Cities have a bad environmental reputation, mostly due to congestion and poor air quality. However, air quality is not the overall picture. Cities, by promoting urban density, allow humans to share infrastructure and reduce their carbon emissions. To reach carbon neutrality in the next decades, we need better cities and that will require further densification, instead of urban flight.
The most recent report from the Intergovernmental Panel on Climate Change (IPCC) showed a stark scenario. It highlighted that little progress has been made in terms of limiting temperatures to 1.5 degrees above pre-industrial levels; and in order to meet such a goal, emissions must peak in the next couple of years. While the report showed some scepticism about the potential of some technologies designed to limit emissions, there was some optimism around cities. Debra Roberts, the IPCC co-chair, recently referred to cities as “a key place for mobilisation“1.
But why does the IPPC focus on cities, an invention from thousands of years ago with a reputation for bad air quality, in a world where electric vehicles and machines that suck carbon from the air are developing rapidly?
The Urban Footprint Shapes Our Carbon Emissions
Cities have smaller carbon footprints than rural areas. Centre for Cities research2 shows that, within the UK, cities on average emit 2.3 tons less of carbon (35 per cent less) per year than towns and rural areas. More than half of this gap is explained by lower transport-related carbon emissions.
The popular comparison between Barcelona and Atlanta3 helps us understand why that is the case. Both cities have around 5 million residents, but the land covered by Atlanta is the equivalent of around 26 Barcelonas. The existing urban environment – compact mid-rise living in Barcelona vs single-family suburbs in Atlanta – shapes how people move and, consequently, their respective transport emissions. The residents of the North American city are likely to have longer commutes and are more dependent on private cars. Public transport is significantly less sustainable in cities like Atlanta, because its low density offers fewer customers in each neighbourhood, which in turn reduces the likelihood of having frequent and good-quality services. Therefore, transport emissions per resident are 10 times larger in Atlanta than in Barcelona.
The Barcelona-Atlanta example is not an exception, and these dynamics can be found even within the same city. This is seen in London in at least two different ways. Firstly, residents living closer to the centre are simultaneously less likely to own a car and they produce lower transport-related carbon emissions. This results from more people living closer to public transport stops in a world-class system (itself sustained by London’s density) and within walking distance of several services and job opportunities. Second, Centre for Cities research4 has shown that in neighbourhoods 11-13km from London’s city centre, the denser areas tend to have higher public transport take-up and a lower carbon footprint, as residential density makes suburban public transport more viable.
Reducing Carbon Emissions Requires Denser and Better Cities
National and local policymakers need to take these trends into consideration when thinking about a greener world. Policies that actively aim to reduce driving, such as congestion charging or driving/parking restrictions, are needed both to reduce car congestion (thereby improving air quality) and also to fund public transport networks. Cities like Singapore, London, and Stockholm have shown that congestion charging is an effective way of reducing driving and improving public transit.
However, these policies need to be implemented in conjunction with building more homes around public transit. Therefore, urban planning is key to building greener cities. Internationally, models such as Barcelona’s car-free super-blocks, Paris’s 15-minutes cities, or the car-free city of Pontevedra5 have one thing in common: they all involve a highly dense urban environment. By having thousands of residents living next to jobs and services, denser neighbourhoods reduce the need to own a car. This meanwhile increases the effectiveness of public transport and active travel schemes, which is likely to make transport schemes cheaper, better quality, and therefore more viable for providers and cities.
Finally, even technological innovation in the field of mobility disproportionately benefits from denser urban living. New, eco-friendly modes of transport such as e-bikes and e-scooters – which emit substantially less carbon6 than electric vehicles during their life cycle – are best suited for the shorter journeys that typically exist in denser cities.
The world is projected to have around 10 billion residents by the second half of this century, so the way we design how we live will be critical to keeping global temperatures within 1.5 degrees. The International Energy Agency7 estimated that if per capita carbon emissions in China and India become similar to those of the US, global emissions will rise by 127 per cent, compared to just 24 per cent if they rise to Hong Kong’s levels – a significantly denser environment. Greening a large, American-style carbon footprint will be much harder.
Denser Cities are Equally Important in a Post-Pandemic World
Since the arrival of COVID and the advent of remote and hybrid work, there has been much discussion on the desire for more space in low-density environments like rural areas. These debates often present homeworking as a climate-friendly lifestyle because it reduces daily commutes. However, there is little evidence that urban flight would make the net-zero targets easier to reach.
Pre-pandemic commutes only accounted for a small percentage of all car journeys in the UK (14 per cent8). This shows that moving away from cities to rural areas and working remotely does not necessarily reduce our carbon footprint, as there is a clear trade-off between longer travel in rural areas (i.e., more car-reliant) and frequent travel in cities (i.e., more prone to use public transport). So, moving to greener rural areas with good air quality may not be as green as we may think.
On top of that, observed trends demonstrate that European cities may be reaching a new post-pandemic equilibrium, where the potential environmental benefits of hybrid work could be mostly offset by a shift towards driving. According to TomTom’s car traffic index, last year’s congestion in major European cities was roughly back to pre-pandemic levels, even though remote work was more frequent than before. To revert this, we need policies to tackle driving and increase the number of residents next to good-quality public transit. Promoting urban density would help on both fronts.
Instead of giving up on our cities, we need to make them denser, and therefore greener.
About the Author
Guilherme Rodrigues is a Portuguese analyst at the Centre for Cities, a London-based think tank that studies urban economies in the UK, where he leads on urban mobility. He holds a masters’ degree in economics from Lisbon’s Nova School of Business and Economics.
1 “The 6th IPCC Report and what it means for cities”, International Union for Conservation of Nature, 3 March 2022. Link: The 6th IPCC Report and what it means for cities | IUCN
2 “Net zero: decarbonising the city”, Centre for Cities, 21 July 2021. Link: Net zero: decarbonising the city | Centre for Cities
3 “Better Growth, Better Climate: cities and the new climate economy”, LSE Cities, 29 January 2015. Link: Better Growth, Better Climate: cities and the new climate economy (lse.ac.uk)
4 “How urban planning is key to net zero: evidence from London”, Centre for Cities, 2 August 2021. Link: How urban planning is key to net zero: evidence from London | Centre for Cities
5 “‘For me, this is paradise’: life in the Spanish city that banned cars”, Guardian, 18 September 2018. Link: ‘For me, this is paradise’: life in the Spanish city that banned cars | Cities | The Guardian
6 “Powered light vehicles can enable transport decarbonisation: Life-cycle analysis shows lighter vehicles can enhance contribution of electrification to climate goals”, Zemo Partnership, 7 December 2021. Link: Zemo Partnership News – Powered light vehicles can enable transport decarbonisation: Life-cycle analysis shows lighter vehicles can enhance contribution of electrification to climate goals
7 “Not a carbon copy of the U.S.”, Los Angeles Times, 28 February 2011. Link: Not a carbon copy of the U.S. – Los Angeles Times (latimes.com)
8 “Net zero: decarbonising the city”, Centre for Cities, 21 July 2021. Link: Net zero: decarbonising the city | Centre for Cities