Impact of Urban Compactness on Carbon Emission Efficiency in Small Towns in China

Maintaining a balance between economic development and carbon emissions reduction is an important part of low-carbon development in modern cities. At present, the positive effect of urban compactness on carbon emission efficiency has been demonstrated in large cities, but few studies have been carried out on small towns. Small towns are an important part of China’s urban system, accounting for 70% of the total population and 60% of the national GDP. Most small towns in China still promote economic growth and enhance the social welfare of residents by large-scale urban construction, which inevitably leads to urban expansion and high carbon emissions. How to reduce carbon emissions by optimising urban form while continuing with economic development and maintaining people’s welfare has become an important issue faced by small towns in China. To guide the low-carbon planning of small towns, it is necessary to understand the relationship between urban compactness and the economic benefit and social-welfare levels associated with the carbon emissions in small towns. This study uses remote-sensing and panel data to quantitatively analyse the relationship between urban compactness and CO2 emission efficiency (including CO2 economic efficiency and CO2 social efficiency) in small towns in China from 2008 to 2017. From the rank of the latest Top 100 Counties of China (2019) (Chinese National Bureau of Statistics, NBS), 10 small towns were selected for their different economic development levels. The calculation of urban compactness was performed on the software FRAGSTATAS 4, using parameters of patch density (PD), landscape division index (DIVISION) and splitting index (SPLIT). CO2 economic efficiency (CEE) is expressed as the ratio of GDP to total CO2 emissions, and CO2 social efficiency (CSE) is expressed as the ratio of the regional Human Development Index (HDI) to total CO2 emissions. The HDI is evaluated by the average number of students per 1,000 inhabitants, the average number of doctors per 1,000 inhabitants, the green area per capita, the area of public facilities per capita, and the disposable income of the residents. In addition, a method to calculate carbon emissions based on end-use energy is proposed to overcome the problem of incomplete statistics of carbon emission data in small towns. This study resulted in four main findings. (i) There is a positive correlation between urban compactness and CEE, but no obvious correlation with CSE. In general, compact urban policies have a positive impact on improving the CO2 emission efficiency in small towns in China. However, a various of socio-environmental issues caused by high compactness ratio are detrimental to CSE. (ii) The CEE and CSE both show an upward trend over the period 2008 to 2017. (iii) The effect of urban compactness on urban CO2 emission efficiency is significantly affected by the level of economic development. The higher the per capita GDP of small towns, the greater the impact of compactness on urban CO2 efficiency. (iv) The relationship between GDP and carbon emissions in small towns did not reach an ideal state, the economies of small towns in China are still strongly dependent on carbon emissions. Furthermore, little difference exists between the level of carbon emissions calculated by the method proposed in this paper and the open data of regional energy statistics, which indicates that the method is accurate. This work has one limitation. Due to the differences in economic development caused by location, most small towns in this study are located in south-eastern China. Future studies should therefore explore the relationship between urban compactness and carbon emission efficiency in small towns in different regions.