长江三角洲国际重要湿地人为胁迫遥感解析

Landsat-based observation of human pressure to wetlands in Ramsar sites over the Yangtze River Delta.

以长江三角洲上海崇明东滩鸟类国家级自然保护区、江苏大丰麋鹿国家级自然保护区、西溪国家湿地公园和江苏盐城国家级珍禽自然保护区4处国际重要湿地为研究对象,以Landsat MSS/TM/OLI遥感影像为基础信息源,采用面向对象的遥感分类方法获取了1980~2015年4个国际重要湿地(Ramsar)的5期土地覆被数据.通过分析湿地面积、景观格局动态及景观指数变化等,定量解析人类活动对湿地景观变化的影响,研究发现:(1)35a间,研究区内湿地面积持续减少,其中上海崇明东滩鸟类国家级自然保护区的湿地损失比例最高,为27.2%;(2)4个国际重要湿地的斑块数量和斑块密度都在增加,湿地趋于破碎化,景观间连通度降低.(3)耕地和人工表面增加是造成湿地损失的主要因素,耕地、人工表面、外来物种入侵和养殖池扩张等人为胁迫呈现上升趋势.(4)总体而言,入选国际重要湿地对人为活动有一定抑制作用,尤其是江苏大丰麋鹿国家级自然保护区湿地保护成效最为显著;但湿地保护有效性仍有待提升.

This study applied an object-oriented classification method to Landsat MSS/TM/OLI images covering four wetland sites with international importance(Ramsar sites)in the Yangtze River Delta,including the Chongming Dongtan Nature Reserve,Dafeng(Elaphurus davidianus)National Nature Reserve,Hangzhou Xixi National Wetland Park,and Yancheng National Nature Reserve,to obtain five land cover datasets during 1980 to 2015.By examining spatiotemporal changes of wetland area,landscape pattern,and landscape matrices,human pressures on wetlands were quantified.Results show that:(1)during the 35 years,wetland area in these four Ramsar sites had declined continuously,with the largest decrease in the Chongming Dongtan Nature Reserve(27.2%drop in area);(2)the number and density of patches in the four Ramsar sites had been increasing,which led to more fragmentation and the decrease in the landscape connectivity;(3)the expansion of cropland and developed land was the dominant driving factor of wetland loss,while enhanced human pressure from the aquaculture pond expansion and exotic species invasion imposed increasing impacts on wetlands;(4)In general,the designation of Ramsar sites played important roles in reducing human disturbances and protecting natural wetland ecosystems,such as in the Dafeng National Nature Reserve.However,protection effectiveness of the four Ramsar sites would require further improvement in terms of reducing wetland loss and human pressure in the sites.