1,000-year-old farming secrets could save the Amazon rainforest

The Amazon covers over 2.5 million square miles. But that number is shrinking all the time, and the widespread deforestation could doom our hopes for averting catastrophic global climate change. That's why some ancient farming secrets could make a huge difference.

Top image: CIFOR on Flickr.

It's probably not even worth trying to comprehend the scale of the Amazon rainforest. It encompasses more than half of all the world's remaining rainforest, and it's home to about a tenth of all the world's known species, with about 90,000 tons of biomass for every square miles. And, perhaps most importantly, the Amazon stores about a tenth of the planet's stored carbon, equivalent to about 100 billion tons.

The rainforest's deforestation would threaten to release vast quantities of that stored carbon, which would greatly accelerate the global warming process. The good news is that, since around 2004, conservation efforts have begun to take hold and, while the deforestation hasn't stopped, it has at least slowed down significantly. The basic problem is how to protect the long-term health of the rainforest — and, by extension, the planet as a whole — with the more short-term economic pressures that lead farmers and developers to cut down parts of the Amazon in the first place.

Now, an international team of archaeologists have made an intriguing discovery — the peoples who farmed the Amazon long before the arrival of Europeans did so without burning down trees to clear room for their fields. That goes against the longstanding assumption that all Amazonian farmers both pre- and post-European contact have relied on fire to hold back the jungle and manage their land.

Instead, these indigenous farmers used something known as raised-field farming, which is pretty much exactly what it sounds like. They built small mounds all along the savannas that form the periphery of the rainforest, and then they farmed on these artificial mounds. While the elevated fields were almost certainly a pain in the ass to make, the benefits were huge — they naturally drained and aerated the soil while still retaining moisture. In a region known in equal measure for floods and droughts, that's a pretty nifty bit of agricultural engineering.

While more labor-intensive than simply burning down parts of the rainforest to make for new farmland, the quality of the land seems to have made up for the reduced quantity. Burning might create new farmland, but it also robs the soil of vital nutrients and organic matter, essentially wrecking its entire internal structure. And, as University of Exeter researcher Dr. José Iriarte observes, there's no reason why this couldn't work today:

"This ancient, time-tested, fire-free land use could pave the way for the modern implementation of raised-field agriculture in rural areas of Amazonia. 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."

Though it's too early to say just how widespread this practice was, previous archaeological finds suggest that the Amazon periphery was a densely populated place. That would indicate this raised-field agriculture was enough to support a large population, and the archaeologists' research suggests the practice dominated Amazonian agriculture for as much as 1,500 years, right up until the arrival of Europeans.

At that point, war and disease wiped out about 95% of the indigenous population, and slash-and-burn farming took hold as these ancient methods were lost. But now that we've rediscovered them, they could prove an extraordinarily powerful tool in controlling global warming, as fellow researcher Doyle McKey of Montpellier University rather eloquently suggests:

"Amazonian savannas are among the most important ecosystems on Earth, supporting a rich variety of plants and animals. 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."

Via PNAS.