Ancient trees are vital to forest survival

A study published in the journal Nature Plants reveals that the oldest trees are living beings that offer more than a majestic presence and a series of ecosystem services to the forest. These ancient and monumental trees of long-term survival —they can be centennial or millennial trees— are vital to preserve the adaptive capacity of the forests on the long run, in a constantly changing environment.

Among the participants in this study are Professor Sergi Munné-Bosch, from the Faculty of Biology, the Biodiversity Research Institute (IRBio) and the Institute for Nutrition and Food Safety Research (INSA) of the University of Barcelona, and the experts Chuck Cannon, director of Center for Tree Science – The Morton Arboretum (United States), and Gianluca Piovesan, lecturer of Landscape, Environmental Planning and Design at the University of Tuscia (Italy).

“As part of the study, we examined the demographical patterns that emerge from ancient forests over thousands of years, and a small proportion of trees result as life history ‘lottery winners’. They even reach higher ages that bridge environmental cycles”, notes Chuck Cannon. “In our models, these rare and ancient trees prove to be vital to the forest’s long-term adaptive capacity, and for the conservation of the global genetic diversity of the plant population, broadening the temporal span”.

The authors state that ancient trees can live up to between 10 and 20 times more than a typical mature tree. In these organisms, death responds to a random process in its natural environment than to an ageing process, like in humans. These unique trees —less than the 1% of forest population— provide a great genetic and biological diversity which is essential in the global population of a forest, and they reflect a wide range of historical environmental conditions that cover hundreds or even thousands of years.

“Millennial trees have survived several environmental changes over hundreds or thousands of years, and this resilience is transmitted to the forest. Also, these old trees provide invaluable services to the forest ecosystem. They provide a habitat to other species, some of them endangered, and capture a high amount of carbon compared to younger trees”, notes Professor Sergi Munné-Bosch.

Ancient forest survivors impossible to cultivate

Now, the oldest forests in the planet are threatened by human activity. As stated in the study, the deforestation of natural forces is progressively advancing worldwide and the death rate of the trees is increasing globally, from boreal biome to the tropics.

According to the conclusions, in a scenario with the highest death rates —for instance, as a result of the climate changes— the ability of trees to reach those ages is limited or practically impossible.

“As climate changes, it is likely for tree mortality rates to increase, and it will become more difficult for ancient trees to survive in the forests”, notes Cannon. “Therefore, if you cut down old and ancient trees, we will forever lose the genetic and physiological legacy they have, as well as the unique habitat for the conservation of nature”.

Despite the actions of forest restoration and tree plantation to improve local and global habitats, old trees cannot be recovered or regenerated without many centuries and generations of trees passing, the experts warn. “

These are emerging properties of the oldest forests that cannot be recreated in new regeneration forests, and that must be protected”, stress the authors.

“These study recalls the urgent need for a global strategy to conserve biodiversity, not only by preserving the forests but also remnants of a few ancient trees. In rewilding projects, ancient trees can thus become the biodiversity hubs of the old-growth forests of tomorrow, providing a unique fitness which will guarantee the ecosystem functionality”, concludes the expert Gianluca Piovesan.

Reference article:

Cannon, C.H.; Piovesan, G.; Munné-Bosch, S. «Old and ancient trees are life history lottery winners and vital evolutionary resources for long-term adaptive capacity». Nature Plants, January 2022. DOI: https://doi.org/10.1038/s41477-021-01088-5