长江三角洲城市群区域滨海湿地利用时空变化特征

应用遥感和地理信息系统技术,以研究区遥感影像为主要数据源,研究了1990～2000年和2000～2005年间长江三角洲城市群区域围海造地行为下滨海湿地利用的时空演变特征。围海造地在不同城市化发展时期分别为农业用地和建设用地扩张所需。以海岸线为基准,通过分别向陆地和向海洋方向进行滨海湿地分区,每个方向设立7个缓冲带,靠近海岸线的前6个缓冲带宽1km,第7个缓冲带宽10km。结果表明,1990～2000年期间,围海造地以农业用地扩张为主,其平均年扩张速率为48.9km2/a,明显大于建设用地的平均年扩张速率(28.2km2/a);而2000～2005年期间,建设用地成为围海造地的主要目的,建设用地平均年扩张速率大幅增大至91.8km2/a,而农业用地平均年扩张率仅为4.2km2/a。在空间分布上,1990～2000年期间,农业用地平均年扩张百分率最大值出现在距海岸线5km的陆地缓冲区;但在2000～2005年期间,各陆地缓冲区农业用地面积在减少,其平均年扩张百分率为-1.3%/a;而建设用地在各缓冲区的平均年扩张百分率由1990～2000年期间的0.62%/a增大为2000～2005年期间的2.66%/a。对长江三角洲滨海湿地土地流转驱动力的分析表明,城市化是建设用地扩张的重要驱动力;一些天然滨海湿地直接转变为建设用地,两个时期建设用地净扩张区域相同,即距海岸线1～3km和>6km陆地缓冲带;还有一些天然滨海湿地,如滩涂,被用于水产养殖,而转变为人工湿地,在1990～2000年期间,农业用地的扩张区域是距海岸线4～6km的陆地缓冲带,在2000～2005年期间,农业用地的扩张区域是1～3km的近海缓冲带。

Temporal and Spatial Variation of Coastal Wetlands Utilization in the City Cluster Area of Yangtze River Delta

In this paper,temporal and spatial variation of coastal wetlands utilization in the largest city cluster area,Yangtze River Delta in China,were investigated in two periods of 1990-2000 and 2000-2005 using the geographical information system and remote sensing techniques.In this area,coastal wetlands reclamation serves as an important measure to meet increasing land demands for agriculture and urbaniation.In order to study spatial distribution of agricultural and construction lands,7 buffering zones were set respectively from the coastline in 2000 to both terristrial and sea directions(1 km wide for each buffering zone from zone No.1-6 and 10 km wide for the No.7 zone).The results indicated that coastal wetlands were mainly reclamed for agricultural land during 1990-2000 with a mean annual growth rate of 48.9 km2/yr,which was larger than that of construction land(28.0 km2/yr).But,during 2000-2005 the mean annual growth rate of construction land rapidly increased and became the important demand for the coastal wetlands reclamation,with a mean annual growth rate of 91.8 km2/yr while that of agricultural land was 4.2 km2/yr.At the spatial scale,the largest annual growth percentage of agricultural land was located at the 5 km terrestrial buffering zone from the coastline with an average annual growth percentage of 1.2%/yr during 1990-2000 but its annual growth percentage values became negative during 2000-2005(averagely-1.3%/yr).On the other hand,the mean annual growth percentage of construction land for the 14 buffering zones was increased from 0.62%/yr during 1990-2000 to 2.66%/yr during 2000-2005.But,the two study periods showed a similar pattern of construction land expansion in the coastal wetlands zones.The main construction land expansion was located at the 1-3 km and >6 km terrestrial zones.Driving force analysis indicated that in the city cluster zone of Yangtze River Delta land use changes were predominately driven by urbanization,which not only occupied directly coastal wetlands but also indirectly occupied coastal wetlands from previously reclaimed agricultural lands.Agricultural land expansion also played an important role in the loss of coastal wetlands,however,with accelerated urbanization from 1990-2000 to 2000-2005,construction land demands became the driving force for the coastal wetlands loss in this city cluster area instead of agricultural land demands.