Fire threatens the integrity of California’s forest offset program

This commentary first appeared as an article at Slate

When you go to buy something off Etsy, you're assured that “Etsy offsets carbon emissions from every delivery.” Shopify offers a program like this, too. You might run into the same thing buying an airplane ticket, by being given the opportunity to purchase carbon offsets to cancel out the emissions from your flight. Southwest even lets you earn extra miles when you do this.

It's great to see companies – and by extension, the public – caring more about the environmental consequences of the economy. But unfortunately, whether you're a consumer or a corporation, buying carbon offsets is far from a foolproof way to ensure the long-term well-being of the planet. The fact is most of the offsets offered for sale don't deliver on their promises. That's because much of the system, like a house in Three Little Pigs, is built out of sticks. Literally.

There's a good chance that your carbon neutral flight or emission-free shipping uses trees to offset your pollution. In fact, nearly 40 percent of all offsets on the market today are tree-based in some way. Offsets work by outsourcing the hard work of reducing carbon emissions. When you buy a credit, you're paying someone, somewhere else to either take carbon dioxide out of the atmosphere or stop the emission of climate-changing gasses in the first place. In the case of trees, you're paying someone to plant new trees or to stop them from cutting trees down. Trees, after all, are an obvious place to store carbon, as they naturally take up carbon dioxide as they grow and store the carbon in their roots, trunks, and leaves.

But the promise of using trees to counteract carbon emissions is, unfortunately, undermined by those same emissions. The warmer world we've created by burning fossil fuels is one where wildfires are more frequent and intense, drought is more prevalent, and forest disease more virulent. Climate change has supercharged these natural, tree-killing processes, leading to an unfortunate irony: the very forests we often depend on as offsets are under threat and increasingly threatened by climate change itself.

Nowhere is this more apparent than California's offset program, a multi-billion dollar market that allows the state's major polluters to offset some of their emissions instead of reducing the amount of carbon they put into the air in the first place. More than 80 percent of the program's offsets derive from protecting trees from being cut down – but there's more than just chainsaws threatening those trees.

Forests, after all, can burn. Or die from disease, or dry up in a drought. California's offset program accounts for these inevitabilities using a sort of tree insurance program. Called the buffer pool, it's a reserve of credits set aside to compensate for losses due to wildfires or other unforeseen events. Each time a forest enrolls in the program, roughly 15 to 20 percent of the credits it generates go into the pool. Any time there is a fire, it's the responsibility of this collectively funded insurance pool to step in and cover any carbon losses. Basically: the offsets come with some back-up offsets.

While a seemingly straightforward and savvy idea on paper, I work for a nonprofit called CarbonPlan that has spent nearly four years studying how the buffer pool actually plays out in the real world. Our research has shown the pool is far too shallow. Large fires have burned through at least six forests participating in California's offset program, including the massive Bootleg Fire in 2021 which blazed through a large offset project in southern Oregon and triggered air quality alerts as far away as New York City. In three of those cases, the damage from wildfire has been so severe that the offset project was canceled altogether.

Collectively, fires have destroyed nearly 11 million offset credits in California's program. But the buffer pool, meanwhile, had only set aside a little more than six million credits to compensate for losses from wildfire. Even more concerning, those six million credits were meant to protect the program for the next 100 years. The program has literally burned through that reserve in a mere decade.

While the buffer pool still contains more credits, those were set aside to protect against other risks to forest carbon, like drought and insects. As temperatures continue to rise and the risks to forest-based offsets grow, it's clear that California's forest offsets program is all but insolvent.

Though California's offset program has been the focus of much of our research, the threats it faces exist for programs elsewhere, too. Forests feature prominently in just about every major offset program around the world – and trees everywhere are under threat from climate change. With climate change, wildfires are larger and burning hotter and more frequently outside of just the US. The record-setting 2023 Canadian wildfire season burned as many acres as burned from 2015 to 2022 combined.

Hotter temperatures and shifting rainfall have made droughts more severe, as well. When the conditions are right, these climate-change-fueled droughts are incredibly efficient at killing trees. The Amazon, home to some of the largest offset projects in the world, has been especially hard hit by drought in recent years and is currently in the midst of its most severe drought on record. As dry trees die en masse, they release millions of tons of carbon dioxide as they slowly decay. Things have gotten so bad that some parts of the Amazon are actually losing more carbon than they can gain in a single year, a transition that threatens the very integrity of these forests and only promises to make climate change worse.

As tempting as it is to think of trees as our ally in fighting climate change, it's time to face the reality that they're increasingly a victim of our pollution. We need to do more than plant more trees, and promise not to cut trees down. Protecting the world's forests requires that we immediately and permanently stop adding carbon dioxide to the atmosphere. It's our responsibility to do the hard work of curtailing carbon pollution, as that's the only way to ensure that the trees and forests that we love can survive.