5,000-year-old tree found in Chile

(ORDO NEWS) — About 5,400 years ago, around the time humans invented writing, the Alerce tree (Fitzroya cupressoides) may have started growing here in the coastal mountains of present-day Chile.

Nestled in a cool, damp gorge, it escaped the fires and deforestation that destroyed many other similar trees, and grew into a huge giant over 4 meters across. Most of the trunk died, part of the crown fell off, and the tree was overgrown with mosses, lichens, and even other trees that took root in its crevices.

Now known as Alerce Milenario or Gran Abuelo (great-grandfather), this tree can now lay claim to a new and unusual title: the oldest living thing on Earth.

Using a combination of computer models and traditional methods for calculating the age of trees, Jonathan Baricivic, a Chilean environmental scientist working at the Laboratory for Climatic and Environmental Sciences in Paris, has calculated that Alerce Milenario is likely to be over 5,000 years old.

This makes it at least 1 century older than the current record holder: Methuselah, a bristlecone pine in eastern California that has 4,853 growth rings under its gnarled bark.

(Some clonal trees derived from a common root system, such as the Utah aspen colony known as “Pando”, are thought to be older, but dendrochronologists usually focus on individual stems with countable rings.)

Many dendrochronologists are likely to be skeptical of Baricivic’s claim, which has not yet been published, as it does not involve a full count of the tree’s growth rings.

But at least some experts are open to the possibility. “I have complete confidence in the analysis that Jonathan did,” says Harald Bugmann, dendrochronologist at ETH Z├╝rich. “That sounds like a very smart approach.”

Aleris are conifers in the same botanical family as giant sequoias and redwoods, and from a distance they can resemble these giants. In the 1990s, Antonio Lara from the Australian University of Chile (Valdivia) proved that Aleris can grow to a critical age.

In their 1993 study, Lara and colleagues reported a halberd stump in southern Chile that had 3,622 growth rings. This made this species the second oldest after bristlecone pines, ahead of sequoias.

But this 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 his grandfather discovered the tree around 1972.

His grandfather and mother worked as rangers in the park where the tree grows, and he suspects he was one of the first children to see it. “This tree is very, very close to our hearts,” he says.

In 2020, just before the start of the pandemic, Baricivic and Lara cut out part of the Alerce Milenario with an incremental drill, a T-shaped drill that scientists use to cut narrow cylinders of wood without harming the wood.

“In a way, the tree gave me the signal that it was time” to take a core, says Baricivic. The wood cork produced approximately 2400 densely spaced growth rings.

Since his drill was unable to reach the center of the tree, Baricivic turned to statistical modeling to determine the full age of the Alerce Milenario.

He used full cores of other Alerce trees and information about how environmental factors and random variation affect tree growth to calibrate a model that simulated the range of possible tree ages at the start of the incomplete core period, along with the probability for each age.

This method yielded an overall age estimate of 5484 years, with an 80% chance that the tree lived to be over 5000 years old.

“It was amazing,” he says; he expected the tree to be about 4,000 years old.

Baricivic presented his results at meetings and conferences and wrote a short, informal account of his methods. Some experts in the field are intrigued.

“The outlook is certainly exciting,” says Nathan Stevenson, USGS Distinguished Scientist who reviewed the report. But he holds back until he sees more. “As a scientist, you want a peer-reviewed publication with all the details.”

Others will be more difficult to convince. Dendrochronologists traditionally view counting actual rings as the gold standard for determining a tree’s age.

“The ONLY way to really determine a tree’s age is by dendrochronological ring counting, and that requires ALL rings to be present or counted,” Ed Cooke, founding director of Columbia University’s Tree Ring Laboratory, wrote in an email.

And inferring growth rates when a tree is young can be fraught, adds Ramzi Tuchan of the University of Arizona Tree Ring Research Laboratory, because a young tree could have less competition and grow faster than in later years.

Baricivic says his method takes those possibilities into account. In the coming months, he plans to submit an article to one of the journals.

Meanwhile, he said, even the possibility that Alerce Milenario could break the record should spur the Chilean government to better protect the tree.

Currently, visitors to the tree, which is located in the park, can walk down from the observation deck and walk around it, which, according to Baricivic, damages the roots and compacts the surrounding soil.

The climate is also becoming drier, making it harder for roots to absorb water and stressing the tree. “People are killing him,” says Baricivic. “It urgently needs our protection.”

Pablo Cunazza Mardones, head of wildlife protected areas at Chile’s National Forest Corporation, which oversees the country’s national parks, agrees that the tree is vulnerable.

He says budget constraints are hampering protection efforts, but adds that the agency has nonetheless increased protection for the tree “exponentially” and increased the number of rangers on the site from one to five.

Whether or not Alerce Milenario is recognized as the world’s oldest tree, this finding highlights that some trees can live much longer than most of their brethren, for reasons scientists don’t fully understand, Bagmann says. “Some species are doing what we think should be impossible,” he says. “There are still mysteries in the forest.”

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