The world’s forests form a vast network of carbon reservoirs, keeping carbon sequestered from the atmosphere, where its presence is disrupting Earth’s climate systems. Many corporate, national and state climate policies rely on forests’ ability to store carbon—often tracked and funded through a system of “carbon credits” issued to polluting industries in exchange for protecting and restoring forests.

But when trees die suddenly—from wildfire, drought or insect infestation—vast amounts of greenhouse gases are released, exacerbating ongoing climate change. And the warming climate is accelerating this problem by making such disturbances more frequent and severe.

New research led by University of Utah scientists in collaboration with international experts sought to determine the likelihood that forests will release their stored carbon over the next 100 years. Along the way, they documented how current carbon-credit systems fail to accurately account for that risk in U.S. forests, particularly the parched U.S. West.

But the research points out ways this problem can be corrected, according to William Anderegg, senior author on the study published in Nature.

“Forests are facing increasing durability risks due to climate change,” said Anderegg, a biology professor at the University of Utah. “Those risks have been underappreciated to date in multi-billion-dollar carbon markets.

“But with better science, we can set these policies up to potentially work better,” continued Anderegg, a leadership team member of the university’s Wilkes Center for Climate Science & Policy. “We’re providing a potential solution as well.”

The trouble with buffer pools

Carbon offset programs try to cover the risk of fire and other disturbances by setting up “buffer pools,” reserves of extra carbon credits set aside to compensate for forests that suddenly lose carbon because their trees burn or die. However, the study found these buffer pools are currently far too small for U.S. forests. On average, they would need to be around six times larger to fully cover expected losses over a century for the projects that have been set up so far.

“Getting to net zero emissions will take a portfolio of solutions,” said co-author Anna Trugman, a forest ecologist at University of California, Santa Barbara. “But in many regions, escalating disturbance associated with climate change makes it riskier to count on forests to sequester carbon.”

The research team, which included scientists from eight other universities and organizations, used forest plot data, satellite observations and machine learning to predict where forest losses are most likely to occur.

“Compared to other natural disturbances, we found that wildfire is the largest climate-sensitive risk to durability for forest nature-based climate solutions,” said co-lead author Chao Wu, now at Tsinghua University in Beijing, China. “Our analysis shows for the first time what a robust, climate-informed buffer pool would look like to handle accelerating climate threats.”

When the research was conducted, Wu was a U postdoctoral researcher in biology.

The study produced maps showing relative levels of risk for carbon loss, with the increased likelihood of climate-driven disturbance concentrated in California and the Intermountain West. Along with the maps, the Wilkes Center is releasing a set of interactive tools to help plan where and how to conduct forest management and conservation efforts with the highest chances of success.

Using forests to keep carbon out of the atmosphere

Carbon credits are among a host of nature-based climate solutions that harness market incentives to encourage investments that keep greenhouse gases out of the atmosphere. Promoting tree growth is a great way to pull carbon and keep it locked up for decades—as long as the trees don’t die prematurely.

Read the full story by Brian Maffly in @ The U.