A detailed analysis of human land use and fire management in the Amazon has revealed that farming techniques used by ancient communities thousands of years ago have had a lasting impact on the rainforest.
“The work of early farmers in the Amazon has left an enduring legacy,” said study co-author Professor Jose Iriarte. “The way indigenous communities managed the land thousands of years ago still shapes modern forest ecosystems.”
“This is important to remember as modern deforestation and agricultural plantations expand across the Amazon Basin, coupled with the intensification of drought severity driven by warming global temperatures.”
Early farmers had a profound effect on parts of the Amazon which were previously thought to have been untouched. According to the study, the ancient farmers introduced crops to new areas, increased the number of edible tree species, and used fire to improve the nutrient content of soil.
The study was conducted by an interdisciplinary team of archaeologists, paleontologists, botanists, and ecologists. The research shows how early farmers intensively cultivated the land and expanded crops without the need to continuously clear new areas of the forest when soil nutrients became depleted.
By analyzing charcoal, pollen, and plant remains from the soil in archaeological sites and lake sediments, the research team was able to trace the history of vegetation and fire in eastern Brazil. The experts uncovered evidence that maize, sweet potato, manioc, and squash were farmed as early as 4,500 years ago in this part of the Amazon.
The farmers adjusted the soil by adding manure and food waste or through the use of fire to increase the crop yields. The findings explain why forests around archaeological sites in the Amazon have an abundance of edible plants.
“People thousands of years ago developed a nutrient rich soil called Amazonian Dark Earths (ADEs),” said study lead author Dr. Yoshi Maezumi. “They farmed in a way which involved continuous enrichment and reusing of the soil, rather than expanding the amount of land they clear cut for farming. This was a much more sustainable way of farming.”
The ADEs allowed for the expansion of corn and other crops to be farmed in areas beyond the nutrient-rich shores of lakes and rivers, increasing the amount of food available for growing Amazon communities.
“Ancient communities likely did clear some understory trees and weeds for farming, but they maintained a closed canopy forest, enriched in edible plants which could bring them food,” said Dr. Maezumi.
“This is a very different use of the land to that of today, where large areas of land in the Amazon is cleared and planted for industrial scale grain, soya bean farming and cattle grazing. We hope modern conservationists can learn lessons from indigenous land use in the Amazon to inform management decisions about how to safeguard modern forests.”
The study is published in the journal Nature Plants.
By Chrissy Sexton, Earth.com Staff Writer
Image Credit: Dr Yoshi Maezumi