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'Green roofs' prove even more effective in fighting global warming than first thought

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September 24, 2009

'Green roofs' like these rooftop gardens atop the Rockefeller Center may go a long way to ...

'Green roofs' like these rooftop gardens atop the Rockefeller Center may go a long way to reducing harmful greenhouse gases (Photo: David Shankbone)

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You only have to watch a TV show in which the camera flies over any major city to realize the numbers of ugly, stark, gray, flat roofs that occupy millions of square feet but contribute nothing to the environment. It’s almost an ‘out of sight, out of mind’ attitude we have with these unoccupied spaces. But what if we could turn these wasted environments into something beneficial to the environment, while at the same time beautifying the tops of our tall buildings and skyscrapers? ‘Green roofs’- urban rooftops covered with plants - are gaining in popularity to help buildings reduce their reliance on air conditioning, and now scientists in Michigan are reporting they could also help fight global warming by eliminating carbon dioxide in cities, more effectively than was first thought.

Previous studies have indicated that painting roofs white can be a low tech way to reduce global warming by reflecting the sun's rays back into space and Prof Steven Chu, the U.S. Energy Secretary, has been heralding the idea.

Now researchers have attempted to quantify the benefits of covering urban rooftops with plants. The scientists found that replacing traditional roofing materials with ‘green’ in an urban area the size of Detroit with a population of about one-million, would be equivalent to eliminating a year's worth of carbon dioxide emitted by 10,000 mid-sized SUVs and trucks. Their study is the first to examine the ability of green roofs to sequester carbon that may impact climate change and the findings are scheduled to appear in the journal Environmental Science & Technology.

Multi-functional

While many researchers understood that green roofs were multi-functional because of their ability to reduce heating and air conditioning costs, detain stormwater and absorb carbon dioxide, it wasn’t until Kristin Getter and his colleagues’ new study that anyone knew how big a positive impact green roofs could have on reducing green house gases, which contribute to global warming.

The scientists measured carbon levels in plant and soil samples collected from 13 green roofs in Michigan and Maryland over a two-year period and found that green roofing an urban area of about one million people would capture more than 55,000 tons of carbon, or the same effect as removing more than 10,000 mid-sized SUVs or trucks off the road a year.

Imagine how much more carbon dioxide could be removed if urban environmentalists and town planners incorporated vertical landscaping into their the cities, like we highlighted recently in Gizmag.

6 Comments

I tried this on a shed roof in the uk,,,,,,,apart from making the roof look natural,,,,,,,,it was good to see flowers where only corrugated iron was before

robinyatesuk2003
24th September, 2009 @ 07:45 am PDT

I am really happy to see this study come out. Cities around the world, such as Paris, Shanghai, Chicago, and New York, have been enjoying the benefits of green roofs for many years. Not only do they reduce air pollution and the urban heat island effect, they also reduce storm water runoff. Funny enough, they also improve the performance of solar cells (http://cleanerairforcities.blogspot.com/2009/06/combining-solar-and-green-roofs.html)

Green roofs are required by law in Switzerland, Tokyo, and now Toronto.

gormanwvzb
24th September, 2009 @ 09:03 am PDT

"The scientists found that replacing traditional roofing materials with "˜green' in an urban area the size of Detroit with a population of about one-million, would be equivalent to eliminating a year's worth of carbon dioxide emitted by 10,000 mid-sized SUVs and trucks."

This is an example of a remarkably common misuse of statistics. The sentence doesn't make sense because it doesn't tell us what length of time it takes for the roofs to save that CO2 (1 second? 10 years? 1,000,000 years?). If it is one year then the sentence should be:

"The scientists found that replacing traditional roofing materials with "˜green' in an urban area the size of Detroit with a population of about one-million, would be equivalent to eliminating the CO2 generated by 10,000 mid-sized SUVs and trucks."

Sorry, but for some reason this type of thing really annoys me.

felix
25th September, 2009 @ 01:06 am PDT

So let me get this straight. By going to the huge expense of putting green roofs on every last structure in a city of 1,000,000 (let's say, conservatively, $500 per roof for 500,000 structures, for a cost of $250,000,000, we get savings equal to removing 10,000 cars - or, about ! to 2 % of all the probable vehicle base in that city. Why would anyone find this impressive? We could just give each of those motorists a $100,000 bribe not to use their cars again and be hundreds of millions of dollars ahead.

Lynn Becker
28th September, 2009 @ 09:00 am PDT

They'd probably buy a plane/ship/space rocket with the $100,000 and that's worse. OR hire someone to drive them around in a hummer.

Shaun Goh
30th September, 2009 @ 03:55 pm PDT

Green roofs are catching up in China,USA and elsewhere.

Dr.A.Jagadeesh Nellore(AP),India

Anumakonda Jagadeesh
3rd February, 2011 @ 06:12 am PST
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