Scientists have traced the oldest forest fires ever detected thanks to 430 million year old charcoal deposits in Wales and Poland. They give us valuable insight into what life on Earth was like during the Silurian period.
At the time, plant life relied heavily on water to reproduce and would likely not have appeared in dry regions for part or all of the year. The wildfires discussed in the study would have burned very short vegetation, as well as occasional plants reaching the knees or waist.
The landscape would have been dominated not by trees but by the ancient fungus Prototaxites, say the researchers. Not much is known about the mushroom, but it is thought to have grown up to nine meters (or nearly 30 feet) tall.
“It now appears that our evidence for fire coincides closely with our evidence for the earliest macrofossils of land plants,” says paleobotanist Ian Glasspool from Colby College in Maine.
“So as soon as there is fuel, at least in the form of plant macrofossils, there is a forest fire pretty much instantaneously.”
To exist, fires need fuel (plants), a source of ignition (which here would have been flash strikes), and enough oxygen to burn.
The fact that the fires may have spread and left charcoal deposits suggests Earth’s atmospheric oxygen levels were at least 16%, the researchers said.
Today, that level is 21%, but it has varied considerably over Earth’s history. Based on their analysis, the team believe that atmospheric oxygen levels 430 million years ago could have been 21% or even higher.
This is all very useful information for paleontologists. The idea is that increased plant life and photosynthesis would have contributed more to the oxygen cycle at the time of these wildfires, and knowing the details of this oxygen cycle over time gives scientists a better idea of how life could evolve.
“The Silurian landscape must have had enough vegetation for the forest fires to spread and to leave a trail of that forest fire”, says paleontologist Robert Gastaldoalso from Colby College.
“At the times we sampled windows, there was enough biomass to provide us with a record of wildfires that we can identify and use to identify vegetation and treat over time.”
The landscape that is Europe today was very different hundreds of millions of years ago, and the two sites the researchers used for their analysis would have been on the ancient Avalonia and Baltic continents as these wildfires raged.
Forest fires then, like now, would also have contributed significantly to the cycles of carbon and phosphorus, as well as the movement of sediments on the Earth’s surface. It’s a complex combination of processes that takes a lot of unpacking.
This discovery certainly contributes to this unpacking – breaking the previous record for the oldest recorded wildfire by 10 million years – and it also highlights the importance that wildfire research could have in mapping history. of the earth.
“Wildfire has been an integral part of Earth system processes for a long time and its role in these processes has almost certainly been underestimated,” says Glasspool.
The research has been published in Geology.