From Nature (Amanda Mascarelli):
It has long been suspected that the Maya relied heavily on agriculture. In the 1970s, researchers began characterizing the remains of elaborate irrigation canals found in wetland areas. But it has not been clear how widespread these canals were or whether the use of wetlands for farming was an important part of the Maya agricultural system.
At the GSA meeting, [Timothy Beach, a physical geographer at Georgetown University in Washington DC] presented the results of two decades’ work aimed at answering these questions1,2. During that time, he and his wife, Sheryl Luzzadder-Beach, a physical geographer specializing in water quality from George Mason University in Fairfax, Virginia, and their colleagues, have performed more than 60 excavations to study and map the different earth layers, or strata, in field sites in northern Belize. “Usually in archaeology there’s an elite focus on the majestic cities that we can wonder at. But the burning question is always how did they feed these populations.”
Working in low-lying wetlands, which are difficult to access and navigate, the team dug trenches some 3 metres deep and 10–20 metres long to study soil and water chemistry. They performed carbon-isotope analyses on soil layers and studied fossilized plant materials to work out how the land was used.
The soil layers revealed signs of rising water tables and the remnants of flood deposits. Fossilized plant remains at these sites show that the Maya were growing crops such as avocados, grass species and maize. Their research suggests that the Maya built canals between wetlands to divert water and create new farmland, says Beach.
As the Maya mucked out the ditches, they would have tossed the soil onto the adjacent land, creating elevated fields which would kept the root systems of their crops above the waterlogged soil, while allowing access to the irrigation water. Beach says that surveys carried out using Google Earth and remote sensing techniques suggest that this wetland system was probably around 100 kilometres across.