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Heat islands dial up the heat for many Milwaukee neighborhoods

an empty lot beside a busy street
Lina Tran
Pavement and asphalt lots amplify heat in neighborhoods like Metcalfe Park.

When heat waves descend, cities amplify the heat — a result of the urban heat island effect. A recent report from the nonprofit Climate Central took another look at that effect to understand where heat is most intense within 44 major American cities, including Milwaukee. It found that nearly 40% of Milwaukeeans feel eight degrees more heat due to the built environment. Some residents are exposed to temperatures more than nine degrees hotter than their rural surroundings.

The work echoes findings from a heat mapping campaign that took place last summer, in partnership between the Wisconsin DNR, the Milwaukee Metropolitan Sewerage District and the environmental nonprofit Groundwork Milwaukee. Citizen scientists recorded a 10-degree difference in the evening between the hottest and coolest parts of Milwaukee, with the hottest spots being in dense urban areas.

WUWM’s Lina Tran spoke with Young Kim, the executive director of Groundwork Milwaukee, and Danell Cross, the executive director of Metcalfe Park Community Bridges, which is located in one of Milwaukee’s hotspots for extreme heat. Below is an excerpt of the conversation, which has been edited for length and clarity.

What is the urban heat island effect and what does it look like in Milwaukee? 

Young Kim: If you've ever been out at say midnight in a grocery store parking lot and it was a hot summer day, you put your hand on that asphalt and it feels really warm. That asphalt stores heat. The heat effect comes from lots of asphalt, lots of paved surfaces, that are storing heat and releasing it back into the atmosphere. When you don't have trees or vegetation absorbing the heat or providing shade, that's when you start to get a heat island.

We don’t experience heat evenly. Often it overlaps with communities that are more vulnerable to that heat. What does that look like? 

Danell Cross: I'm looking at how it impacts the people that live there. Because our community is so hot, is that the vibrancy that we want to see, we don't see it. Children outside playing, people doing things like taking a walk. And then our elderly, the impact that it has on them and their health and their inability to be outside and in a comfortable environment and amongst other people. In our community right now, it's burning up. It's not a regular heat. It's a different type of heat — it's on fire. People are not getting the activity that they need. It causes isolation.

Kim: There's a direct link between a practice during the Great Depression in the 1930s, called redlining, that the Franklin Delano Roosevelt administration did in trying to provide federally backed home loans to Americans who were in danger of losing their houses. They went in and they decided certain neighborhoods should get loans and certain neighborhoods should not. If we look at those geographic areas that were lined — literally lined in red ink on maps — and we track the ground temperatures — the data we have is from 2015 to 2020, July, August and September. On cloudless days, redlined areas are showing five degrees hotter than non-redlined areas. Those non-redlined areas have a lot more tree coverage and a lot less impermeable pavement. So there's a direct historical connection between redlining and the current environmental conditions on the ground now, like at Metcalfe Park, lots of abandoned factories, lots of industrial sites that just reflect heat.

A satellite map of Milwaukee shows a cluster of red at the core of the city
Wisconsin DNR
Air temperature data collected in the city of Milwaukee during last summer's heat mapping campaign demonstrates the urban heat island effect, where densely developed urban areas tend to be hotter than more open, rural spaces.

What solutions would you like to see? 

Cross: One of the things that's really concerning to me is the fact that abandoned factories are still sitting there wasting away. I want some solutions from the city about what they're going to do about the abandoned properties. We are continuing to have conversations with the city about tree canopy, but trees that communities like ours, with the income that we have, can maintain.

My aunt died from heat. The windows were painted shut. Another thing that we got to look at is that we have some predatory landlords in our community. Are they able to open a window? Are they able to be able to install air conditioning? Is the electricity in good enough shape to hold that? We have a lot of deep-rooted problems. We're going to look at what we can do on our end, but it's limited. This problem is bigger than us, so it's going to take more than us to fix it.

What solutions is Groundwork Milwaukee involved in, and how does environmental justice shape that work?

Kim: The quick answer is to plant trees. However, trees are not something that you can just dig a hole, stick a sapling in, fill it in, water it once, and then walk away. A tree is something that needs follow-up care in order for it to grow properly. It's a carefully managed process. I do think that there are jobs to be had from tree care. Training people from within neighborhoods, like Metcalfe Park, to take care of trees and to manage the tree stock.

This issue will only become more pressing going forward. If folks are interested in getting involved, where would you point them?

Cross: If they wanted to share their skill and knowledge about trees and share that with the community, I would appreciate that.

Kim: There are plans in place by the City of Milwaukee and the Milwaukee Metropolitan Sewerage District to replace gray infrastructure like asphalt and concrete with green infrastructure. I think the key for these efforts will be a door-to-door relationship-based outreach effort to residents like those who live in Metcalfe Park.

Like, “This is what we’re doing and why?" Not just going into a place and saying, “We’re making these changes here.”

Cross: In order to be successful, the people need to bring the people that's affected into this. This is a generational solution. It’s going to take the people that live there, that’s invested in this community, and then for them to bring their children. They have to be involved, and they have to be educated on what the problem is. In most cases, they should be a part of the solution because people are more invested when they are part of the solution. It's time for the community to be made aware of these plans and what role they could play in helping them be part of the solution.

Lina Tran is a WUWM news reporter.
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