Trees do not pay taxes. Some seem to avoid death as well. Many of the world’s most ancient organisms are trees, including a 3,600-year-old cypress in Chile and a sacred fig in Sri Lanka that was planted in the third century B.C.
But according to a paper published in the journal Trends in Plant Science, time ravages us all in the end. The paper, “Long-Lived Trees Are Not Immortal,” argues that even the most venerable trees have physiological limits — though we, with our puny life spans, may never be able to tell.
Sergi Munné-Bosch, a plant biologist at the University of Barcelona, wrote the article in response to a January study on ginkgo trees, which can live for more than 1,000 years. The study found that 600-year-old ginkgos are as reproductively and photosynthetically vigorous as their 20-year-old peers. Genetic analysis of the trees’ vascular cambium — a thin layer of cells that lies just underneath the bark, and creates new living tissue — showed “no evidence of senescence,” or cell death, the authors wrote.
Munné-Bosch said he found the paper “very interesting,” but disagreed with how some readers of the study in popular media and beyond had interpreted it.
“In my opinion at least, there is no immortality,” he said.
Those tree species that can live for centuries or millenniums have a lot of tricks for staying youthful. They have simple body plans, and develop modularly, so they can replace parts they lose. They also build on their own dead tissue, which provides support and volume at a low metabolic cost. The trunk of a very old tree might be 95% dead, Munné-Bosch said, a strategy used also by other plants.
For these reasons, it is much more likely that such a tree will die of external causes than age-related ones. In some populations, this can result in “negative senescence” — a phenomenon where the durability of older trees means they actually have a greater chance of survival than younger ones, Munné-Bosch said.
Still, “everything seems to indicate” that individual trees are mortal, he said.
But others have a different take.
“A modular organism such as a tree could hypothetically live forever,” said Peter Brown, a forest scientist who runs an ancient tree database called the OldList. “I don’t think there is any real physiological or anatomical limitation for them not to just keep going.”