Protecting old trees helps mitigate climate change

The longest-living trees, many hundreds or even thousands of years old, play a vital role in preserving ecosystems because they can resist and buffer climate change, new research says.

A team of ecologists highlights the importance of preserving these monumental organisms and presents an initiative to guarantee their protection and longevity, in a review article published in the journal Trends in Ecology & Evolution.

Some of these trees, like the bristlecone pines of the White Mountains in the United States, can live up to 5,000 years and act as a huge store of carbon.

"Despite their rarity in forests and cultural landscapes, ancient trees contribute disproportionately to biodiversity conservation, forest restoration efforts, and human societies," say the authors, who include Gianluca Piovesan, professor at the University of Tuscia (Italy), and Charles H. Cannon, director of the Center for the Science of Trees, in the United States.

Protect old trees

Your unique contribution cannot be recovered without extensive passage of time. Temperate and tropical tree species can live for several centuries, and a small fraction can live for substantially longer periods of time. The largest known is that of the bristlecone pines (Pinus longaeva) of the Sierra Nevada and the White Mountains of the USA, which can live up to 5,000 years.

Ancient trees are hubs of mycorrhizal connectivity, that is, they help maintain networks of underground fungi called mycorrhizae that act in symbiosis with plants and provide them with many of the nutrients they need to survive. This symbiosis with fungi also helps reduce drought in dry environments. Ancient trees play a disproportionate role in conservation planning, yet they are being lost around the world at an alarming rate.

Therefore, the researchers propose a two-pronged approach to protecting ancient trees: first, the conservation of these trees through the propagation and preservation of the germplasm and meristematic tissue of these ancient trees, and second, a planned integration of protection and complete afforestation.

"Mapping and monitoring of ancient forests and ancient trees can directly assess the effectiveness and sustainability of protected areas and their ecological integrity," they write. To carry out this ambitious project, a global monitoring platform is needed, based on advanced technologies, together with public contributions through community scientific projects”.

Ancient trees in forests

At present, the protection of ancient trees in forests, woodlands, historic gardens, and urban and agricultural areas remains limited by national policies.

“The current revision of the Convention on Biological Diversity and Sustainable Development Goal 15 of the 2030 Agenda must include the mapping and monitoring of ancient trees as key indicators of the effectiveness of protected areas in maintaining and restoring the integrity of forests for a sustainable future, the authors recommend.

We call for international efforts to preserve these centers of diversity and resilience. A global coalition using advanced technologies and community scientists is needed to discover, protect and propagate ancient trees before they disappear."

More trees against climate change

According to the calculations of this study published in Science, adding a trillion hectares would reduce carbon dioxide in the atmosphere by 25%. For the research, developed at ETH-Zurich in Switzerland, they used software based on Google Earth engineering. With it they generated a predictive model to show the areas of the planet where more trees could be planted.

Professor Robin Chazdon, the lead author of this research, has stated that " forest reforestation is the best currently available climate change solution available and provides strong evidence to justify the investment." If acted now, carbon dioxide in the atmosphere could be reduced by up to 25%. This would reach the levels last seen almost a century ago.

Not taking into account existing trees, agricultural land and urban areas, the researchers found that there were 0.9 billion hectares that could be used for new trees. Once mature (50 to 100 years old), these trees could extract up to 200 gigatonnes of carbon dioxide from the atmosphere.

Recovering the forest mass is a global imperative. Especially in places where deforestation has been carried out more intensively. The strategy consists of reforesting the affected areas and planting trees in areas with fertile land where there are still no trees. A review of the study suggested that there is "no other current carbon reduction solution quantitatively as large in terms of carbon sequestration" than reforestation.

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