Published on May 21, 2025
Cities sometimes get a bad rap when it comes to the environment.
But dense, well-connected urban areas produce fewer emissions per person, and when designed thoughtfully, they offer people lower-carbon ways to live, work and move. As the climate crisis intensifies, cities are not just vulnerable — they’re also on the frontlines of the fight.
That makes urban planners and designers some of the most important players in climate action. The way we shape our cities — especially our public spaces — can have an outsized impact.
To learn more, we spoke with Hélène Chartier, Director of Urban Planning and Design at C40 Cities, a global network of nearly 100 mayors working together to confront the climate crisis.
Hélène, who previously served as an advisor to the Mayor of Paris, Anne Hidalgo, helps cities bring bold climate goals to life by embedding them into land use policy and planning regulations. She’s also spoken and written about how good urban planners can be the best climate activists.
We spoke with her about how cities can lead climate action, why public space matters, and what inspires her work.
Evergreen: How can urban planning tackle the climate crisis?
Hélène Chartier: Cities were once compact, with jobs, shops, and essential services located close to where people lived. After World War II, our cities have been totally transformed because of mobility patterns. We also began specializing neighbourhoods — residential, business and commercial areas, all connected by car-oriented planning.
We know cities expand 50% faster than their population. That means urban sprawl is not just because we have more urban population. Not only are we extending the distance and commute time, but it has also created a lot of environmental problems, like air pollution. Additionally, so much of urban expansion is happening in areas already identified as high risk for floods or other climate hazards.
So, we need to stop urban sprawl, and we need to stop single-use zoning. A mixed-use neighbourhood with residential and office components is more resilient to crises and reduces transportation distances.
The Intergovernmental Panel on Climate Change suggests that if we adopt a better urban planning model, we could reduce greenhouse gas emissions by about 25%. Good urban planners consider how to reduce emissions from buildings, from transport, from public space, from increasing the potential from nature. The climate crisis is multiple crises. As a good urban planner, you come with multiple challenges and objectives and you need to find a way to make it happen.
Evergreen: What’s the role of public spaces in climate resilience, and how can cities design for it?
HC: The urban environment is more sustainable from a greenhouse gas perspective. But if you don’t make it desirable, people will want to leave their cities. If you want to make the case for a Compact City, you need to develop public spaces where people can go outside and enjoy what we call the ‘living room of the neighbourhood.’
You can’t have Compact Cities without public spaces that are high quality, green and offer access to nature. Otherwise, people don’t feel it’s a good living environment for them and their children. Public space, maybe in addition to good housing, is probably the two necessary conditions for people accepting living in a Compact City.
We know that green space is a very important element of public space design. There are a lot of studies showing the importance of green space for physical health and mental wellbeing, but it’s also critical from a climate perspective.
The other part is about creating an environment that is walkable and safe. That’s what Jane Jacobs was thinking with ‘the eyes on the street.’ People often choose to drive even for short distances because they don’t think it’s a nice environment to walk in, especially with children. So even for five minutes, they prefer to use their car. But if you design public space, including an active ground floor, you can create a place where actually it becomes a nice moment to walk. And then there’s a direct reduction of emission from transport.
Evergreen: What small urban planning ideas can make a big difference in tackling the climate crisis?
HC: School Streets are an amazing intervention that can happen in every neighbourhood. You can close streets to traffic, but if you don’t have another use, if you don’t have life happening there, people don’t see the benefit. But if you remove cars from the streets near schools, you will immediately see families and children there.
You can see the life we are trying to produce in every neighbourhood; it starts here. Then you see things like shops and cafes for parents while the children are playing. In Milan, they put ping pong tables to create life in the area. Paris invested more money and brought in green spaces.
One other thing that I like is seeing cities opening their school yards after school, during weekends and holidays, which can actually be combined with School Streets. It becomes a new park, and it’s another intervention that doesn’t cost a lot but can quickly change the environment, both in terms of climate and in terms of quality of life.
Parc Rives de Seine, Paris. Photo credit: Mairie de Paris
Evergreen: What have you found most inspiring in your work?
HC: It’s very clear that people want more green space. They want more public space for walking, for cycling and for children to play. We can see this already happening in a lot of cities, in dense urban areas.
Paris has done this super quickly in the past five years, transforming 50% of their street parking spaces into public space and developing 200 School Streets. Medellin, Colombia, has been a pioneer on green corridors and green streets, way before a lot of the Global North cities. They have done measurements to show that they could reduce urban heat island by 3-5 degrees by bringing in more natural shading from trees.
Before joining C40, I was an advisor to the Mayor of Paris, Anne Hidalgo. Another thing I really admired was the political courage. The government in the 1960s decided to create a highway in the middle of the most beautiful part of the city. When we started the transformation of the highway [to ban vehicles], there was a lot of pushback. I remember the public consultation meeting was very hard — people were saying we should wait for more public transport to be built. But she said: we cannot wait; the pollution is terrible, and we need to solve it now.
And today, I think you see the polls, or the proposal recently passed with 66 percent of the vote [to approve more car-free streets], you can feel the transformation. Even the opponents of Anne Hidalgo would never transform it back again. She’s leaving the role of mayor in a few months, but even if another political party wins, they will never transform it. I think this is very inspiring.
