Study On The Impact Of Human Activities On Yancheng Coastline And Coastal Wetland Types

Yancheng coastal wetlands are in areas where the interaction between nature and humans is frequent.Coastal line erosion caused by sea level rise and siltation of the shoreline caused by sedimentation are the most important natural factors affecting Yancheng coastal wetlands.Port engineering construction and reclamation Activity and Spartina alterniflora invasion are important human factors in coastal wetland changes.This paper systematically sorts out the changes of coastal wetland coastline and wetland habitat types in Yancheng from the long-term scale and large area from 1987 to 2018,and uses the principle landscape ecology,with the help of remote sensing and GIS technology,the impact of human activities on the coastline and wetland types of Yancheng coastal wetland was analyzed and studied.The main results are as follows:(1)Reclamation has shown a general decrease in shoreline length,but the proportion of artificial shorelines has continuously increased from 12.03% to 43.92%.From 1987 to 1992,the coastline changes were dominated by natural factors,and the law of south silting and north erosion was maintained.After 1992,human activities such as reclamation gradually became the dominant factors of coastline changes.The law of coastline changes was basically consistent with the law of reclamation coastline changes.In addition,the natural wetland habitat type changes caused by reclamation mainly occur in the stable bank section(bank section(3))and siltation bank section(bank section(4))that is the area north of Sheyang River.During the 31 years from 1987 to 2018,the native natural salt marsh habitats in the coastal areas of Yancheng(grassland marshes,Suphan swamps and reed marshes)directly lost 67131.4hm2 due to reclamation,accounting for 62.9% of the increased land area;The center of gravity of reclamation continues to move southwards,and the greater the proportion of area loss in the habitat type of bare flat towards the south,the larger area of bare flat is developed into unused land and breeding ponds.(2)The port construction has significantly promoted further siltation of the coastline.From the morphological point of view,the spatial pattern of siltation on both sides of the port guide embankment has evolved from "double arch" to "arch / S" and then to "arch / slope";from the perspective of siltation dynamics,from 1987 to 2018,The shoreline length of Sheyang Port area increased by 1289.5m,the artificial shoreline ratio reached 25.45%,and the overall flow into the sea silt was 984.1m;after the port was built in 2011,its length increased by 1173.7m,and the overall flow into the sea silt was 252.8m,with an average silting rate of 36.1m/a.The coastline of Dafeng Port has increased by 4346.5m over the past 31 years,and the proportion of artificial coastlines has reached 47.43%.The overall flow into the sea silt is 4660.4m;during the 20 years after the port was built in 1998,the overall flow into the sea silt was 3831.9m,with an average silting rate of 191.6m / a.(3)The impact of Spartina alterniflora invasion on the coast of Yancheng is very prominent.First of all,the expansion of Spartina alterniflora marsh promotes the reclamation activities,and the area of Spartina alterniflora marsh occupied by the reclamation accounts for 18.98% of the entire reclamation area.Secondly,Spartina alterniflora encroached on the land to occupy Suaeda marsh and to the sea to occupy the bare flat,which had a huge impact on the native salt marsh wetland habitat and coastal wetland landscape pattern.During the 31 years from 1987 to 2018,the center of mass of Spartina alterniflora moved generally towards the ocean,resulting in the loss of 34265.3hm2 of bare flat and 1877.6hm2 of native Suaeda marsh,accounting for 93.68% of the newly added Spartina alterniflora area and 5.43%.Spartina alterniflora mainly grows south of the Sheyang River,and the wetland area occupied by Spartina alterniflora swamps on the eroded bank is small,accounting for 6.00% of the whole.The types and areas of wetlands occupied by shoreline(1)and shoreline(2)are different due to different shoreline trends.(4)Strengthen the coordination of regional ecological protection and economic development.The coast of Yancheng is one of the most biodiversity-rich areas and has a prominent position in global ecological protection.Over the past few decades,reclamation,port construction and Spartina alterniflora invasion have promoted regional economic development and have had a serious impact on regional wetland ecology.Therefore,on the one hand,the sustainable development of the region in the future depends on wetland ecological protection,restoration and Spartina alterniflora management in key areas;on the other hand,for non-key ecological protection areas,the scale and speed of reclamation are limited,and the functions of Spartina alterniflora to promote siltation and bank protection are given full play to reduce the impact of sea level rise.