The Amazon rainforest is often thought of as an untamed wilderness. But a growing number of studies, for example one in 2015 and another in 2017, show that local people have domesticated the forests for millennia, weaving patches of useful trees and plants into its natural tapestry. Now, a recent, much more comprehensive study in Frontiers in Ecology and Evolution captures for the first time how people put the forest to work across the entire Amazon basin.

The study suggests that people commonly used subtle management practices such as clearing non-useful plants to favor trees and plants used for food and fibers. In fact, the vegetation that makes up the forests today is due in large part to the activity of past dwellers, the study concludes.

Many forest patches created long ago are still in use today, says Carolina Levis, a lead author of the work and PhD candidate in historical ecology at Wageningen University in the Netherlands and the National Institute of Amazonian Research in Brazil. She and her group conducted an extensive literature review as well as interviews with locals—who, when traveling across the forest to marry and trade, often share their knowledge of forest management. “All across the Amazon basin, people share knowledge of forest management and have been doing so for a long time,” says Levis.

The literature review revealed eight key forest management practices that Amazonian people employ. The practices include, for example, planting and protecting useful species such as brazil nuts (Bertholletia excels) and palm trees (Euterpe precatoria). Another practice entails communities finding ways to attract animals that help disperse seeds. Activities also included enriching soil with human and animal waste.

Levis and her team visited 30 contemporary villages located on the banks of four rivers across the Amazon basin. There, they collected data on management practices in use today and the composition of forest patches. “This is the biggest and most detailed study to date documenting anthropogenic forest management,” says Clark Erickson, an ecological anthropologist at the University of Pennsylvania in Philadelphia who was not involved with the study. Most previous studies were run by small teams looking at just one or two sites, he notes. “This study brings science to the debate on the human impact on forests,” he says.

Data on present-day forest composition and management practices helped the researchers glean what happened hundreds or thousands of years prior. For example, the team found forest patches around archeological sites, and inferred that these were the result of activities of past communities. Using such insights, they created a conceptual model that explains the changes from wilderness in late Pleistocene to domestication today. The model maps how interactions between the eight management practices across space and time can form domesticated forests. Taken individually, the impacts of the practices are difficult to see. But the model demonstrates that together these practices can dramatically transform the forest.

Data and samples that the team collected, for this paper and previous work, suggest that productive patches of trees throughout the forest basin yield a broad range of food, fiber, and fuel products without largescale cutting or burning “People work with the natural ecology to transform a forest from pristine to domesticated, making subtle changes rather than cultivating the land,” she explains.

Levis hopes this research will add weight to arguments that discourage cutting down forests to make way for cattle grazing and annual crops such as maize and soy in the Amazon. Large swathes of the forest are already being put to work to produce different kinds of food, such as nuts and fruits, with no need for deforestation, she says. She hopes future production focuses on these less environmentally destructive foods rather than on annual crops. “The forest is already producing useful products, so why not maintain it,” she argues.

The study also disputes the idea that people must be kept out of forests in order to protect the environment and biodiversity, adds Erickson. Dramatic slash-and-burn practices aside, the more subtle practices of locals appear to be relatively innocuous. “People have lived in the Amazon forest for centuries without destroying it,” he says. “They know what they were doing.”