Abstract
Abstract Urban land cover is dominated by impervious surface that degrades both terrestrial and aquatic ecosystems relative to predevelopment conditions. There are significant opportunities for designers of urban landscapes to use alternative land covers that have multiple functions, benefiting both human and nonhuman components of the urban ecosystem. Vegetated (green) roofs are one form of alternative land cover that has shown the potential to provide a variety of ecological benefits in urban areas. We evaluated how stormwater retention, building energy and temperature, and rooftop habitat are influenced by the use of green roofs using test plots in Georgia and Massachusetts. Green roofs were shown to recreate part of the predevelopment hydrology through increasing interception, stormwater storage, evaporation, and transpiration on the rooftop and worked extremely well for small storm events. Temperature reductions were found on the green rooftop as compared to an asphalt surface, although other roof technologies that minimize temperatures, such as lighter colored membranes, provide similar benefits. Novel habitat was created on the rooftop, although the extent of this habitat was limited in part by plant survivability and the need for additional water inputs for diverse plant communities to survive. Despite the challenges, the green roof benefits reported here suggest that green roofs can be used effectively as a multifunctional land cover in urban areas. Keywords Green roof; urbanization; stormwater; energy; habitat.
Highlights
In the past 40 years, the global human population has doubled to over 6.5 billion people, and the U.S population alone exceeds 300 million (US Census Bureau 2006)
Green roofs convert the impervious surface of a rooftop into multifunctional spaces in urban areas using vegetation, growing media, and specialized roofing materials
The modular green roof system was monitored from October 2004 – September 2005 and tested both total stormwater retention and the effect of plants and growing media on stormwater retention performance
Summary
In the past 40 years, the global human population has doubled to over 6.5 billion people, and the U.S population alone exceeds 300 million (US Census Bureau 2006). New residential subdivisions may use cluster development and other low impact development (LID) techniques to minimize impervious surface cover of the site (Arendt 2004) While this strategy is effective for areas experiencing urban growth, it is not always practical in urban areas that are already highly developed. Green roofs convert the impervious surface of a rooftop into multifunctional spaces in urban areas using vegetation, growing media, and specialized roofing materials This practice has been used expansively in Germany for over 30 years. This paper will evaluate the potential for extensive green roofs to provide increased ecological function in urban areas as compared to impervious surface rooftops by discussing two green roof case studies from the Southeastern and Northeastern United States as well as previously published data. We will discuss limitations of the current technology in replicating predevelopment land cover functions
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