Urban Heat Island Effect & How To Combat It!

By Harry Cooper

Throughout the past couple centuries more and more people have been moving into cities. This, combined with exponential population growth, has greatly increased the amount of urban area on the globe.

This urbanization has numerous affects on the environment in and around cities. Urbanization can be linked to everything from light pollution to habitat fragmentation, but one of the most notable aspects of an increased urban environment is the urban heat island effect.

Hotter Cities

The urban heat island effect is a phenomena where cities and urban areas become notably hotter than the area around them. Cities can be warmed anywhere from 1-7°F during the day and 2-5°F during the night.

On top of this, climate change is already making many parts of the world hotter. When these two effects combine they cause cities to reach dangerously high air temperatures.

While the urban heat island effect is affecting cities across the world, there have been efforts to counteract it. Proper urban planning and green design are helping to make naturally cooler cities.

What Causes the Urban Heat Island Effect?

There are many forces in nature that help to naturally cool areas. However, when an area becomes urbanized, many of these forces get replaced with heat inducing ones, resulting in heat islands.

Less Vegetation

Plants are excellent at naturally cooling their surrounding environment. Not only do they provide shade, but they help cool the air around them through a process called evapotranspiration.

Normally plants act as a natural way to keep temperatures cool and regulated. But as cities are built and ultimately expand, more and more plants and trees are replaced with concrete.

Dark, Paved Surfaces

In urban areas, vegetation is usually replaced by dark materials such as metal or concrete. Not only do these materials provide no natural cooling benefits, but they work to make the environment around them much hotter.

Dark surfaces such as concrete absorb and store more heat during the day than natural surfaces, and reach much higher surface temperatures. These surfaces eventually release this heat and make the air around them much hotter.

In addition, paved concrete and other sealed surfaces can’t absorb water, forcing most rain water to run off. This prevents the process of evapotranspiration, which would normally help to cool an area off.

Human Generated Heat

A lot of everyday human activity releases heat into the atmosphere. In dense, highly populated cities, these actions can add a lot of heat into the atmosphere.

This heat mainly comes from using technologies and infrastructure such as air conditioning, carbon dioxide emitting vehicles, and latent energy usage from buildings. These all produce heat and contribute to the urban heat island effects.

Localized Urban Heat Islands

The heating caused by urban heat islands is only a localized effect within urban areas, not a large scale shift in global temperature like climate change. However, there are still many negative impacts associated with urban heat islands.

Positive Feedback Loop of Urban heat Islands

Air conditioning requires a lot of energy to run. This makes it one of the more prominent causes of urban heat islands.

However, as temperatures rise in cities the demand for air conditioning grows. This creates a positive feedback loop where buildings use more heat creating energy the more air temperature rises.

This causes a massive spike in demand for energy and air conditioning, making midday during the summer one of the highest times for energy demand throughout the year. On top of this, as urban heat islands cause people to use more energy, more greenhouse gases are burned, contributing to global climate change as well.

Human Health Effects

When urban heat islands create levels of extreme heat, human health is put at risk. As cities grow hotter, people become more at risk of experiencing heat related illness, such as heat cramps, heat stroke, heat exhaustion, respiratory problems, and even death.

People who are at higher risk for these effects include the elderly, young children, people who work outside, lower-income individuals, and people with preexisting health conditions. But as city temperatures continue to rise, anyone outside in extreme heat is at risk of contracting a heat related illness.

Combating The Urban Heat Island Effect

While urban areas across the world are warming at unprecedented rates, there are ways of making them naturally cooler. By using environmental city planning methods such as green architecture, increased vegetation, and decreased dark surfaces, cities can make themselves less susceptible to becoming urban heat islands.

Green Architecture

Energy intensive buildings made of dark materials are some of the primary causes of the urban heat island effect. However, when architects design buildings with the environment and heat islands in mind, it can make a big difference.

One strategy cities have used is implementing cool roofs and cool pavements. These are essentially the same as regular roofs and pavements, except made from a lighter colored material.

Materials that reflect sunlight rather than absorb it can have a big impact in helping to make cities cooler. Many cool roofs and pavement can reflect up to 60% more sunlight than traditional dark concrete.

Another way that buildings can reduce the amount of heat they contribute is by installing green roofs. These are roofs with vegetation planted on them.

Much like cool roofs, green roofs are a good way to reduce the amount of heat absorbed by buildings. On top of that, green roofs cool the air around them, further reducing the heat emitted by buildings, and reducing the need for air conditioning inside the building.

Increasing Vegetation

Another good way to combat heat islands is by planting trees, bushes, flowers, and other plants around the city. Plants naturally cool the air around them through evapotranspiration, and replace what would otherwise be heat absorbing concrete.

While green roofs are a more innovative way to increase plant cover in cities, planting things anywhere can be helpful. Adding green parks and planting trees along roads is a great way to beautify a city while helping to cool it down.

Increasing vegetation throughout a city is also a great way for everyday citizens to help fight heat islands. Planting trees or a garden in your yard is something almost everyone can do to help green up cities.

How Religions are Fighting the Urban Heat Island Effect

Laura Bliss wrote for Grist about how Louisville is beating urban heat with the help of local faith communities. This article offers an inspirational example of how faith communities are coming together in Louisville, Kentucky, the nation’s fastest warming “urban heat island.” While certain religious groups show much less concern than others for environmental issues, Bliss writes about how “a growing contingent of religious groups — including Evangelical Protestants, a group that represents the majority of believers in the Louisville area — are squaring their faith with science’s climate warnings. Some call it ‘creation care.‘”

The growing concern for climate change among religious people, and their particular experience of the intense heat in Louisville, helped catalyze a partnership between the local Nature Conservancy and the Center for Interfaith Relations (CIR). These organizations worked together “to develop a landscape ‘audit’ designed especially for religious communities,” which started by recruiting participants from “an all-boys Catholic high school, an Episcopal church, and a mosque— all located in particularly hot spots around Louisville.”

Using the Conservancy’s Healthy Trees, Healthy Cities App, participants were able to get a real-time understanding of the “environmental, economic, and health benefits of individual tree species, which helps users understand how landscaping choices can serve them or not.” Using this and similar tools and questionnaires, participants were able to get a much better understanding of the nature around their institutions, and this translated to real changes in their attitude and approach.

For example, Sikander Chowhan, chief strategic officer at Muslim Americans for Compassion and former board member at the River Road Mosque, was the point of contact for the mosque’s auditing work and as Bliss describes, had his perspective transformed by the experience:

Prior to the audit, Chowhan says, his mosque had never appreciated how an overgrown wooded expanse in the back of its property could tie into Islamic teachings. Now, armed with scientific knowledge on how to put that tangle of trees to better service, Chowhan is spearheading plans to clear a small nature trail and plant a wildflower garden. The very act of revamping the landscape will serve as a conversation starter among congregants, and maybe even a topic at services. He quotes the Quran: “And do good as Allah has been good to you. And do not seek to cause corruption in the Earth.”

Our religious institutions are often vestiges for nature in cities and centers for spiritual growth. Using these institutions as platforms for fighting the urban heat island effect and other environmental issues is a wonderful way to bring religious values to life. We only have one planet. May God help us to protect it.

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