Study On Ecological Risk Assessment Of Guangxi Coastal Zone Based On 3S Technology

Coastal zone is a transition region between the sea and the land,which is consisted of coast,intertidal zone and the underwater bank slope.It is the mutual transition zone of the earth surface layer,lithosphere,hydrosphere,atmosphere and biosphere.While it is alternated by something like material,energy,structure and function system in two eco-system of land and the sea.With abundant species resources,high production ability and the social and economic value,in terms of energy development and utilization are also exists great potential.Guangxi coastal zone is the important economic construction and development in the economic zone area of Beibu gulf,and it is the forefront of opening up and cooperation by Guangxi and ASAN.With a rapid development of economic construction.People's exploitive and transformational strengthen on the coastal zone development is increasing constantly,all kinds of landscapes have different degrees of damaged,which poses a threat to the adjustment and recovery ability of coastal zone ecosystem.Guangxi is located in the low latitudes where suffered by a perennial subtropical monsoon climate and maritime monsoon climate,with influence of the typhoon,flood,drought and other natural disasters,which made serious influence for Guangxi coastal zone,and the increased risks of eco-system brought the survival and development of human potential hazards.Now,on the theory of landscape ecology and regional ecological risk guidance,we can use multi-temporal remote sensing data and "3 s" technology to monitor the landscape pattern changes in Guangxi coastal zone.We take the landscape index and regional ecological risk assessment for the analysis of Guangxi coastal zone landscape ecological risk and the development trend in future.Put forward opinions and suggestions for the ecological environment influence of natural resources exploitation and utilization in Guangxi coastal zone,which is of great significance to promote ecological civilization construction,harmonious sustainable development between human and nature.This paper takes Guangxi coastal zone as the study area,following the standards of land use type,divides the coastal zone of ecological landscape into seven kinds of natural wetland landscape types such as woodland,farmland,grassland,water,urban land and wetlands.Using TM data of 2000,2005,2005 and 2015 such four years,with the CART decision tree algorithm,for analysis the characteristic of types of landscape's remote sensing image and build decision tree rules of landscape classification to extract information classification.Analyzing of the evolution process of the landscape pattern in Guangxi coastal zone in nearly 15 years,we may understand the distribution characteristics and change rules.Combined with the natural disaster data,we use of landscape index and the related risk interference degree and construct ecological risk evaluation model in Guangxi coastal zone for ecological risk assessment results of Guangxi coastal zone.The main conclusions are as follows:(1)Based on the spectral characteristics of landscape in remote sensing image,using the object-oriented method,collecting effect characteristics and forming image feature set.By the comparison of SEaTH algorithm and CART decision tree algorithm,the optimal characteristics and the separation threshold of differentiating the two land types can be obtained quickly and accurately through the two methods,classification accuracy is above 80% in similar threshold value;SEaTH algorithm is not high in analysis sample and have strongly flexibility.sample size is only 2% ~ 5% of the global object segmentation and it is applicable to the thematic information extraction;CART decision tree which include the optimal feature of classification,threshold value as well as the logical relationship of classification was strong in hierarchy and was suitable for classification of larger sample size.Evaluation accuracy of model was determined by sample size.(2)Through the feature analysis of the spatial and temporal distribution of landscape,finding that coastal zone landscape type structure of Guangxi are mainly composed of forest land,farmland,town land and constructed wetland,the proportion of which were 57.88%,29.16%,7.8% and 57.88% respectively.Farmland,town land and constructed wetland were mainly distributed in the eastern coastal zone,forest land was mainly distributed in the west of coastal area as well as northwest area,all kinds of landscape were distributed uniformly in the central area;From 2000 to 2015,Total area of vegetation of guangxi coastal zone increased by 5%.But great change happens in the inner structure of vegetation area,grassland was developed into farmland and then into forest land.(3)The losing degree of the ecosystem of Guangxi coastal zone presented a gradual upward trend during the period of 2000 to 2015.The losing degree declined in distribution from east to west and inland to the sea.The ecological loss degree index,which correlation coefficient was 0.46,was closely associated with population distribution.The higher the population density areas,the higher the ecological loss index.The higher the degree of damage when suffer persecution risk source.(4)The High and less high risk area of ecosystem of natural hazard in Guangxi coastal zone mainly distributed in Beihai and Hepu county.Meanwhile,drought disaster ecological risk value declined from east to west,flood disaster ecological risk value declined from northeast direction to southwest direction,typhoon disaster ecological risk value declined from southeast coastal zone to inner land in the northwest direction.(5)Each level area of ecological risk of Guangxi coastal comprehensive zone declined from east to west,which has a percentage of 4.2%,10.62%,20.53%,31.09%,33.57% respectively.High risk area which has a gross area of 589.9 km2 was mainly distributed in Beihai city,Lianzhou town,Shiwan town,Changle town and Wudaohu village of Hepu county,was concentration region of urban land landscape and farm land landscape.