Analysis Of Wetland Evolution And Ecological Security Assessment In The Yellow River

Wetlands are an integral part of the city’s green infrastructure network,which plays an important ecological role and has a crucial impact on the overall ecological security pattern of the city.The Yellow River Delta wetland is the youngest,most extensive and best-preserved wetland ecosystem in the warm temperate zone,which plays a very important role in the connectivity and security of terrestrial and water ecosystems.However,due to the adverse effects of human activities such as urbanization and agricultural production,the Yellow River Delta region has lost a large number of natural wetlands.Therefore,research on the ecological security of local wetlands is crucial to protect the overall ecological security of these cities and even the ecological security of wetlands in the entire Yellow River Basin.Aiming at the ecological security of wetlands in the Yellow River Delta,this thesis takes the main areas of the Yellow River Delta as an example,firstly,based on the Landsat data in 2000,2010 and 2020,the distribution of wetlands in different periods is extracted by object-oriented classification methods,a wetland land use change database is established,and the spatiotemporal analysis of wetlands in 20 years is carried out based on the centroid function model and spatial autocorrelation.Secondly,based on the CA-Markov model,the suitability atlas of all land types was constructed,three land use scenarios of trend development,rapid urban development and wetland ecological protection were set,and the overall transformation direction of wetlands in the Yellow River Delta and the distribution pattern of wetlands in space under the three scenarios were analyzed.Finally,based on the P-S-R model,15 indicators such as economic development,environmental protection,various resource utilization and policy factors were selected to construct the ecological security evaluation index system of wetlands in the Yellow River Delta and graded the safety level,and finally the wetland ecological security evaluation was carried out on the status quo of the Yellow River Delta and three simulation scenarios.Finally,corresponding regulatory countermeasures are proposed.The main conclusions are as follows:(1)The total wetland area of the Yellow River Delta showed a continuous downward trend,and the wetland area decreased rapidly from 2000 to 2010 and slowed down in 2010-2020.The center of mass of the wetland first migrated to the northeast from 2000 to 2010,and then turned back to the southwest from 2010 to 2020,showing a trend of oscillating change.The degree of spatial distribution and aggregation of wetlands in the Yellow River Delta has increased,and the high-high accumulation area has shown an increasing trend,while the low-low accumulation area has a decreasing trend.(2)The ecological security level of wetlands in the Yellow River Delta has decreased,and the ecological security status of wetlands in the Yellow River Delta shows that the ecological security level of wetlands in the east and north is better,and the ecological security level of wetlands in the west and south is poor.The ecological security index of wetlands in the Yellow River Delta decreased from 0.6429 to 0.5648 and then to 0.5298,slowing down the downward trend,and the ecological security level dropped from early warning level to unsafe level.In terms of spatial pattern,from two very unsafe in the south to four very unsafe in the west and south,the ecological security of wetlands in some areas of the Yellow River Delta showed a trend of deterioration,especially in Dongying District,Kenli District and Zhenhua District,the ecological security of wetlands in Wudi County and Lijin County improved,and Hekou District and Guangrao County tended to be stable.(3)It is predicted that the wetland area of the Yellow River Delta will increase under the three scenarios in 2025.In addition to the rapid urban development scenario,the ecological security of the wetlands in the Yellow River Delta has been improved to a certain extent.The wetland rate reached 10.06% under the wetland ecological protection scenario,9.41% under the trend development scenario,and 9.24% in the urban rapid development scenario.In the trend development scenario and wetland ecological protection scenario,wetlands mainly outflow is cultivated land,and in the rapid urban development scenario,wetlands are mainly outflow as construction land.The ecological security evaluation value of wetlands in the Yellow River Delta increased significantly in the wetland ecological protection scenario,reaching 0.5889,the ecological security evaluation value of wetlands in the trend development scenario increased slowly,reaching 0.5554,while the ecological security evaluation value decreased slowly in the urban rapid development scenario,and the lowest value was 0.5277.In addition,under different scenarios,the ecological security level of wetlands in local areas changes differently,so it is managed according to different levels in the wetland protection system.