The urban heat island (UHI) effect is a phenomenon experienced around the world.  It relates to metropolitan areas that are significantly warmer than the surrounding rural areas.

The UHI effect is caused by an increase in heat-absorbing, impervious surfaces such as concrete roofs, walls and pavements and a lack of green space within cities.  Heat is absorbed into concrete and asphalt during the day and released slowly throughout the night, leading to slower cooling rates.

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The UHI effect has the potential to adversely affect the health of residents.  Increased temperatures can cause heat stroke, exhaustion, syncope, and death.  As UHIs can lead to an increase in the magnitude and duration of heatwaves, the effect of heatwaves on health is often more pronounced in cities.

The City of Melbourne has recognised the effects that extreme heat is having on Melbourne and the health of its trees.  The Urban Forest Strategy, released in 2012, seeks to double canopy cover within the City of Melbourne over the next 20 years and improve vegetation health to protect against future vulnerabilities.  An aim of the strategy is to mitigate the UHI effect by bringing inner city temperatures down.

Another technique being explored is the greening of roofs.  Ecological artist Lloyd Godman has installed eight Tillandsia flowering plants at different levels of the 297-metre Eureka Tower in Melbourne.  The plants are native to South America and do not require soil or watering, instead soaking up water that falls on the leaves.  Two plants installed on the roof are thought to be the tallest ‘rooftop garden’ in the world, amazingly surviving 200 kilometres per hour winds.  The City of Melbourne is supportive of the idea, hoping that in the future buildings without green roofs or walls will look out of place in the City.

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While Melbourne is moving in the right direction, our European counterparts are once again one step ahead.  In March of this year a new law was passed in France that mandates all new buildings built in commercial zones must be partially covered in plants or solar panels.  The Growing Green Guide for green roofs, walls and facades was released by the State of Victoria in February 2014 but as yet, we do not have any clear green roof policies in our planning controls.

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Is this what the cities of the future will look like?  Above is an artist’s impression of what Melbourne might look like if it was covered in green walls and roofs.  The image was created by Anton Malishev as part of the City of Melbourne’s Urban Forest Art and Design competition.