| The dramatic changes of ecological system,environment,landscape patterns in coastal areas are driven by the global changes and increasing human activities.Coastlines are the areas where the land and sea interact intensively,and the spatial-temporal characteristics of coastline evolution have siginificant contributions to es Tablelishing coastal environmental policy,protecting the environment of residents,exploiting the coastal resources,developing coastal economy sustainably,and reducing the damage of ocean disaster.In addition,since the announcing of Maritime Silk Road,the development of coastal zones along Maritime Silk Road have attracted more concerns around the world,and the spatial-temporal characteristics of coastline changes along Maritime Silk Road will supply scientific evidence to evaluate the status of development for the regions in Maritime Silk Road.Referencing vast literatures and the field visits on China coastal zones and achievements from our research team,the categories criterion of coastlines were es Tablelished based on Landsat images.Visual interpretation method was selected to extract the coastlines for 2000 and 2015 over the coastal zones of Maritime Silk Road,and the accuries of position and category were both receivable.Based on this dataset,the changes of coastline length,structure,fractal dimension,position and land-sea pattern were analyzed to demonstrate the spatial-temporal characteristics of coastlines around Maritime Silk Road,and the driving forces for coastline changes were researched from natural and human perspectives.The detailed processes of this research are as follows:1)the length and proportion of each category of coastline were acquired with the geospatial analysis techniques;2)index of coastline utilization degree was constructed by referring to the concepts and calculation methods of same indices in the field of land cover/use to research the characteristics of coastline exploitation;3)the grid method was used to calculate the fractal dimension(FD)of multi-temporal coastline,in this way if the change of coastline morphology had tended to be more complicated could be certified;4)the speeds of coastline swings were calculated by the method of End Point Rate(EPR)provided by DSAS and used to demonstrate the changes of coastline location;5)the areas of patches encircled by two periods of coastline data were calculated based on geospatial analysis techniques and hot spots were identified to demonstrate the patterns of land-sea interchanges;(6)many natural and human elements were selected to acquire their driving degree on coastline changes.The principal conclusions are as follows:1)The lengths and structures of mainland coastline changed significantly around Maritime Silk Road.From 2000 to 2015,the total length of coastline increased from81490.18 km to 83005.18 km,however,the length of natural coastline decreased by1897.52 km,and its proportion decreased from 85.27%to 73.25%,and the length of artificial coastline increased siginificiantly with 3415.52 km.West Asia experienced the fastest growth in artificial coastline length,followed by Southeast Asia,and the artificial coastline length in these two continent areas increased by 1368.98 km and897.89 km,respectively.The artificial coastline increased by 487.02 km in South Asia,and the intensity of coastline artificialization in South Asia was lower than those in West Asia and Southeast Asia,but the intensity of coastline artificialization was still higher compared with the intensities of coastline artificializations in Northeast Africa and South Europe,the length of artificial coastlines in these continent areas had the increase of 374.92 km and 283.70 km respectively.2)The modes and intensities of coastline artificialization had significant differences at continent and country scales.The groins and jetties,harbors and wharfs,and urban areas represented violently increases in West Asia,especially in United Arab Emirates,Saudi Arabia,Qatar and Iran.The coastline artificializations of Southeast Asia were mainly concentrated in Vietnam and Malaysia,where the constructions of harbors and wharfs,urban areas and aquaculture dikes were intensively.In South Asia,the harbors and wharfs had a certain degree of constructions in India and Pakistan,and the aquaculture dikes showed obvious increase in India,meanwhile,the urbanization of whole South Asia developed most slowly and the urban areas had almost no increase.The constructions of urban areas and harbors and wharfs were main exploitation activities in Northeast Africa and South Europe,where the increase of urban areas and harbors was mainly concentrated in Egypt and Spain respectively.3)The morphology of coastline verged to be complex.In the period of nearly 15years,the coastline had been pushed towards the sea with irregular shapes under interference driven by human activities,such as the constructions of aquaculture dikes,harbors and wharfs,and sea reclamations,as a result,the fractal dimension(FD)of coastlines over the Maritime Silk Road increased from 1.085 to 1.087,with same tendencies of FDs and coastline morphologies at continent scales.As the scales decreased,the influences on coastline morphology changes driven by human activities were more intensively,the morphology of coastlines became obviously complicated with FD increasing violently in many hot spots and port cities.However,in few hot spots and port cities,where the natural coastlines were originally tortuous,human reclamation activities,such as constructions of harbors and dikes,often had straightened and simplified the tortuous morphology with FD decreasing.4)The