Editing IPCC:AR6/WGIII/Chapter-8 (section)

=== Box 8.1: Does Urbanisation Drive Emissions? ===

<div id="h2-39-siblings" class="h2-siblings"></div>

Urbanisation can drive emissions if the process is accompanied by an income increase and higher levels of consumption ( [[#Sudmant--2018|Sudmant et al. 2018]] ). This is typically observed in countries with a large urban-rural disparity in income and basic services, and where urbanisation is accompanied by economic growth that is coupled to emissions. In addition, the outward expansion of urban land areas often results in the conversion and loss of agricultural land ( [[#Pandey--2018|Pandey et al. 2018]] ; [[#Liu--2019|Liu et al. 2019]] ), forests ( [[#Austin--2019|Austin et al. 2019]] ), and other vegetated areas, thereby reducing carbon uptake and storage ( [[#Quesada--2018|Quesada et al. 2018]] ) ( [[#8.3.1|Section 8.3.1]] ). Furthermore, the buildup and use of urban infrastructure (e.g., buildings, power, sanitation) requires large amounts of embodied energy and carbon (Figures 8.17 and 8.22). Building new and upgrading existing urban infrastructure could produce cumulative emissions of 226 GtCO 2 by 2050 ( [[#Bai--2018|Bai et al. 2018]] ).

However, for the same level of consumption and basic services, an average urban dweller often requires less energy than their rural counterparts, due to higher population densities that enable sharing of infrastructure and services, and economies of scale. Whether and to what extent such emission reduction potentials can be realised depends on how cities are designed and laid out (i.e., urban form – see [[#8.4.2|Section 8.4.2]] ) as well as how urban infrastructure is built and powered, such as the energy intensity of the city’s transportation system, type and level of urban services, the share of renewable energy, as well as the broader national and international economic and energy structure that supports the function of the cities (Sections 8.4.3 and 8.6).

Although population-dense cities can be more efficient than rural areas in terms of per capita energy use, and cities contribute less GHG emissions per person than low-density suburbs ( [[#Jones--2014|Jones and Kammen 2014]] ), there is some, albeit ''limited'' , evidence that larger cities are not more efficient than smaller ones ( [[#Fragkias--2013|Fragkias et al. 2013]] ; [[#Ribeiro--2019|Ribeiro et al. 2019]] ). A number of studies comparing urban and rural residents in the same country have shown that urban residents have higher per capita energy consumption and CO 2 emissions ( [[#Chen--2019a|Chen et al. 2019a]] ; [[#Hachaichi--2021|Hachaichi and Baouni 2021]] ). There is some evidence that the benefits of higher urban densities on reducing per capita urban GHG emissions may be offset by higher incomes, smaller household sizes, and, most importantly, higher consumption levels, thus creating a counter-effect that could increase GHG emissions with urbanisation ( [[#Gill--2018|Gill and Moeller 2018]] ).

Many studies have shown that the relationship between urbanisation and GHG emissions is dependent on the level and stage of urban development, and follows an inverted U-shaped relationship of the environmental Kuznets curve ( [[#Wang--2016|Wang et al. 2016]] , 2022; [[#Zhang--2017|Zhang et al. 2017]] ; [[#Xu--2018a|Xu et al. 2018a]] ; [[#Zhou--2019|Zhou et al. 2019]] ) (Sections 8.3.1 and 8.6, and Figure 8.20). Considering existing trends, earlier phases of urbanisation accompanied by rapid industrialisation, development of secondary industries, and high levels of economic growth, are correlated with higher levels of energy consumption and GHG emissions. However, more mature phases of urbanisation, with higher levels of economic development and establishment of the service sector, are correlated with lower levels of energy consumption and GHG emissions ( [[#Khan--2021|Khan and Su 2021]] ).

<div id="8.4" class="h1-container"></div>

<span id="urban-mitigation-options"></span>