Mangrove landscape changing process and land use coverage change of its surrounding areas in Yingluo Bay, southern China during the past 20 years

Based on GIS and RS technology, the Landsat TM images from 1991 to 2010, associated with the ground truth data in 2011 and the thematic maps on mangrove forests, were hierarchically extracted to identity mangrove and other land use coverage surrounding Yingluo Bay, southern China. Together with the local expert knowledge, 7 land use types were identified, namely farmland, forestland, construction area, water, unused area, aquiculture pond and mangrove forests respectively. The spatial process of mangrove forests landscape change and the dynamics of land use coverage as well as the rate and cause of the changes nearby the Yingluo Bay were analyzed in this paper. The results indicated that both anthropogenic and natural factors had influenced mangrove forests in the study area. During the period of 1991-2010, the area of mangrove forests decreased at first and then increased, the net loss reached about 7%. The mangrove forests had been extending seaward and the vegetation coverage had increased continuously since 1991. The changing trajectories of mangrove forests were analyzed to retrieve the spatial and temporal features of mangrove change. The loss speed had been much faster significantly than that of natural expansion and afforestation during the period of 1991-2000. The loss of mangrove distributed mainly on the landward, the mangrove forests outside the forest boundary had decreased and the reclamation from mangrove forests for aquaculture was the major reason. Mangrove forest area had increased due to the ecological restoration and natural expansion during the period of 2000-2010, the increased mangrove area distributed mainly on seaward of mangrove and nearby the rivers mouth. In addition, the extent of mangrove forests also changed as a result of the erosion and accretion near the river. In the past 20 years, the significant changes on land use coverage occurred in the coastal areas nearby the Yingluo Bay. Forestland and farmland had decreased because of the rapid rural urbanization and industrialization; the construction area had increased significantly, particularly in the period of 2000-2010. The area of aquiculture pond had increased continuously and was distributed along the rivers and adjacent to mangrove forests. In the former phase, the increased area of aquiculture pond was converted mainly from the mangrove deforestation, while in the later phase those mainly from the paddy rice under the related policy support.