Raised field agriculture in southwest Tlaxcala, Mexico, is a sophisticated, intensive traditional system of wetland cultivation that dates back to as early as 300 B. C. It provides an exceptional example of how farming practices can fit into and even take advantage of ecosystem processes. The raised fields appear to be largely self-reliant in energy and nutrients. Tlaxcalan farmers use canals, aquatic plants, polycultures, alder (Alnus firmifolia) and other trees to intensify the nutrient input into their fields and minimize nutrient losses through leaching and runoff Although the raised field system is an impressive, functioning example of a historically sustainable farming system, it is endangered by modern pressures to increase production through higher use of inputs and alteration of agroecosystem design.
