If you pay a person to save a tree in Uganda, does the tree stay in the ground?
The answer to that is "yes, probably." And it turns out these kinds of payments are a great, cost-effective way to curb greenhouse gas emissions, according to a new research study that is the first to study these "avoided deforestation" programs using randomized control trials.
One of the cheapest ways to slow global warming is to stop cutting down the world’s forests, scientists and economists say. Countries have been spending about $500 million annually on a variety of anti-deforestation initiatives, and are supposed to commit more as part of the Paris climate change deal struck last year.
The number of these programs that pay local and indigenous populations every year to preserve their trees is growing. The strategy, called "payment for ecosystem services," began about 20 years ago in Costa Rica. The payments make up for lost economic opportunity that comes with cutting a tree, whether for fuel, farming, or selling timber.
But with payment programs, it quickly starts to get complicated, and it is controversial how well these programs work. Many studies have had to look at the question after-the-fact and get conflicting results. Think about the complications of this: How do you measure the carbon savings when something that might have happened—chopping down a tree—doesn’t happen? Or how do you know that the money isn’t wasted by saving a tree that would have been safe anyway? Say you are paying a family to conserve a particular tract of land—how do you know they aren’t going to just chop down trees somewhere else instead, negating all the greenhouse gas savings?
Four researchers, from Northwestern and Stanford Universities, the Carnegie Institution, and the Porticus Foundation, conducted a randomized control trial to get a better grasp at these questions. These are the kind of "gold standard" studies, with a control group, that are the standard in medical research but are only starting to be used in social science research (and are hardly used at all in conservation work).
"To the extent that people have done randomized trials, they have focused on tree planting. It’s easier to measure the impacts, but that’s a little bit of looking under the lamppost," says Seema Jayachandran, an economist at Northwestern University.
The researchers tried to get at the avoided deforestation question instead. They surveyed landowners in western Uganda, and then selected 121 villages with forest cover to participate. Working with a conservation group in Uganda to implement the program, half of the villages were randomly selected to receive payments the equivalent of $28 from 2011 to 2013 to preserve their forests, with spot checks and monitoring conducted to make sure they complied. They could also get extra money if they agreed to plant more trees. The other half of villages received no payments or outreach.
The results, measured by detailed satellite surveys of tree cover before and after the program, seemed conclusive.
Tree cover declined by 7% to 10% in the control villages and only 2% to 5% in the villages that got the payments. The researchers also surveyed the surrounding areas to make sure the landowners just didn’t shift their tree cutting elsewhere. In the end, after comparing the costs of the program and the payments to savings of avoiding a ton of carbon dioxide emissions, they say the program to be "cost effective"—especially compared to more expensive strategies to reduce CO2 emissions, such as subsidizing electric cars.
"It looks like a very cost-effective program. The revenue that people are generating from cutting down trees, or using that land for growing cassava, it’s a lot of money to them—you can’t ask them to volunteer to give that up, but it’s relatively small in global terms," says Jayachandran.
Of course, this is one limited study in Uganda, and it doesn’t say whether PES programs work everywhere. But, she says, that’s the beauty of greenhouse gases: "The value to society of a tree in Uganda is the same as a tree in the U.S."
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