Spatiotemporal Dynamics Of Island Urbanization In Response To Integrated Ocean And Coastal Development

With the marine economy boom worldwide,islands have been the frontier areas among coastal regions and the coorperation between island and mainland has been intensified.The fragility and vulnerability of island ecosystem determine the necessary of island sustainable development and ecological protection.However,the current development of islands has always focused on economic advance rather than ecological issues,with lack of dynamic monitoring and scientific management.It is urgent to identify the spatiotemporal features of island urbanization and its driving forces and potential effect,which will provide a scientific basis for island sustainable development.This paper integrates remote sensing,geographic information systems,landscape ecology and spatial regression to characterize the spatiotemporal dynamics of land use changes and urbanization on six island counties in Zhejiang Province,from 1980 to 2013.On the perspectives of integrated ocean and coastal development,we tracked the historical patterns of island urbanization and explored the development differences between coastal and island cities.Furthermore,potential impacts of urbanization on island landscape changes had been discussed by spatial regression analysis.Taking Dongtou region as a typical case,we applied the minimal cumulative resistance method to evaluate the land development suitability for coordinating ecological protection and urbanization process.Finally,we put forward scientific suggestion for rational exploitation and sustainable development of islands.The major contents and conclusions were summarized as follows:(1)Based on the long historical remote sensing data(1980-2013),we identified the land use changes among islands of different types and geographic zones,and highlighted their reclamation evolustions.Results showed that with acceleration of island urbanization,the islands in Zhejiang province has experienced extensive reclamation to gain 241.26 km~2 land areas,of which 47.58%area transition to built-up and 23.67%to water surface.Meanwhile the hotspots of land use have also moved.The land use changes initially concentrated withine island regions and then spread to peri-ocean areas over the last decade,where reclamation areas are more flat and favorable for construction.The most evident land transions were built-up rapid expansion and losses of farmland,forest,and water areas.By comparison with the various types of islands,the remarkable land use changes were mostly concentrated on the three island types:comprehensive,port and industry,and tourism.They are mainly the outcome of the spatial cooccurrence of port,logistics,and coastal industries or tourism establishments.It can be conclued that in the primary stage of island development,location conditions and economic factors dominates dynamic degree of land use;while lately the government playes a leading role in the land use mode and development direction.Through monitoring the spatial and temporal dynamics of islands' land use changes and reclamation process provides a scientific support for furture planning optimization and reseanoable development.(2)Furthermore,the temporal and spatial pattern of islands urbanization during 1980-2013 was analyzed,and the influence mechanism of location conditions and social economic factors were quantified.The results showed that the study islands experienced remarkable economic prosperity over that period,with an exponential growth of GDP and economic patttern alteration from traditional production to industrial-dominated production.Built-up land increased 394.85 km~2 during 1980-2013;and expaneded areas of 2000-2013 were three times of the previous 20 years(206.46km~2 v.s.73.31km~2).New construction land mainly concentrated in the coastal areas that altitude was below 50 meters and slope was less than 5 degrees.With the process of urbanization in an all-round way,the construction land spread to the high altitude and high slope areas.And then we quantified the socioeconomic drivers of urban expansion using multivariable regression.Generally,the major drivers were secondary and tertiary industry growth because of the effect of governmental interventions and changing economic conditions on coastal industries and tourism development.The demographic factors in this study did not show a significant relationship.Landscape pattern and lacuanarity dimension analysis indicated that built-up areas became more aggregated and irregulated.The role of urban centers had been greatly improved.More than that it also reflected the extensive and contiguous land occupation by construction in island areas.Combined with the theory of intensive land use and urban growth,we examined and compared the intensities and spatial patterns of urban expansion in six island counties in response to governmental policies.The results revealed that Yuhuan region experiencd the most intense urban growth,mainly due to the positive adjustment of the industrial structure and spatial distribution in recent years,as well as guiding the urban expansion in a more orderly and intensive direction.The results also revealed that Dinghai and Putuo districts had been in the process of coalescence with the guidance of governmental planing,while Daishan,Shengsi and Dongtou were still largely in the process of diffusion and extensive development.In general,infilling expansion of urban land in the whole study regions had gradually increased,with a decrease of outlying expansion percentage.It proves that the governmental interventions play a certain role in supervsing the island land use.However,there are still gaps between island development and land resource shortage.Therefore,improving land use efficiency and optimizing the land use layout is still the key to the islands' development in the future.It is necessary to allocate the construction land index with considering the utilization and developmental goal of various types of islands.