires owing to 430-million-year-old charcoal deposits discovered in Wales and Poland. They provide invaluable information on life on Earth during the Silurian epoch.
Plant life would have relied substantially on water to reproduce back then, and would have been unlikely to appear in areas that were dry for part or all of the year. The study's flames would have burnt through fairly short vegetation, with the occasional knee- or waist-high plant thrown in for good measure.
According to the researchers, the ancient fungus Prototaxites would have dominated the environment rather than trees. The fungus's exact size is unknown, however it is said to have grown to a height of nine meters (almost 30 feet).
"It looks now as though our evidence of fire coincides closely with our evidence of the earliest land plant macrofossils," states paleobotanist Ian Glasspool of Colby College in Maine.
"So as soon as there's fuel, at least in the form of plant macrofossils, there is wildfire pretty much instantly."
Wildfires require fuel (plants), an ignition source (here, lightning strikes), and enough oxygen to burn to survive.
According to the researchers, the ability of the flames to spread and leave charcoal deposits indicates that Earth's atmospheric oxygen levels were at least 16 percent.
That percentage is currently around 21%, although it has fluctuated drastically over Earth's history. According to their findings, atmospheric oxygen levels 430 million years ago may have been as high as 21% or perhaps higher.
All of this knowledge is extremely important to paleontologists. Increased plant life and photosynthesis, according to the theory, would have contributed more to the oxygen cycle around the time of the wildfires, and understanding the specifics of that oxygen cycle across time offers scientists a clearer sense of how life would have developed.
"The Silurian landscape had to have enough vegetation across it to have wildfires propagated and to leave a record of that wildfire," explains Colby College paleontologist Robert Gastaldo.
"At points in time that we're sampling windows of, there was enough biomass around to be able to provide us with a record of wildfire that we can identify and use to pinpoint the vegetation and process in time."
The geography that is now Europe looked very different hundreds of millions of years ago, and the two sites that the researchers studied would have been on the old Avalonia and Baltica continents during the time these flames were burning.
Wildfires would have played an important role in carbon and phosphorus cycles, as well as the movement of sediment on the Earth's surface, both then and now. It's a complicated set of procedures that need a lot of unpacking.
This finding aids in that unpacking, since it breaks the previous record for the oldest wildfire on record by 10 million years, and it also emphasizes the importance of wildfire study in chronicling Earth's history.
"Wildfire has been an integral component in Earth-system processes for a long time and its role in those processes has almost certainly been underemphasized," adds Glasspool.
