基于土地利用变化的珠江三角洲生态风险评价

为了探讨经济快速发展地区土地利用变化对土地生态系统造成的风险，该文以珠江三角洲为研究对象，分析了其1990－2006年土地利用变化特征，构建了区域生态风险指数，并以5 km×5 km的单元网格进行系统采样，借助空间自相关和半方差分析方法，探讨了珠江三角洲的生态风险空间分布及变化特征，结果表明：1990－2006年，珠江三角洲土地利用发生变化的面积高达12 105.05 km2，占土地总面积的29.35%，建设用地快速扩张，基塘持续增加，耕地、林地迅速减少；整个珠江三角洲的生态风险指数由1990年的0.2713增至2006年的0.3318，风险程度增加了22.31%，在空间分布上具有明显的正相关性，空间集聚逐渐增强，深圳、东莞、广州市区、花都、南海、顺德、佛山市区及中山等是生态风险指数高值聚集区，指数变化更为明显，风险程度明显提高；高、较高生态风险区面积快速增加，由1990年的4874.52 km2增加到2006年的12 494.93 km2，占土地总面积的比例由11.82%增至30.30%；生态风险程度呈现明显的圈层结构，以佛山市区－广州市区－深圳为轴向外风险程度逐渐降低。研究结果为区域土地可持续利用提供新的思路和方法，从而促进土地利用与生态环境的协调发展。该研究为生态风险管理政策的制定提供科学依据。

Ecological risk assessment for Pearl River Delta based on land use change

Abstract: Land use changes not only affect the land structure and types, but also affect the degree of health of the land ecological system. In order to explore the ecological risks caused by the land use change, and provide scientific support for the formulation of the relevant policies and the measures, this paper described a case study on the Pearl River Delta. The characteristics of land use change were analyzed during 1990 to 2006, and the ecological risk was conducted based on the land use change, the ecological risk plots of 5km×5km were applied. Spatial distribution and gradient differentiation characters of the ecological risk in the study area were analyzed by means of spatial autocorrelation and sub-analysis of variance. The conclusions were as follows: 1) The changed land (12105.05km2) occupied 29.35% of the total land in the Pearl River Delta during 1990 to 2006. The area of construction land expanded quickly, while dike-pond increased intensively, and farmland and forests evidently decreased. Population growth, economic development, industrialization, urbanization, and the swarm of foreign investment were the main factors which led to the land use changes. 2) In 1990, the ecological risk value of the whole region was 0.2713, which increased to 0.3318; the degree of risk has increased by 22.31%. Moran's I was used to estimate the spatial autocorrelation of the ecological risks. From 1990 to 2006, the global Moran's I from 0.6451 increased to 0.7137. The spatial distribution of ecological risk showed a positive autocorrelation and significant local spatial clustering pattern. The spatial variability was primarily the result from structural factors. The high-value regions included Shenzhen, Dongguan, Guangzhou Urban District, Huadu, Nanhai, Shunde, Foshan Urban District, and Zhongshan. The changes of ecological risk in these regions were more significant, and the degree of risk increased intensively. 3) The area of high risk region and relatively high risk region expanded quickly, from 4874.52 km2 in 1990 to 12494.93 km2 in 2006, and the proportion of the total land from 11.82% to 30.30%. Meanwhile, the area of low risk region and inferior risk region decreased from 18901.54 km2 in 1990 to 13983.87 km2 in 2006, and the proportion of the total land from 45.84% to 33.91%. 4) Ecological degree of risk showed an obvious ring structure, and decreased from the axis of Foshan Urban District-Guangzhou Urban District-Shenzhen to other regions. From 1990 to 2006, the high and relatively high risk region expanded gradually from the two banks of Pearl River Estuary to the middle area of Pearl River Delta, and the degree of risk reduced gradually towards the west and the east of the Pearl River Delta. With the speeding up of the economic development and urbanization course in the Pearl River Delta, land use has intensively changed, which obviously increases land ecological risks. These conclusions can provide new ideas and methods for sustainable land use and ecological risk management, and help promote the coordination of land use and the ecological environment.