What Can Ancient Farmers Teach Us About Saving The Amazon?
April 10, 2012

What Can Ancient Farmers Teach Us About Saving The Amazon?

For the better part of the last half-century, the Amazonian forests have been plagued by deforestation from human farming activities, and now, new research suggests that farming without the use of fire, like the indigenous populations did in the Pre-Columbian times, could be the key ingredient in feeding people and managing sustainable land in the Amazon and other regions threatened by deforestation.

For hundreds of years before Columbus arrived in Central America, indigenous cultures converted large areas of tropical savanna into agricultural fields with raised beds for growing crops without the use of fire-intensive techniques, which are common in today´s agricultural setting and a major contributor to greenhouse gas emissions.

An international team of archaeologists and paleoecologists, led by Dr José Iriarte of the University of Exeter and Dr. Mitchell Power, curator of the Garrett Herbarium at the Natural History Museum of Utah and assistant professor in the Department of Geography at the University of Utah, have for the first time found that from 2,000 years worth of soil, there was a sharp rise in uncontrolled burns that swept through Amazon´s coastal regions soon after 1492, when Columbus first set foot on the new land.

Findings of their research are published in the journal Proceedings of the National Academy of Sciences (PNAS).

The team of researchers said that the results of their research -- which were exactly the opposite of what they expected to find -- reveal an unexpected picture of the pre-Columbian agricultural practices. They said the findings suggest that the secret to a sustainable future may lie in the past.

The Amazonian savannas are under intense pressure today, with the land being rapidly transformed for industrial agriculture and cattle ranching.

For their study, the team of scientists analyzed records of pollen, charcoal and other plant remains in 2,000 years worth of soil taken from the Amazonian region. By analyzing the soil, the team was able to create the first detailed picture of land use in the Amazonian savannas of French Guiana, giving them a unique perspective on the land both before and after Europeans first arrived in 1492.

Previous studies have shown that burning was common in pre-Columbian times in the forested regions of the Amazon. But as indigenous populations collapsed with the advent of European diseases, the forests were able to retake control and burning quickly subsided.

Scientists had long assumed that the patterns seen in the deep-forest regions of the Amazonian also occurred in the coastal savanna regions of Central and South America. But new research shows that this was not the case. Instead, it reveals a sharp increase in fires with the arrival of the first Europeans, an event known as the ℠Columbian Encounter.´

The Old World diseases carried over by European settlers wiped out nearly 95 percent of the indigenous population, and along with them, the labor-intensive approach to sustainable farming that served the region well for hundred, if not thousands, of years. And in turn, European settlers relied heavily on their fire-intensive farming techniques which have resulted in an increase in dangerous carbon emissions that affect the climate.

“In a time of climate change, we need an alternative way of managing these savannas that is fire-free, and this is a lesson we can learn from the past,” said Iriarte. “They [indigenous people] were managing the savannas in what we can say today was a sustainable way.”

The time-tested, fire-free land use of ancient Amazonians could “pave the way for the modern implementation of raised-field agriculture in rural areas of Amazonia,” noted Iriarte. “Intensive raised-field agriculture can become an alternative to burning down tropical forest for slash and burn agriculture by reclaiming otherwise abandoned and new savannah ecosystems created by deforestation. It has the capability of helping curb carbon emissions and at the same time provide food security for the more vulnerable and poorest rural populations.”

“Amazonian savannas are among the most important ecosystems on Earth, supporting a rich variety of plants and animals,” said Professor Doyle McKey of the University of Montpellier. “They are also essential to managing climate. Whereas savannas today are often associated with frequent fire and high carbon emissions, our results show that this was not always so.”

With global warming, it is more important than ever before that we find a sustainable way to manage savannas. The clues to how to achieve this could be in the 2,000 years of history that we have unlocked,” he added.

The soil samples researchers dug up gave them a good look into the past of farming practices in the region. They noted the area was a perfect environment for sampling because wetland soil is oxygen-deprived, allowing pollen and other identifiable plant materials to survive for centuries without the threat from bacteria.

They found through the samples that between around 1,000 to 1,200 years ago rice-field farmers first arrived in the region, and to everyone´s surprise, a near absence of charcoal in those early layers indicates there were very few fires during this time.

But soon after the arrival of Columbus and European settlers, charcoal particles in the soil became more evident, indicating a more than 100-fold increase in fire frequency compared to pre-Columbian times.

Iriarte said he believed the pre-Columbian farmers kept their savannas mostly fire-free to prevent the loss of nitrogen and phosphorous from the soil and to keep the ground more fertile. Instead of burning, they opted for more labor-intensive practices to battle weeds and grow maize and other crops.

“They understood how to micromanage their environment for greater productivity,” said William Woods, an anthropologist at the University of Kansas in Lawrence, who added that agricultural burning now accounts for 30 percent of all the carbon released into the atmosphere around the world.

Restoring traditional methods could make tropical lowland farms more productive while also easing the burden on the environment and climate.

“If we look at old techniques and educate people to apply them,” Woods said, “We´ve got the fix there.”

The study was carried out by researchers from the University of Exeter (UK), Natural History Museum of Utah (US), Centre National de la Recherche Scientifique (France), University of Edinburgh (UK), Université Montpellier II and Centre d´Ecologie Fonctionnelle et Evolutive (France).

Funding for the research was provided by two CNRS Programs: ℠Amazonie´ and ℠Ingénierie Ecologique´, and by the Arts and Humanities Research Council and The Leverhulme Trust.


Image Caption: An aerial view shows the pre-Columbian agricultural raised fields in seasonally flooded savannas of French Guiana. Credit Sephen Rostain, 1987