A land use change model to simulate the global development of irrigated cropland areas

On global average, irrigated cropping systems achieve two to three times higher yields per hectare than non-irrigated systems, enabling higher production volumes for a growing world population with its increasing demand for food, fiber and bioenergy. Moreover, they are more resistant to expected climatic changes such as heat waves and droughts. Therefore, irrigation agriculture is and will remain a keystone of global food security policies. In order to end hunger, as it is the aim of SDG 2, an expansion of irrigated cropland areas will be indispensable. However, Irrigation agriculture it is by far the largest water use sector, responsible for 70 percent of global freshwater withdrawals and more than 90 percent of global consumptive water use. Hence, an expansion of irrigation agriculture can easily come into conflict with SDG 6 (sustainable withdrawals and supply of freshwater) as well as with SDG 15 (sustainable use of terrestrial ecosystems). In order to avoid or at least to minimize these conflicts, to achieve global food security on the one hand and a sustainable supply of freshwater on the other, reliable and accurate estimations of the future extent of irrigated cropland areas are needed. To this end, we developed an integrated, spatially and temporally explicit land use model within the modeling framework of LandSHIFT that allows to allocate current and future irrigated crop production and resulting area on global land use grid maps with a cell size of 5 arc-minutes. It is a significant improvement compared to the first attempt by Schaldach et al. (2012). We developed a new allocation algorithm, used more input data and improved the suitability assessment. Model results can provide crucial input for other global studies related to water use, food production or climate change. It can be a useful tool for politics of large-scale and long-term planning.