Mapping center pivot irrigation systems in global arid regions using instance segmentation and analyzing their spatial relationship with freshwater resources

Ensuring freshwater availability and supply sufficient for socio-economic development is important for human health and productivity. Globally, increasing industrial agriculture is driving crop productivity, with increasing surface water and groundwater being withdrawn for irrigation. This study mapped center pivot irrigation systems (CPIS), which are indicators of intensified industrial agriculture and large-scale investment in agriculture, with satellite data using a convolutional neural network in global arid areas. A cascade instance segmentation network was adopted, and both the convolutional block attention module technique and PointRend technique were used to increase the performance of off-the-shelf algorithms. Geospatial analysis methods were used to derive the relationships between CPIS and freshwater resources. Overall there were about 10.26 million hectares (Mha) of irrigated areas equipped with CPIS in global arid areas in 2021, and there were 4.41 Mha of CPIS-equipped irrigated fields added in the past twenty years at a relative increase of 75% compared with those at the beginning of this century. Although the largest extent of increased CPIS-equipped irrigated fields was in North America, the other five continents had higher relative increases, with Africa having the highest relative growth of 253%. The analysis of spatial relationships between CPIS and freshwater resources indicates that the stress on freshwater resources from industrial agriculture is intensifying in arid areas globally. Overall, the world's arid regions with the highest water stress from CPIS are mostly located in western North America, northern Africa, and the Arabian Peninsula. The results facilitate a better understanding of the current status of freshwater stress and ecosystem sustainability in relation to the development of agricultural intensification in global arid areas. The outcomes support governments to judge better the environmental consequences of agricultural modernization and further help them make balanced agriculture and water management policies.