Land-cover change and its time-series reconstructed using remotely sensed imageries in the Zhoushan islands

Coastal islands are located in transitional environments where land and sea interact. It is main frontier to develop oceanic economy and to utilize oceanic resources. Insular environment is isolated and its ecosystem is also vulnerable. The exploitation and development of islands make result on its land-cover and land-use transition and the trace of the landcover change indicates the impact on it conversely. Many changes have taken place in coastal area of East China within past four decades, especially in rapidly developing large islands. For monitoring environmental changes in such area, this paper, taking Zhoushan Island and its surrounding islands as an example, explored the temporal composition and spatial configuration of the land-cover trajectories. The recent land-cover data derived from both SPOT5 imageries and the last land-use data which came from investigation department. The historical distribution in 1980 was obtained from visual interpretation of CORONA photograph. Then the land-cover changed map could be derived through previous and last land-cover map. And the following time-series of land-cover was acquired from the supervised classification results of TM/ETM imageries which ranged from 1986 to 2000. The classification result was improved by limitation the sample selection in unchanged area in land-cover changed map in classification procedure. All these used satellite imageries were registered to the SPOT5 panchromatic imagery which was rectified using DGPS data in advance. Therefore, the temporal-spatial distributions of land-cover have been examined, reconstructed and analyzed with the support of GIS software. Based on those work, we revealed that the land-cover had changed rapidly in Zhoushan Island.