On 15 December, California approved an ambitious plan to reach . Among other things, it mandates that all passenger vehicles use zero-emission technologies by 2035, with the aim of reducing greenhouse gas emissions by 85 per cent below 1990 levels before mid-century.
鈥淐alifornia is leading the world鈥檚 most significant economic transformation since the Industrial Revolution 鈥� we鈥檙e cutting pollution, turning the page on fossil fuels and creating millions of new jobs,鈥� Governor Gavin Newsom said in a after the plan was approved.
Yet despite setting aggressive decarbonisation goals, what some experts noticed was what the plan failed to do: address growing criticisms of California鈥檚 carbon offsets programme, which is theoretically responsible for as much as half of the state鈥檚 emissions reductions.
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Carbon offsets are at the heart of net-zero emissions plans around the world. The success of the programme in the most populous US state 鈥� not to mention, the world鈥檚 鈥� is seen as a bellwether for how similar schemes may work elsewhere, and is already being used as and countries鈥� climate policies.
But researchers warn that there are fundamental flaws in how these offsets are being implemented 鈥� shortcomings that, at best, mean the programme is inefficient and, at worst, suggest that it may actually be doing more harm than good.
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How do carbon offsets work?
Cranking carbon dioxide into the atmosphere has disastrous consequences, which become more painfully clear by the day. Carbon offset programmes, like those underway in California for the last decade, allow companies to balance out their emissions by paying to protect forests. Trees capture carbon dioxide from the air, so protecting forests can act like a bulwark against rising greenhouse gases. Landowners can earn credits for maintaining forests 鈥� thus keeping carbon sequestered 鈥� and polluters can buy these credits to compensate for their own emissions.
California鈥檚 carbon offsets programme is administered by the California Air Resources Board, the body responsible for setting the state鈥檚 emissions standards. (The agency declined an interview request from New 杏吧原创.) Landowners can apply to participate in the programme, agreeing to keep carbon stocks above a certain threshold known as a 鈥渂aseline鈥�. To verify this is happening, third-party analysers a sample of trees.
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What are the problems with offsets?
Getting the maths right is difficult, but crucial. 鈥淚f your calculations are not perfect, you鈥檙e doing harm,鈥� says , policy director at the non-profit CarbonPlan and a member of the California Environmental Protection Agency鈥檚 Independent Emissions Market Advisory Committee. The problem starts with the carbon cycle, he says. The consequences of adding carbon dioxide to the atmosphere extend centuries, if not millennia, into the future. Meanwhile, forests have much more ; when , some of the carbon they have sequestered goes back into the air. Under California鈥檚 law, however, all carbon reductions are required to be permanent. 鈥淭here鈥檚 really no way to square that circle,鈥� Cullenward says.
In a 2021 study, Cullenward and his colleagues found that California鈥檚 offsets programme of its offset properties by nearly a third. More recently, he and his colleagues used satellite data to precisely measure the amount of carbon being sequestered in 37 of the state鈥檚 offset sites. They found in these forests than would have been without the programme.
What鈥檚 more, the researchers found no evidence that the programme has reduced logging. Some of the offset properties are on land already at less risk of harvesting because they contain less commercially valuable timber. Conversely, other sites owned by industrial timber companies have continued to harvest trees at similar rates, even after enrolling in the offset programme.
It should raise a red flag that timber companies appear to be meeting the state鈥檚 baseline requirements without actually doing anything differently, says , a postdoctoral researcher at the NASA Goddard Space Flight Center in Maryland and a co-author of the study. 鈥淵ear after year, they鈥檙e getting new credits put into these projects, without direct evidence of improved management,鈥� he says.
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How are drought and wildfire affecting forest offsets?
Meanwhile, the forests in the American West are changing rapidly: in many, trees are now as climate change of wildfire, insect infestations, disease and drought. 鈥淭he consequences of the warming and the precipitation changes on forest ecosystems are blowing everybody鈥檚 minds,鈥� says Cullenward.
