Mapping the Way to Climate Justice


About the Author: Jad Daley directs the Climate-Smart Cities Program at The Trust for Public Land. The program is advanced through deep partnership with cities, community groups, and others to advance multiple-benefit green infrastructure for climate action and climate justice. Learn more about Climate-Smart Cities Program in this video.


Heat risk became a reality for me after my wife was in a car accident. During her in-bed recovery, an extreme heat wave hit Washington, D.C., and the air conditioning unit in our tiny apartment gave out. As my wife lay in bed, unable to walk, the temperature steadily climbed in our apartment.

That night was truly terrifying. I ran to the store and bought a fan, which was just enough to cool her through the night. Within a day, we were able to find a technician to fix the A.C. unit but at a cost that I am still paying off today – a few years later. Regardless, we are fortunate to have this financial capacity.

Heat Island Map

This map highlights Urban Heat Island Hotspots (The Trust for Public Land).

Many Americans in low income communities are not so lucky. In such situations they are reliant on cooling centers or other means for protection. The recent climate health report from the U.S. Global Change Research Program highlighted extreme heat from climate change to be a primary threat to human health. Low income families without air conditioning, the elderly, and people with pre-existing health conditions are at greatest risk.

With a phenomenon known as the “Urban Heat Island Effect,” our cities make heat risk worse. This effect occurs when city pavement and other built materials absorb and re-radiate heat, which creates an oven-like effect. A report published by the EPA reveals that heat islands can raise local temperatures as much as five degrees Fahrenheit during the day and as much as 22 degrees at night.

Low income communities are further disadvantaged. Home design can dramatically impact indoor air temperature, and many low-income communities, rental homes, and public housing units are not well designed to lessen heat. For example, in some cases renters are unable to access enough power to run window air conditioning units.

In addition to building design, tree canopy and other green infrastructure are complementary and cost-effective natural solutions to reduce urban heat islands and protect people’s homes. Here is where climate justice comes in. In virtually every American city, tree cover strongly correlates with income—wealthy neighborhoods generally have significantly more tree cover.

How can we bring more protection to the neighborhoods that need it the most?

I believe a catalyst can be the power of Geographic Information Systems (GIS) mapping to illustrate our green infrastructure deficits, like how insufficient tree canopy overlaps with our most vulnerable 2populations. The latest version of the EJSCREEN, the EPA’s environmental justice screening and mapping tool, includes this very information.

We also overlay other issues in these neighborhoods like the increased rate of flooding from extreme rainfall patterns resulting from climate change. After all, the problem that triggers urban heat islands — too much pavement, not enough greenspace — is the same land use pattern in many low income neighborhoods that leads to problems like basement flooding. If we see where these problems of heat islands and water management overlap, then we can develop green infrastructure solutions like green alleys that are designed to address both issues.

Mapping this threat is urgent because it is not a clearly assigned responsibility. Cities have water departments, transit departments, but not “urban heat island departments.” This risk is infrequently covered by the health department, but those agencies are not well positioned to advance strategies to protect key neighborhoods.

That is where GIS mapping comes in.1

My organization, The Trust for Public Land, maps heat islands, who is at risk in these areas, and how strategies like trees and other green infrastructure can help protect these neighborhoods.

If you can’t map climate justice, it is very unlikely that cities and their partners will make the focused investment to solve problems like urban heat islands and flash flooding. But if a picture is worth a thousand words, a map is worth a million. We have gotten immediate attention from city agencies and even mayors by using GIS to show where these climate justice issues exist, which is leading to unprecedented collaboration for climate justice by city agencies in cities such as Boston, New Orleans, and Chattanooga.

It is clear to me that finding the road to climate justice will take a very good map!


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