Uban areas face numerous environmental challenges because of their dense human populations and high percentage of impervious surfaces, such as rooftops and parking lots. As world population increases and urban populations expand, finding solutions to environmental issues becomes increasingly imperative to maintain viable and habitable cities.
Despite consisting largely of a built environment, urban areas still may contain diverse ecosystems, all of which provide various services that help maintain life. Trees, parks, gardens, rivers, streams and lakes offer air filtration, noise reduction, food production, micro-climate regulation, rainwater infiltration, flood control and recreation. Finding ways to improve, expand or increase the number of urban ecosystems may offer solutions to many environmental challenges.
Green, or vegetative, roof systems are one of the ways we can introduce and improve ecosystem services in urban areas. Vegetative roofs can manage storm water runoff, reduce energy use and noise, mitigate the urban heat island effect, alleviate air pollution, increase biodiversity and wildlife habitat, and add value to a building.
In 2010, in Green Roofs for Healthy Cities' annual vegetative roof industry survey of member companies, more than 710 reported projects representing 4,341,394 square feet of vegetative roof systems were installed in North America. This number is up from 2,051,736 square feet reported in 2009 and represents a significant industry growth rate. In 2010, Chicago vegetative roof space increased by more than 500,000 square feet, and in Toronto vegetative roof space increased by more than 400,000 square feet. With urban roof systems being installed or replaced annually, the potential for vegetative roof system use in the urban, built environment is an open market.