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Discussion on the role of urban designers in the fight against climate change

Interviewer: Antoine Rondelet, Founder @ Ganddee

Guest: Hélène Chartier, Director of Urban Planning and Design @ C40


C40 is a network of mayors of nearly 100 world-leading cities collaborating to deliver the urgent action needed right now to confront the climate crisis. The initiative was founded in 2005 with the aim of driving urban action to reduce greenhouse gas emissions and improve the resilience of cities to climate impacts. C40 cities work together to develop and implement policies and programs that accelerate the transition to a low-carbon, resilient future. Key areas of focus include energy, transportation, buildings, waste, and adaptation to climate change. (More info here).

Hélène Chartier is the Director of Urban Planning and Design at C40. The team she leads develops programs and activities that support cities to accelerate sustainable and resilient urban planning policies and design practices. Her team runs the Reinventing Cities competition that delivers zero carbon buildings and resilient urban regeneration projects; C40’s Land Use Planning network which supports cities to institutionalize climate action through urban planning policies; as well as the Green and Thriving Neighbourhoods program that turns the 15-minute City concept into reality and implements ambitious pilot neighborhoods on the ground. Hélène previously served as an advisor to the Mayor of Paris, Anne Hidalgo. She also worked for the Paris Urbanism Agency and the global consulting firm Arup. Hélène holds a Master’s degree in science and engineering from the École Centrale with a specialization in building and civil engineering. (More info here)


Antoine Rondelet: According to the UNEP, cities are responsible for 75% of global CO2 emissions, with transport and buildings being among the largest contributors. What was done wrong in the design of today’s major cities? i.e. why do we pollute so much in a city today?

Hélène Chartier (C40): First, I think it is important to say that cities aren’t the problem in themselves. I would even say that cities are part of the solution. By nature, the typology of the city produces fewer emissions. That being said, cities concentrate people, buildings, transport, and they concentrate most of the activities. Cities are also the home of the wealthy, the richest people that consume a lot. So, cities are where consumption-based emission are the most important.

As I said, the typology of the city is not the problem in itself and can lead to less energy consumption and lower GHG emissions. Inhabitants of cities tend to be less dependent on cars, energy consumption tends to be more efficient and better conserved within buildings, as opposed to single family houses, etc. In cities, the two main contributors of GHG emissions are: buildings and transport. We estimate that buildings represent 50% of the emissions, while transport represent 35% of the emissions in cities.

So, what has been designed wrong? I would say quite a lot of things, especially since the introduction of cars after World War II. At that time, there were these modernist rationalists, Le Corbusier and others, who have really organized the city in a way that artificially increased the need for transport. Their theory promotes urban sprawl which consumes natural land, which creates more dependency on cars etc. This was definitely car-oriented planning along with an over-specialization of the neighborhoods. In France for instance, Marne-la-Valée and the East part of the Greater Paris area has been designed as a residential area, while the business district is located on the opposite side. These areas have been connected by public transport in the best case scenario, or by roads, for car commuters, in the worst case scenario.

This post World War II urban planning strategy has created a lot of the problems cities are facing today such as very long commute, poor quality of life, high GHG emissions due to transport, more GHG emissions from houses in these residential areas etc. So, there is a need to rethink these urban models, which forms some of the current discussions about urban planning today.

I think you’ve just answered my follow-up question, which was “What is the role of urban designers and urban architects in tackling climate change?”. As far as I understand what you say, their role today is to address the poor urban design choices that were made a few decades ago. So, in concrete terms, the job today is to limit urban sprawling, reshape neighborhoods to be more diverse, reduce the over reliance on transport etc. Is that correct?

We need to work both at the building-level, but also at the urban planning level. As you formulated it, it’s really about focusing on urban regeneration rather than greenfield development, and see how we can create these polycentric cities, made of multiple complete neighborhoods, where there is a mix of use, a mix of people, etc. We need a minimum density to develop a transport system and make urban services financially viable. Then, you can connect each of these multiple complete neighborhoods through a good transport system.

Now, you also need to ask “How do you combine density with livability?” because, while we need some level of density, we also need people to be happy to live in a city, otherwise, they might just leave to go somewhere else. This is where I think it is important to provide proximity to cultural services and to provide access to nature.

Bad urban planning has pushed nature outside the city, creating more and more impermeable soil, which have created several problems. First, in terms of quality of life, and I think the pandemic has really showed that people were a little bit frustrated to be disconnected from the outdoors, stuck in their neighborhood etc. There have also been studies showing that urban nature is the best solution to tackle and to adapt cities to climate change. In fact, nature creates freshness and cools our cities down. For example, Medellín has been one of the pioneer city to really develop their green corridor, replant, and everything. A lot of studies have shown that they have managed to reduce urban heat effect island by 2 to 3 degrees (Celsius), which is quite important. Urban nature is also important to combat flooding. Natural soils capture excess water while impermeable soils, with concrete everywhere, aren’t. So, we now see a trend in big cities to bring nature back to have permeable soils and develop a nature shedding strategy to improve the quality of life for inhabitants. This, along with the proximity to cultural services, allows creating a “happy density” that makes the urban life enjoyable.

