Many of the companies promising “net-zero” emissions to protect the climate are relying on vast swaths of forests and what are known as carbon offsets to meet that goal.

On paper, carbon offsets appear to balance out a company’s carbon emissions: The company pays to protect trees, which absorb carbon dioxide from the air. The company can then claim the absorbed carbon dioxide as an offset that reduces its net impact on the climate.

However, our new satellite analysis reveals what researchers have suspected for years: Forest offsets might not actually be doing much for the climate.

When we looked at satellite tracking of carbon levels and logging activity in California forests, we found that carbon isn’t increasing in the state’s 37 offset project sites any more than in other areas, and timber companies aren’t logging less than they did before.

The findings send a pretty grim message about efforts to control climate change, and they add to a growing list of concerns about forest offsets. Studies have already shown that projects are often overcredited at the beginning and might not last as long as expected. In this case we’re finding a bigger issue: a lack of real climate benefit over the 10 years of the program so far.

But we also see ways to fix the problem.

Forest carbon offsets work like this: Trees capture carbon dioxide from the air and use it to build mass, effectively locking the carbon away in their wood for the life of the tree.

In California, landowners can receive carbon credits for keeping carbon stocks above a minimum required “baseline” level. Third-party verifiers help the landowners take inventory by manually measuring a sample of trees. So far, this process has only involved measuring carbon levels relative to baseline and has not leveraged the emerging satellite technologies that we explored.

Forest owners can then sell the carbon credits to private companies, with the idea that they have protected trees that would otherwise be cut down. These include large oil and gas companies that use offsets to meet up to 8% of their state-mandated reductions in emissions.

Forest offsets and other “natural climate solutions” have received a great deal of attention from companies, governments and nonprofits, including during the U.N. climate conference in November 2022. California has one of the world’s largest carbon offset programs, with tens of millions of dollars flowing through offset projects, and is often a model for other countries that are planning new offset programs.

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