Credit: © Andy Müller

Soil erosion rates in the Lake Salpetén drainage basin, Guatemala, were higher during the ∼1,900-year period of ancient Maya settlement than before or after, according to a new quantitative analysis of lake sediment cores and a quasi-three-dimensional seismic survey. The most rapid erosion occurred during initial land clearance, despite subsequent increases in population density.

Flavio Anselmetti from the Swiss Federal Institute of Technology and colleagues1 seismically surveyed the sediments of Lake Salpetén, which is in the tropical lowlands of Northern Guatemala and is situated in a closed drainage basin where deposits directly reflect erosional and runoff processes. Combining these data with radiocarbon dates from lake sediment cores, the researchers estimated the total sediment transported to the lake during various periods of Maya occupation. They found that the greatest soil loss occurred in the Middle and Late Preclassic periods (700 BC to AD 250), which are associated with relatively low population densities. After the decline of human disturbance (from AD 950), soils and forests recovered partially, contrary to expectations of soil degradation after abandonment.

The study suggests that soil erosion rates and population density are not necessarily linked. Instead, the susceptibility of top soils to erosion and the sustainability of land-use practices are also important.