A recent study conducted by two Chilean researchers examined a remarkable specimen of a tree known locally as the Millennium Alenen or the Great Grandfather. The tree sits in Alenen Costero National Park, within the La Unión region of Chile. Scientists estimate its age at approximately 5,484 years, a figure that positions it as the oldest living tree on record at present. By comparison, the bristlecone pine known as Methuselah in the United States has been credited with an age around 4,853 years. The finding marks a significant shift in our understanding of ancient trees and the longevity of the species present in Chilean forests.
The result surpassed even the highest expectations held by the study’s co-authors, including Jonathan Barichivich and Antonio Lara, and was achieved in collaboration with several institutions such as Alenen Corporation, Universidad Austral de Chile, and Conaf. Barichivich, a forest engineer and expert in global ecology and climate, has long been associated with researchers who study ancient larch ecosystems. He explained that the Great Grandfather project is part of a broader initiative to explore the functioning and growth of forests dominated by this species.
In explaining the research framework, the team notes that permission was secured to study elderly alder trees with extreme care. Growth rings offer a direct method to determine a tree’s age by counting annual rings from a sample, often reaching toward the interior. Some studies rely on samples extracted through cautious procedures that avoid harming the tree. The researchers emphasize that the central portion of very old trees is challenging to access because cores must be drilled through substantial wood, sometimes requiring holes greater than two meters in diameter to reach the center. Additionally, ancient trees frequently experience center decay, which can obscure the true number of growth rings and complicate age estimates.
A Statistical Method
So how did the team arrive at a reliable age for such a colossal specimen? Barichivich described a statistical approach designed to model growth in portions of the tree that could not be sampled. At a depth of 90 centimeters, the observed rings correspond to about 2,400 years and represent roughly 43 percent of the tree’s radius. The researchers devised a method that integrates the entire growth history observed across multiple sampled specimens from the population. This approach allows them to infer the age distribution for the portion of the tree that remains unobserved in a direct sample.
Barichivich added that the team is confident in their method. Whether or not the Great Grandfather is the absolute oldest in the world matters less than demonstrating that it is a unique example of extraordinary longevity. The method enables researchers to estimate the probability distribution of growth epochs. In the age range between roughly 3,500 and 6,000 years, the method indicates an 80 percent probability that the tree exceeds 5,000 years. The peak probability aligns with an age of 5,484 years, which presents the most likely age among the plausible scenarios. The researchers acknowledge that while they expected ages above 4,000 years, the result exceeding 5,000 years was surprising and noteworthy.
Further exploration of these ancient trees continues to illuminate how forests—especially those with hardy species like alenmeyer—have persisted through millennia. The project underscores the importance of careful sampling, robust statistical modeling, and collaborative research across institutions to deepen our understanding of long-term forest dynamics.
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