Parklets create more green space in cities on the street level but what about fourteen stories in the air? Green roofs are becoming a popular addition to many homes, apartment complexes, businesses, and hotels. Similar to parklets, green roofs are an effective way of making ‘green’ already constructed space in an urban environment. While initially very expensive to develop, their upkeep overtime is minimal.
Several benefits of turning a rooftop into a sky-high garden full of soil and vegetation include reducing rainwater runoff by 50-90% and offering an additional habitat for insects and birds. They also help mitigate the urban island effect: a phenomenon where temperatures around and above urban environments are 2-12º C degrees warmer than surrounding rural areas. This is because of sealed and impermeable constructions like buildings and roadways. Green roofs help lower these temperatures because of plants’ evaporation and transpiration processes.
Recently, Walmart broke ground for a new store in Portland, Oregon, which will have the largest green roof in the state. The 90,000 square foot store will have a 40,600 square foot green roof. As well as helping the area with the aforementioned benefits, the city will use this space for soil testing. Using three different levels of soil depth in different areas, they hope to determine the most efficacious level to reduce rainwater runoff.
Ironically, this test could end up costing Walmart more in construction costs, claims one landscape architect: “The thicker the soil, the heavier the weight and the more structural upgrading to hold the weight,” he said. “That means more money for building.” However, Rachel Wall, senior manager of community affairs for Walmart says that despite the additional cost and construction: “We’re proud to incorporate [the green roof] as we continue to strive to create a more sustainable world.”
I can’t help but find this quote extremely ironic. Is it environmentally friendly to build a green roof on top of a store that destroyed 90,000 square feet of natural land? While I do not want to discredit Walmart’s initiative to create a green roof, I wonder about other ways that they are aiming to create a more sustainable world as the largest retailer in the world. Although they created a Sustainability Index of sustainable company goals, only 2% of their energy sources are from wind and solar power; their greenhouse gas emissions grew by 7% in the U.S. and nearly doubled in Asia between 2005 and 2009. While a green roof is a step in the right direction, green roofs cannot be the only answer to environmental sustainability.
Construction of a LEED building or furthering initiatives for more clean energy use would be better steps. I believe this example highlights one of the problems of environmentally friendly urban inventions: what are the necessary actions that need to be taken in tandem with these inventions? Recycling, clean energy, and zero waste need to be top priorities to create a truly sustainable life style. While concepts, such as green roofs, are great creations for urban life, they cannot be overvalued.
By: Megan Rilkoff