When summer arrives is when they are talked about the most and it is that day in and day out, they are the sad protagonists of the news. However, forest fires and fire have been present on our planet for millions of years, long before we humans appeared on the scene. A group of researchers led by Ian Glasspool, from Colby College, in the United States, has found evidence of the oldest fires on record in Wales (United Kingdom) and Poland. They would have taken place 430 million years ago , in the Silurian.
For a forest fire to occur, three circumstances must occur: the existence of a fuel source, an ignition source and a sufficient amount of atmospheric oxygen, the expert points out. It seems that in the Silurian there was a sufficient amount of vegetation that would have facilitated the spread of fires . The traces of carbon that have been found coincide in time with the appearance of the first fossils of land plants. So, “as soon as there was fuel, there was a wildfire almost instantly,” says the researcher.
Silurian plants.
The plants that existed 430 million years ago were nothing like those that live with us today. Instead of trees, flowers, and grasses, the vegetation consisted of flat plants about two or three centimeters tall . There were also some plants that would have reached our waist or knee, but they were less frequent. Defying the norm, in the Silurian there was a fungus called Prototaxites that would have reached 9 meters in height. The fungus would have needed water to live and would most likely not have been found in seasonally dry areas.
Going back to the ingredients necessary for a forest fire to start, the level of atmospheric oxygen. In this regard, the publication points out that modern burning experiments indicate that if there is less than 16% oxygen in the atmosphere, the fire is unlikely to spread . “If it drops below that level, it can start a fire, but it won’t spread,” says Glasspool.
It is believed that levels of atmospheric oxygen equivalent to or even higher than those existing today, which represent 21% of the gases in the Earth’s atmosphere, were reached in the Silurian, because the photosynthesis of plants increased.
From all of the above, scientists believe that forest fires during the Silurian would have been global and important phenomena . In fact, they would have played an important role in the movement of sediments and in the carbon and phosphorus cycle.
The current findings push back the oldest fires on record by ten million years.
Fuente: Glasspol, I.J., Gastalado, R. A. 2022. Silurian wildfire proxies and atmospheric oxygen. Geology. DOI: https://doi.org/10.1130/G50193.1