swings of coastlines exhibited significant differences at continent scales.The coastline swayed violently under natural evolution in Southeast Asia and South Asia,in addition,the high-intensitive human activities also pushed the coastlines towards sea,so the length and proportion of these two countries was 5528.50 km(26.61%)and 3162.31 km(30.12%),respectively,and obviously higher than those in other three continent areas.Though the highest intensity of coastline artificialization in West Asia,the overall intensity of coastline was behind those in Southeast Asia and South Asia owing to the low intensities of natural coastline swings,and the length and proportion of coastline swings was 1793.89 km and 8.37%,respectively.The coastline swayed gently in Northeast Africa and South Europe,and the length and proportion of coastlines swings in these two continents was only 800.78 km(4.67%)and 556.68 km(3.28%),respectively.5)The land-sea interchanges showed obvious spatial cluster distribution in many hot regions at country scales.The land expanded violently in Myanmar,India,Bangladesh,Vietnam,United Arab Emirates,Saudi Arabia and Iran,and the increase of land in thess countries was 625.71 km~2,285.34 km~2,281.57 km~2,278.70 km~2,189.48km~2,83.11 km~2 and 72.52 km~2,respectively.Specifically,in some hot regions,such as Gulf of Mar Tablean,Ganges River Mouths,Northern of Rakhine State,Red River Delta,Gulf of Khambhat,the Middle-East shore of United Arab Emirates and Khaki Swamp,the land expanded with area of 356.93 km~2,260.71 km~2,201.31 km~2,158.48 km~2,121.90 km~2,120.32 km~2 and 99.81 km~2,respectively.Besides violently land expansion,the land also showed violently retreat in Myanmar,India and Bangladesh,in addition,the land retreated severely in Pakistan.The land decreased by 380.97 km~2,246.46 km~2,116.44 km~2 and 161.38 km~2 in these four countries,respectively.The hot regions of land shrinking were mainly concentrated in Gulf of Mar Tablean,Khaki Swamp and Ganges River Mouths,and the area of land shrinking was 289.93 km~2,263.28 km~2 and101.88 km~2,respectively.6)Some important port cities had higher intensities of coastline exploitations.Among those traditional well-developed port cities,the land of Dubai and Doha expanded violently towards sea with 67.92 km~2 and 32.47 km~2 for the constructions of port and urban areas,and Bombay,Jeddah and Barcelona had relatively less expansions of harbors compared with Dubai and Doha,however,the land growth nearly stagnated in other traditional well-developed port cities.Among the medium-developed port cities,the land expanded violently for constructions of harbors and urban areas in Abbas,in addition,the land of Haiphong showed obvious expansion for the constructions of harbors and aquaculture dikes.The land increase of Abbas and Haiphong was 64.90km~2 and 15.42 km~2,respectively.Among the most of newly-developing port cities,land expanded slightly and represented almost no land growth,except for the certain amount of land expansion in Kuantan,Gwadar,Djibouti,and Port Sudan for port constructions.7)Natural factors are still the basic factors that affect the coastal zone at macroscopic and long-time scales.The sediment deposition was still the basic driving force for the coastline expansion towards sea under natural evolution,though the sediment depositions showed decreasing tendency in many river deltas.The land still expanded violently in Red River Delta,the Mekong Delta,the Ganges River Delta,the Irrawaddy River Delta,and the Deltas of Tigris,however,the land of some river deltas had slightly expansion or stagnate under the influences of the reduced sediment depositions,land subsidence and human activities,even some river deltas had experienced land shrinking.Besides sediment depositions,the coastlines of many low-lying coastal zones retreated violently towards land under the influences of sea level rise(SLR),frequent storm surges and landforms,especially in the Indian Peninsula,the Ganges Delta,Myanmar and the Andaman Sea coast.8)Human factors are the main factors that cause drastic changes of coastlines at local scales and over short periods of time.The urban areas in Southeast Asia and West Asia had increased significantly driven by population growth and urbanization.Specifically,in some areas of Malaysia,United Arab Emirates,Saudi Arabia and Qatar,both population growth and urbanization had significant driving effects on the construction of urban,meanwhile,urbanization also had a significant driving effect on the construction of urban in Vietnam and Iran.By contrast,though the population had rapid growth,urbanization still developed slowly and the urban areas had no significant increase in South Asia and Northeast Africa,moveover,the urban areas had almost no increase in South Europe for that both population growth and urbanization had slowed down considerably.Besides the population growth and urbanization,the development of port economy,planting and aquaculture were also important driving factors that caused drastic expansion of land.The development of port economy led to the continuous expansion of port land in some developed and medium-developed port cities;in addition,due to their own development needs and the investment of Chinese enterprises,many newly-developing and small port cities also had built and expanded the port land to some extent.Planting and aquaculture developed intensively and pushed the coastlines towards sea violently in the Ganges Deltas in India and Bangladesh,the Irrawaddy Delta in Myanmar,the Red River Delta and the Mekong Delta in Vietnam. |
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