The Impacts of City Size and Density on CO2 Emissions: Evidence from the Yangtze River Delta Urban Agglomeration

With rapid urbanization, cities plays an increasingly key role in addressing CO2 emission-related issues. This study aims at analysing the spatial relation between city size and CO2 emissions in the case of Yangtze River Delta Urban Agglomeration (YRDUA) in China over the years from 2006 to 2016, making a contribution to the existing body of knowledge of the relationships between urban form and CO2 emissions. This paper identified the following main findings: (1) There is a U-shape relationship between population size and CO2 emissions in YRDUA; (2) There is a negative sublinear relationship between CO2 emissions and city density in YRDUA; (3) The ideal urban form for low CO2 performance in YRDUA is 2.716 million people living in high population density; (4) Increasing population size is an effective but not a long-term approach for CO2 emissions reduction, because for every marginal increase of city density, the marginal reduction of CO2 emission will decrease. (5) A demographic change in YRDUA from low-density cities to high-density cities would benefit CO2 emission performance. These findings confirm the important roles of population size and density for CO2 emissions reduction in urban agglomeration and so help shape current policy debates.