摘要
Monitoring and analyzing changes in the extent of cultivated land may inform strategic decisions on issues of environmental and food security.The dry cropland area of 12000 km^2in the Three Gorges Reservoir Region(TGRR)of China is essential for feeding the local population of^20 million,but is highly prone to soil erosion,leading to the delivery of excessive amounts of sediment and associated pollutants to the Three Gorges Reservoir(TGR),and causing serious eco-environmental consequences.Against this background,this paper used Landsat images and a digital elevation model to analyze the altitudinal distribution of,and dynamic changes in,the area of dry cropland during the period 1990 to 2015.The results suggest that dry cropland was mainly distributed in the elevation range of 200-600 m.The dry cropland area decreased from 12525.37 km^2to 11796.27 km^2during the 25-year study period,including a particularly significant decrease in the rate of decrease from 6.93 km^2/yr to 43.99 km^2/yr after 2000.The largest decline in the dry cropland area occurred in the elevation range of 600-900 m.The transformations between dry cropland and forest revealed the impact of the TGR operation on the extent of dry cropland.A total of 528.79 km^2of dry cropland with slopes>25°were converted to forest after 2000,whereas a total of 642 km^2of forest was converted to dry cropland during the study period,and these conversions mainly occurred between the elevation of 200–900 m.These spatiotemporal changes in the dry cropland area are likely to raise new issues concerning food security in the TGRR.
Monitoring and analyzing changes in the extent of cultivated land may inform strategic decisions on issues of environmental and food security. The dry cropland area of 12000 km^2 in the Three Gorges Reservoir Region(TGRR) of China is essential for feeding the local population of ～20 million, but is highly prone to soil erosion, leading to the delivery of excessive amounts of sediment and associated pollutants to the Three Gorges Reservoir(TGR), and causing serious eco-environmental consequences. Against this background, this paper used Landsat images and a digital elevation model to analyze the altitudinal distribution of, and dynamic changes in, the area of dry cropland during the period 1990 to 2015. The results suggest that dry cropland was mainly distributed in the elevation range of 200-600 m. The dry cropland area decreased from12525.37 km^2 to 11796.27 km^2 during the 25-year study period, including a particularly significant decrease in the rate of decrease from 6.93 km^2/yr to43.99 km^2/yr after 2000. The largest decline in the dry cropland area occurred in the elevation range of 600-900 m. The transformations between dry cropland and forest revealed the impact of the TGR operation on the extent of dry cropland. A total of 528.79 km^2 of dry cropland with slopes >25° were converted to forest after 2000, whereas a total of 642 km^2 of forest was converted to dry cropland during the study period, and these conversions mainly occurred between the elevation of 200–900 m. These spatiotemporal changes in the dry cropland area are likely to raise new issues concerning food security in the TGRR.
基金
This work was supported by the National Natural Science Foundation of China(41201273,41771321,and 41571278)
the Science and Technology Service Network Initiative of CAS(KFJ-SWSTS-175)
The contribution of ALC was funded by the UK Biotechnology and Biological Sciences Research Council(BBSRC)institute strategic programme grant BBS/E/C/000I0330(Soil to Nutrition project 3).
