| Wetland is the most productive ecosystem in the world.It not only provides a unique habitat for organisms,but also provides many economic and service functions,such as water supply,water quality improvement and entertainment services.As a result of human activities,about 50%of the world’s wetlands have disappeared in the last century,and the existing wetlands are continuing to degenerate.The degradation of wetlands has caused serious environmental problems,such as floods,water shortages and soil erosion.The total area of wetland in China is 650 thousand km~2,ranking the first in Asia and the fourth in the world.Because of the unreasonable utilization of wetland resources,the wetland ecosystem has obviously degraded.The middle and lower reaches of the Yangtze River wetlands have the highest density of water area in China and the main geographical latitude areas in the world.It is the most important area for the flood storage,and thus it is in a very important position in our country and even the global wetlands ecological protection.Compared with 1950s,70%of the wetlands in the middle reaches of the Yangtze River have disappeared.The decrease of wetland caused the degradation of water ecosystem in some lakes,the decrease of biodiversity and the damage of fishery resources.Under the framework of environmental health diagnosis by remote sensing,based on the wetland ecosystem evaluation index system in the book International Important Wetland Ecosystem Assessment in China,this study improved and finally constructed the remote diagnosis index system of wetland ecosystem health which is suitable for the middle and lower reaches of Yangtze River Lake wetlands,combined with the theory and technology of remote sensing and landscape index.Using analytic hierarchy process(AHP),the diagnosis model was constructed.Based on this diagnostic model,two wetlands in the middle and lower reaches of Yangtze River including Hongze Lake wetland and Liangzi Lake wetland were diagnosed by remote sensing,and comparative analysis was conducted to provide technical and decision-making support for wetland management and protection.The main contents of this study are as follows:(1)Construction of remote sensing diagnosis model of wetland ecological health:In combination with remote sensing and landscape theory and technology,this study improved the evaluation index system of wetland ecosystem health in the book International Important Wetland Ecosystem Assessment in China.Using data of Landsat satellite and Sentinel-2 satellite,combined with the landscape index to improve the existing index system,this research constructed a diagnostic index system by remote sensing that can reflect the scale of wetland ecosystem health.By using analytic hierarchy process(AHP)and index weight calculation by literature research and experts scoring,a remote sensing diagnostic model suitable for wetland ecosystem in the middle and lower reaches of Yangtze River is constructed.(2)Diagnosis of wetland health in the middle and lower reaches of Yangtze River by remote sensing:Using Landsat satellite and Sentinel-2 satellite remote sensing data,population density data products,statistical data,questionnaire and field experiment data,this study applied the wetland ecological health remote sensing diagnosis model in Hongze Lake Wetland in Jiangsu Province and Liangzi Lake wetland in Hubei province,and got the wetland health remote sensing results.Based on the accurate analysis of the results,the advice and suggestions,such as“returning fishing nets to lakes”and increasing the protections sense of surrounding residents,are provided for the monitoring and management of these two wetlands respectively.(3)Comparable analysis of wetland health remote sensing diagnosis in the important wetlands in the middle and lower reaches of Yangtze River:Based on the results of two wetlands in the middle and lower reaches of the Yangtze River,the health status of two important wetlands was compared and analyzed in the three aspects including the wetland elements,landscape and social level.This study contrasted the differences between Hongze Lake wetland and Liangzi Lake wetland in the use of statistical methods.And the reasons of the differences was mined,with a comprehensive analysis of the middle and lower reaches of Yangtze River Wetland health.The main innovations of this study include:(1)Based on the characteristics of wetland,remote sensing and landscape method,the existing wetland ecosystem health evaluation index system has been improved and the diagnosis model of wetland ecological health by remote sensing was constructed.(2)The diagnosis and comparative analysis of the health status of the wetland in the middle and lower reaches of the Yangtze River were carried out. |
