Impact of urban heat islands on humans, environment


THE urban heat islands (UHI) effect in Kuala Lumpur (KL) causes a staggering 6°C of temperature increase compared to rural areas with greener canopies and fewer buildings. In perspective, if rural areas with the abundant natural land and green canopy and fewer buildings have temperatures of 30°C, UHI in KL can increase the temperature up to 36°C.

UHI is a heat phenomenon that is common in urban areas and it occurs when areas of vegetation are replaced with heat-absorbing materials, such as concrete roads and buildings, and this matter would absorb and trap heat. Consequently, as urban population densities increase and green areas decrease, UHI becomes more intense.

Ir Dr Zambri Harun, Senior Fellow, and Chairman of the Department of Mechanical and Materials Engineering at Universiti Kebangsaan Malaysia (UKM) spoke to The Petri Dish concerning UHI in Malaysia.

“UHI is primarily caused by unrestrained anthropogenic or human activities. This includes cutting trees, constructing buildings very close to each other, and using asphalt to cover roads. All these factors entrapped heat within the cities making the city areas exceptionally hotter compared to rural areas,” said Zambri.

Based on the laws of physics, dark materials tend to absorb all wavelengths of light and convert them into heat which is why you sweat more if you wear darker clothes as heat is being absorbed into your clothes.

He said: “Naturally, people affected by UHI in the cities will install air-conditioners at their houses to fight off the sweltering heat but this creates a problematic cycle than a solution. As the temperature in the urban area reaches new heights, people become more reliant on air-conditioners.”

Air conditioners are power-hungry machines that use a lot of energy and release heat in the process. The dependency on air-conditioners as coolers create a feedback loop whereby as the temperature gets hotter, urbanites install more air-conditioners, and thus, more heat is radiated off to the environment.

Installing air-conditioners should not be the knee-jerk solution to heatwaves. What is even worst is air conditioners release chlorofluorocarbons that damage the ozone layer making earth inhabitants more susceptible to harmful ultraviolet rays.

When asked if climate change contributes to UHI, Zambri said: “Urbanites experience more extreme heat due to climate change and the increase in the number of vehicles in the city centre further aggravates the UHI.”

According to a report, the number of vehicles in the federal capital has increased from 26.51 million in December 2019 to 46.76 million in December 2021. More vehicles in the city result in higher greenhouse gas emissions such as carbon dioxide and methane in the atmosphere which entraps more heat within the localities of the city.

Nature-based approach and proper city planning should be the focus to tackle the issues.

“Instead of convincing people to not use the air-conditioners regularly as human behaviour is hardly controllable, proper city planning should aim to avoid overcrowding of buildings.

“Do not remove water bodies. A lot of water bodies in KL have been replaced with highways and buildings which results in UHI,” stressed Zambri.

Malaysia could benefit from more tree planting in resolving UHI as the green leaves are able to reflect off heat from the city during the day.

“Putrajaya has a UHI temperature of 2°C compared to 6°C in KL. This is attributed to strategic town planning that consists of the presence of water bodies, buildings are not crowded in one place and the trees are abundant and well-distributed within the city,” said the expert.

There is no major health impact from UHI, but the heat makes heat stroke-related disorders more common in the city, especially to vulnerable people such as young children and the elderly who are unable to cope with the rising temperature.

“The worry for UHI is not so much on its impact on human health but more to economic reasons due to enormous energy consumption and utilities cost to combat the blazing heat in the city,” added Zambri.

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