基于潮位校正的中国潮间带遥感监测及变化

Remote-sensing monitoring and analysis of China intertidal zone changes based on tidal correction

潮间带位于海洋和陆地的过渡地带,在生物多样性保护、社会经济发展以及全球环境变化等方面具有重要价值.由于潮汐的动态性,潮间带的卫星遥感监测存在很大挑战,迄今为止还没有完整的全国滨海潮间带的相应数据.本文综合遥感与地理信息系统方法,利用1995和2015年覆盖全国滨海的156景LandsatTM/OLI卫星影像,反演了中国滨海潮间带的时空分布,并基于高分辨率影像,目视解译了潮间带开发的土地利用类型.在此基础上分析了中国潮间带变化的时空特征和潮间带变化的驱动力因素.结果表明:(1)2015年中国潮间带总面积约为14070 km^2,其中潮间带分布面积最多的为福建省(18%),其次是辽宁省(15%)、山东省(14%)、江苏省(12%)和广东省(11%);面积最小的是海南省(2%).(2)1995～2015年全国潮间带面积净减少了1375km^2,减少约8.9%.全国不同省市潮间带面积表现了增加与减少不同的趋势,其中潮间带面积减少最多的是浙江省,面积减少为1189km^2;江苏省潮间带面积由1995年的全国第1缩减为第4.而福建省潮间带增加最多,达453km^2.(3)潮间带被开发利用的趋势持续增强. 1995年中国沿海潮间带被开发占用的面积为3490 km^2,到2015年达到4581 km^2.潮间带开发利用类型由农业用海为主(41.8%)转变为围海养殖;城镇建设占用比例也达13%.同时围垦中(在建/未知用途)的潮间带面积持续增长,由1995年的18.1%增长为29%.(4)人为和自然两种因素叠加的"挤压效应"造成了我国潮间带面积的减少.经济发展和滨海生态环境保护的矛盾依然表现突出.

Intertidal zones are located in the transitional area of sea and land and are important to biodiversity protection, social and economic development, and global environmental changes. However, due to the irregular dynamics of the tides and the regular local time of satellite transit, it is challenging to monitor the extent of intertidal zones using only satellite remote-sensing methods. Until now, there has been no complete dataset of China’s coastal intertidal zones and knowledge about their distribution is limited. In the work described in this paper, we first used 156 Landsat Thematic Mapper/Operational Land Imager images covering the entire coastal area of China in 1995 and 2015 to extract the instantaneous shoreline water boundaries. Then, by combining the tidal level information at the transit of the satellite, we simulated the average high-and low-tide lines and determined the spatial and temporal distribution of intertidal zones by the geographic information system method. At the same time, the land-use types across the intertidal zones were manually interpreted based on high-resolution images from Google Earth. On this basis, the spatial and temporal characteristics of intertidal zone changes across China’s coastal areas and their driving factors were researched. The results follow.(1) In 2015, the total area of the intertidal zone in China was approximately 14070 km2, of which Fujian Province(18%) was the most distributed in the intertidal zone, followed by Liaoning Province(15%), Shandong Province(14%), Jiangsu Province(12%), and Guangdong Province(11%);the smallest area was distributed in Hainan Province(2%).(2) From 1995 to 2015, the national intertidal zone area decreased by 1375 km2, approximately 8.9%. The intertidal zone area of different provinces and cities showed different increasing and decreasing trends. The largest reduction of intertidal zones was in Zhejiang Province, with an area decrease of 1189 km2. The intertidal zone area of Jiangsu Province was greatly reduced, by which its first position of having the most intertidal zone area of China in 1995 decreased to the fourth in 2015. The intertidal zones in Fujian Province exhibited the greatest increase, reaching 453 km2. The area of intertidal zones between the ports of Shanghai Luchao and Zhejiang Jintang exhibited the greatest decrease, reaching 56.5%. The area of intertidal zones between Fujian Shui’ao and Anhaiwan estuaries increased the most, reaching 37.28%, an area of 445.59 km2.(3) The trend of development and utilization of intertidal zones continues to increase. In 1995, the coastal intertidal zone area occupied was 3490 km2, and by 2015, it had reached 4581 km2. The type of development and utilization of intertidal zones changed from agricultural sea(41.8%) to marine aquaculture;the proportion of urban construction occupied also reached 13%. At the same time, the intertidal zone area in the cofferdam(under construction/unknown use) continued to grow, from 18.1% in 1995 to 29% in 2015. The intertidal zone showing the greatest level of development and utilization among the coastal provinces is Jiangsu Province, with an occupied area of 1646 km2, accounting for 35.9% of the developed and utilized national intertidal zone, with the main types of utilization being agricultural sea and mariculture. The other provinces that developed intertidal zones are Guangdong(13.7%), Shandong(12.5%), Liaoning(10.9%), and Shanghai(10.3%). The main development and utilization types of intertidal zones are urban construction and mariculture, with a large number of intertidal zones presently under development.(4) The "squeezing effect" caused by the combination of artificial and natural factors have caused the reduction of intertidal zones in China. Human development mainly includes marine aquaculture, industrial development, port expansion, urban construction, and reclamation. And the actual high-tide line has moved towards the sea by artificial intertidal zone development. The velocity is even higher than that of low-tide line, resulting in the reduction of intertidal zones. Natural factors mainly include rising sea level and other factors, such as changes in the sediment concentration of rivers entering the sea and coastal hydrodynamic forces, which are also important factors affecting the change of coastal intertidal zones. These factors contribute to the drift of some intertidal zones towards the sea and the expansion of the area. The contradiction between economic development and coastal ecological environmental protection is still outstanding.