Evaluation of ecological risk and carbon fixation from land use change: A case study of Huanghua City, Hebei ProvinceE

The rapid development of social economy has had a profound impact on the change of land use pattern. Ecological risk assessment had played an important role in controlling ecological risk and realizing sustainable development. Changes in land use pattern will exert an effect on regional ecological risk and carbon sequestration. Combined evaluation of ecological service value and ecological risk assessment has become the new mode of studying ecological problems. This paper used Huanghua City in Hebei Province, China as a case study and remote sensing images for 1995, 2005 and 2015 as the basic data to analyze this pattern change. While ecological risk index was constructed based on the pattern of change in land use, InVEST was used to analyze the change in carbon storage. Finally, we analyzed the correlation between changes in ecological risk and carbon stock. The purpose of the study was to determine rational utilization of land resources for healthy development of ecological environment. The results showed that:1) cultivated land, saline land and construction land were the main land use patterns in Huanghua during 1995-2015. Compared 2015 with 1995, the degrees of fragmentation and separation in cultivated land, grassland and construction land increased, while the separation and fragmentation of garden plot and saline land decreased. While the loss index of garden plot and the saline land reduced, that of other land use types increased. 2) Total ecological risks of Huanghua City in 1995, 2005 and 2015 were 12.58, 10.32 and 11.10, respectively. During the study period, low risk and high risk area constituted the main risk areas. The area of the low risk gradually increased and was concentrated in the south. Then the area of high risk gradually decreased and was concentrated in the central and eastern coastal zones. 3) According to InVEST simulation results, the carbon storage in Huanghua City increased and then decreased eventually. In 1995, 2005 and 2015, total carbon storages in Huanghua were 23.870 5 million tons, 24.915 1 million tons and 20.288 6 million tons, with respective carbon densities of 107.63 t·hm^-2, 112.34 t·hm^-2 and 93.16 t·hm^-2. Change in carbon storage under each land use pattern was more consistent with change in the corresponding land area. 4) Correlation between changes in ecological risk and carbon stock was significant. The determinants of the correlation between changes in ecological risk and carbon stock in 1995-2005 and 2005-2015 were 0.69 and 0.72 (P < 0.01), showing a significant negative correlation. It suggested that ecological risk assessment and ecosystem services valuation were concurrently assessable. This was one of the innovative points of the research. The assessment of ecological risk and carbon storage in Huanghua using change in land use pattern was important for the realization of sustainable utilization of land resources and improvements in regional ecological environment.