Sustainability transitions require an understanding of smaller cities

As we approach an era where more than 60% of the global population lives in cities, urban areas must be our focal point in the transition to the flourishing societies of future decades. While much attention has been paid to understanding urban consumption patterns over the past decade, the overwhelming majority of recent urban metabolism research has focused on larger cities with populations over 1 million inhabitants. Meanwhile, estimates show that more people live in urban areas with populations between 300,000 and 1 million people than in mega cities. Indeed, given their relatively small size, there are many more of these cities to study than larger cities; many more urban governments need to be informed of the solutions that are relevant to the context of their less dense populations. Our goals to decarbonize and dematerialize societies require discussions of measures that are applicable to different types of urban areas across various population scales. We take the example of the town of Reading, United Kingdom to illustrate how per capita urban metabolic flows differ within small- and medium-sized cities, as well as for megacities. For example, relative to Reading, we find that there is substantial variability in energy demand for small cities (i.e., Le Mans is 150% higher) and for larger cities (50% higher for other European and North American megacities). This underscores the need to explore this under-researched area of urban metabolism, as well as the development of a typology to enable comparisons and differentiate strategies for sustainability transitions.