Ancient bald cypress trees archive climate secrets, future clues

A new research study led by UGA anthropology alumna Katherine Napora (Ph.D. '21) reveals how dramatic shifts in climate can have long-lasting effects on even the toughest, most iconic trees – and offers a glimpse into the powerful forces that shape our natural world.

Researchers from Florida Atlantic University and the UGA Museum of Natural History studied bald cypress trees from a buried subfossil deposit at the mouth of the Altamaha River near Darien, Georgia:

Deep in the swamps of the American Southeast stands a quiet giant: the bald cypress (Taxodium distichum). These majestic trees, with their knobby “knees” and towering trunks, are more than just swamp dwellers – they’re some of the oldest living organisms in Eastern North America. Some have been around for more than 2,500 years, quietly thriving in nutrient-poor, flooded forests where most other trees would wither.

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Results of the study, just published in the Proceedings of the National Academy of Sciences, reveal that beginning around 500 A.D., the trees began to live shorter lives and grow at a faster pace. Before this period, bald cypress trees in the region commonly lived for more than 470 years. However, after 500 A.D., their average lifespan declined sharply to just 186 years.

This coincided with a major climate downturn in the sixth century known as the Vandal Minimum, a time of cooling temperatures and global upheaval likely caused by volcanic eruptions and possibly even a comet impact. After this period, the trees not only lived shorter lives – they also grew faster, which may have made them more vulnerable to stress and damage over time. The last of the post-500 A.D. long-lived trees died during the Little Ice Age, which lasted from about 1200 to 1850 A.D., another chilly period with big environmental changes.

Despite these troubling trends in the past, hope still stands tall in the Southeast’s old-growth swamps. In some rare pockets of preserved forest, bald cypress trees between 800 and 2,600 years old are still alive today.

Interestingly, scientists found no signs of fire, logging or human interference in the death of these trees, which makes the exact cause a mystery. However, the pattern is clear: after 500 A.D., bald cypress trees at this location on the Georgia coast never again reached their former longevity.

“This shift wasn’t a brief disruption. Even centuries later, the trees never regained their former longevity. In fact, their lifespans continued to decline over time,” said Katharine G. Napora, Ph.D., senior author and an assistant professor in the Department of Anthropology within FAU’s Dorothy F. Schmidt College of Arts and Letters . “The last of the long-lived trees found in the deposit died during another major climatic event, the Little Ice Age. Our findings underscore how long-lasting the localized effects of major climate shifts can be, especially for coastal forests that are already vulnerable to wind damage, saltwater intrusion and rising seas.”