Habitat Quality Assessment And Its Degradation Mechanism In South Subtropical Islands Of China

There are a large number of islands in China, which are characterized by special location and abundant resources. These islands play important roles in the economic, social development and national defense in China. The resources and ecosystem services of islands assume even greater importance with the enhanced importance of ocean in national economic development. The study and assessment of the island habitat, which is a component of island ecosystem, are becoming more important and urgent.Aiming to provide technical support for assessment and management of island ecosystems in south China, the present study, supported by the 908 special project, carried out the habitat quality assessment of islands ecosystems in south-subtropical region with 908 special project investigation data, and studied change tendency and degradation mechanism based on data in recent two decades. Theories of environmental science, landscape ecology and marine ecology were applied in this study. The study contents and corresponding results are:The general situation of south subtropical islands was introduced by analyzing natural characteristics, and then 10 typical islands have been selected for further study. To assess the habitat quality, indicators that reflect the qualities of habitat components were selected based on the analysis of composition and characteristics of island habitat. In addition, biodiversity indexes of phytoplankton and macrobenthos were selected to indicate the ecological response of island habitat quality in the sea areas.After the indicators were selected, the status and change tendency of habitat quality in the sea areas of south subtropical islands were assessed by the application of methods, which included analysis method of combining single factor with multi-factors, methods for assessment of eutrophication in seawater and potential ecological risk of sediments. One-way ANOVA and Two-way ANOVAs analysis were done to test the effects of habitat quality on biological community. The results showed that many islands were suffering from eutrophication problem of seawater while the sediment quality was generally in healthy condition. Coastal pollutions in islands situated in the estuarine areas were more serious than those in oceanic areas. Significant ecological responses were found in the validation according to the correlations between biological community parameters and habitat quality. Over the past 20 years, the concentrations of the following indicators, DIN, Cu and oils, were found to increase in seawater, and eutrophication state has become much more serious for most island sea areas. The indicators of which the concentration increased were sulfide and organic carbon. Concentrations of heavy metals and their potential ecological risks were found to decrease.The status and change tendency of habitat quality in the land areas of south subtropical islands were assessed with the index technique of landscape spatial pattern. The results showed that the features of landscape spatial pattern appropriated to the development process of local economy in these islands. In Xiamen Island, the high-function landscape area significantly decreased while the values of landscape fragmentation index increased from 1987 to 2004. The diversity index as well as evenness index of landscape increase from 1987 to 1993, and then decrease from 1993 to 2004 in Xiamen Island.The driving forces that caused the degradation of island habitat were analyzed. Pollutants and nutrient input from watershed, municipal wastewater discharge and mariculuture pollution, poor hydrological condition were the main factors that resulted in the eutrophication in seawater. Pollutants from vessel activity were also the cause of marine pollution. Marine sediment pollution was due to pollutants from watershed and coastal areas. Rapid population growth and economic development were the primary driving forces to change the landscape pattern, and government polities and market mechanism were also major factors caused this change. Based on the study, a series of strategies were proposed to improve the protection and management of island habitat.