BARCELONA, SPAIN -- According to a Science News report, the Casarabe people, who lived in what is now northern Bolivia between A.D. 500 and 1400, built a network of drainage canals and ponds so that they could produce two maize crops per year on the Amazonian savannas. Previous research had shown that the Casarabe consumed maize, tubers, squash, peanuts, and yams, but no evidence of agricultural fields had been found. Geoarchaeologist Umberto Lombardo of the Autonomous University of Barcelona and his colleagues examined satellite images of Casarabe territory, and identified clusters of human-made ponds. Deep canals moving away from the pond clusters were spotted through the use of lidar equipment mounted on drones. Analysis of soil samples taken from the edges of the canals and ponds contained maize phytoliths. Radiocarbon dating of the samples at one of the ponds indicates that it was used between about 1250 and 1550. "As the population grew and environmental pressures increased, perhaps they looked for more reliable and stable sources of proteins," Lombardo said. "Maize could have offered that to some extent," he concluded. Read the original scholarly article about this research in Nature. To read more about identifying Casarabe settlements using lidar, go to "Around the World: Bolivia."