| With the speeding up of industrialization and urbanization,the intensity of human intervention with natural ecological environment is constant increasing,the area of natural ecological system is shrinking,the construction land use is increasing rapidly,human demand and utilization of all kinds of fossil energy is growing,the issues with global climate change caused by large amounts of carbon emissions is becoming more and more serious.Land,which is an important part of terrestrial ecosystem,is a key tie of man-land relationship.Human social and economic activities depend on land use,and throughout the whole process of development of human history,the carbon dioxide emissions caused by human social and economic activities are closely related to land use,land use type has a significant influence on climate change.Furthermore,it also can affects the health of human living environment.Carbon-oxygen balance,a quantitative characterization of the regional natural and social economic system balance,is good for revealing important regional ecological processes.It can also effectively coordinates the relationship between economic construction and ecological land protection by explaining the relationship of the ecological land and the carbon-oxygen budgets.The calculation of ecological land demand based on carbon and oxygen balance aims at solving four key issue.The first one is whether the urban economic system has caused pressure on the ecological system.Secondly,calculating the running efficiency of urban ecological and economic system.Thirdly,whether the city’s economic development has caused the regional ecological responsibility transfer.Fourthly,how much is the ecological land demand from the perspective of carbon and oxygen balance.Through the analysis of these problems,from the perspectives of interregional equity,the equity in generation and intergenerational equity.We aims at providing some theoretical basis for the establishment of measure method of carbon and oxygen balance,ecological land measure method,and city’s healthy development strategy.On the basis of reviewing the correlated studies both on ecological land and carbon-oxygen balance,this paper puts forward the connotation and classification of ecological land,and puts forward the concept and system structure of the carbon and oxygen balance.Taking Nanjing city as a case,integrating the measure method of carbon and oxygen balance,this paper calculates the carbon emission and oxygen consumption of the economic system and the carbon sequestration and oxygen emission of ecosystem of Nanjing from 1996 to 2013,and established the regression equation accordingly,calculates the carbon emission and oxygen consumption of Nanjing in 2020.Then viewing from the perspective of carbon and oxygen balance,put forward measures for optimization and regulation of the ecological land.Results show that,(1)The carbon emission and oxygen consumption of urban system,mainly came from industrial production and transportation,so adjusting the industrial energy structure is the key to the carbon and oxygen balance.Industrial energy consumption is the main source of the carbon emission and oxygen consumption of Nanjing,and industry had decisive effect on the carbon emission and oxygen consumption of the whole city,which is mainly caused by the consumption of coal,oil,other oil products and electricity.The carbon emission and oxygen consumption from transportation played a second role in the carbon emission and oxygen consumption of the whole city,mainly caused by the consumption of diesel,and water transport and road transport energy consumption occupied the main position in the carbon emission and oxygen consumption from transportation.(2)Carbon sequestration and oxygen emission of urban system mainly rely on cultivated land and forest land,the effect to the carbon sequestration and oxygen emission of urban green land was also very important.So appropriately increasing the scale of ecological land is an important aspect to the carbon and oxygen balance.The carbon sequestration and oxygen emission of cultivated land was the largest,the forest land took second place.Benefit from the returning farmland to forest national policy and the "Green Nanjing" ecological project of Nanjing,urban green land played a more and more important role in the carbon sequestration and oxygen emission.But the carbon emission and oxygen consumption from natural ecosystem is still not enough to satisfy the development of urban economy subsystem,the relationship between the ecological subsystem and economic subsystem of Nanjing is not harmonious.(3)Carbon emission and oxygen consumption had a high correlation with GDP,urbanization rate,gross industrial output value,population,construction land area and municipal district area.Industry,as an energy consumption industry,was the largest cause to the environmental stress.The improvement of urbanization level was also an important factor to cause the increasing of carbon emissions from energy consumption.Population expansion,construction land expansion,and municipal district area had the incremental effect to the increasing of the carbon emission and oxygen consumption,construction land expansion played a positive role in increasing the carbon emission and oxygen consumption.(4)The intensity of the carbon emission and oxygen consumption of every area of land,the intensity of the carbon emission and oxygen consumption of every area of construction land and the intensity of the carbon emission and oxygen consumption per unit GDP were the three important indicators to weighing the balance of carbon and oxygen.To adjust the industrial structure,to cut down the energy consumption per unit GDP,to implement the low carbon economy were important methods to keep the carbon and oxygen balance.For example,the CO2 emission intensity per unit GDP was far below the national average level and the city average level,but was far away with the top 100 cities in China.(5)The city’s economic development produced the ecological environment influence in the two scale of regional and interregional.The electricity from production and life consumption of Nanjing came all from outside Nanjing in 1996-2013.The railway,aviation and waterway transportation were to serve the city’s economic development,while the carbon emission and oxygen consumption caused by their energy consumption was mainly outside.According to the carbon and oxygen balance evaluation model,leaving out any indirect carbon emission and oxygen consumption,the city’s carbon balance coefficient increased from 5.32 to 5.32 and the city’s oxygen balance coefficient increases from 3.47 to 3.47 from 1996 to 1996 of Nanjing.Compared with indirect carbon emission and oxygen consumption,carbon balance coefficient increased by an annual rate of 9.07%,oxygen balance coefficient increased by an annual rate of 8.33%.(6)From the perspective of carbon balance,according to the forest land conversion,the additional demand for ecological land was 3.58 million hectares in 2020 in Nanjing.From the perspective of oxygen balance,according to the forest land conversion,the additional demand for ecological land was 2.35 million hectares in 2020 in Nanjing.Strengthening the management of urban ecological system of Nanjing to enhance the capacity of carbon emission and oxygen consumption of ecosystem,controlling the carbon sequestration and oxygen emission of economic system to promote the development of low carbon city,comprehensively promoting the urban ecological civilization construction to realize the sustainable development of urban ecological land,would be the important paths to guarantee the health,efficient and sustainable development of the regional economy. |
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