So, that’s for urban planning. Now, there is also work to do on buildings, because as I’ve said, 50% GHG emissions in cities are coming from buildings.

First, I think it is important to retrofit and focus on what is existing. There are parts of the world with big demographic growth, but it not the case in the Global North anymore. So, we have to ask ourselves, “should we continue to build so much?”. I think it’s important to think about that. There are estimates that say that we are building, on average, the equivalent of one floor area of the city of New York every month in the world. That’s a lot. So, even if we build zero carbon, is that sustainable to continue to build in this way? I don’t think so. There are more and more people who are measuring the vacancy of the buildings. In France, for example, they estimate that 7 to 8% of homes are totally empty. If you add secondary home, which represent 12%, you have almost 20% of the stock of homes that are either not used at all or used three to four weeks a year. At the same time, there is a housing crisis for people, and if you look at the offices this gets even worse, especially since the pandemic, after which the number of under-used offices has grown by a lot. So, there is a need to think about how we can tackle empty buildings, empty offices etc. More and more cities are taking action on this. In Vancouver, for example, they have passed a bill called Empty Homes Tax in 2021. The tax was one percent of the value of the asset, if the building was empty, and then they tripled it last year, and they want to multiply by five in 2025. Cities like Lisbon, Brussels, and others are also thinking about this type of thing.

So, we need to find a way to really push people to use or to rent their housing. We also need to think about the real needs for offices and to focus construction investments to retrofit the existing buildings rather than continue to build new ones. Then, there is all the methodology to build itself that is starting to be transformed to incorporate safe design, to incorporate renewable energy, and to also use materials of construction that are less carbon intensives, such as wood and others. It is really the whole picture that we need to look at for buildings. Reducing first, retrofitting, and then transforming the way we build.

Can we design sustainable cities today, or are we blocked by the need to get access to specific new technologies/new green materials? Can we design “green cities” with concrete and steel?

I tend to think that we have most of the solutions. I think it’s even important to say it because sometimes there is a little bit of greenwashing to promote some of the new technologies and everything. But, that doesn’t mean that technology doesn’t have a role to play. I definitely think it has a role in terms of getting better data, better materials etc. For example, now, as an architect, when you design a building, you can access a bank of information on the materials you will use, get the quantity of material you can use to reduce the embodied emissions connected to the building you’re designing etc. So, the technology can support and can really help accelerate the work of architects and urban designers.

That being said, I think we can already stop doing a few things. In France, for example, there are all those discussions about the ZNAs, Zero Net Artificialization, which is really about stopping urban sprawl. We know what we need to do on that, but this is complicated, and I think the major discussion is around how we can stop urban sprawl without weakening the economy. That’s a big thing.

We also need to lower consumption-based emissions, for example. Today, most cities and countries calculate scope 1 and scope 2 emissions mostly. They basically calculate emissions produced in their territory, but they don’t include, what we call, the imported emissions, and the imported emissions are mostly the things people buy. My jeans, your food, the type of things that are produced somewhere else. If we include consumption-based emissions in the scope of emissions of global North’s cities, it will add approximately 60% of additional emissions. It’s very important, and so we need to think about reducing consumption, for sure. But all of this thinking is in a way, I would say, opposite to how we have built our markets and our economy. That’s the main challenge. The main limit is not technologies. The same goes for the built environments. We know that we should reduce building and focus on existing, but we need to create the viability, the financial viability for developers, in order to focus on the existing rather than build brand new, on which they make much more money.

That’s more of this type of thing that we need to discuss, plus, of course, consider the support of technology. You’ve also asked about alternative materials such as wood. Of course, you know, to be able to switch to construction in wood, that means structuring a little bit the wood sector. In France, we have forests etc., like the Nordics, but the Nordics have invested so much more money in the management of their forests than we have. So, we need to improve the ways in which we manage our forests to include this type of production for construction, which is not the case at all today. So there are a few things that we can do, but I don’t really believe that one big technology is going to save us all.

By their very nature, cities seem centered around humans, but can we design them to account for the rest of the natural world? i.e. make sure our cities have a lower impact on biodiversity.

If you think about nature as a whole, I would say the main problem is the consumption of natural land. So, I think the first thing we should do is to stop developing our cities so much because we push, you know, we consume natural land, we consume biodiversity and everything. Of course, we can also talk about our agricultural system etc. But, within cities, to be honest, there is a lot of space for nature I think.

