American researchers in the forests of bald cypresses in the United States have just confirmed it: the rings of trees not only tell us about their age but they also allow us to read the weather in the past.
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Each ring, each ring, corresponds to the layers of cells that develop each year, to make the trunk grow and circulate the sap. In the 16th century, Leonardo da Vinci had already made the link between the width of these rings and climatic variations. What various works have since scientifically confirmed. Very recently, American researchers from the University of Alabama have just shown that there is also a link between the occurrence of hurricanes and additional rings on the tree trunk.
Cypress trees that have faced hurricanes had more rings than their age. The researchers were able to see this by taking very fine cores the size of a pen from 120 bald cypress trees, which grow along the Gulf of Mexico. They found that the seasons marked by the passage of a hurricane sometimes appeared as an additional ring. Normally, each new ring starts in the spring and expands through the fall. But in the event of heavy rainfall or flooding – which happens in the event of a hurricane or storm – the tree is deceived, it thinks it is spring and therefore begins a new phase of growth, hence the appearance of an extra ring. These researchers have thus found a correlation between these additional rings and the occurrence since 1932 of hurricanes and floods in the region where these cypresses grow.
This discovery serves on the one hand to study how the tree manages to resist the stress of a hurricane. Because when scientists analyze the chemical composition of each streak in tree trunks, this provides information on the physiological functioning of the tree at a given time and therefore on its weather resistance strategy. Above all, by scrutinizing the trunks of trees, these American researchers can read the weather of the past and trace the frequency of hurricanes over the last centuries to compare it to that which appears with global warming. Because today we know for example that the 2020 season with 30 storms in the Atlantic was one of the most active since 1850, but it is difficult to know how it was before. Next step therefore for these American scientists, led by the geographer Clay Tucker, to take an interest in taking samples of tree rings, which are more than 1,000 years old, to go back in time and count the hurricanes since the time that corresponds to the end of the Middle Ages, with us.