| Infrastructure is the material basis for urban development and the improvement of human well-being,but its construction,use,and scrapping process are also accompanied by a large amount of material and energy consumption,which has a profound impact on the local and cross-regional ecological environment.In previous studies,due to the difficulty in obtaining fine spatial data and information on the flow of materials across regions,the research on the spatiotemporal evolution of material metabolism at the urban scale associated with the cross-regional ecological environment impact is very limited.In order to solve the above-mentioned problems,this study takes 11 types of major infrastructure in Shanghai as an example,and builds a coupling model of material flow analysis(MFA)and geographic information system(GIS)based on multi-source data such as remote sensing,geographic information,historical maps,statistics,and survey data.We analyzed spatiotemporal patterns of the material stocks and flows at a high spatial resolution(500m×500m)for the city from1920 to 2019.The socioeconomic and physical geographic driving factors behind the material metabolism of infrastructure were revealed;and the impact of urban infrastructure development on the cross-regional ecological environment was quantified.We put forward policy recommendations to reduce resource consumption and environmental impact.The main conclusions of this study are as follows:(1)From 1920 to 2019,the accumulated material stock in urban infrastructure increased from 15.3 million tons to 1288.9 million tons,with an average annual growth rate of 4.6%.In the past 100 years,the material metabolism has gone through five periods.In the initial period(1920-1950),the average annual growth rate of the amount of material stocks,inflows and outflows were 4.9%,5.6% and 6.7% respectively.During the slow growth period(1950-1980),the average annual growth rates of material stocks,inflows and outflows were 2.7%,2.2% and 3.2% respectively.During the period of steady growth(1980-2000),the average annual growth rates of material stocks,inflows and outflows were 4.7%,3.1% and 6.1% respectively.During the acceleration period(2000-2015),the annual growth rates of material stocks,inflows and outflows were 8.2%,4.1% and 8.5%,respectively.During the deceleration period(2015-2019),the average annual growth rate of material stocks,inflows and outflows were 3.1%,-11.5% and 4.9% respectively.Among the 11 types of infrastructure,residential and plant buildings have the largest material stock,accounting for 71.8%-84.2% of the total material stocks;the top three materials are sand,brick and cement,accounting for 93-97% of the total material stocks.The total material inflow showed a fluctuating upward trend,reaching a peak of 308.7 million tons in 2005,with an increase of 42 times.There are differences in the timing of peak material input flows for different types of infrastructure.The material inflows of residential buildings peaked in 2005.Then,material inflows of plants,schools,stores and railways peaked in 2010.The material inflows of warehouses and hotels buildings with roads and subways reached the peak in 2015.However,the inflection point of the material inflows of office and hospitals buildings has not yet occurred.The total material outflows showed a clear and rapid growth trend.The average annual growth rate of material outflows was higher than the material stocks,reaching 6.3%.The total material outflows increased from 0.16 million tons in 1920 to 37.2 million tons in 2019.The total material outflow of residential and plants buildings and highway accounts for the largest proportion.After2010,the waste coming from roads became the biggest source in Shanghai’s infrastructure.(2)Spatially,the proportions of total material stocks,residential material stocks,non-residential material stocks and transportation material stocks in the central urban area showed a decreasing trend,while the proportions of all kinds of material stocks in the suburbs showed an increasing trend.The central city and suburban areas have accumulated more than 79.7% of the total material stocks,more than 84.6% of the residential material stocks,more than 73.8% of the non-residential material stocks,and more than 65% of the transportation material stocks.All kinds of material stocks in the suburbs have surpassed those in the central urban areas.The high-value of material stocks show a trend of spreading from the central urban areas to the suburbs and outer suburbs.The high-value of material inflows has obviously shifted to the suburbs and outer suburbs,and the material input of various infrastructures in the central urban area is below 25%.The material outflows mainly come from the central urban area and suburbs,and the outflows of waste material accounts for more than 70% of the total.The high value of residential material outflows was mainly in the central urban area.However,the high-value of non-residential and traffic material outflows are gradually shifting to the suburbs and outer suburbs.(3)The driving mechanisms for the evolution of different types of infrastructure material stocks and flows are different.For the material stocks,there is a significant inverted U-shaped relationship between GDP and total material stock,residential material stocks,non-residential material stocks and transportation material stocks.Population growth promotes the increase of total material stocks,residential material stocks and non-residential material stocks,but it inhibits the increase of transportation material stocks.The normalized vegetation index(NDVI)inhibits the growth of total material stocks,residential material and non-residential material stocks,and promotes the growth of transportation material stocks.Splitting Index(SPLIT)restrains growth in the total material stocks,residential and non-residential material stocks.In terms of material inflows,GDP has an inverted U-shaped relationship with total material inflows,non-residential material inflow and transportation material inflow,while GDP inhibits residential material inflows.Population density promotes the total material inflows and non-residential material inflows,but it suppresses traffic material inflows.NDVI suppresses material inflows for all types of infrastructure.SPLIT suppresses total material input,residential,and nonresidential material inflows.For outflows,GDP has an inverted U-shaped relationship with total material outflows,residential and nonresidential material outflows.Population density promotes total material,residential and non-residential material outflows.NDVI inhibits material outflow of all types of infrastructure.The SPLIT suppresses material outflows residential and non-residential material outflows.(4)Due to the limitation of data acquisition,the study took steel inflows as an example to evaluate the cross-regional ecological and environmental impacts of material metabolism.The results showed that the inflows of steel in Shanghai reached a peak in 2010.Spatially,the high-value of steel inflow in space gradually shifted to suburban proliferation.After 1990,the steel required for Shanghai’s infrastructure construction mainly relied on the input from other provinces,of which the largest proportion came from Jiangsu Province.Due to the outsourcing of steel materials,the impact on the cross-regional ecological environment has gradually shifted from the periphery of Shanghai to the distant provinces,and the impact on the ecological environment of the distant provinces has shown a gradual upward trend.After 1990,the total cross-regional eco-environmental impact was higher than the total local ecoenvironmental impact.In 2005,the total eco-environmental impact of infrastructure material metabolism reached its peak value,573 times that of 1920.While the local and trans-regional eco-environmental impact reached its peak value in 2005 and 2010,respectively.In the category of ecological and environmental impacts from 1920 to2019,fossil depletion was the most significant(61.6%),followed by climate change(32.8%)and human toxicity(5.6%).(5)Policy recommendations for the sustainable development of infrastructure and resource management in Shanghai are as follows: 1)The spatial layout of new residential and non-residential infrastructure needs to be compact at a moderate level,rather than scattered,so as to provide more social and economic services;2)the life of the building is extended to further reduce the consumption of native resources and alleviate the contradiction between supply and demand of resources;3)to coordinate the development of gray and green infrastructure to realize the organic combination of man-made infrastructure and natural ecological space,which can reduce the ecological and environmental impacts of material metabolism in urban infrastructure;4)develop new steel and strengthen technology sharing with the central and western regions;5)Shanghai should actively explores a cross-regional ecological compensation.Capital and technical compensation should be given to the provinces where iron and steel building materials come from,to reduce the ecological environmental impact of steel production and processing from the upstream of the industry.Through the quantitative research on the spatial and temporal pattern of material metabolism of urban infrastructure in Shanghai and the impact on the cross-regional ecological environment in the past 100 years,we provide important method support and decision-making basis for in-depth understanding of the material metabolism process,driving factors and ecological environment effects of urban development in rapidly urbanizing areas,and formulating sustainable urban infrastructure planning and resource management policies. |
PDF Full Text Request