An ancient bald cypress predating the Christian Crusades by a millennium has just been discovered in a North Carolina swamp, making it the oldest known wetland tree species in the world – and there could be more.

Taxodium distichum is at least 2,624 years old and was first discovered along the Black River in 2017. Now, dating techniques suggest that at least two other trees in the same Three Sisters Cove are also over 2,000-years-old and several others at least a millennium.

“The discovery of living bald cypress trees well over 2,000 years old provides quantitative evidence for the ecological integrity of this wetland system, extends the proxy paleoclimate record of precipitation variability for the Southeast by over 900 years, and will help advance public and private preservation of the Black River,” wrote the authors in Environmental Research Communications.

Dating such an old tree can be difficult as many experience heart rot, a fungal disease that causes the wood to decay at the center of the trunk and branches. To combat this, researchers deliberately took nondestructive core samples from more than 100 of the healthiest trees in a previously unvisited wetland forest in order to determine their minimum age. They aged the tree by counting its tree rings, a method known as dendrochronology. As a tree grows, it forms new cells that make a circle around its center called annual growth rings that show how much wood was produced during one growing season, helping researchers estimate annual precipitation and other climatic conditions during that time.

The growth rings match up with records from 1985 to present of growing season precipitation totals over the southeastern United States, as well as Northern Hemisphere atmospheric data. Radiocarbon dating confirmed this analysis, suggesting that the tree samples could provide the longest exactly-dated measurement of climate yet developed in the eastern part of the country.

“It is exceedingly unusual to see an old-growth stand of trees along the whole length of a river like this,” said lead researcher David Stahle in a statement. “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.”

The ancient cypresses allow us to see what Northern American ecosystems might have looked like in colonial and pre-colonial times. The oldest trees predate even the oldest paleoclimate record in the southeast US by at least 900 years, telling us about droughts and flooding that occurred throughout the continent’s history.

And there could be ones that are even older yet.

Found on a part of the 6,400-hectare (16,000-acre) preservation owned by The Nature Conservancy, the researchers say the trees provide an incentive to promote public and private conservation efforts in the Black River watershed. That’s because the preserve is recognized as one of the cleanest and high-quality waterways in the state, but the area is still threatened by logging, water pollution, and sea level rise.  

“The area of old growth bald cypress was 10 times larger than I realized,” Stahle said. “We think there are older trees out there still.”

Currently, there are still thousands of additional hectares in the area with high-quality ancient forests that the researchers say are still unprotected.