An alerce tree (Fitzroya cupressoides) may have grown in the coastal mountains of present-day Chile around 5400 years ago, when humans were inventing writing. Sheltered in a cool, damp ravine, it avoided fires and logging that claimed many others of its kind, and it grew into a giant more than 4 meters across. The tree was festooned with mosses, lichens, and even other trees that took root in its crevices after a lot of the trunk died.
The tree known as the Alerce Milenario or Gran Abuelo may be the oldest living individual on Earth.
Jonathan Barichivich, an environmental scientist who works at the Climate and Environmental Sciences Laboratory in Paris, has estimated the age of the Alerce Milenario using a combination of computer models and traditional methods. The current record holder is a bristlecone pine named Methuselah, which has been in eastern California for over four centuries. The Utah-based aspen colony known as "Pando" is thought to be older than some of the clonal trees that originate from a common root system.
Barichivich's claim doesn't involve a full count of tree growth rings, which is likely to be questioned by many dendrochronologists. Some experts are open to the possibility.
From a distance, alerces can look like giant sequoias and redwoods. The alerces can grow to extreme ages, as demonstrated by Antonio Lara in the 1990s. The alerce stump in southern Chile had 3622 growth rings and was reported in a 1993 study. The species was the second oldest after bristlecone pines.
The study didn't include the Alerce Milenario, an ancient tree in a rainforest west of the city of La Union. The tree was discovered by Barichivich's grandfather. He thinks he was the first child to see the tree because his grandfather and mother were park rangers.
In 2020, just before the Pandemic hit, Barichivich and Lara cored part of the Alerce Milenario with an increment borer, a drill that scientists use to excise narrow cylinders of wood without harming the tree. The wood plug yielded over 2200 growth rings.
Statistical modeling was used to determine the full age of the tree because the borer couldn't reach the center. He used complete cores from other alerce trees and information on how environmental factors and random variation affect tree growth to calibrate a model that assumed a range of possible ages the tree had reached by the beginning of the period covered by the partial core. The method yielded an overall age estimate of 5484 years old, with an 80% chance that the tree has lived for more than 5000 years.
He was expecting the tree to be about 4,000 years old.
At meetings and conferences, Barichivich has presented his findings and written a report on his methods. The prospect is exciting, according to Nathan Stephenson, a scientist at the U.S. Geological Survey. He is withholding judgement until he sees more.
Others will be more difficult to convince. The only way to determine a tree's age is by counting the rings, and that requires all of the rings to be present. Ramzi Touchan of the University of Arizona's Laboratory of Tree-Ring Research says that inferring growth rates during a tree's youth can be fraught.
The method used by Barichivich accounts for such possibilities. He is going to submit a paper to a journal.
He says that even if the Alerce Milenario is the record holder, the government should protect it. Visitors to the tree can climb down from a viewing platform and walk around it, which Barichivich says harms the roots and compacts the surrounding soil. The climate is becoming more dry, making it harder for the roots to take up water.
The National Forest Corporation, which oversees the country's national parks, agrees that the tree is vulnerable. The agency has increased protections for the tree despite budgetary limitations, and has increased the number of rangers from one to five.
Bugmann says the finding highlights how some trees can live longer than most of their peers for reasons scientists don't fully understand.
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