Impact Of Urban Construction Land Expansion On Carbon Emissions From The Perspective Of The Yangtze River Delta Integration

The utilization and expansion of urban construction land mainly carry a large amount of energy consumption activities,and promote the continuous increase of carbon emissions.In 2020,China put forward the "Double Carbon" commitment of carbon peaking and carbon neutrality,and carbon emission reduction will be an important theme of China’s future socioeconomic development.The Yangtze River Delta shoulders the strategic mission of exploring the new regional development pattern and realizing the goal of "Double Carbon".This paper chose the Yangtze River Delta as the research object,probed into the spatial-temporal evolution pattern of urban construction land expansion and carbon emission.Further,by building the geographical regression discontinuity model,accurately and comprehensively identified the impact of urban construction land expansion on carbon emissions and its internal mechanism,and put forward countermeasures and suggestions.This paper finds that:(1)From 1990 to 2020,the urban construction land in the Yangtze River Delta showed a continuous expansion trend,and the average land use dynamic index was the highest among all land types.The expanded area in the eastern and central part of the study area was significantly larger than that in the western and northern parts of the study area.In the middle and later period,the area of outlying expansion increased and the spatial distribution was more extensive.(2)The expansion intensity of urban construction land in the study area showed an upward trend,and the change trend of expansion intensity of each city was strongly consistent with the whole.The expansion rate in the central and southern regions of the study area was higher than that in the northern regions.The hot spots of expansion in the early period were concentrated in the central and eastern core areas,and the middle and high-speed expansion areas were more widely distributed in the later period.The center of gravity of expansion intensity migrated from the core area to the west,and the migration distance became shorter in the later period,which reflects the trend of gradual narrowing of the gap in urban development level under the background of integrated development.(3)Carbon emissions in the study area showed a trend of increasing first and then stabilizing,the growth rate of all cities decreased significantly in the later period.The spatial distribution of carbon emissions was significantly different,which generally showed a decreasing pattern from Shanghai as the center to the outer circle,and the carbon emission hot spots had a tendency to expand slightly outward with time.The center of gravity of carbon emission showed a moving trajectory from southwest to northwest.The migration distance increased in the later stage,which reflects the difference of industrial structure and the change characteristics of the carbon emission contribution structure among cities.(4)The urban construction land expansion will significantly promote urban carbon emissions,for every 1%expansion of urban construction land,carbon emissions will increase by 0.047%,and the conclusion is robust.Economic development level,public budget expenditure and road network density had significant positive effects on carbon emissions.Urbanization rate,population density,technological progress level and urban greening rate had significant negative effects on carbon emissions.The effect of foreign investment intensity on carbon emission was not significant.(5)There was a robust inverted"U" shaped relationship between urban construction land expansion and carbon emissions.For most cities,the inflection point of urban construction land expansion on carbon emissions has not yet arrived.The proportion of residential land area had no significant effect on carbon emission intensity.The proportion of industrial land,public management land and public service land had significant positive effects on carbon emission intensity.The proportion of land area used for commercial service facilities and logistics and warehouse had significant negative effects on carbon emission intensity.(6)The urban construction land expansion significantly promoted the level of industrial non-agriculture,industrial structure upgrading,per capita consumption expenditure and financial investment in science and technology,and reduced the Engel coefficient of the city,thus affecting carbon emissions.There were inverted"U" curve relationships between industrial non-agriculture and carbon emissions,industrial structure upgrading and carbon emissions,per capita consumption expenditure and carbon emissions,investment in science and technology and carbon emissions.There was a "U" curve relationship between urban Engel coefficient and carbon emissions.Finally,based on the research conclusions,the countermeasures and suggestions put forward in this paper are as follows:First is to take regional integration development as the starting point to realize intensive and low-carbon development of urban.Second is to control the expanding scale of urban construction land and take the connotative development road.Third is to promote industrial transformation and upgrading,reduce industrial energy consumption and carbon emissions.Fourth is to alleviate the high carbon trend of household consumption by advocating green and low-carbon consumption mode.Fifth is to increase the green bias of financial input and promote energy conservation and emission reduction through scientific and technological development.