Land-Cover-Reconstruction and Change Analysis Using Multisource Remotely Sensed Imageries in Zhoushan Islands since 1970

Islands are hotspot areas with intensive interactions between land and ocean, and they are also the most vulnerable places to human activities and environmental change. As the frontier zone of oceanic economic development, coastal regions of China have undergone enhanced changes in land-cover change during recent decades. This study was conducted to investigate how land cover in Zhoushan Island and its surrounding islands, which are typical islands of China, has changed since the economic reform by using multisource remotely sensed imageries. The earliest land cover in 1970, 1976, and 1980 was interpreted and digitalized from CORONA and KH-9 photographs, respectively. For the period of 1986-2000, TM (Thematic Mapper) and ETM (Enhanced Thematic Mapper) imageries were classified to build land-cover maps with the supervised classification method. The most recent land-cover data in 2006 and 2011 were generated by inventory land-use vector map and SPOT5 imageries. The reconstructed land-cover time series indicate that Zhoushan Islands have involved substantial land-cover change since 1970. The arable land has changed into built-up types, mainly, and rate of change reached its peak in 2000, while the spatial distribution of transition was not uniform. Nevertheless, water bodies and woodlands have been well preserved during the past 40 years. During the urbanization process, the tidal zone of these islands shrank sharply, and some of them turned to built-up land-cover directly.