Trees play a critical role in mitigating global carbon emissions and now a new study in Uganda shows that the cost of giving landowners a modest fee to refrain from cutting down their trees is substantially lower than the carbon-related costs that are incurred when trees are lost. Curbing deforestation in low-income countries, where most deforestation occurs today, is viewed as one of the most cost-effective ways to reduce global carbon dioxide emissions. Incentive programs may help minimize deforestation; however, their effectiveness is largely unknown, as some people may engage in the environmentally friendly behavior without payment and some enrollees may simply shift their tree-cutting from land covered by the program to other nearby areas. Therefore, to better understand the effects of such programs, Seema Jayachandran and colleagues conducted an experiment in 121 villages in Uganda. Over the course of a two-year program, landowners were promised 70,000 Ugandan shillings ($28 in 2012 U.S. dollars) per year for each hectare of forest in which they left trees unperturbed. Forest monitors conducted spot checks of enrollees' land to inspect for recent tree-clearing, and satellite data was used to measure overall treetop cover throughout the program. The average tree loss in the treatment group, which was offered the incentive, was 4%, about half of the 9% tree loss in the "business-as-usual" control group, the authors report. They found no evidence that enrollees shifted their deforestation to nearby land. An economic analysis of the delay in carbon emissions over the course of the two-year program suggests that its benefits are 2.4 times as large as the program costs. Remarkably, the authors report that benefits of the program still outweigh its costs if landowners try to play "catch up" - by cutting down the trees that would have been lost over the course of the two-year program - immediately once the incentives ended.