To compensate for these risks, the Air Resources Board created an insurance programme called a buffer pool, aiming to ensure that the carbon in the offset programme would stay put for at least a century. Landowners pay into the pool when they sell credits. When there are unintentional reversals 鈥� when wildfire burns down trees that were supposed to be storing carbon, for example 鈥� the state can withdraw credits from the buffer pool. It was a good idea, Cullenward says. The issue is that the Air Resource Board 鈥渘ever explained where they came up with their numbers鈥� for the buffer pool鈥檚 allowances. 鈥淚f you were in the business of providing insurance for earthquakes or floods, you鈥檇 want to know how frequent the events are,鈥� he says.
When Cullenward and his colleagues analysed the buffer pool鈥檚 actual performance, they found that in the last 10 years, fires have depleted a jaw-dropping that was intended to manage the next century鈥檚 wildfire risks.
The scientists also found that the impact of one single disease, on a single tree species called tanoak, would be enough to completely wipe out the credits set aside for all disease- and insect-related mortality. A catch-all 鈥渙ther catastrophic risk鈥� category does mention wind, ice and flood damage explicitly, but these credits are capped at 3 per cent, no matter the size or location of the offset site. What鈥檚 more, the buffer pool makes no specific allowances for drought, an increasing driver of tree mortality as the south-western US endures the most extreme drought in more than 1000 years.
These problems are likely to get worse: many properties in the offset programme pipeline are in increasingly fire-prone areas, like those around the Sierra Nevada mountains. If you鈥檙e a timber company, there鈥檚 now a good chance your land will burn before your logging rotation cycle, Cullenward says. But with the offset programme, 鈥測ou can socialise those future wildfire losses,鈥� he says. In other words, logging companies can make money 鈥� and get good PR 鈥� on what might otherwise just be a financial loss.
Since their research on the buffer pool was published, offset sites have reported recent wildfire damage to the regulator 鈥� and the actual losses were than the cautious predictions Cullenward鈥檚 team made.
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Is it time to abandon carbon offsets?
Concerns about the offsets programme prompted a series of from the Air Resource Board last year. 鈥淢ost of the members of the Task Force either represent organizations that have a vested interest in expanding the use of offsets or have ties to industries and organizations that stand to benefit financially from offsets,鈥� wrote Brian Nowicki, the senior public lands advocate at the Center for Biological Diversity, the Compliance Offsets Task Force.
Yet the state, both Cullenward and Coffield say, has been dismissive of these concerns.
Both scientists have public comments as part of a response to the Air Resource Board鈥檚 November on updating the forest offset programme. Yet during the meeting, 鈥渟taff failed to provide any evidence or quantitative analysis to support their complete dismissal of our peer-reviewed findings,鈥� Cullenward wrote.
California鈥檚 history of landmark legislation to address the climate crisis and its role as a climate leader makes it even more important to appropriately address where the programme is failing to meet its goals. Coffield says incorporating improved satellite data, for example, could help foresters look for evidence of improved management or .
Last year, the Berkeley Carbon Trading Project released a of global voluntary carbon projects, which demonstrates that forest-based mitigation has boomed, even as concerns over offset quality grow. A of the database notes 鈥渧ery high rates of over-crediting by all major offset programs鈥�. In the EU, a 2021 study revealed that 85 per cent of offsets failed to reduce emissions. In response, EU member states decided offsets would not count toward European climate goals after 2021.
In 2019, a study similarly found that of California鈥檚 offset credits do not provide climate benefits. California has not changed tack with the offset programme in response. 鈥淐alifornia has opted for rhetorically relying on the programme and keeping a low carbon price at the expense of being on track for our climate policy goals,鈥� says Cullenward.
Many experts now suggest the state shift away from relying on offsets altogether. By not meaningfully accounting for how the programme is meeting its goals, California is losing time the world desperately needs to forestall the worst climate outcomes 鈥� while also diverting resources from other initiatives, like low-income electrification, that could. Cullenward says, 鈥淗onestly, it鈥檚 really demoralising.鈥�
Lois Parshley is an independent investigative journalist. Follow more of her climate reporting @loisparshley on , 听or .
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