Impact Of Sea Level Rise On The Distribution Of Mangroves In Guangxi Pearl Harbor

Mangroves are especially vulnerable to sea level rise because of their location betweenmean sea level and mean high water spring level. We predict the centennial(from1990-1999to2090-2099) change in mangrove distribution of Guangxi Pearl Harbor by analysis of globalsea level rise, crustal vertical movement, surface deposition, seawalls, mean sea level, meanhigh water spring level and digital elevation model based on Landsat TM imagery.The results show that,(1) The migrating distance of the mangroves is about70m,56m,46m,24m respectively, and the area will increase280hm~2,225hm~2,187hm~2,89hm~2respectively given low, moderate, high, and extremely high sea level rise.(2) The migratingdistances of different areas have a great difference even given the same sea level rise.Migrating distance of the eastern coast near Po Awei village is significantly greater than otherregions because of its gentle slope.(3) Given different sea level rise, migrating distance of thesame mangrove plaque is low mode＞moderate mode＞high mode＞extremely high mode.(4)Crustal vertical movement of the study area is rising, and the rising rate is1.5-2.5mm/a, butrelative sea level is still rising because of the global sea level rise rate greater than crustalrising rate.(5) Fallen leaves, deadwoods of the mangroves and the sediment from the riversresult in surface deposition of the study area, and the deposition rate is6.7mm/a averagely.(6)With the relative sea level rise of the study area, mangrove landward margin remains stablebecause of the seawalls; and the seaward margin migrates landward theoretically, butdeposition causes mean sea level line migrating seaward, and the deposition rate greater thanrelative sea level rise rate, so mangrove landward margin migrates seaward actually. Anyway,the area of the mangroves will increase in the future.We display future mean sea level line, mean high water spring level line and seawall basedon Landsat TM imagery of the study area, resulting in future mangrove distribution ofGuangxi Pearl Harbor. It predicts migrating path, distance and changed area of the mangrovesin the future, and this will provide scientific support to define forestation zone and to proposepolicy of protecting mangroves of the study area.