California program overestimates climate benefits of forest offsets -study

A view of the Garcia River Forest near Longvale, California July 27, 2009. REUTERS/Peter Henderson

WASHINGTON, April 30 (Reuters) - California's forest carbon offset program has generated tens of millions of credits that have questionable value in fighting climate change, a nonprofit group of scientists said this week.

CarbonPlan, a group that researches the integrity of programs designed to offset carbon emissions, said that 29% of the forest carbon offsets it analyzed in California's cap and trade program overestimated the amount of carbon emissions they were offsetting, totaling 30 million tonnes, worth about $410 million.

"Rather than improve forest management to store additional carbon, ecological and statistical flaws in California's offsets program create incentives to generate credits that do not reflect real climate benefits," said the analysis.

Carbon offset plans encourage polluters to cut their emissions or purchase credits from companies or projects that reduce carbon, by setting a gradually reduced cap on pollution. California's cap and trade program, for example, allows oil companies and other emitters to purchase offset credits from a forest owner who agrees to reduce or delay a timber harvest.

The CarbonPlan study said the carbon offset plan did not always consider the variability of tree species in storing carbon, leading to flaws in the accounting.

The California Air Resource Board, the agency that implements the state's program, said that the methodologies used in the forest protocol it approved were developed through a public process. Carbon credits issued to projects in the program "represent real, quantifiable, permanent, verifiable, enforceable, and additional reductions," it said.

Scientists are likely to scrutinize carbon offsets programs more as President Joe Biden pushes his plan to put the country on a path to fully decarbonize the economy by 2050. The California forest carbon offset program, worth more than $2 billion, is the biggest such program in existence.

The CarbonPlan study was released on the web to spark public comment and early versions were shared in February with journalists at ProPublica. It has also been submitted for publication in a peer-reviewed journal.

Reporting by Timothy Gardner; Editing by Aurora Ellis

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