An Urban Heat Island or UHI is an Urban or Metropolitan area that is at a significantly higher temperature as compared to the less crowded, rural areas around it. These heat islands usually occur in large cities. The phenomenon occurs due to the extremely low ratio of naturally occurring environments like plants, trees and grasslands and increased artificial surfaces that reflect heat into the surrounding areas.
Most cities are built of concrete and glass in the forms of buildings, sidewalks, roads that are poor in conducting heat and reflect this heat onto more surfaces and the surrounding atmosphere, which creates an overall microclimate of heightened temperatures. In addition to this, buildings being spaced very close to each other also allow for no proper airflow. Lack of greenery reduces transpiration in the air and human pollution from vehicles, factories, and in the form of “waste heat”, worsen the condition.
A UHI also decreases the quality of air, since there is an increased level of pollutants in it. A UHI also worsens due to the absence of freshwater sources that are typically polluted in an urban setting. UHIs can reduce public health through heat waves, heat strokes, sleep deprivation, and increased mortality rates. The creation of ‘ectotherms that attract insects like ants, mosquitoes, lizards directly impacts the UHI.
Urban heat islands are one of the most basic examples of the human effect on nature and our planet. Many cities around the world are or have UHIs and the phenomenon is becoming an increasingly dangerous problem. While the building of structures, skyscrapers, streets, etc. is necessary, heat islands are also quite dangerous. Climate change and global warming are found to increase the effect of an urban heat island although there has been no research to believe that UHIs’ could be the cause for them.
With heightened temperatures, energy usage also raises a substantial amount of the population will use coolers and fans.
With the ever-growing population of the globe, large metropolitans are hubs for jobs, work, and easy access to a plethora of facilities where large numbers of people move into the developing cities from rural areas.
Some examples of which are:
New York City, USA
New York City is said to be about 4°C hotter than its surrounding areas, in the summer. While this may not sound too excessive, it can cause problems like dehydration, etc.
What was once known as “Garden City” with beautiful lakes and greenery has now turned into an Urban Heat Island owing to the vast number of concrete high rises, industrial parks, roads, and contamination of its lakes.
Las Vegas, USA
The city of Las Vegas, already present in the middle of a desert showed an increase of 7.3°F as compared to rural areas during the summer. This is because of the wide streets and pavement and buildings like the City Centre which are 100 floors of glass covered buildings that reflect a lot of heat to its surrounding areas.
While Urban Heat Islands pose a great ecological threat to society, they can be mitigated using various ways. With the increasing awareness of Climate Change, individuals and governments alike are recognizing the effect that UHIs have made developments in trying to reduce their influence.
The most basic way to reduce an Urban Heat Island is by planting trees and plants in public areas. Trees cause cooler microclimates and also help in ridding the air of toxins. Greenery can also be increased by planting them on rooftops and terraces. This is known as “Green Rooftops” and they also behave much like trees and in addition, keep the building below, cool.
Infrastructure-wise, many cities are using lighter shades of concrete and asphalt on streets and sidewalks. Either by painting or manufacturing custom, the lighter shades are less likely to absorb heat. For example, structures in small towns in Greece are all painted white and blue, to reduce the Urban Heat Island Effect. Planting hedges, bushes, and creepers along walls can have the same cooling effect. Furthermore, installing solar panels into rooftops and terraces can reduce heat reflection and also turn solar energy into electrical energy.
Urban Heat Islands are definitely a growing concern in all metropolises. While development is necessary to accommodate and keep up with human growth, it is important to consider the environmental effects of such developments which could be catastrophic in some aspects and have long-term negative effects. Using natural and artificial methods to mitigate these is paramount to have a balanced ecosystem where society can develop in a secure and peaceful environment.