Metropolitan Melting
Heat Islands are normally the result of a built-up, urban area that is hotter than surrounding rural areas. Average annual air temperatures in cities of with 1 million people can be 1-5 degrees Fahrenheit higher than circumferential expanses, in the evenings that difference can be up to 22 degrees. Heat islands develop when urbanization spreads, once permeable surfaces become dry and impermeable when buildings and infrastructure go up. Many of these impermeable surfaces are exposed to almost constant sunlight during the day and the materials they are made of absorb the light and heat, releasing it slowly into the atmosphere once the sun goes down.
Why the Fever Fervor?
Why do we care about the Heat Island Effect? Elevated temperatures from urban heat islands can have a negative affect a community’s environment and quality of life. Higher summer temperatures will create higher energy demand and need for cooling, which puts pressure on existing energy grids. It is estimated that heat island effect is responsible for a 5-10% hike in demand for electricity at peak times. In turn, increased energy demand results in increased emissions of greenhouse gases and other air pollutants from power plants. And higher temperatures encourages the development of an ozone layer at ground level. Hotter days and nights compounded with higher levels of pollution can contribute to heat related, cardiac and respiratory ailments. The heated impermeable surfaces transfer heat to stormwater which will find its way to streams, rivers, ponds and wetlands where rapid temperature increase can stress aquatic ecosystems.
Urban Oasis Opportunities
What can we do to counteract the effects of urban heat islands? Increasing tree and vegetative cover, using green roofs (also called roof top gardens or eco-roofs) or reflective materials for roofing and installing “cool” pavement materials are all steps in the right direction. Heat island mitigation is normally a part of a larger community action plan which will include the community’s efforts toward energy, air and water quality and sustainability. There are many opportunities for individual contribution for the reduction of heat island effects such as volunteer initiatives, organizing and/or attending product demonstrations and seminars, frequenting and becoming vocal at municipal committee or local government meetings and most importantly becoming educated about this issue. Visit the EPA’s site for more information on getting involved and ideas for heat island mitigation: http://www.epa.gov/heatisland/mitigation/index.htm
