The agricultural practices of the Native Americans inhabiting the American Southwest, which includes the states of Arizona and New Mexico plus portions of surrounding states and neighboring Mexico, are influenced by the low levels of precipitation in the region. Irrigation and several techniques of water harvesting and conservation were essential for successful agriculture. To take advantage of limited water, the southwestern Native Americans utilized irrigation canals, terraces (trincheras), rock mulches, and floodplain cultivation. Success in agriculture enabled some native Americans to live in communities which may have numbered as many as 40,000 people as compared to their former lives as hunter-gatherers in which their bands numbered only a few dozen.