Slash-and-burn farming was blamed for destroying rainforests, but a study of 18,000 forested areas found that community rules could limit clearing and allow trees to bounce back.Published in the Proceedings of the National Academy of Sciences, the research shows that unwritten social rules in small communities keep land use under control, providing food while protecting long-term forest health.The global study was led by Sean Downey, associate professor of anthropology at The Ohio State University. It focused on Swedish agriculture, one of the oldest methods of farming by humans. For about 10,000 years, villagers in warm climate areas have cut down small plots of trees, burned dry branches to feed the soil, and then grown crops until the land was no longer needed.Many critics have long argued that this practice devastates entire rainforests, but satellite images and computer models show a different picture.
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How unwritten rules protect trees?
The research team brought together experts in anthropology, physics, mathematics and satellite imagery to study farming locations in Central and South America, sub-Saharan Africa and parts of Asia. They tracked how people chose land and shared daily tasks.In traditional villages, a farmer cannot clear a plot alone and needs help from neighbours. Dependence on local help keeps the size of agricultural land small.“If a farmer demands too much — say, a 20-acre (8-hectare) farm instead of a 2-acre (0.8-hectare) farm — then fewer people come to help,” Downey said.Without adequate help, the farmer cannot clear a large plot. Over time, this unwritten social rule teaches everyone to demand smaller farms, keeping the total amount of forest cut down.This shared understanding of right and wrong guides everyday actions. This process fits with the work of Nobel Prize-winning economist Elinor Ostrom, who proved that small towns can protect shared nature by relying on peer pressure and refusal of help, rather than relying on official laws or police.“Until now, there have not been many formal models that can show how small-scale dispersed communities regulate land without top-down regulations,” Downey said.When farmers work together to cultivate these local habits, the forests form a bizarre mosaic pattern that protects against permanent damage.
Patchwork forest on the border
Downey began taking a closer look at Belize in the early 2000s. Satellite maps showed a clear gap along the country’s border with Guatemala. On the Guatemalan side, vast tracts of forest were completely cleared for cattle farms. On the Belizean side, where Maya villages reside, a healthy mix of small farms and growing trees cover the map.In Belize, the stages of farming follow a simple pattern. Farmers cut down a small area and allow the wood to dry. Burning dry wood releases carbon back into the dirt, which acts as a natural fertilizer.Crops such as corn are sown when the rains begin and harvested for a year or two until the soil loses its strength. The field is then left alone, giving the forest time to grow again.“It is a cyclical pattern of reciprocal exchanges of agricultural labor, social norms that help regulate land use, and fire and ecosystem services that regenerate the fertility of cleared forest areas,” Downey explains.
Clearing small areas helps wildlife
The study showed that this style of farming does not automatically ruin the soil. Clearing small areas can actually introduce a wider variety of plants and animals than leaving an old forest completely untouched.“When you create degraded patches, you create new ecosystems during the fallow phase where different species thrive,” Downey said, “and you end up with a higher level of biodiversity across the landscape than mature forest alone.”Cutting too much land will turn dense forests into open grasslands. However, the short breaks between harvests provide new space for different plants and wildlife to grow.
Helping rural communities protect the land
These findings provide clear considerations for global climate policies and environmental protection. They show that legal restrictions and government laws often miss how well local customs already work.“The key thing for policy makers is that small-scale rural communities have the capacity to manage community forests in sustainable ways, and they need support to solve problems using their traditional practices,” Downey said. “It’s going to look different in Belize than in Africa or Indonesia.”
More about slashing and burning
Slash-and-burn farming, or shifting cultivation, is an ancient agricultural technique used by about 200 to 300 million people globally, primarily in tropical forest areas. The process begins during the dry season when farmers clear small plots of forest trees and wild vegetation. This cleaned material, called “slash”, is left on the ground to dry before being burned as the rainy season approaches. The resulting layer of ash acts as a rich, natural fertilizer, pumping essential nutrients such as potassium, calcium and phosphorus into tropical soils. Additionally, the intense heat of the fires kills weeds, fungal spores and harmful insects in the topsoil, allowing crops such as maize, rice and cassava to grow without synthetic chemicals.Since tropical soils quickly lose their fertility, crops can usually only be harvested on a freshly burnt plot of land for two or three years. Once the nutrients in the soil become depleted, farmers abandon the site and leave it “fallow” for 5 to 20 years. During this rest period, native seeds take root, the deep roots of trees draw minerals from underground, and natural wild vegetation returns to completely replenish the soil. When practiced with sufficiently long rest cycles, this rotation allows forest soils to recover naturally, enabling farming families to return to the same plot decades later without permanently destroying the surrounding land.