Heat Islands

Last May 31, the City Government of Mabalacat held an event dubbed “Laro ng Lahi”. It was a friendly competition of traditional Pinoy games between city officials and employees. It was a day filled with fun and enjoyment as participants enjoyed being “kids” again.

Traditional Filipino games are rarely played today. One reason is that barangay roads and open spaces have been paved. How can you play the shato (stick game) and tambubung (patintero) on cemented roads? As progress and development seeps in, barangays, towns and cities are transformed into concrete jungles. While urbanization is good, it carries with it some unintended negative consequences. It’s not just the loss of playgrounds for kids, but something more. Urban areas become heat islands.

An urban heat island occurs when a place experiences much warmer temperatures than nearby rural areas. As areas develop, more vegetation is lost and more surfaces are paved or covered with buildings. The change in ground cover results in less shade and moisture to keep urban areas cool. Cemented areas also evaporate less water, which contributes to higher surface and air temperatures.

Structures such as buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies. Heat is also created by energy from all the people, cars, buses, and trains. Nighttime temperatures in heat islands is high because cemented areas block heat coming from the ground from rising into the cold night sky. Because the heat is trapped on lower levels, the temperature is warmer.

Heat islands increase demand for air conditioning to cool buildings. As demand for electricity increases, the emission of greenhouse gases and other air pollutants also goes up. Hot pavement and rooftop surfaces can heat up stormwater runoff which may raise the temperature of receiving bodies of water such as rivers and lakes. Rapid temperature changes can affect aquatic life.

Heat islands also contribute to heat-related deaths and heat-related illnesses such as general discomfort, respiratory difficulties, heat cramps, heat exhaustion, and non-fatal heat stroke. A recent study published in The Lancet and led by the Barcelona Institute for Global Health (ISGlobal), revealed that over four percent of deaths in cities during the summer months are due to urban heat islands. The study results were obtained with data from 93 European cities.

One simple way to mitigate the heat island effect is to plant trees. Trees and vegetation lower surface and air temperatures by providing shade and through evapotranspiration. According to the ISGlobal study, one third of the deaths could have been prevented by increasing tree cover up to 30%, thereby reducing temperatures.

According to the US EPA, the use of trees and vegetation in the urban environment brings benefits beyond mitigating urban heat islands including reduced energy use, improved air quality and lower greenhouse gas emissions, enhanced stormwater management and water quality, reduced pavement maintenance and improved quality of life.


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