Spatial-temporal evolution of agricultural ecological risks in China in recent 40 years.

Excessive use of agricultural chemicals and unreasonable utilization of agricultural wastes have led to severe agricultural non-point source pollution (ANPSP) problems in China. Based on the agricultural pollution loads and pollution control strength, the ecological risk index (ERI) was constructed and was used to explore the spatial-temporal pattern of agricultural ecological risks in China during 1978-2017. The findings indicated that Chinese agricultural ERI was gradually increased from 0.031 to 0.348 in 1978-2017, which has the same phased change characteristics as the succession of agricultural policies. At present, the ecological risk grade of ANPSP was present in the stair-step distribution characteristics of "high in the east and south and low in the west and north" as a whole. Southern China, as the main producing area of aquatic products, had the higher ecological risks. Northeastern China, the Huang-Huai-Hai Area, and the middle and lower reaches of the Yangtze River, as the grain-producing bases, had moderate ecological risks, but Southwestern China and Northwestern China with the poor agricultural production conditions had the lower ecological risks. It evidently showed that the ecological risk problems faced by the high-quality development of Chinese agricultural industrialization are increasingly severe.