Pay to prevent deforestation


To objectively evaluate an anti-deforestation programme, an international team of researchers carried out a randomised study in Uganda, the first of its kind in environmental science. The surprising results have been published in the journal Science.

Human activity (heating, transport, various industries, etc.) emits large amounts of carbon dioxide (CO2) into the atmosphere. This phenomenon is a fundamental cause of climate change.

Among these activities, deforestation alone accounts for 9% of annual CO2 emissions of human origin. The reason: ‘Through photosynthesis, trees trap the atmosphere’s carbon and absorb it to form plant matter’, explains Prof. Éric Lambin of the UCL Earth & Life Institute (ELI). ‘So vegetation is simultaneously a carbon reserve and a carbon pump. When you cut and burn trees, not only are you destroying the pump, but the carbon stored in the trees is released into the atmosphere.

Paying nature for services rendered

Numerous human populations destroy the forest to create farmland or extract timber or fuel. How can they be convinced to limit deforestation if they are not given the means to find, use and/or buy alternatives? ‘This is why countries like Costa Rica and Mexico implemented payments for ecosystem services (PES)’, Prof. Lambin says. ‘PESs are based on the idea that nature supplies goods and services to humanity. So the private owner of a piece of nature is paid to not exploit its resources. He is thus compensated for the profits of which he is deprived.’

Some question the value of such programmes. Do they really work? Do farmers respect contracts or do they pocket the PES and continue to cut trees either on the land in question or elsewhere? Prof Lambin and his colleagues wanted to find out.

Randomised study

Western Uganda is one of the world’s most deforested regions. The country is poor and had never implemented a PES programme. Moreover, the area chosen by researchers for their study1 is one of the last reserves for wild chimpanzees. In short, it was an ideal area for a controlled study on the impact of PESs on deforestation.

First, researchers selected 121 villages bordering the forest and randomly divided them into two groups: a test group of 60 villages and a control group. ‘Randomised studies are systematic in medicine and are used increasingly in economics’, Prof. Lambin says. ‘But this was the first time one was used to assess environmental policy.

Second, researchers collaborated with local NGOs to explain the project to test group villages. And to make a deal: in exchange for $28 per year and per hectare,2 villagers would abstain from cutting down trees for two years; 32% of villagers accepted and signed a contract.

Surprising results

After two years, using very high spatial resolution satellite images, researchers measured 4.2% less forest cover in the villages compared to 9.1% in control villages – over twice as less, even though only a third of test group villages participated. ‘Surely, there was an awareness-building effect among neighbours and relatives’, Prof. Lambin says. ‘88% of signatories respected the contract. As for the negative effects that we feared – recruiting farmers who had been deforesting less than others, geographic displacement of deforestation to other areas or neighbouring villages, etc. – we rigorously demonstrated  that they did not occur.

                                                              déforestation vue satellite Eric Lambin

Additional benefits

Researchers drew other lessons from the study. ‘Considering the social costs of CO2 emissions, the benefits of these PESs were 2.4 times greater than the cost of payments to farmers. Which makes these PESs much more profitable ecologically than subsidies for solar panels or electric cars in Belgium for example. And don’t forget the social benefits: the cash that signatories receive improved their standard of living. It’s certain the money paid for children’s schooling, fuel that is less harmful to human health, etc. These are benefits that, while more difficult to quantify, are still appreciable in a developing country.

Permanent programmes ?

It remains to be seen whether the programme’s effectiveness is sustainable. To have a long-term effect on forest cover, do PESs have to last forever, just a few years, or the time it takes for participants to find and adopt viable alternatives to deforestation? In Uganda, do project participants cut down less forest than previously? How were other villagers and villages influenced by the experience? ‘We’ll soon be able to answer these questions by analysing satellite data collected two years after the study’s end’, Prof. Lambin explains. ‘As for the randomised method, we count on using it to assess other environmental policies. This scientific approach will provide objective arguments to those who wish to implement such policies.

Candice Leblanc

(1) S. Jayachandran et al., ‘Cash for carbon: A randomized trial of payments for  ecosystem services to reduce deforestation’, Science, 21 July 2017.
(2) The $28 represented the price of charcoal at the local market; villagers cut trees mainly to produce charcoal for cooking.


A glance at Éric Lambin's bio

1985                   Bachelor of Science, Geographical Sciences, UCL

1988                   PhD in Sciences, UCL

1989                   Guest Researcher, Joint Research Center (Italy)

1991                   Assistant Professor, Boston University (USA)

1993                   Associate Professor, UCL

Since 2005         Full Professor, UCL

2009                   Prix Francqui, Sciences

2009                   Foreign Associate, U.S. Academy of Sciences

Since 2010         Professor, Stanford University (USA), six months per year

2013-16             President, Department of Earth System Science, Stanford University

2014                   Prix Volvo for the Environment

Prof. Lambin’s research was funded by the Global Environment Facility of the United Nations Programme for the Environment and by the International Initiative for Impact Evaluation.

Published on September 26, 2017