Fires put California’s forest offset program at risk of collapse

Wildfires are threatening to wreck a key part of California’s climate mitigation plans: the trading of carbon “offsets” pulled from the atmosphere into the state’s forests, a new study has found.

The ravages of destructive fire have destroyed enough of the state’s “buffer pool” of forests that California’s offset programs are at risk of insolvency, according to a study published on Friday in Frontiers in Forests and Global Change.

The findings call into question the use of forest-based financial tools to counterbalance the emission of planet-heating greenhouse gasses.  

“Fossil CO2 emissions have permanent consequences, but carbon stored in trees won’t last forever,” Danny Cullenward, the policy director at climate research nonprofit CarbonPlan, said in a statement.

The scientists cautioned that any fossil fuel emissions dependent on California’s existing forest offset program need to stop now, as those forests cannot be guaranteed to remain standing.

California’s forest carbon offset program requires companies to guarantee that their trees — and the carbon that makes them up — would remain intact and out of the atmosphere for 100 years, according to the state’s Air Resources Board.

In particular, California’s forest offset program depends on an intact “buffer” of trees that can be substituted for losses in the forests that companies have paid to protect —  a form of tree-based “self-insurance” for the loss of other tree-based assets.

These backup landscapes have lost nearly 20 percent of their carbon in just a decade, the scientists found.

Those losses have brought the program to the point that a single disease- or insect-related die-off would wreck the program.

“In just 10 years, wildfires have exhausted protections designed to last for a century,” said co-author Oriana Chegwidden, a research scientist at CarbonPlan.

“It is incredibly unlikely that the program will be able to withstand the wildfires of the next 90 years, particularly given the role of the climate crisis in exacerbating fire risks,” she added.

That’s a problem because the point of California’s forest carbon offset program — like other such systems — is that the protection and growth of those forest reserves was supposed to counterbalance, as well as license, the burning of fossil fuels by industry, as ProPublica reported last year.

Previous studies by CarbonPlan already suggested that this math didn’t work out, creating tens of millions of “ghost credits” that generated no actual climate benefits.

Companies that purchased these credits were allowed to release more greenhouse gas pollution than they otherwise would have.

“Our work shows that California’s forest offsets program increases greenhouse gas emissions, despite being a large part of the state’s strategy for reducing climate pollution,” Cullenward told ProPublica at the time.

If those forest stocks cannot be guaranteed to remain standing, that would wreck the assumption of “permanent” storage that the whole system rests on.

“The problems we observe here aren’t unique to the California program and raise broader concerns about the integrity of offsets’ permanence claims,” concluded co-author Freya Chay, a program manager at CarbonPlan.