Comparing 20 Century Trends in U.S. and Global Agricultural Water and Land Use

Globally and in the United States, agriculture is the major user not only of water but also of land. This paper compares trends in aggregate and per capita water and land use by the agricultural sector in the United States and the world during the 20 century. It finds that although cropland use per capita has been declining in both areas since the early 1900s, agricultural water use per capita only began declining in the latter half of that century. That the increases in efficiencies of agricultural water use lagged behind the increases in the efficiency of cropland use is consistent with the fact that farmers (and farming communities) have traditionally had stronger property rights to their land than to their water. As a result, through much of the 20 century, farmers had a greater incentive to improve the efficiency of land use than that of water use and to substitute water for land (or irrigated land for dryland) in producing crops.