Monday, September 1, 2008

Roof-top (Urban) Gardens

I have always been a strong supporter of roof-top gardens. They make sense in so many ways. Whether the garden is composed of vegetables, flowers, trees, grass, or a combination, they accomplish so many things just by being.

The urban garden is a rural escape in the centre of the city. Tenants of the building would be able to go up and enjoy the plantings and fresh air. If there is a vegetable component to the garden, it will help supply fresh produce to the tenants’ diets. Install a few tables and chairs, maybe a small utility room where a little tea or coffee could be brewed and it’s an instant, free, delightful place for the seniors, stay-at-home moms or others in the building to use an open-air social club. Not to mention, in summer, the roof-top garden will help absorb much of the sun’s heat and stop it from causing sauna-like conditions inside the building.

Contrastingly, in the winter, the garden acts as an extra layer of insulation to the building making it easier and cheaper to heat because less heat is lost. The roof-top garden can still be used occasionally in the less inclement weather. There will always be a few hardy souls (**me, me**) that will brave almost any kind of weather.

One of the most important contributions of urban gardens to the environment is that every roof-top garden will help to clean the surrounding air and lessen pollution in areas where they are plentiful.

It seems now that I am not the only one who has found a love for roof-top gardens. London, England’s mayor, Boris Johnson, has unveiled his secret weapon in the war on climate change. With the roof-top garden playing centre stage (absorption of rainwater), Mr. Johnson has developed a plan to help Londoners deal with global warming. This adaptation strategy is being billed as the worlds first and will address the challenges of flooding, extreme temperatures and drought.

Some of the components to this plan are compulsory water metering, greater awareness of flood risks, more tree planting, and stronger efforts to resist attempts by local authorities and insurance companies to fell existing urban trees.

A tree bank could be started to help maintain the older growth. Traditionally when trees are felled for a project, they are discarded and small saplings are planted around the project when finished. These larger trees could be removed with an intact root ball and sheltered. When the project is finished, some of the mature trees could be returned to be replanted. The other trees that could not be used could be passed on to other projects that require trees. Not only are mature trees more beautiful, they process more oxygen. Why wait years for these saplings to mature when the original can be returned with just a little effort?

The mayor and his team said they were also looking to copy a heat wave emergency plan used in US cities where old and vulnerable people are collected in air-conditioned buses and taken to cool public buildings, such as libraries, shopping centers, churches and offices. About 600 Londoners died during the 2003 heat wave that killed about 15,000 in France.

Johnson said he wanted to obtain the target set by the previous mayor, Ken Livingstone, to cut carbon emissions by 60% by 2025. His team will be introducing incentives for Londoners to better insulate their homes and switch to more efficient condensing boilers.

Fifteen per cent of London is at high risk from flooding due to global warming - an area including 1.25 million people, almost half a million properties, more than 400 schools, 75 underground and railway stations, 10 hospitals and London City airport. At stake is an estimated £160bn worth of assets, not just in London, but along the Thames estuary, where large housing developments are planned.

Boris Johnson has also promised to address the stifling summertime temperatures on the underground light-rail system. Air cooling on subsurface light-rail lines will begin in 2010. He says that all subsurface lines (approx. 35-40% of the system) will be air cooled by 2015.

The draft adaptation strategy, which will be finalized next year, calls for a citywide "urban greening" programmed, using green spaces and trees to absorb and retain rainwater (low rainfall during 2004 and 2005 led to water shortages in London), and pledges to map London's drainage network to reduce surface water flood risk. It also recommends greater use of rainwater harvesting and "grey water" recycling in new buildings, as well as London-specific guidance for designers and architects to reduce the risk of buildings overheating in summer.

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