(3)Taking Ningbo-Zhoushan,an integrated development zone in eastern Zhejiang,as a case study to explore and compare the spatiotemporal characterisctis of island and coastal region urbanization.The results indicated that economic level and industrial structure of Ningbo city was far ahead of Zhoushan city,and built-up intensity and expansion rate were also higher than the latter region.Although two regions have experienced the same trend that urban expansion intially occurred around centers and then spead across the regions,the different spatial changes could be found.Within Ningbo city,the eastern part showed more intense development than the west,where land use were more agglomerated;Zhenhai and Beilun Districts gradually developed as the sub-centers.For Zhoushan City,Zhoushan new zone had broken the administrative boundaries between Dinghai District and Putuo District to be the new center of the island development,stimulating the development along the island coast.Gradient analysis further explored the different spatial patterns of coastal and island integrated development.With the accelerated urbanization and the strategic adjustment of coastal development,Ningbo and Zhoushan were used to be independent development and gradually upgraded to the interactive model.The completion of Islands Link project and cross sea bridges thoroughly broke the administrative boundaries and natural barriers among Ningbo-Zhoushan region.It greatly motivated the built-up expansion and economic development along the east coast of Ningbo city and its Daxie Island,but also made the west islands in Zhoushan region and its northern port areas revitalized."Coastal city-island" integrated model has been active.What's more,different strategic orientation determined the diversified integrated development patterns.For example,the radiation effect of Zhoushan Island had stimulated the development of surrounding islands,promoted by the "island-island" linkage within Zhoushan city.Meishan port of Ningbo city strenghened the interaction with industrial areas of Liuheng Island in Zhoushan region,"Port-island" linkage promoted the regional cooperation and development.In the future,Ningbo city will continue to play as a core role in regional agglomeration,while Zhoushan region should enhanc the reciprocal contribution.This paper reveals the great effect of breaking administrative boundary,improvement of transporation infrastructure and targeted integration patterns in coastal and island development,which enrich the domestic research on the joint development of the island and the mainland.It also provides an important reference for regional economic development in coastal countries.(4)Rapid urbanization of the study islands imposed great challenge to landscape heterogenization and ecosystem vulnerability during the past three decades.A large number of reclamation projects shortened the coastlines of 2577.85 km,with a decline of coastline fractal dimension,which greatly reduced the natural value and aesthetic value.We also applied landscape index to explore the fragmentation,dominance,aggregation and diversity information of the island landscape patterns at county scale and grid scale.At the county scale,results showed that strong human disturbance led to the rapid conversion of different landscape types,and the ecological landscape connectivity continued to decline.Grid scale analysis further revealed the hot spots of island landscape pattern changes,reflecting the spatial and temporal variation characteristics of those changes in repsonse to the urban expansion and human activities.Spatial regression was used to explore geographical factors of urbanization impact on island landscape changes,taking Yuhuan region as a case study.Results showed that built-up intensity intensified the landscape fragmentation during the three periods,and the patch density and regularity of built-up landscpae also induced the overall landscape pattern changes.However,there was no significant correlation between the road factor and the city center variable to the island landscapechange.With the development of city center close to saturation,the center radiation effect was gradually weakened,and the traffic system was one of important reason restricting the development of Yuhuan city.Besides that the spatial error model tended to be more suitable for the analysis of landscape changes in island area,reavling that the potential driving forces becoming more complex.Thus we should consider the time scale and spatial scale in the future research.To narrow the gap between island ecological protection and rapid urbanization,this paper,taking Dongtou islands as an example,applied minimum cumulative resistance model to construct island land suitability zoning.Results showed that the proporion of land suitable for development was low,and the potential development areas were scattered.Different islands showed the obvious difference in land resource,so that island development should consider their own characteristics and advantages.Under the context of current economic booms in maritime China,the islands urbanization in Zhejiang province will undoubtedly continue in the future.The current focus on the economic development more than protection,with lagging planning and management,extensive construction and reclamation,landscape fragmentation,as well as lacking reasonable layout.Understanding the different manifestations among various island types helps the government to enact an integrated island development plan by considering the overall change features.Tourism island should pay more attention to the natural resources,prohibiting excessive reclamation and exploration,with an eco-friendly development mode.The development of islands should strictly execute sustainable principles,with improvement of land intensive utilization,upgrading industrial structure,and strengthening ocean and coastal integration and even international cooperation.Finally,we must improve the scientific supervision and law enforcement system,as well as optimizing management mechanism and breaking the administrative boundaries;and implement the "Digital Ocean" platform to achieve dynamic monitoring of island exploitation.