关键词: 遥感, 熵, 城市扩张, 农田流失

Abstract: The current fast economic growth is accompanied with rapid urban expansion and great loss of agricultural land in the Pearl River Delta. The lack of information and technology hinders planners and local officers to achieve sustainable development. This paper tries to demonstrate the potential of the integration of remote sensing and GIS for monitoring and analysing of land development in the Pearl River Delta. It is found that wasteful use of land resource exists with ‘blind' development patterns. The fast diffusion of urban areas has caused loss of large amount of agricultural land. Based on GIS analysis, some protection measures can be formulated to curb the tendency of swallowing agricultural land for urban development. The area of urban use rapidly increased from 16234.6 ha to 41087.9 ha. in 1988~1993 in the study area, Dongguan. This means that 10.4% of the total land area was converted to urban use just within this short period. Moreover, most of the conversion only occurred in 1990~1993. It is found that the land loss in Dongguan in 1988~1993 mainly took place within a few kilometers nearby urban (town) centres or roads. Actually, 90 percent of the total land loss occurred within an average distance of 1.38 km from roads and 5.63 km from urban (town) centres. The result is not very surprising given that the proximity is a very important factor for land development. It is very clear that the city proper is under a quick expansion of its urban areas in recent years. A transition period with more land loss occurring in a further distance exists because of the diffusion process. It is interesting to see that there is a strong contrast between the diffusion in 1988~1990 and that in 1990~1993. The diffusion of the urban areas was limited in 1988~1990 while the diffusion was astonishingly strong in 1990~1993. It is because a large amount of agricultural land has been encroached for the development of real estate since 1992. However, the diffusion pattern is not identical as there is obvious variation for each town.

Key words: remote sensing, entropy, urban expansion, agricultural land loss