Study On The Change Of Sea Area Utilization And Its Environmental Impact In The Yellow River Delta In Recent 50 Years

With the rapid growth of population,shortage of land resources,deterioration of ecological environment and other problems,coastal cities have accelerated the development of sea space and utilization of marine resources.Developed marine fisheries,coastal industries,port and shipping industries,coastal tourism and coastal town construction has become an important measure to alleviate the contradiction between people and land,develop and utilize marine resources.The Yellow River Delta sea area has superior geographical location and rich natural resources.In the past 50 years,the large-scale marine exploitation and utilization activities in this region have greatly changed the natural landscape and ecological pattern,and made the fragile ecological environment of the Yellow River Delta rapidly deteriorate.Therefore,we should have a thorough and systematic understanding of the development and utilization process of the Yellow River Delta sea area,master the temporal and spatial evolution information of various sea use activities,identify the relationship between the development and utilization of the sea area and the change of the marine environment.This is of great significance for improving the efficiency of sea area utilization,optimizing the management of sea activities,and promoting the healthy and sustainable development of marine economy.This paper takes nearly 50 years as the research time interval.The Yellow River Delta and its nearby sea area are taken as the research objects.Ten Landsat series remote sensing images from 1976 to 2020 are used to extract the sea area use type information of each study year by combining object-oriented method and visual interpretation.On this basis,an evaluation system of sea area utilization was established to evaluate and analyze the area and spatial evolution characteristics of each sea area type,the structure of sea area utilization,the efficiency of sea area exploitation and utilization,the intensity of exploitation and utilization and the environmental pressure of the sea area.Based on the marine environment survey data,the impact of sea area exploitation and utilization on the environmental quality of this sea area was analyzed.In order to provide reasonable suggestions for the rational development and scientific utilization of the Yellow River Delta sea area,and to provide decision-making support for regional ecological environment protection and sustainable development.The main research conclusions are as follows:(1)During the evolution of sea area utilization,the area of tidal flat was changed largest,and most of it was transformed into aquaculture and salt industry.Among them,the distribution center of aquaculture gradually moved closer to region A which located in the west of the study area,and the distribution center of salt industry gradually moved closer to region C which located in the southeast of the study area.By 2020,the sea area used for aquaculture will account for 50.5% of the total sea area,becoming the main type of sea area used in the Yellow River Delta.In recent years,the sea use types in the study area have gradually become diversified and balanced.(2)In the process of sea area development and utilization,the overall development rate of the research area was the fastest from 1985 to 1995,and it tended to be flat after1995,while the utilization rate was lowest around 1981.The increase in the rate of sea area development is often accompanied by the decline in utilization,and the two show a significant negative correlation.In the past 10 years,the utilization rate of sea area has been continuously improved,gradually reaching more than 90%;As of 2020,Area A has the highest development rate,and Area B which located in the northeast of the study area has the lowest development rate.(3)In terms of the current situation of sea area development and utilization: the development and utilization intensity of Area A is the largest,and the environmental pressure of development and utilization is also greater.Area B has the least environmental pressure on the development and utilization,but its carrying capacity is the weakest.In the future,more sea area development and utilization activities may be considered in Area C,where environmental pressure is low and sea area carrying capacity is strongest.(4)In terms of the relationship between sea area utilization and marine environmental quality: the spatial difference of sea area water quality in recent years is obvious,and the water quality in Area A is the worst,while that in Area C is the best;There is little difference in sediment quality,including inferior sediment quality in Area B and better sediment quality in Area A.Since the 1990 s,the water quality in the study area has deteriorated obviously,and the main influencing factors are suspended solid,inorganic nitrogen and petroleum.The sediment quality is always in good condition,but the accumulation trend of petroleum content is obvious.Water quality and sediment quality are greatly affected by land-sourced pollutants carried by rivers into the sea,but are less directly affected by marine development and utilization activities.We should pay major attention to reducing the discharge of land-sourced pollutants into rivers.At the same time,attention should be paid to sea using activities such as aquaculture,port shipping,oil and gas exploitation and urban industrial construction,which may damage the marine environment.