Landscape Ecological Risk Assessment In The Coastal Area In Yancheng City During The Last 35 Years

Coastal zone is an interactive zone between the sea and the continent,which is influenced jointly by such factors as ocean,land and atmosphere.Moreover,Coastal zone is also the typical region,which is characterized by intensive human activity,strong sensitivity responding to the global change,as well as the ecosystem changes.Land use and land cover change(LUCC)is a direct consequence of human and nature interactions,which has been regarded as the main reason of global change,and LUCC research has become the front in global change and hot question at present.With the accelerating coastal development,the coastal zone land use has changed significantly,and the regional ecological security is being threatened.The ecological risk assessment is currently the advanced method to study the relationship between the ecological environment and development.Regional ecological risk assessment can provide scientific suggestions for the ecological environment management.The study of ecological risk is helpful for understanding local ecological environment,reducing ecological risk,and finally improving the interactions between human beings and nature.Therefore,this paper takes the coastal zone in Yancheng as an example,and use remote sensing images of Landsat in 1980,1995,2005,2015 as the main data source.Based on the calculation of the landscape indices,this paper see the land use as the risk source and construct ecological risk index.In specific,the study area was divided into 512 units with a size of 5 km×5 km.The ecological risk index in 512 units in 1980,1995,2005,2015 was calculated.By the GIS and Geostatistical analyst,the distribution level of ecological risk was mapped.The ecological risk of the study area was classified into five levels,extremely low ecological risk,low ecological risk,moderate ecological risk,high ecological risk and extremely high by relative index method.Generally speaking,this paper conducted a study of following aspects:(1)Based on remote sensing data and land use data supporting by the GIS and RS technologies,the land use changes and its transformation have been quantitatively analyzed in the coastal area in Yancheng city during 1980?2015.Farmland,construction land and grassland were the main landscape types from 1980 to 2015,farmland accounts for more than 70%of the total area.A large amount of farmland is occupied in the periphery of the town,but the farmland maintained at the current scale,this is due to the contribution of tidal flat reclamation to ensure food safety.Construction in urban and coastal port land expanded significantly,but the total quantity decreased,this is due to a large number of low productive saltern transformed to other land type.Mariculture and unused land rapidly expanded in the past 10 years.Grassland was reduced by 76.65%,and the tidal flat was decreased by 69%,which was mainly converted to construction and mariculture.(2)From 1980 to 2015,coastal land use types in Yancheng are significantly changed,the integrated land use dynamic index increases from 0.67 to 49.44.In terms of single land use type,the unused land and mariculture land are greatly increased,and the tidal flat and grassland are significantly reduced.(3)On the basis of land use types in Yancheng coastal zone,the landscape pattern index is calculated and analyzed.The results show that numbers of landscape patches increased from 4406 to 8813,patch density increase from 0.38 to 0.77,shape index reduced from 33.93 to 29.90,shannon diversity index increased from 0.92 to 0.94,which showed that the landscape fragmentation increased,the spatial heterogeneity was strengthened,and the landscape shape tended to be simple.(4)Temporal and spatial variations of ecological risk in the study area mainly show out the features as below:the average ecological risk in the coastal zone of Yancheng increased from 0.5894 in 1980 to 0.7236 in 2015.The area of higher level of ecological risk increased from 3.93%in 1980 to 40.72%in 2015,which shows that the overall ecological environment quality of Yancheng coastal zone has deteriorated.During the study period,the whole area is under moderate ecological risk.Moderate ecological risk was located in the middle of the study area.From 1980 to 2005,the narrow coastal zone of Yancheng has been in extremely low ecological risk level,high level ecological risk area mainly distributed in Sheyang and Dongtai urban center and the northeast of Binhai and Xiangshui.Between 2005 to 2015,the coastal areas have been covered with a high risk area.The western boundary of the study area has been in a low level ecological risk area.The correlation analysis of ecological risk index showed that the spatial distribution of ecological risk in the study area had obvious scale effect,and the correlation was gradually weakened with the increase of particle size.On the other hand,the ecological risk distribution has obvious high accumulation and low accumulation,and has certain regional differentiation characteristics.