In this episode from our archives, Ramanan speaks with Karen Seto, the Frederick C. Hixon Professor of Geography and Urbanization Science at the Yale School of the Environment.
She is an urban and land change scientist whose central research focus is how urbanization will affect the planet. A geographer by training, she integrates remote sensing, field interviews, and modeling methods to study urbanization and land change, forecast urban growth, and examine the environmental consequences of urban expansion. Seto is co-leading the urban mitigation chapter for the IPCC 6th Assessment Report and co-lead the same chapter for the IPCC 5th Assessment Report.
In this conversation, they discuss the urban heat island effect, carbon lock-in, and the social and environmental dimensions of sustainability. Time stamps and the full transcript are below. This episode is also available on Apple Podcasts and Spotify.
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[00:00:14] Ramanan Raghavendran: Hello everyone. I'm speaking today with Karen Seto, who is the Frederick C. Hixon Professor of Geography and Urbanization Science at Yale University School of the Environment. An urban and land chain scientist, she is one of the world's leading experts on contemporary urbanization and global change. Very excited about talking to her today. Her research focus is on how urbanization will affect the planet. She has conducted this research in China for 20 years and in India for more than 10. Her research has generated insights on the links between urbanization and land use, food systems, biodiversity, and climate change. She co-leads the Urban Mitigation Chapter for the IPCC's Sixth Assessment Report and co-led the same chapter for the IBCC Fifth Assessment Report. She was co-editor in chief of the journal Global Environmental Change for the last six years. She has many honors. Two or three of them are, she is an elected member of the U.S. National Academy of Sciences, the Connecticut Academy of Science and Engineering and the American Association for the Advancement of Science. Karen, thank you for joining me today and I'm just going to launch right into it.
[00:01:26] Karen Seto: Thanks for inviting me. It's nice to be on your podcast.
[00:01:30] Ramanan Raghavendran: What drove you to pursue the career you have now?
[00:01:35] Karen Seto: I think maybe the highlights that are important in the context of my career, I'm an immigrant. I was born in Hong Kong and we immigrated to the U.S. When I was about five and a half. I can't remember exactly how old I was, but at some point we went back to Hong Kong to visit my relatives. I was maybe I'd say 10 or something like that. We went back to visit my relatives and we took the train from Hong Kong to China. Back then, way back when, Hong Kong had a very distinct identity. We were clearly British Hong Kong. We were riding the train into communist China. Hong Kong is bustling, it's a global metropolis. It's filled with economic activity and life. You take the train out of Hong Kong and very quickly you see the scene shifting from city to rice patties and people were still wearing mao suits back then and I remember it was incredibly poor and this struck me so much. To go from rich Hong Kong to poor China countryside really struck me.
That's one thing that I think has had a big impact is just seeing this transition and clearly this big change in the landscape was because of policies and government. I didn't know that at the time as a child, but it definitely made a big impact on me. I went to grad school with the original intention of pursuing a career as a foreign service officer. I went to grad school and two classes transformed my life. One is I took an economics class, an economics of natural resource use, and I took a remote sensing class. I saw earth from space for the first time in 1992. I remember downloading from the NASA website, an image of Hong Kong, and I could see the border between Hong Kong and China. It was like someone had drawn a line and I thought, "I know why that is."
This is because of government, governance, economic policies. Those are big events in my life that have shaped my career, but I've always been interested in humans and societies and always been interested in the environment. Ultimately, I'm a data nerd. That wraps everything together.
[00:04:14] Ramanan Raghavendran: I can see the data nerd element loud and clear in the several papers that you were kind enough to send me. That's a good segue to question two.
[00:04:24] How can politicians engage with urban science and scientists?
[00:04:29] Karen Seto: The city is comprised of many component parts, transport system, the buildings, the people, the vegetation, but it also operates as a single system. The urban science framework is a powerful tool, conceptual tool, as well as an analytical tool to understand how the urban system works. It brings together a number of ally, traditional, urban fields, like urban planning, and geography, and engineering, and design, and energy studies. These are things that we normally think about studying the city in its component parts and the urban manager, or the mayor may have operations to deal with the buildings, and transport, and urban energy, and maybe street trees. But you need a comprehensive urban system science to understand how the entire system operates. I have a really concrete example that might help. There are a lot of cities now that are trying to transition their city into a low-carbon city or a more sustainable city.
How do you know what strategies are the most effective to lower your carbon footprint? We know that there's the jurisdiction within the city. Cities can make decisions that are purely based on their territory, but cities import food. As urban residents, we consume products that are produced elsewhere. There's a science to understand the supply chains, and the material, and energy that's embodied in these products. The science would help the manager or the mayor understand how does a policy or a strategy to lower your carbon footprint here, how would that actually reduce the carbon footprint as a system? That's, I think, a concrete example of where science, urban science could help urban decision-makers. I'm seeing so much interest in cities and local governance from so many different perspectives. It's partly the climate and environment, but it's also about wellbeing.