Now, sometimes people ask me “isn’t there a contradiction between making the case for density, which I think is important, and keeping a place for nature? How can you combine both?”. I definitely think there is a lot of space for re-naturing our cities. I will take the Parisian example. The Mayor of Paris has decided to remove 50% of the parking slots within Paris, which is possible to be honest: if you look at the public transport structure of Paris, there is a capacity for Parisians to shift their mobility mode. So, if you remove 50% of the parking slots, it means creating space that equates to six times the Jardin du Luxembourg. Six times, it’s huge! So, it’s really about, you know, finding and optimizing space. And if you look in even less dense areas, we were discussing with some Mayors who said, you know, sometimes nature is removed simply for a question of maintenance. It’s easier for them to put bitumen, concrete, than to let nature grow. Because you know, it’s easier to maintain something where there is nothing, than to maintain nature. So, the way people look at public space needs to change. People need to understand the role of nature, the role of permeable soils, which may not look as perfect as concrete, but which provide resilience and fulfil an important role in cities. Once we acknowledge that, we can start to see all the possibilities we have to bring back nature in cities, even in dense areas.

Barcelona and even cities like Houston in the US, have developed major plans to replant the cities etc. So, it’s just about changing the way we have done before. Let’s start from here before saying “Okay, let’s go back to the countryside etc.”, because we will create more problem if we all go back to the countryside instead of focusing on how we can transform our cities.

How do you prioritize between the needs of the present and future generations when reshaping existing cities? If we look at modernization of public transport infrastructure, e.g. renovating train lines, it is a great investment for the future, but when such work is carried out, it generally affects the day to day of commuters. How to reshape our cities to be more sustainable without compromising - or minimizing impact on - the needs of the present?

That’s a good question, but I think there is also capacity to change. Sometimes there can some situations where change is complicated, but there are a lot of situations where it’s just a matter of getting used to do in another way. Let’s look at Paris, for example. Within Paris, nobody can complain there is no public transport. If you have no disability, public transport is pretty cheap and very convenient. So, sometimes, I believe that we need to be pushed to transform the way we do things. For vulnerable people, people who really can’t give up on their cars, like, you know, workers who need their cars etc., I think we need to adjust the rule first. We need to have flexible rules to support them to, you know, maybe transform their cars or something like that. You can also use flexible approaches to develop your city. Many cities don’t only invest in underground public transport, for example. If you look at a city like Jakarta, they have doubled their public transport network’s capacity, through buses. From an investment’s and speed of execution’s perspective, such a plan is different from building a subway, and can cause less disruption in the short term. So, I think what’s needed is to have a vision, a plan and execute it long term.

While there are some people that you should protect, e.g. by making some exceptions or by supporting them financially, adjusting the rules for them etc., I think that some people could be and should be pushed to give up on their way of living. When I was advisor of the Mayor of Paris, for instance, and they closed the Berges de Seine, the first lobby was not at all the workers and the people with disability, it was the people from the West of Paris, the very rich and wealthy people who were used to drive through the riverbank to easily get in Paris. These people didn’t want to take the subway. So, at one point, many people can change their habits and need to be forced to do so. It’s the same when it comes to flying around the world and with food etc. At one point, we need to be pushed a little bit out of our way to change the way we live. At the end, people find that it is not so complicated to do. They complain first, and then they change. So I think we need a good balance of protecting vulnerable people, all without stopping the transition.

Thank you for taking the time, Hélène. Is there something you’re working on, a book, a paper, a project, that you’d like to tell us about and share with the community?

There are a few things. First, C40, the organization I’m working with, has developed a platform called C40 Knowledge Hub, which in my opinion is a really fantastic source of information. Basically, C40 is working with 100 cities, like the largest cities, but a lot of cities weren’t able to enter the network. We thought it would be too complicated to work with 1,000s of cities and instead, we thought it was more interesting to work, deeply, with 100 cities, and make a real difference. So, what we’ve decided to do was to create a knowledge hub where we share every information, organized per topic and everything. There is a ton of information that we post there and that is open to all. The second thing I would say, is that we have recently produced a guidebook with Arup that is called “Green and thriving neighborhood” to really see how we could transform, you know, local areas, with some concrete example, indicators and everything. And I think it’s an interesting resource, so maybe have a look at this one.


Further reading


We originally published this interview on OCRA, a climate forum and community that we started. This interview has been moved to our blog following the closure of the OCRA forum.

Ganddee interviews offer an opportunity to put some guest community members at the center stage. During these interviews we ask questions to our expert guest to better understand their work, learn from them, and understand how they contribute to the fight against climate change. We hope these interviews will serve as an invitation to expend the discussion on the forum.

If you liked this interview, please be sure to hit the “like” button on this post to let us know. If there are specific topics you would like to see covered in an interview, please let us know by either sending an email at: or by dropping a comment below.

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