Pre-Columbian Farming Methods Helped Biodiversity in Amazon, Study Says

Farming methods introduced by humans in South American savannahs altered Amazonian ecosystems before Europeans arrived in the Western Hemisphere and appear to have increased biodiversity, according to a new study. Examining unusual mounds in the savannahs of French Guyana, researchers at the University of Montpelier 2, France, concluded that the mounds — about five feet across and a foot high — apparently were built by farmers as crop beds that would drain effectively during the rainy season. After testing the drainage capacity of the mounds, researchers found that they drained nine times faster than the surrounding savannah, which floods seasonally. Researchers discovered that once humans abandoned the mounds, roughly 400 to 800 years ago, the raised beds emerged as a new ecosystem for plants, insects, and animals. Certain insects preferred to build nests in the beds, and the Acromyrmex octospinosus, a fungus-growing ant, carried organic materials to the nest, helping plants to grow larger. “It’s clear that a savannah with this heterogeneity will have a higher biodiversity than just a flat savannah,” said Doyle McKey, lead author of the study published in the Proceedings of the National Academy of Science. “Human actions cannot always be characterized as bad for biodiversity.” Similar mounds have been found in Surinam, Belize, Venezuela, Ecuador, Bolivia, and Mexico.