There's a lot that could be done at the local level, where we expect our local decision makers to respond to our local and regional needs. There are a lot of communities and people who want to make a difference in their local community and polar bears are iconic and important, but at the same time, there's a real interest in improving their local communities. Cities and local decision-making and local efforts become the gateway to larger issues, whether it's about pandemics, or wildfires and disasters, or issues of justice.
[00:07:36] Ramanan Raghavendran: Can you tell us about your research on the Urban Heat Island effect?
[00:07:41] Karen Seto: Well, it might be useful to just quickly describe what the urban heat island is, or UHI. It is a phenomenon where urban areas are much warmer, significantly warmer, than the surrounding landscapes. This phenomenon is most pronounced in the evenings. So the evenings are much warmer, but even during the day, the temperatures in urban areas are elevated compared to surrounding areas. One reason for this is the materials that are in cities. It's the impervious surface, it's the tarmac and concrete, it's our stucco houses, these trap heat. During the day they trap heat and at night they slowly released the heat that they trap. The other reason why we have the urban heat island effect is that cities use energy so there're human sources of heat. You think of air conditioners, or one of the biggest sources is cars. They generate a lot of heat.
These two are some of the main factors, it's the built environment itself and then it's also human sources of heat. We developed the first ever spatially explicit forecast of urban land going out to 2050. What we did was we took the UN forecast, but then we took other data like transportation networks and where existing urban areas are, density, economic activity. Then we forecasted scenarios of urban land expansion. What we found is that between 2015 and 2050, we're expecting to see about 1.3 million square kilometers of new urban land. It basically translates to, or is equivalent to building not just Manhattan, but all of New York City, every eight days for the next 35 years. That's significant. It's happening now. This is not something that's happening in the future. It is already happening now.
This paper forecasts urban areas and then very importantly, with regard to the urban heat island, we look at how urban expansion will affect the urban heat island. The principal finding of that analysis is that we're expected to see an increase in temperatures on average of half degrees Celsius, but in some places up to three degrees Celsius. Some of the easiest ways to adapt to the elevated temperatures is planting trees. That's also another way to mitigate the urban heat island. What we're going to see with the urban heat island is these local climate effects are actually going to exacerbate and compound the global effects of greenhouse gas emissions. You've got climate change, and then you've got locally induced changes in climate. Our study looked at only urban heat, but there are studies that also show that there are urban effects on precipitation and changes in rainfall patterns as well.
[00:11:00] Ramanan Raghavendran: What is “carbon lock-in”?
[00:11:02] Karen Seto: Carbon lock-in, in a nutshell, is a type of path dependency. It occurs when there are very large capital costs. Another aspect of carbon lock-in is that the thing that you invested in has a very long lifespan. Then really important is that there are mutually reinforcing relationships between the thing that you've invested in and then society, in terms of our behavior, and then also institutions. The research that we've done breaks this carbon lock-in into these three different components. There's the infrastructure part, there're institutions or a governance component that reinforces the infrastructure, and then there's a behavior part of it.
The classic example of carbon lock-in is coal-fired power plants. They last 40 to 50 years, they cost a lot of money. They lock us into fossil fuel-based futures. You mentioned initial conditions. This is really, really important in the context of cities. The initial design of cities sets in motion, believe it or not, what you buy to eat, how frequently shop for food. There's this whole domino effect that is set in place by these initial conditions. Then it's very difficult to break out of them because we have zoning. We have institutions that reinforce the car-centric urban design, and then we get used to always drive it, regardless of whether we need to drive.
[00:12:52] Ramanan Raghavendran: How can we bring together the social and environmental dimensions of sustainability?
[00:13:00] Karen Seto: I think that these pathways are already intertwined. I think that if we look at the history of the environmental movement, it was very much about the environment for the environment. It was environment out here and humans out here, nature and humans. That's crystallized in the way we hit... Parks have originally been conceptualized as keep nature pristine and keep humans out of it. I think where the environmental and sustainability literature has gone and continues to go is recognizing that the environment and environmental conditions are supremely important for human wellbeing. It's not just the environment for the sake of the environment, but for protection of let's say, ecosystem services for humankind. There's a growing literature that shows that the design of our cities has a clear link to human health. Cities that are designed around the car, people are much less mobile, their heart disease and other non-communicable diseases increase, right? The natural environment, the built environment, and our wellbeing are clearly all intertwined.
[00:14:20] Ramanan Raghavendran: Karen, I could go on for a while and you've been amazingly kind with me. You're a super busy person. I think everything you have said will be hugely interesting to my audience. I want to wish you the best. I know I'll talk to you again. So thank you.