Use of RS and GIS to Identify of Farmland Loss in the Coastal Area of Pearl River Estuary

The speed of urbanization has been most prominent in the Pearl River Delta in South China during the past two decades. The rapid urbanization process caused an unprecedented scale and rate of land use change in this area. The Coastal Area of Pearl River Estuary (CAPRE) is the core and sensitive ecotone of Pearl River Delta. As urban built-up areas sprawl, transform, and envelop the surrounding landscape, one of the important land use changes in CAPRE were farmland loss and fragmentation. Using the remote sensing data (MSS 1979 and TM 1990,1995,2000,2005) and combining GIS with landscape metrics, we attempted to quantify Farmland losses and Fragmentation in CAPRE. The results showed that rapid urbanization has significantly changed the spatial pattern of landscape from 1979 to 2005. The natural and agricultural landscape transforming to urban built-up area with increasing economy were dramatics. While declines in farmland have been a total trend since the early 1980s. Between 1979 and 2005 overall farmland area had fallen by 2406.75km2 (63.6%) and its proportion dropped from 48.8 to 17.7 percent of the total land. The farmland loss rate is 92.57 km2/yr, especially outstanding from 1990 to 1995 farmland shrank by 657.86 km2 or 131.58km2/yr. Meanwhile a significant increases in urban built-up land area. The built-up area proportion had risen from 1.3%(1979) to 36.8%(2005). Results from the landscape metrics analysis indicated that farmland patch density (PD), edge density (ED) increased obviously. The mean patch area (MPA) decreased at the same time. There are relationships between farmland loss rate and fragmentation degree. The faster is loss rate, the higher is the fragment degree. Farmland fragmentation took place dramatically in 1990~1995 and the farmland loss rate is most fast. The tendency of farmland fragmentation became slowly with farmland keep a stable proportion.