Urbanization has greatly contributed to global warming as vehicle transmissions have increased, tropical forests have been cleared for expansion, and many other anthropogenic activities. Evidence of climate change in cities is seen in the urban heat island effect, where developed areas have grown warmer than surrounding rural areas.
Many cities around the world are reaching hotter temperatures every year as global warming worsens. Urban heat islands also increase energy demands and consumption as well as air and water pollution.
According to the U.S. Environmental Protection Agency, climate change may give the city of Chicago up to 30 more days of hot temperatures above 100 degrees Fahrenheit. Extreme heat in urban areas needs strategies to reduce urban heat island effects.
Vegetation to Mitigate Urban Heat Islands
One strategy to mitigate climate change and excess urban heat is to grow vegetation within limited spaces such as roads, buildings, back or front yards, and rooftops. For example, explained Carolina Gomez-Navarro from the University of Utah, standing on a lawn during a hot summer day is significantly cooler than being on the pavement. But more research needs to be done to develop the best strategy for America's semi-arid cities.
In a recent study, researchers from the University of Utah proposed to replace artificial surfaces with vegetation. Cities such as Salt Lake Valley receives very little rainfall, so vegetation would serve as an alternative to cooling urban temperatures.
Temperature and humidity records from the last few years revealed that lawns reduced temperature more than surrounding trees. Trees provided shade while lawns and turfgrass or artificial grass cooled the temperature as water moved through the grass and evaporated.
Moreover, open vegetation gave more room for urban heat to escape while areas with a lot of trees had a greenhouse effect by trapping heat near the ground. The researchers determined that combining grass and disperse trees would effectively cool down Salt Lake Valley.
Read Also: The World Meteorological Organization Reports the Consequences of Anthropogenic Climate Change
Importance of Urban Planning
"Understanding how ground cover impacts temperature is crucial for city planners to weigh the benefits and costs of its landscape design," said Gomez-Navarro. Salt Lake Valley used to be covered with bushes and bare soil. Adding vegetation to the city would require a lot of irrigation and dramatically modifying the landscape.
Increased turfgrass areas were correlated to lower temperatures. Increased canopy cover from trees also helped reduce the temperature. Gomez-Navarro explained that although air temperature may be warm, people "feel much cooler under the shade of a tree because it blocks some of the radiation."
The next step would involve urban planning such as vegetation landscapes affecting people's comfort in cities and determining the best types of plant covers. As temperatures get warmer due to climate change, people would be able to find refuge from the heat at parks.
Technology such as satellite imaging and temperature and humidity sensors make it easier for researchers to measure climate conditions in urban areas, explained by Professor Diane Pataki. However, researchers need to discover how effective vegetation can cool the air and which plants would maximize cooling for better urban planning and designing future parks.
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