Food production has more than kept pace with global population growth. On average, food supplies are 24 percent higher per person than in 1961, and real prices are 40 percent lower. Agriculture faces an enormous challenge to meet the food needs of an additional 1.7 billion people over the next 20 years. Agroecosystems cover about a third of the global land area, but almost three-quarters of the land has poor soil fertility and about half has steep terrain, constraining production. While the global expansion of agricultural area has been modest in recent decades, intensification has been rapid, as irrigated area increased and fallow time decreased to produce more output per hectare. About 66 percent of agricultural land has been degraded in the past 50 years by erosion, salinization, compaction, nutrient depletion, biological degradation, or pollution. Over 40 percent of agricultural land has been strongly or very strongly degraded.