Oldest tree of the World.

Patagonian cypresses, also known as alerces, are native to Chile and Argentina and have long been recognized as the world’s second longest-lived tree species. The previous record-setting alerce was identified in the early 1990s by counting tree rings on a cut stump; it was more than 3,600 years old. (The oldest known giant sequoia, the third longest-lived species, was identified the same way and lived to 3,266.)

But earlier this month, a story in Science by Gabriel Popkin revealed that environmental scientist Jonathan Barichivich and the researcher who first identified that old alerce had been studying another tree in a Chilean national park. The researchers used a T-shaped increment borer to drill in and remove a core sample from the moss-draped cypress. The boring device couldn’t reach the center of the tree, which is more than a dozen feet in diameter. But by combining their core sample with tree-ring information from other alerces, and using computer modeling, the pair estimated the tree was roughly 5,400 years old, with an 80 percent chance it was more than 5,000 years old.

The research has not been peer-reviewed yet, but Barichivich has shared his findings at conferences. Nate Stephenson, an emeritus scientist with the U.S. Geological Survey, who has studied giant sequoias for four decades, finds the results interesting, but is withholding judgment until Barichivich publishes a paper detailing his methods. Still, “the prospect is certainly exciting,” Stephenson tells Popkin.

Others, though, are quite skeptical. Peter Brown, founder of Rocky Mountain Tree Ring Research, which gathers information on the world’s oldest trees, says Barichivich’s approach is too novel to make such a bold claim before publication. “There are many assumptions necessary for extrapolating total age from that,” Brown says.

Brown doesn’t doubt the tree is significant. The partial core alone seems to show the tree was at least 2,400 years old, which would put it among the top 10 oldest trees on Brown’s list. But Brown has other reasons to be suspicious. For example, “this new estimated age is over 1,500 years older than the oldest known (alerce) tree to date,” Brown says.

Brown also sees significant differences between the types of environments that tend to support the very oldest trees and the surroundings of the Patagonian cypress. In an isolated, austere landscape, like the snowy, rocky homes of slow-growing bristlecone, trees can just keep on going. Mossy rainforests, on the other hand, are full of life—and threats.

Scientists still argue about why some trees are able to live so long. “My contention is that trees don’t necessarily die from old age like mammals,” Brown says. “Something has to come along and kill them.”

Barichivich understands the skepticism. He says his colleague has found another alerce stump whose tree rings can all be counted and show it to be about 4,100 years old. (That data is also not yet published.) He also argues that tree-ring data suggests alerce actually grow more slowly than bristlecones, meaning their wood is also very dense.

And as part of a recent research team that analyzed the relationship between the world’s longest-lived trees and climate, Barichivich believes the two species’ worlds are similar in the most important ways. The Chilean Coast Range is nothing like the American West, he says, “but there are special conditions here, too.”

His ancient alerce grows on a cloudy south-facing slope, where the annual mean temperature is roughly 45 degrees Fahrenheit. It’s found in a ravine, protected from fire and until recently from humans. Barichivich says his own Chilean grandfather, who worked as a ranger in the park, discovered the tree in the early 1970s and may well have been the first person to touch it.