Efforts to slow the climate crisis have long sought to harness nature, often through carbon "offsets," aimed at bolstering forests, wetlands, and agriculture, but have generally had only marginal success so far.
"Nature-based climate solutions are human actions that leverage natural processes to either take carbon out of the atmosphere or stop the emissions of carbon to the atmosphere," said lead author and forest ecologist William Anderegg, a professor of biology and past Wilkes Center director.
"Those are the two main broad categories. There are the avoided emissions, and that's activities like stopping deforestation. Then there's the greenhouse gas-removal pathways. That's things like reforestation where you plant trees, and as those trees grow, they suck up CO2 out of the atmosphere."
The U-led study, which includes leading scientists from nine other universities as part of a Wilkes Center Working Group effort, identifies four components where nature-based climate actions have not lived up to their billing and proposes reforms to improve their performance and scalability.
Forests are the focus because of trees' ability to store vast amounts of carbon that would otherwise be in the atmosphere exacerbating the climate crises. Conversely, deforestation, especially in the Amazon rainforest, is releasing carbon at an alarming rate.
About half the emissions associated with human activity are absorbed into plants, through photosynthesis, and oceans, with the rest building up in the atmosphere where these gases trap heat. Terrestrial ecosystems pull 31% of anthropogenic emissions out of the atmosphere, according to the study.
While forests are seen as Earth's most vital carbon sponge, current rates of deforestation release 1.9 gigatons of carbon a year, on par with Russia's annual emissions. Thus, "actions to halt and reverse deforestation are a critical part of climate stabilization pathways," the authors write.
"There are widespread problems with accounting for their climate impact," said Blanchard, the paper's second author who has extensively studied the impacts of offset programs. "For example, despite the potential for albedo to reduce or even negate the climate mitigation benefits of some forest carbon projects, calculating for the effect of albedo is not considered in any carbon-crediting protocols to date."
To succeed, according to the study, a nature-based climate solution should
+ lead to net global cooling;
+ result in additional climate benefits;
+ avoid carbon "leakage;"
+ store carbon long enough to make a difference.
Finally, the study proposes structural reforms aimed at encouraging corporations to financially contribute to climate mitigation, as opposed to claim credit for something that may ultimately provide little climate benefit. A contribution approach would be more scientifically accurate and legally defensible than the current system, potentially resulting in higher quality projects, the authors argue.
"If you go in an ecosystem that is mostly snow covered and you plant really dark conifer trees, that can actually outweigh the carbon storage benefit and heat up the planet," Anderegg said.
Next, the project must result in actions that that would not have otherwise occurred.
"You have to change behavior or change some sort of outcome," Anderegg said. "You can't just take credit for what was going to happen anyway. One great example here is if you pay money to keep a forest from deforestation, but it was never going to be cut down to begin with, then you haven't done anything for the climate."
The third problem is known as "leakage," which occurs when a climate action simply pushes a land-disturbing activity from one place to another.
And the fourth component address climate actions' durability, or how long they will keep carbon out of the atmosphere. This is particularly important given the longevity of carbon dioxide molecules. When fossil fuels are burned, carbon that was permanently locked in geological formations is released into the biosphere where it will cycle in and out of living things and landscapes for thousands of years.
A climate solution should always aim to keep carbon locked up for as long as possible, preferably at least a century. But drought, storms, insects, wildfire and other climate-related hazards can quickly negate any gains by killing trees.
"You have to know how big the risks are, and you have to account for those risks in the policies and programs," Anderegg said. "Otherwise, basically you're going to lose a lot of that carbon storage as climate change accelerates the risks."
The methods now in place, known as "buffer pools," to account for these risks are not robust or rigorous currently, according to research by Anderegg's lab, which expects to release a study soon highlighting potential fixes.
Research Report:Towards more effective nature-based climate solutions in global forests
Related Links
Wilkes Center for Climate Science and Policy
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet
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