An ancient method of raised-field farming now being revitalized on the plains surrounding South America's Lake Titicaca offers valuable environmental lessons for modern agriculture, according to an aquatic scientist. The system of raised, cultivated beds separated by deep channels of water successfully filters out nutrients and sediment, making them available for crops and preventing downstream water pollution, reports Heath J. Carney, a researcher in environmental studies. His findings appeared this summer in the journal Nature. "What is great about this system is that here we have something that is pre-Columbian, and the more you look at it, the more ecological wisdom you see," says Carney of the raised-field method of agriculture. Carney and colleagues analyzed water quality in both raised-field sites and conventional fields devoted to dry-land farming and found that the nutrients phosphate and nitrate were being taken up by the aquatic plants found in the raised-field channels. Farmers, who primarily grow potatoes, spread the aquatic plants as well as the nutrient-rich sediment from the channels on the raised beds as organic fertilizer.