Earth's Oldest Trees Help Us Reconstruct Ancient Climate Conditions


Researchers have identified a group of ancient bald cypress trees which are over 2,000 years old in the forested wetlands of North Carolina’s Black River. Staggeringly, the scientists found that one of the trees was 2,624 years old. The ancient group—consisting of perhaps 50 individuals—was discovered in 2017 by lead author of the study David Stahle from the University of Arkansas and his colleagues, who took 110 core samples measuring about 0.2 inches in diameter from various trees without harming them. "We think there are older trees out there still" Stahle says. The trees form part of an intact ecosystem of wetlands that extend along most of the 65-mile length of the Black River, which the researchers call one of the “great natural areas of eastern North America.” The river has been recognized as one of the cleanest and high-quality waterways in North Carolina, and Stahle’s work has helped boost preservation efforts in the area. "It is exceedingly unusual to see an old-growth stand of trees along the whole length of a river like this," Stahle said. "Bald cypress are valuable for timber and they have been heavily logged. Way less than 1 percent of the original virgin bald cypress forests have survived." Aside from their impressive age, the trees can also help to reconstruct ancient climate conditions in the region. This is because their growth is affected in different ways by both dry and wet conditions, and this shows up in the core samples. In fact, the researchers say that the tree samples have provided the longest exactly-dated climate proxy—a source of climate information taken from natural material which can be used to estimate past conditions—in eastern North America, showing evidence of drought and flooding during pre-colonial times. "The old bald cypress trees at Black River record the history of growing season precipitation for the mid-Atlantic region extending back into prehistory over 2,000 years," Stahle said. "The precipitation record in these trees is amazingly accurate and detailed." "It includes the droughts recorded with rain gauges during the 20th and 21st centuries, and the severe multi-year droughts of 1587-1589 associated with the disappearance of the Lost Colony of Roanoke Island and the drought of 1606-1612 concurrent with the hardships suffered during the early years of the Jamestown Colony, the first successful English settlement in the New World," he said. To date, only 8 species have been proven to live for more than this amount of time—6 of which are found in the western US, one in Chile and, now, the bald cypress trees in North Carolina. Only individual trees of Sierra juniper (2,675 years old), giant sequoia (3,266 years old), alerce (3,622 years old) and Great Basin bristlecone pine (5,066 years old) have been demonstrated to live longer. Nevertheless, the bald cypress tree is the oldest-known wetland tree.

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