Ecological Risk Of Land Consolidation Appraisal Based On GIS

Beiliu is a famous industrial city which located in the southeast of Guangxi Zhuang Autonomous Region, covering a total area of 2457 square kilometers. The urban features and karst landform determine that Beiliu is a densely populated city. Moreover, its reserved cultivated land resource is severely inadequate. The area of unutilized land only accounts for 3.45% of total area. Under these circumstances, land consolidation projects in Beiliu are imperative for the sake of keeping the "red land" of cultivated area. Nevertheless, land consolidation is a highly comprehensive work that employs engineering, biological and other approaches to change the ecosystems of woodland, farmland, roads, water, villages and so on. It is bound to bring ecological risks.Ecological risk assessment of land consolidation is a systematic project which contains management and decision-making. Ecological risk of land consolidation refers to the appearing probability of one or more of the ecological pressure sources and the adverse reactions of land ecosystems after suffering from pressure. Compared with other single ecological risk assessment, ecological risk assessment of land consolidation has the following characteristics:risk sources, risk recipients and ecological endpoints involve uncertainty; simply focuses on the harmful effects on ecosystems; emphasizes the intrinsic value of ecosystems; the land ecosystem is a dynamic system.This study divides Beiliu into 22 research areas according to the township boundaries. After collecting basic data and related materials, the author identifies 5 major habitats which are easily affected by land consolidation in each research area,4 categories of potential risk sources and 3 possible ecological endpoints in the Beiliu’s land consolidation projects. Then, based on these preliminary data, this paper attempts to build a Exposure-Response Model of ecological risk in the light of ecological risk assessment framework of land consolidation and Beiliu’s actual situation, followed by segmentedly assigning values to the exposure coefficients and response coefficients of the model according to prior related research results. Then, the author not only introduces 2 parameters which named ’pressure density’and ’the loss of habitat abundance’into Relative Risk Model (RRM), but also standardizes the data of 4 categories of potential risk sources and 8 habitat changes in the Beiliu’s land consolidation. These two steps, which make the discrete data become continuous grading, facilitating a more genuine reflection of the ecological risk situation in the Beiliu’s land consolidation.By calculating the risk characterization, the results indicate that in Beiliu there are 3 townships belonging to high risk area,11 townships belonging to relatively high risk area,7 townships belonging to medium risk area,9 townships belonging to low risk area and 2 townships are at extremely low risk. In terms of risk sources, land leveling is the largest risk source in the region, next comes tillage & fertilization, followed by infrastructure construction. In comparison, the construction and expansion of settlements brings the lowest risk. Among 8 categories of habitat changes, there are 3 changes should be noted: the first one is the road & ditch construction, which almost has an effect on every township, may lead to the decrease of heterogeneity and fragmentation index of farmland landscape, and then destroys the integrity of natural ecosystems; the second is the reduction of mud flats which results in the loss of ecological benefits; the expansion of settlements and human migration also brings subsequent ecological pollution. As to 3 ecological endpoints, it is most likely to happen in 3 townships (Baima, Shiwo and Tang’an) whose relative risk index are all above 0.28. On the contrary, Qinshuikou’s potential risk of 3 ecological endpoints is almost zero due to few construction projects in here.The results of this study is a predictive evaluation of the Beiliu’ land consolidation. It can provide specific policy recommendations for the implementation of land consolidation projects and offer a theoretical basis to the project risk management.