基于景观格局-服务的景观生态风险评价——以广州市为例

城市化对景观的结构和功能造成极大干扰,城市景观变化引起的生态风险受到城市生态建设的关注,但景观生态风险评价技术体系尚待深化,以促进风险防范决策。研究选取植被碳固定、土壤保持、水源涵养与提供和栖息地提供等景观服务改进景观脆弱度的评价方法,以广州市为案例研究区,评价了1990—2015年广州市城市景观生态风险及其时空变化特征。研究结果表明:(1)基于景观格局与服务的景观生态风险评价能够有效地评估城市景观生态风险的空间分布,但评价需要关注结果验证和辅助情景分析,方可为景观生态风险的预警和预测提供科学依据。(2)1990—2015年广州市的景观干扰度先增加后降低,2000年是景观干扰度变化的转折点;25年间,景观脆弱度不断增加,中脆弱度和高脆弱度比例之和维持在60%以上;2000年是景观生态风险的转折点,1990—2000年景观生态风险趋于增大,2000—2015年景观生态风险趋向降低;景观干扰度、脆弱度和生态风险在空间上呈现南部高于北部,西部高于东部的分布特征。(3)近25年,广州市景观生态风险与景观变化具有较好的空间一致性。维持低风险的比例为40.74%,基本都分布在北部山区,而维持高风险的比例为6.67%,由低风险向高风险的转变比例为32.28%,由高风险转变为低风险的比例为20.31%。

Assessing landscape ecological risk based on landscape pattern and services in Guangzhou during 1990-2015

Landscape ecological risk assessment (LERA) is an effective tool developed in recent years to support landscape ecological construction and management. The ecological risk caused by landscape change or land-use and land-cover change has received increased attention by policy-makers. High-intensity human activities disturbed the pattern and function of ecosystem and the hotspot of landscape change in urban areas, which contributed to the uncertainty of ecological risk. Therefore, it is urgent to improve the LERA method to provide quantitative analysis for landscape management and comprehensive risk prevention. There are several methods used for LERA such as landscape metrics and landscape source-sink risk. However, the classic model of traditional ecological risk assessment followed the mode of risk source identification-receptor analysis-exposure and hazard assessment. In order to improve the LERA method in urban areas, this research followed the landscape metrics method, but improved the algorithm of vulnerability for landscape services. A series of landscape services indicators were reselected to denote landscape vulnerability, including carbon storage, water provision and purification, soil conservation, and habitat quality. This study used multi-source data to analyze the spatio-temporal changes and characteristics of landscape ecological risk based on 1 km×1 km spatial resolution in Guangzhou, a typical area experiencing rapid urbanization, for the period 1990-2015. The results were as follows: (1) LERA based on landscape pattern and landscape service can effectively evaluate the spatial distribution of urban landscape ecological risk. The low landscape ecological risk type is typical and these areas were regularly distributed over the 25 years. In the study stage, the year of 2000 was the transition period. (2) The landscape disturbance degree of Guangzhou increased first and then decreased over the 1990-2015 period; 2000 was the year when the degree of landscape disturbance changed. Landscape vulnerability is increasing. Together, medium vulnerability and high vulnerability areas accounted for more than 60% of the area; these areas were more common in the south than the north, and more common in the west than in the east. The landscape ecological risk in Guangzhou was increasing before 2000, and showed a tendency to decrease after 2000. (3)The landscape ecological risks transition showed that landscape changes and ecological risk have a good spatial consistency in Guangzhou during the 25-year study period. The area with a low landscape risk was 40.74%, and this area was mostly distributed in the northern mountainous areas. The area with a high landscape risk was 6.67%, the transition from low risk to high risk was 32.28%, and high risk change to low risk was 20.31%. This shows that landscape changes in urban area has a high risk after rapid urbanization. However, the uncertainty of LERA still plagued the application of LERA in policy-making. Further research can pay more attention to the verification of assessment results or use scenario analysis to quantify spatiotemporal characteristics of risk to improve the scientific basis for the early warning and prediction of landscape ecological risk. Then, the LERA applications in urban areas can be acceptable for landscape management or policy-making.