Regionalization of suitable development of unutilized lands in Huanghua City

Unutilized land is an important reserve of land resources, the study on its suitability and development modes is an important measure for sustainable land use. Also unutilized land development is an important action towards food security, economic growth and eco-civilization. It is the focus of scientific and technological innovations of land, and the guidance of development and utilization of unutilized lands to evaluate development suitability and to regionalize rationally the exploitation of unutilized lands. Huanghua City was used as a case study to evaluate the suitability of cultivation, construction and ecological risk of unutilized lands. The indexes systems were established for cultivation suitability evaluation according to land type from aspects of soil property, water resource and vegetation coverage; for construction suitability evaluation from aspects of natural quality, landform and engineering geology; and for ecological risk evaluation from aspects of salinity degree, vegetation coverage, soil thickness and waterlogging degree. The synthetical index method was used to evaluate the suitability of unutilized land for cultivation and construction and ecological risk of exploitation. A coupling model and genetic algorithm were used to evaluate triplet coupling exploitation partitions of unutilized lands. The case study was meant to provide a methodological demonstration of the development and utilization of unutilized lands in the study area and beyond. The results showed that 1) the exploitation suitability for cultivation of unutilized lands had four grades, with the largest unutilized land area belonging to the N grade (not suitable for cultivation) which was in the east of Huanghua City. 2) Construction suitability of unutilized lands had three grades, and the third grade (low suitable) had the biggest area, which concentrated in the center and west of Huanghua City. 3) There were five grades of ecological risk, with high ecological risk regions in the east of Huanghua City and low ecological risk regions in the west of the city. The main region was the middle-to-low and middle-to-high ecological risk grade. 4) The study area was divided into three key exploitation partitions, including exploitation partitions of cultivation lands, construction lands and ecological lands. The exploitation partition of cultivation lands was mainly concentrated in the center and west of the city. The exploitation partition of construction lands was mainly located in the central of Huanghua City. Then the exploitation partition of ecological lands was mainly concentrated in the east of the city. The results could provide scientific support for resolving the dilemma of land supply and demand in the study area.