Protecting large trees for wildlife also benefits climate, study says

Standing beneath especially tall trees in a forest and looking up can invoke a feeling of awe. Large trees — especially those that are 21 inches in diameter or more — offer valuable benefits to forests, as well as outsized help with the biodiversity and climate crises. They provide unique habitat for wildlife, as well as disproportionate absorption and storage of atmospheric carbon dioxide, a major driver of climate change.

A new study explores the connection between protecting mature trees in national forests and objectives related to habitat conservation, forest resilience and climate change mitigation.

“These are public lands that are providing a natural climate solution and performing multiple additional services at no cost,” said systems ecologist with Eastern Oregon Legacy Lands David Mildrexler, who was the lead author of the study, as Phys.org reported. “We suggest policy to keep existing forest carbon stores out of the… atmosphere and accumulate additional amounts while protecting habitat and biodiversity.”

The study, “Protect large trees for climate mitigation, biodiversity, and forest resilience,” was published in the journal Conservation Science and Practice.

A previous study found that trees protected by a rule that prohibits the logging of trees 21 inches or wider at breast height — known as the “21-inch rule” — only make up three percent of forest stems, but account for 42 percent of aboveground carbon storage, reported Phys.org.

However, the U.S. Forest Service recently relaxed this vital rule, which means these essential, majestic carbon stores can now be felled on millions of national forest lands in Washington and Oregon.

“Forests account for 92% of all terrestrial biomass globally, store about 45% of the total organic carbon on land in their biomass and soils, and removed the equivalent of about 30% of fossil fuel emissions annually from 2009 to 2018, of which 44% was by temperate forests,” the study’s authors wrote, as Phys.org reported.

Some ancient trees can live as long as 5,000 years and accumulate and store a massive amount of carbon in that time.

“There is no action required from us but to leave these large trees standing so they can continue to store and accumulate carbon for climate mitigation and provide critical habitat,” said co-author of the study Beverly E. Law, a professor of global change biology and terrestrial systems science in the Department of Forest Ecosystems and Society at Oregon State University, as reported by Phys.org.

The researchers said more than half of the habitats of all identified plant and animal species on Earth are found in forests.

“Ancient trees are unique habitats for the conservation of threatened species because they can resist and buffer climate warming,” wrote the authors of another study, including Gianluca Piovesan and Charles H. Cannon, as SciTechDaily reported.

The study, “Ancient trees: irreplaceable conservation resource for ecosystem,” was published last year in the journal Trends in Ecology & Evolution.

“We call for international efforts to preserve these hubs of diversity and resilience. A global coalition utilizing advanced technologies and community scientists to discover, protect, and propagate ancient trees is needed before they disappear,” the authors of the earlier study wrote, as reported by SciTechDaily.

Cutting down any number of inherited large trees means not only eliminating vital habitat, but destroying valuable carbon stores and releasing huge amounts of carbon dioxide back into the atmosphere when we need to be doing the opposite.

The authors of the new study said the 21-inch rule is a good example of effective policy that addresses biodiversity and habitat conservation and recovery along with climate change adaptation and mitigation. The scientists added that these mature trees have been contributing important climate change mitigation across large tracts of Pacific Northwest forest.

“Society has a narrow window of opportunity left to avert catastrophic consequences from the intertwined climate and biodiversity crises, and forests offer major solutions at the intersection of these urgent imperatives,” the authors of the recent study wrote, as Phys.org reported.