Coastal Land Use/Land Cover Change And The Ecological Environmental Effects In Pearl River Estuary

With advantageous location,abundant resources,and economic prosperity,the Pearl River Estuary(PRE)is the core area of the Greater Pearl River Delta Metropolitan area.With the continuous expansion of construction land and the rapid growth of traffic and road systems,the sustainable development of the regional ecological environment is under tremendous pressure.In this study,the PRE is the study area.Based on remote sensing and geographic information technology,the evolution of the geographic spatial pattern and coastal environment in the area from 1960 to 2015 was monitored and analyzed,and the influencing factors behind the changes were further explored.The findings are as follows:In the PRE,construction land expanded 33 times during 1960 to 2012.On the contrary,compared with 1960,the area of farmland and forest decreased by 56.70%and 47.53%,respectively,in 2012.The area of forest decreased sharply during1990~1995.Land for fishery cultivation increased from nearly 0 to 648.06 km~2 during1979~1995.Before 1990,reclamation area was also nearly 0 km~2,which increased with the strengthening of reclamation activities afterward.In this study,it is found out that the source of systematic errors in conventional CART algorithm for estimating impervious surfaces should be the underestimation of high-density impervious and overestimation in low-density impervious surfaces.An improved method for effectively estimating impervious surfaces was then demonstrated based on the error analysis of CART algorithm and LSMA.With these improvements,the pixels poorly estimated by conventional CART were discerned and modified.In Panyu,Guangzhou,the impervious surfaces increased from 133.37 km~2 to 265.35 km~2during 2004~2014,which has close relationships with infrastructure construction.During 1960 to 2012,the length of coastline in the PRE increased from 1134.95km to 1508.02 km with an increasing speed of 7.17 km per year.Driven by reclamation activities,most of the natural coastline has been converted into the artificial coastline.During 1960 to 1979,the total area of newly-added land(reclamation)in PRD was878.11 km~2.Nansha(Guangzhou),Futian(Shenzhen)and South Zhuhai are places where large areas of newly-added land locate.Anthropogenic activity is the main factor of the change of coastline.The results remote sensing inversion shows the water quality in the estuary of Dongjiang River and Beijiang River is better than that of Xijiang River.The difference of distribution is driven by both anthropogenic and natural factors.The anthropogenic activity brought long-lasting and irreversible impact to the coastal environment.Consequently,the coastal mangrove wetlands in Nanlang(Zhongshan),Chang'an(Dongguan)and Bao'an(Shenzhen)become extinct.However,environmental initiatives applied after 2000 thoroughly changed endangered situation of the coastal mangrove wetlands.