Spatial-Temporal Evolution Characteristics And Development Suggestions Of Reclamation In Bohai Sea

Coastal area plays an important role in socioeconomic development.As the only sea in northern China,it is of great significance to develop and utilize Bohai.Reclamation is the main way to make use of coastal areas.Since 1985,the scale of reclamation in Bohai has been expanding,and causing a series of problems,such as ecological environment deterioration,marine disasters occurrences frequently and biodiversity decline.Based on this,China issued a prohibition about new reclamation in 2018 to mitigate the negative impact of reclamation.Under this background,it is of great practical significance to clarify the present situation,analyze the characteristics and driving factors of reclamation evolution.Based on the Landsat images,ENVI and ArcGIS were used to process and extract the reclamation coastline and utilization types in each period from 1985 to 2019,and the characteristics of reclamation evolution were analyzed by fractal dimension,reclamation intensity coefficient,development intensity index and transfer matrix.In addition,the driving mechanism of reclamation activity was discussed by using grey correlation degree method,the driving effects of natural and policy factors were analyzed qualitatively.The results show:from 1985 to 2019,the reclamation coastline increased from 2797km to 4483 km,the fractal dimension increased from 1.1710 to 1.2185,the average reclamation intensity coefficient was 3.4hm²a^-1km^-1;the reclamation area reached 4.25×10⁵ hm²,and the development intensity index was 87.6%,with an average of 2.6%.Massive vegetation land,natural sea and unused land converted into aquaculture water,construction land and salt land.During the peak I,the area of aquaculture water and natural sea increased significantly,showing a trend of land transfer to water.During the instability I,aquaculture water and salt land increased quickly,and construction land began to increase.During the peak II,aquaculture water,construction land and salt land entered a period of comprehensive and high-speed development,while other land types were encroached.During the instability II,the development of reclamation slowed down,aquaculture water and construction land decreased slightly,but vegetation land,natural sea and unused land increased slightly.During the restricted,the proportion of vegetation land,natural sea and unused land decreased again,and the proportion of aquaculture water area also decreased slightly.Reclamation is the compositive result of natural,ecological,policy,social,economic and other factors.The suitable natural ecological environment is the foundation of reclamation,but it also restricts the development of reclamation.National policy is the external driving force of reclamation,favourable policies act as facilitators,while restrictive policies act as disincentives.Socioeconomic factors are the endogenous driving force of reclamation,different factors have different intensity and direction to different utilization types.In general,aquatic products output,regional population and fishery output have great effect on vegetation land,aquaculture water,natural sea and unused land;tourists amount,fixed assets investment and cargo throughput of coastal ports have a significant driving effect on construction land;GDP of primary industry and tertiary industry has a certain driving effect on salt land.At the present stage,the speed of reclamation expansion has been effectively controlled.We should focus on planning of reclamation functional zoning and creating regional characteristic industries to alleviate the bad competition between regions.We should expand the idea of reclamation,try to use the vertical space of coastal areas to help improve the coastal ecological environment.We should improve the comprehensive benefit assessment model of reclamation,strengthen the research on automatic extraction of reclamation information from multi-data source images,to provide technical support for the formulation and implementation of reclamation management control measures.