So apparently, plants can do it all. I knew that vegetation aided in ridding the air of pollutants, but I thought it was to a limited extent- not to up to 711,000 metric tons per year per urban city. I think the numbers in support for green roofs speak for themselves; if 20% of all buildings in DC built green roofs, the result on the decrease in air pollution would be the same as if we were to plant 17,000 street trees. In addition to all the air benefits that green roofs provide, I was sold by the practicality aspect of implementing them as well. The conventional roof lasts for about 20 years and when they need to be replaced, the old roof will take up space and leach pollutants; green roofs last 45 years longer and are therefore more cost effective. The further I read through the article, the more and more benefits I saw green roofs can offer- from the possibility of urban rooftop agriculture to positive effects on human health.
After reading about all of the great things green roofs do for us, I couldn’t seem to understand why there weren’t more of them in the city, and I was glad to see that addressed in the last paragraph. Strictly speaking in terms of money costs I understand that a green roof is more expensive at first glance but if you factor in the effects on stormwater, energy, and air pollution, it’s pretty fair game to say that green roofs are more cost effective in the long term. If we’re thinking about spending a little extra money on a green roof now, we won’t have to think of some even more drastic, and probably more expensive, method to combat increased levels of carbon dioxide when they get to a higher deleterious level. After looking at how green roofs would benefit NYC in particular, I found that their absorbent property is of integral importance to us. Because the city is built on islands around a harbor and two rivers, we have long struggled with excessive run-off after heavy downpours, so our drainage systems are often overwhelmed and overflowed with raw sewage. Green roofs’ ability to alleviate this issue by being able to absorb up to 70% of the rainwater that would otherwise drain away, is one of the most helpful things to the city.
