The Temporal-spatial Pattern Change Of Carbon Metabolism In Coastal Urbanization

Cities,especially coastal cities,are the most densely populated and economically concentrated regions with the most concentrated carbon emissions meanwhile.The increasing carbon emissions in the global urban areas will continue to exert pressure on climate change.Besides,cities can also become a part of global environmental governance.City managers can influence carbon emissions changes through the formulation of land-use planning and infrastructure,and many management measures have the effects of increasing carbon sequestration.It quantitatively studied the effects of changes in sea and land-use/cover types(SLUC)on carbon metabolism,which included carbon sequestration and emission in coastal cities,and analyzed the spatial-temporal change of carbon metabolism during coastal urbanization.Thus,it can clarify the status of regional carbon metabolism in the process of coastal zone urbanization,and then put forward reasonable policy recommendations for urban planning and management from the perspective of carbon metabolism.Xiamen is a typical coastal city.From 2000 to 2015,it experienced rapid urbanization.Taking Xiamen City as the study area,it setted up the SLUC system and collected statistics on population,economics and energy consumption,some natural/semi-natural SLUC carbon sequestration coefficients and Landsat satellite images.Software tools including eCognition Developer and ArcGIS were comprehensively used to interpret and obtain SLUC data of Xiamen City in 2000,2005,2010,and 2015,and to map the calculated carbon emissions,carbon sequestrations and carbon metabolism data to spatial data of SLUC.Finally,the increments and decrements of carbon emissions,carbon sequestration,and carbon metabolism(net carbon sequestration)were calculated to analyze the spatial and temporal pattern change of carbon metabolism in Xiamen.The results showed that the carbon balance index increased from 8.44 in 2000 to 40.73 in 2015,and the rate of change of the three-phase carbon balance index was 108.35%,71.33%,and 35.19%,respectively.From 2000 to 2015,Xiamen remained in a state of negative carbon imbalance.The carbon imbalance has been increasing,but the rate of change has decreased.Xiamen City as a whole has been a carbon source,land as a carbon source area,whose net carbon emissions were from 877.68 ×104t in 2000 to 3976.88×104t in 2015.The ocean and the coastal zone has been a carbon sink whose net carbon absorption is between 18.55?21.86×104t.Carbon emissions played a leading role in the imbalance of carbon metabolism.This is because in the change of carbon metabolism,the amount of carbon emissions changes were much larger than that of carbon sequestrations.The difference between the maximum and minimum total carbon emissions in Xiamen was 3083.78x 104t,while the total amount of carbon sequestration was 15.86×104t in 2000?2015.The largest land-based carbon emission SLUC,that is,the other construction land(CA)has the greatest impact on the change of carbon metabolism.Carbon metabolism showed an increasing trend with time went.In the analysis of carbon metabolism,the trade-offs between socio-economic development and eco-environmental benefits existed.Besides the trade-offbetween the improvement of carbon metabolism and other eco-environmental benefits also existed.Finally,the paper put forward corresponding policy recommendations,including raising concerns about carbon metabolism in coastal cities,strengthening the management of carbon metabolism in coastal zones,formulating and implementing long-term sustainable development plans for land and sea use,and strengthening the management and control of sea-land use/coverage.To avoid inefficient sea-land use/coverage shifts,etc.The innovative points of this research are to take the coastal cities,which were less studied in urban carbon metabolism research,as the research area,and to take mariculture,mangroves,tidal flats,beaches,and seawater in the study of temporal-spatial evolution of urban carbon metabolism.It established seven categories with 23 sub-catrgories and in the subcategory of SLUC type system,the relationships between marine/coastal use/coverage types and coastal carbon metabolism changes were further discussed.More elaborate land-sea use/cover classification can reduce the estimation error of carbon absorption to a certain extent.Mapping the carbon metabolism changes of coastal cities into finely classified spatial data can make it deeper to analyze pattern change characteristics of carbon metabolism in coastal cities.This paper provides a simple framework for the analysis of carbon metabolism in coastal cities.The calculation of carbon balance,carbon emission and carbon sequestration in coastal cities can provide a basis for coastal cities to participate in urban greenhouse-gas-emission-reduction activities as well as urban carbon emission trading systems.Analysis of the temporal and spatial changes in carbon metabolism in coastal cities can provide information for urban managers to make land and sea plans for city management.