Empires have risen and fallen, languages have been born and forgotten — but this tree stood the test of time: The 5,400-year-old Gran Abuelo, or great grandfather in Spanish.

Jonathan Barichivich, a renowned Chilean scientist working in France, grew up in the temperate rainforest now protected in Alerce Costero National Park. His grandfather, Anibal, discovered the Gran Abuelo tree in 1972 while working as a park ranger. That moment, he says, changed the course of his family's history — and the tree's.

"I took my first steps in this forest with my grandfather. He taught me the names of the plants before I could even read," Barichivich recalled. "The memories of my childhood are fuel for my scientific passion."

Now, Barichivich and his mother, along with a team of researchers, are unlocking the secrets stored in the Gran Abuelo and other trees — information that could shape how we understand and fight climate change.

The alerce trees in this forest , also known as Patagonian cypress, or Fitzroya cupressoides, don't just grow older than many other trees. The species is also one of the most climate-sensitive trees in the world. Each ring inside its trunk is a yearly........

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