ABSTRACT
From the beginning of agriculture in the Middle East until the mid-twentieth century, cropland area expanded as agriculture spread from valley to valley and then from continent to continent. Throughout this period, growth in food output came largely from expanding the cultivated area. Thus the history of agricultural yields divides neatly into three periods: a time of expanding area until around mid-century, a time of mostly expanding yields with some modest growth in area until 1981, and a time when all additional output has come from raising land productivity. Worldwide, gains in cropland area from year to year are the result of various cropland expansion initiatives, including the conversion of forest, new irrigation projects that permit the farming of land otherwise too dry to farm, and drainage of wetlands. Future cropland losses are likely to be concentrated in Asia, with gains in Latin America.
