The great-grandfather in the rainforest
In a damp, cool valley of Chile's Alerce Costero National Park stands a colossal tree known as the Alerce Milenario, or Gran Abuelo (Great-Grandfather). This specimen of Fitzroya cupressoides, or Patagonian cypress, has a trunk diameter of more than 4 meters and towers over the surrounding Valdivian temperate rainforest. For decades, it was known to be old, but its true age was a mystery. The standard method for aging a tree, dendrochronology, requires a core sample from bark to the central pith to count every growth ring. The Gran Abuelo's sheer size and potentially rotten core make this impossible without a tool long enough to pass through its entire width—a procedure that could irrevocably harm the organism.
The established record-holder for the world's oldest non-clonal tree is "Methuselah," a Great Basin bristlecone pine (Pinus longaeva) in California, with a confirmed age of 4,853 years. Another Patagonian cypress was previously verified by ring count to be 3,622 years old, establishing the species as one of the planet's longest-lived. The Gran Abuelo, however, was a unique scientific challenge: how to determine the age of a tree you cannot fully measure.
A controversial calculation
In 2020, scientist Jonathan Barichivich, who grew up near the park, took on the challenge with colleague Antonio Lara. Using the longest available increment borer, they extracted a partial core from the Gran Abuelo. This sample, reaching only partway to the center, contained an astonishing 2,400 tightly packed growth rings. To account for the missing rings, Barichivich developed a statistical model. The model incorporated data from complete cores of other alerce trees and factored in how environmental variations affect growth rates.
The result of this modeling was an estimated age of 5,484 years. This calculation suggests the Gran Abuelo is 600 years older than Methuselah. Barichivich's model indicates an 80% probability that the tree is over 5,000 years old. The finding, however, remains controversial within the dendrochronology community because it is not based on a complete and direct ring count. The research has been presented at scientific conferences but has not yet passed through formal peer review, which is a necessary step for official verification. Until then, the Alerce Milenario is a potential record-holder whose greatest secret—its exact age—is protected by its own immense size.