三大沿海城市群滨海湿地的陆源人类活动影响模式

随着陆源人类活动对滨海湿地的干扰日益强烈,研究滨海湿地陆源人类活动影响规律对于滨海湿地资源管理和保护具有重要的现实意义.以我国三大沿海城市群(环渤海湾、长江三角洲、珠江三角洲)滨海湿地为研究对象,分别选取围海造地(直接因子)和流域污染物(营养盐、非点源无机污染物)输入(间接因子)表征1990-2000年间滨海湿地的陆源人类活动影响强度及规律.研究发现,虽然围海造地仍然以农业用地为主(＞50％),但城市建设用地比例随人口城市化率增高而增加,以珠江三角洲城市群最高；在环渤海湾和珠江三角洲城市群区域超过60％的滨海湿地面积受到高或中等污染物输入强度影响,长江三角洲城市群区域则有44.7％的滨海湿地面积处于中等污染物输入强度及以上.通过叠加围海造地和污染物输入双重陆源人类活动的综合影响强度表明,珠江三角洲城市群平均强度指数达到0.79,且处于中等及以上影响强度区域面积比例达到78％,均高于其他两个城市群滨海湿地区域.空间分析结果表明,陆源人类活动对滨海湿地的强影响区域多集中分布于河流人海口、较为发达城市滨海区以及海岸线附近.

Patterns of terrestrial anthropogenic impacts on coastal wetlands in three city clusters in China

Coastal wetlands are increasingly affected by terrestrial anthropogenic impacts associated with urbanization along the worlds'' coastlines. There is a strong need to balance utilization and protection of coastal wetland resources via understanding of patterns of coastal wetland changes in response to terrestrially derived anthropogenic impacts. This study was carried out to characterize impacts of wetland reclamation (a direct anthropogenic impact) and contaminant influxes of nutrients and non-point inorganic contaminants (an indirect anthropogenic impact) on coastal wetlands in the three largest city clusters in China between 1990 and 2000 using a GIS-based approach. The three coastal city clusters were 1) the city cluster surrounding the Bo Sea (BSS), the Yangtze River Delta city cluster (YRD), and the Pearl River Delta city cluster (PRD). Thirty-eight TM or ETM+ Landsat images from 1990 and 2000 were assembled and nutrient influxes were generated from the Global NEWS2 and Global Nutrient Export WaterSheds2 models by the Workgroup of UNESCO''s Intergovernmental Oceanographic Commission for each city cluster. Non-point contaminants were estimated from impervious area in the coastal cities according to the world impervious area map for 2000 produced by the US National Oceanic and Atmospheric Administration (US NOAA). The "intensity" of contaminant loading was calculated by normalizing both nutrient loads and non-point contaminant loads between 0-1.Results indicated that although wetland reclamation for agricultural land use was predominant in all three city clusters (over 50% of the area), wetland reclamation to urban land use (directly from wetland reclamation and indirectly from wetland-derived agricultural land) increased along with urban population between 1990 and 2000. The PRD area showed the largest conversion of coastal wetlands to urban land while the BBS area showed the largest conversion to agricultural land use. Over 60% of the BBS and PRD areas were contaminated above a mid-level of intensity, whereas 44.7% of the YRD area received contaminants at mid-level intensity or above.Integrating the two factors with weights (0.5 for land use/cover change and 0.25 for influxes of nutrients and non-point contaminants, respectively), the combined impact intensity was highest in the PRD area, with an average index of 0.79 and 78% of its area influenced by two anthropogenic impacts at mid-level intensity or above. Combined impact was lower in the BSS (0.65) and YRD (0.63) areas with approximately 30% of these areas at mid-level impact intensity or above. Spatial analyses were very useful for illustrating the nature and extent of terrestrially-derived anthropogenic impacts on coastal wetlands and should be useful for assessing development impacts on estuaries and coastal wetlands in many areas.