Urban agglomeration can lead to economies of scale, technological progress, lower transaction costs — and therefore lower energy consumption and lower carbon emissions. The spatial distribution of population and economic activity is a key factor influencing energy consumption and emissions, including the distribution of people within and between urban clusters.
China’s urbanisation policy has instigated a process of rapid relocation that has seen more than 20 million people move from rural areas to urban areas annually over the past decade. This was supported by the implementation of preferential regional development programs and industry relocation policies. These policies can have significant environmental consequences.
International institutions and national governments have long considered the idea of developing compact cities as an approach for reducing energy consumption and greenhouse gas emissions. One assumption is that compact cities are less dependent than others on private vehicle use, which leads to lower energy consumption and lower emissions.
But many authors argue that the impact of urban density on carbon emissions is more complicated. As researchers debate whether compact cities perform better than dispersed ones in terms of energy efficiency, environmental policymakers may safely adopt a comprehensive urban-wide approach to such efficiency, instead of considering just the effects of commuting or transport.
In our recent paper for the 2016 China Update, we conduct a comprehensive examination of the relationship between urban density and carbon dioxide emissions. Our results suggest that compact cities are more environmentally friendly than dispersed ones. On the other hand, we also find that denser cities in China depend more on public commuting and therefore create more carbon dioxide emissions through intra-city travel.
China has experienced rapid urbanisation in the past few decades. The country has a scarcity of arable land relative to the rest of the world. In 2011, per capita arable land in China was approximately 1023 square metres, 40.9 per cent of the global average of 2500 square metres. The Chinese government has implemented stringent land regulation policies throughout the urbanisation process, a consequence of which is a continuous increase in urban population density.
China’s eastern cities tend to have much higher average population densities than the central and western cities. In China, the best public services — such as education, health care and public facilities — are in large cities due to the concentration of administrative power. This leads to further concentration of population in large cities. A trend of increasing urban population density in China is expected in coming decades.
The effect of urban density on transport-related emissions is negative. In other words, in terms of the transport sector, denser cities are more environmentally friendly than dispersed ones.
In China, local protectionism hinders market integration. As a result, most Chinese cities tend to be more autarkic than cities in developed countries. The fragmentation of Chinese regional markets may reduce intercity transportation, particularly in larger cities. This could partially explain why more densely populated cities generate less carbon dioxide emissions from transport.
Higher urban population density tends to mean lower carbon emissions arising from the transport sector and the urban system as a whole. At the same time, a denser population means higher emissions generated by intra-city public commuting.
Our results also highlight some significant differences in commuting patterns between China and developed countries. In particular, Chinese cities depend more on public modes of commuting, while cities in developed countries rely more on private vehicles.
As for China, due to strict land regulations, more and more apartment towers are being constructed to accommodate the influx of rural migrants into cities. As a result of such trends, Chinese cities are much more compact than cities in most developed countries. In recent decades, increased urban density has been driven mainly by land-saving policies rather than environmental concerns. But our findings suggest these compact city arrangements are positive from a carbon dioxide emissions perspective.
Broader environmental policy should be based on a comprehensive assessment of various pollutants, such as sulphur dioxide, particulate matter and nitrogen dioxide, that are generated by urban systems. The mode of urbanisation we select today will have significant environmental consequences in the future. It must be considered as carefully as possible.
Jianxin Wu is Associate Professor at the School of Economics, Jinan University, Guangzhou.
Yanrui Wu is Professor of Economics at the University of Western Australia Business School.
Xiumei Guo is Research Fellow at the Curtin University Sustainability Policy Institute.
This article is a digest of the authors’ chapter from the publication for the latest China Update, which was held at the ANU on Friday 22 July. A free e-book is available here.