ALERSE COSTERO NATIONAL PARK IN CHILE—Some 5400 years ago, around the time people invented writing, the warning tree (Fitzroia cupressoides) may have started growing here in the coastal mountains of present-day Chile. Sheltered in a cold, damp ravine, it escaped fires and logging required by many other species, and grew into a gray giant more than 4 meters in diameter. A large part of the tree died, part of the crown fell off, and the tree became decorated with mosses, lichens, and even other trees that took root in its cracks.
Now, a tree — known as the Alerce Milenario or Gran Abuelo (great-grandfather) tree — could be given a new and extraordinary title: the oldest living person on Earth.
Using a combination of computer models and traditional methods to calculate the age of the tree, Jonathan Baricivic, a Chilean environmental scientist working at the Laboratory for Climate and Environmental Science in Paris, estimated that Allerce Milenario was probably more than 5,000 years old. That would make it at least 1 century older than the current record holder: Methuselah, a bristly pine tree in Eastern California with an annual growth rate of 4853 years below its bumpy bark. (Some clonal trees from the common root system, such as the Utah-based aspen colony known as Pando, are thought to be older, but dendrochronologists tend to focus on individual trees with numerous rings.)
Many dendrochronologists are likely to be skeptical of Barivic’s claim, which has not yet been published, because it does not include the full number of tree growth rings. But at least some experts are open to that possibility. “I completely believe in the analysis made by Jonathan,” says Harald Bugman, dendrochronologist at ETH Zurich. “Sounds like a very smart approach.”
Allerces are conifers in the same botanical family as giant redwoods and redwoods and, from a distance, can look like those giants. And the warning can grow to an extreme age, Antonio Lara of the Australian University in Chile, Valdivia, proved in the 1990s. In a 1993 study, Lara and her colleague reported a stump in southern Chile that had 3,622 growth rings. This made this species the second oldest recorded, after the bristly pines, which beat the redwoods.
But that study did not include Alerce Milenario, which stands apart from other ancient trees in the rainforest west of the city of La Union. Baricivic says that his grandfather discovered the tree around 1972. His grandfather and mother worked as guardians in the park where the tree lives, and he suspects that he was one of the first children to ever see him. “It’s a tree that is very, very close to our hearts,” he says.
In 2020, just before the pandemic struck, Baricivic and Lara pierced part of Alerca Milenario with an incremental drill - a T-shaped drill that scientists use to cut narrow cylinders of wood without damaging the wood. “In a way, the tree called me that it was time” to take the core, says Baričivić. The wood plug yielded approximately 2400 tightly spaced growth rings.
Since his drill could not reach the center of the tree, Baričivič turned to statistical modeling to determine the full age of Alers Milenari. He used complete cores from other warning trees and information on how environmental factors and random variations affect tree growth to calibrate a model that simulated the range of possible ages the tree reached by the beginning of the partial core period, along with probability for all ages. The method gave an overall age estimate of 5484 years, with an 80% chance that the tree lived for more than 5000 years.
“It was amazing,” he says; he expected the tree to be about 4,000 years old.
Baricivic presented his findings at meetings and conferences and wrote a short, informal report on his methods. Some on the ground are intrigued. “The prospect is certainly exciting,” said Nathan Stevenson, an emeritus scientist at the U.S. Geological Survey who reviewed the report. But he denies the verdict until he sees more. “As a scientist, you want a peer-reviewed publication with all the bad and dirty details.
Others will be harder to convince. Dendrochronologists traditionally believe that the number of real rings is the gold standard for determining the age of a tree. “The ONLY way to really determine the age of a tree is to dendrochronologically count the years, and that requires ALL rings to be present or counted,” wrote Ed Cook, founder of the University of Columbia’s Tree Rings Laboratory, in an email. And judging growth rates during a tree’s youth can be difficult, adds Ramsey Touchan of the University of Arizona’s Ring Research Laboratory, because young trees may have had less competition and grown faster than in later years.
Baricivic says his method explains such possibilities. He plans to submit a paper to the magazine in the coming months.
Meanwhile, he says even the possibility that Alerse Milenario could be the record holder should encourage the Chilean government to better protect it. Currently, visitors to the tree, which is located here in the park, can get off the observation platform and walk around it, which Baricivic says harms the roots and compacts the surrounding land. The climate also becomes drought, which makes it difficult for the roots to absorb water and burden the tree. “People are killing it,” Baricivic said. “Urgently demands our protection.”
Pablo Kunaca Mardones, head of the Department of Wildlife Protection at Chile’s National Forest Corporation, which oversees the country’s national parks, agrees the tree is vulnerable. He says budget constraints have hampered protective efforts, but adds that the agency has nevertheless increased protection for wood “exponentially” and increased the number of guards at the site from one to five.
Regardless of whether Allerce Milenario is accepted as the oldest tree in the world, the discovery emphasizes how some trees can live much longer than most of their peers, for reasons that scientists do not fully understand, says Bugman. “Some species do things that we think should be impossible,” he says. “There are still mysteries out there in the woods.”