Spatio-temporal Evolution And Multi-scenario Simulation Of Coastal Wetland In Hangzhou Bay

Coastal wetlands are sources of abundant biodiversity and valuable ecological services,and these wetlands contribute to the long-term prosperity in Hangzhou Bay.However,the rapid growth of both the human population and the economy has dramatically increased the environmental pressure on coastal ecosystems and caused serious losses and degradation of coastal habitats.So,it is of great significance for wetland conservation and sustainable development to analyze the historical evolution trend of wetland,drive mechanism and forecast future evolution trend.In this paper,11Landsat images between 1984 and 2016 are used to monitor the changes in the coastal wetlands of Hangzhou Bay,and then CLUS-S model is used to simulate land use maps for 2046 in different scenarios.The results show as following:(1)From 1984 to 2016,the coastline slowly expanded toward the sea,rivers and croplands exhibited statistically significant shrinking trends of-0.38 km~2/year and-7.77km~2/year,respectively;At the same time,out-of-phase patterns were noted between the canal,farm pond,fish pond and non-wetland areas throughout the period.Specifically,the canal areas showed a significant increasing trend(0.79 km~2/year,p<0.05).The farm pond and fish pond areas showed significant increasing trends of 0.85 km~2/year and3.52 km~2/year(p<0.05),respectively.The non-wetland areas showed the fastest increasing trend(13.76 km~2/year,p<0.05).(2)Based on the wetland evolution trend of wetland in history,four scenarios—general changes scenario,economic development scenario,agriculture protection scenario and mudflat resources protection scenario-were settled.The result show significant differences in the four scenarios.In the general changes scenario,the change trend of various wetland types was the similar with the evolution trend from 1984 to2016.The coastline continues to expand outward.In the economic development scenario,beach is rapidly shrinking due to the excessive speed of reclamation,which decreased 81.35 km~2(50.36%)compared to the general changes scenario.The area increased 181.5 km~2 in the beach protection scenario,which was effectively protected.The cropland area has little changed in the agriculture protection scenario which has been effectively protected.And the trend was decline in other scenarios.Non-wetland areas showed a remarkable increased,and the growth rate(10.55 km~2/year)is the fastest in the economic development scenario,which increased 41%compared to the general changes scenario.(3)This research has found that the main driving factors of the coastline extending to the sea and beach instability are urban development and human activities.The increase area of fish pond mainly comes from the reclamation of the beach.The main drivers of the decline in cropland are population growth and urban development.The increase of non-wetland area has been carried out from other wetland types,and has hardly changed to other.By the scene simulation found that,the wetland is still in the declining trend under natural growth trend,and in particular scenario,rice paddies and muddy beach area is not reduced.Therefore,this study puts forward three suggestions for promoting the protection and sustainable development of wetland resources:human disturbance should be in the appropriate range,the reclamation rate shouldn’t exceed the silt deposition rate,to establish protected areas for special areas.