Urban Heat Islands and What They Can Teach Us About Climate Change

Urban areas typically get much hotter than rural or natural areas. The higher temperatures in cities are caused by the presence of lots of buildings and streets, which heat up in the sun because they are made of materials that can not hold much water. In hot urban areas, called urban heat islands, people and animals stay cool by sweating, panting, and staying in shady areas. Even urban trees can stay cool by transpiring, which is like sweating. In fact, trees transpire so much that they can cool down the air and reduce the urban heat effect—like natural air conditioning. Although the urban heat effect is typically viewed as a problem, scientists can study the plants and animals living in urban heat islands to understand the effects that rising temperatures due to climate change will have on these species in their natural habitats.

to absorb a lot of solar radiation (sunlight) and gets much hotter than grass or other plants. So, the fewer plants a place has-and the more pavement-the hotter it gets!

MANMADE SURFACES IN CITIES LEAD TO HEAT ISLANDS
Cities tend to be full of impervious streets, buildings, and parking lots. All these manmade surfaces absorb and retain a lot of heat, creating

URBAN HEAT ISLANDS
Developed areas that are significantly hotter than surrounding rural areas due to the replacement of natural, vegetated areas with impervious surfaces like pavement and buildings, which absorb solar radiation.
urban heat islands (Figure ). Urban heat islands are developed areas (cities or towns) that are significantly hotter than surrounding rural areas (farms and countryside), due to the replacement of natural, plant-containing areas, like forests and wetlands, with impervious surfaces like pavement and buildings. For example, the city of Washington, D.C. can be up to • F ( • C) hotter in the summer than nearby forested neighborhoods! This may not sound like a huge di erence, but all that extra heat can have a big impact on the health and behaviors of the people, plants, and animals living in cities.

Figure
The urban heat island e ect causes urban areas with more impervious surfaces to be hotter than suburban or rural areas that have more vegetation. This graphic shows how temperatures (illustrated by the orange line) are hottest in downtown areas and lowest in rural and farmland areas.

STAYING COOL IN URBAN HEAT ISLANDS
To avoid overheating, living things need to thermoregulate, which THERMOREGULATE To maintain or regulate internal temperature (plant or animal), even when surrounding temperatures may be hotter or colder. means they must use specialized traits and behaviors to control their body temperature. For example, one of the main ways that humans thermoregulate when they get too hot is to sweat. When sweat dries and evaporates, it cools the skin by taking heat away from the body and releasing it into the air. When we are exposed to really hot temperatures for too long, or when we do not have enough water to drink, we can not sweat enough to stay cool and we can develop health issues caused by heat stress and dehydration.
Lots of species besides humans live in cities and can also overheat when temperatures get too high. Dogs can not sweat, so they is basically how plants sweat, and just like sweat helps to keep us cool, transpiration helps plants to keep their leaves cool.
The amazing thing about plants is that when they transpire, they cool themselves and the air around them. This means that plants can help to keep cities cool by both creating shade and by transpiring. Because of their cooling superpowers, plants are very important for weakening the urban heat island e ect. In fact, many urban areas have started programs to plant more trees and create more green spaces such as parks, community gardens, and green roofs (roofs with vegetation planted on them). You can help reduce urban heat by planting a tree in your yard or planting a garden at school! Plants are only part of the solution. There are many ways that we can reduce urban heating and keep our cities healthy. For example, some cities have started using types of asphalt, concrete, paving stones, and other building materials that can absorb and hold more water than the impervious versions of these materials can. These "wet" materials do not get as hot, and they help to keep temperatures lower in cities. Other cities have started installing lighter-colored or reflective pavements and roofs that do not absorb sunlight, so they stay cooler.

WHAT CAN URBAN HEAT ISLANDS TELL US ABOUT CLIMATE CHANGE?
Climate change is the term we use for changes in long-term weather patterns. Present-day climate change is caused by air pollution from burning fossil fuels, which releases greenhouse gases like carbon dioxide. well, and they grow more slowly than trees living in cooler parts of cities [ -]. In other words, even though trees help keep cities cool, the trees themselves may be starting to overheat. As the world gets hotter, trees may start to overheat even outside of cities. Trees are extremely important and do lots of wonderful things, which scientists call ecosystem services. For example, trees keep us cool, they help

ECOSYSTEM SERVICES
The many benefits humans receive from the natural environment. For example, natural places provide wood, fuel, climate regulation, foods, and places to explore and have fun.
to filter water, they take pollution out of the air, they give us wood to build our houses, and they give us food to eat. If we make the world so hot that trees overheat, it will be bad news for all of us! SUMMARY Cities tend to be hotter than rural or natural areas. This is because cities have lots of buildings and streets that trap the sun's heat.