Ancient Amazon farming methods offer lessons for rainforest conservation, scientists say

View of the Amazon river, Brazil. CIAT/Neil Palmer
11 August 2018

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BONN, Germany (Landscape News) — Ancient peoples sustainably farmed the Amazon more than four millennia ago, according to a new study by researchers from Britain’s University of Exeter (UOE). Their paper, recently published in Nature Plants, provides a glimpse into past practices that could offer solutions to deforestation for today.

A multidisciplinary, international team carried out their study in the Brazilian Amazon, near the confluence of the Amazonas and Tapajos rivers. The region supported sizable populations throughout the pre-Colombian era and is now the location of many archeological sites. The main research focus was a shallow lake, archeological soil profiles, and botanical surveys in the Floresta Nacional do Tapajós, a swathe of rainforest of just over 500,000 hectares, protected since 1974.

Researchers extracted and analyzed sediment samples two-and-a-half meters deep from the bed of the lake, and soil samples from a nearby archeological site. Based on the charcoal, pollen, and plant remains in the soil, those profiles allowed them to come up with a historical picture thousands of years old and divided into three phases.

“What we see is that people arrive in the area as early as 13,000 years ago, but around our site, about 4,500 years ago,” said Yoshi Maezumi, a paleoecologist at the UOE’s Department of Archeology and lead author of the paper. “The populations grow, the culture gets more complex, and the material culture gets more elaborate. So what that is showing is that the subsistence strategy they are using is adaptable. It is growing to meet continual population growth or continual subsistence demands.”

Farmers planted maize, squash, sweet potato and manioc, supplementing their diet with fish and turtles. They used low-intensity burning to boost soil fertility, as well as adding all kinds of human and animal waste. The enriched soil they created, known as Amazon Dark Earths (ADEs), can be found in and around archeological sites.

“With the formation of these ADE soils, you increase subsistence output,” Maezumi explained. “So you were able to feed more people as the populations are growing.”

Some indigenous communities are still using and making ADEs, but on a large scale they are no longer being made, she said. The arrival of European colonists may well have caused the loss of that tradition.

The creation of nutrient-rich ADEs also allowed people to move beyond the nutrient-rich lake area upland into forested hills, where they planted gardens and possibly larger plots for crops, she added. “What this shows, is that you can stay in one place, and use the same area, without clear cutting. They were keeping some of the forest tree species.”

That also explains why forests around archeological sites have a greater abundance of edible plants, with “domesticated species five time more likely to be hyper-dominant than non-domesticated species,” according to the paper.

“Through the maintenance of closed canopy forest enrichment of edible plants, with limited clearing for crop cultivation and low-severity fire management, long-term food security was attained despite climate and socio-economic changes, the paper states,

Those farming methods stand in stark contrast to the way the region is usually farmed today. Massive stretches of rainforest are burned, the nutrient-poor oxisol soils are planted with soybeans or grass, and yields quickly fall after a few years. Then more and more of the rainforest must be destroyed.

“If you keep doing this, eventually at some point you are going to reach some kind of tipping point, and there’s no going back,” said Maezumi. “So the lessons we could learn potentially are that using this nutrient rich soil, you can stay in one place. You can reuse the land over and over again, and you can still increase subsistence yields without massive deforestation.”

The Tapajos study was part of a five-year, European Research Council-funded project that will look at several regions of the Amazon.

Meanwhile, researchers funded by the São Paulo Research Foundation (FAPESP) have been making similar findings in the Southwestern Amazon, near the upper Madeira River.