城市三维空间结构对碳排放影响的尺度效应

Analyzing the impact of urban three⁃dimensional spatial structure on CO2 emissions at multiple scales

城市是碳排放最集中的区域,全面厘清城市空间结构对碳排放的影响对碳减排规划具有重要意义。以往研究主要关注城市二维结构与碳排放的关系,表明城市扩张是碳排放剧增的主要原因。虽然城市三维空间结构也会显著影响碳排放,然而其影响的尺度效应依然缺少深入分析。为此以广州市为例,结合相关性分析、随机森林探究三维空间结构与碳排放的关系,并揭示三维空间结构影响的尺度效应。研究结果表明:(1)(高层)建筑物密度、建筑覆盖率、容积率与人口密度是碳排放的关键影响因素,主要通过直接增加人类活动或加剧热岛效应使得能源消耗和碳排放增多;(2)三维空间结构对碳排放的影响具有明显的尺度效应。随着分析尺度的变化,碳排放受三维空间结构的不同方面主导;(3)广州作为紧凑型城市的代表,如果片面追求城市三维空间的紧凑布局将不利于低碳城市的发展。因此,相关部门应重视宏观尺度下的三维空间结构的合理布局,合理开发城市边缘地区,降低城市中心建筑物的紧凑布局,构建多中心的城市格局,以有效降低碳排放水平,促进低碳城市的构建与可持续发展。研究所得成果可为城市建筑三维空间布局的合理优化提供参考依据,助力“双碳”目标的实现。

Carbon dioxide(CO2)is the primary greenhouse gas that has emerged as a serious threat to environmental conditions and public health.Many studies have shown that cities are the areas with the highest CO2 emissions.It is of great significance to comprehensively analyze the impact of urban spatial structure on CO2 emissions so that CO2 emission can be reduced through reasonable urban planning.Previous studies have mainly focused on the relationship between urban two-dimensional spatial structure and CO2 emissions,indicating that urban expansion is the main reason for the sharp increase in CO2 emissions.Although the urban three-dimensional spatial structure also significantly affects CO2 emissions,the relationship between them still lacks in-depth investigations.Therefore,the purpose of this research is to explore the relationship between three-dimensional spatial structure and CO2 emissions and to reveal the associated scale effect at multiple grid scales by taking Guangzhou as an example.These tasks were conducted by using the Pearson correlation test,random forest regression,and scale analysis.The results indicated that:(1)The effect of three-dimensional spatial structure on CO2 emissions is greater than that of two-dimensional land cover.Among them,(high-rise)building density,building coverage ratio,floor area ratio,and population density were the key factors affecting CO2 emissions,which could increase energy consumption and CO2 emissions by directly increasing human activities or intensifying urban heat island effects and the associated energy consumption.(2)Scale effect is obvious in terms of the relationship between three-dimensional spatial structure and CO2 emissions.Although the three-dimensional spatial structure is the major influencing factor at all scales,the order of importance of influencing factors varies among different scales.The dominance of high-rise buildings is stronger in small and large grid scales,and the dominance of the overall layout of buildings is stronger in moderate grid scales.Therefore,determining a reasonable analysis scale is another important aspect of revealing the influencing mechanisms of CO2 emissions.(3)As a representative of modern compact cities,Guangzhou should not unilaterally pursue the compact layout of the urban three-dimensional space,which is not beneficial to the development of low-carbon city.Rational planning of the urban three-dimensional spatial structure is an important approach to low-carbon city construction.In conclusion,it is necessary for policy-makers to pay attention to the reasonable layout of the three-dimensional spatial structure at macro scale and the difference in the impact of three-dimensional spatial structure at different scales.Additionally,policy-makers should attach importance to the reasonable development of urban fringe areas.Furthermore,policy-makers should reduce the compact degree of urban central buildings and develop a multi-center urban development pattern,which can effectively reduce the CO2 emissions and promote the sustainable development of low-carbon cities.In summary,this research can support the rational optimization of urban three-dimensional spatial structure,and can help to achieve the carbon peaking and carbon neutrality goals of China.