In Uganda, some villlages were paid not to cut down trees. Credit: Macduff Everton/NGC

A two-year project that paid a total of US$20,000 to 180 people in 60 Ugandan villages not to cut down trees on their land was worth the money, researchers say. By delaying carbon dioxide emissions, the project’s benefits to society were more than double its costs.

The study, published in Science1 on 20 July, is an “incredibly rare” example of a rigorous evaluation of efforts to pay people to preserve forests, says Shahid Naeem, an ecologist at Columbia University in New York City.

The findings can’t necessarily be extrapolated to conclude that handing out cash payments to prevent trees being cut down is always an economically worthwhile activity, Naeem says: the particular conditions in Uganda might not be relevant in other places. But it’s proof that, at least in one case, the strategy does work.

Billions on trees

Over the past two decades, individual countries have authorized billions of dollars in cash payments to preserve trees. In 2008, the United Nations launched the REDD+ (Reducing Emissions from Deforestation and Forest Degradation) programme, which permits countries to offset their emissions by paying people in other nations to halt deforestation.

But it’s hard to tell whether the payments are worthwhile, usually because projects aren’t well evaluated: Naeem co-authored one review2 of 118 projects that made payments to protect ecosystems, and found that it was impossible to judge the effectiveness of 60% of them.

Projects can fall into traps such as not checking whether ecosystems have actually been protected, or not paying a sufficient sum of money to incentivize people to preserve trees. “There’s been a lot of projects that expect people to do a lot for the price of a Coca Cola,” says Ina Porras, a market-based-conservation researcher at the International Institute for Environment and Development, based in London.

Why Uganda worked

By contrast, says Porras, the Uganda study gave meaningful payments to villagers: around $28 per year per hectare of forest they conserved — equivalent, on average, to the amount they would have earned by cutting down the trees for timber. The study ran from 2011 to 2013; villagers were paid cash at the end of each year if they complied with their contract.

In the study — which was paid for by the Ugandan government from UN funds — a team led by Seema Jayachandran at Northwestern University in Evanston, Illinois, chose villages at random in Uganda's Hoima and Kibaale districts to be offered payment, and used satellite imaging to track whether trees were cut down. “You could see every tree with your eye,” she says. “It’s really useful when the pattern of tree cutting is a few here and a few there.” Tree cover fell by 4.2% in the 60 villages that were paid to preserve their trees — but by 9.1% in the 61 villages that were not.

On that basis, Jayachandran’s team estimate that the project's economic costs ran to around $0.46 per avoided tonne of carbon dioxide. That makes it more than worthwhile, they say: using estimates by the US Environmental Protection Agency (EPA) to determine the damage caused by carbon dioxide emissions — a figure also known as the ‘social cost’ of carbon — they say that the benefit of delaying the emissions of a tonne of carbon dioxide by two years runs to $1.11, more than double the project's costs.

Even if the villagers were to immediately cut down the trees that they’d been paid to preserve once the project was over, the payments would still have been worthwhile, Jayachandran says — a promising sign for other projects. “I hope our study makes people more optimistic that it will work and that they can measure it,” she says.

Participants in the program received payments for conserving trees. Credit: courtesy of Chimpanzee Sanctuary and Wildlife Conservation Trust