Paying people to conserve their trees could be a highly cost-effective way to reduce deforestation and carbon emission and should be a key part of the global strategy to fight climate change, scientists say.

The study, led by Seema Jayachandran, associate professor at Northwestern University in the US, sought to evaluate how effective “Payments for Ecosystems” (PES) is at reducing deforestation.

PES is a programme in which people are given financial rewards for pro-environment behaviours.

In the study, people who owned forest in 60 villages in western Uganda were given cash rewards if they kept their forest intact and refrained from deforesting it. Forest owners in another 61 villages in western Uganda received no monetary incentives.

“We found that the programme had very large impacts on forest cover. In the villages without the programme, 9 per cent of the tree cover that was in place at the start of the study was gone by the end of it, two years later,” said Jayachandran.

“In the villages with the PES programme, there was 4 to 5 per cent tree loss. In other words, there was still deforestation, but much less of it,” she said.

The payments changed people's behaviour and prompted them to conserve. And we did not find any evidence that they simply shifted their tree-cutting elsewhere. This truly was a net increase in forest cover in the study region.

The first of its kind, the study applies the method of field experiments, or randomised controlled trials, to the question of how effective PES is.

Jayachandran said the cost effectiveness of the programme compared to other approaches to reduce carbon emissions, such as subsidies for hybrid or electric vehicles in the US, was eye opening.

“This is an estimate that others have come up with for the economic damage to the world from each tonne of CO2 that is emitted,” Jayachandran said.

“We found that the benefit of the delayed CO2 emissions was over twice as large as the programme costs. For many other environmental policies, the value of the averted CO2 is in fact smaller than the program costs,” she said.

The findings highlight the advantages of focusing on developing countries when working to reduce global carbon emissions, researchers said.

The study was published in the journal Science.