Calls to protect the Amazon rain forest, which supports immense biodiversity and holds about 123 billion metric tons of carbon, are growing desperate as the ecosystem’s destruction accelerates. Indigenous peoples in the Amazon have tried to protect the region by monitoring territorial boundaries, blocking dam construction, and more. But deforestation has continued at a rapid pace.

Now a new effort that combines in-person monitoring by members of Indigenous communities with satellite data and smartphone technology holds promise to help put the brakes on deforestation in the Amazon—and potentially other forests elsewhere in the world—a study suggests.

Illegal logging, agriculture and coca cultivation for drug production particularly threaten the Amazon in the Peruvian region the study focused on. Outsiders to the community are often the culprits. A team of researchers wondered if training local people to use satellite-based “early deforestation alerts” could help.

As part of a pilot program to test the idea, the scientists collaborated with a total of 76 Indigenous communities in Peru, 36 of which participated in using the alerts to monitor the forest. Three people from each community in the pilot program received training to use an early-deforestation-alert system on a smartphone app, as well as to patrol forests and document damage to them. Over the next two years, these participants were paid to work as forest monitors and received monthly alerts via the app when satellite data indicated local forest losses. As monitors, they patrolled the rain forest to investigate alerts, watched for deforestation in other areas and then reported back to their respective communities. Each community decided what to do from there—whether to deal with the culprits on its own or report them to state authorities.

The researchers analyzed the same forest-loss satellite data from that time period in all 76 communities. They found the early alert program reduced forest loss by 8.4 hectares in the first year, a 52 percent reduction, compared with the average deforestation in the control communities, says study co-author Tara Slough. “This reduction in deforestation was concentrated in communities facing the largest threat” of forest loss, she says.

“The implication of this finding is that if one were to continue the program, targeting it to the communities facing the biggest threats should avert the most tree cover loss,” says Slough, a political economist at New York University. “Given that it is implementable at the community level, this represents an important and scalable tool to empower communities to reduce deforestation.” The results were published in July in the Proceedings of the National Academy of Sciences USA.

The monitoring program was less effective in its second year, when forest loss was reduced by only 3.3 hectares, compared with control communities. Slough and her co-authors think a Peruvian government campaign against coca cultivation that year may have discouraged deforestation in both experimental and control communities’ territories, shrinking differences between the two groups in the pilot program.

Experts say this approach to addressing Amazonian deforestation—community monitoring, combined with smartphone early alerts—looks promising. “What they found is what you would hope to find,” says Catherine Tucker, a forest governance researcher at the University of Florida, who was not involved in the study. “Would this work in all communities that have high risk of deforestation? Given the results, it’s worth a try.” She points out, however, that the communities in the region are diverse—different factors influence their risk of forest loss and capacity to monitor it. For example, some communities may not have access to the resources or training needed for a deforestation monitoring program, or their territories may hold valuable minerals or petroleum that would increase the risk of deforestation by outsiders despite monitoring efforts, Tucker notes.

Tropical forest conservation efforts worldwide are often expensive and have a small effect, says Krister Andersson, an environmental policy expert at the University of Colorado Boulder, who also was not involved in the research. “Any study like this one that shows something actually seems to be working—that’s good news,” he explains. Andersson notes that the study would have been more useful if it had compared the monitoring program with other policy interventions.

Indigenous communities may also continue the work they started in the pilot program. “We want to replicate this [effort] in other communities. In doing so, we are making a contribution to the world,” wrote Francisco Hernandez Cayetano, a community member involved in the research and president of the Federation of the Ticuna and Yaguas Communities of the Lower Amazon, in a translated statement to Scientific American. “We as Indigenous peoples ask the world for support.”