Green roofs create natural habitat as part of an urban wilderness. Even in high-rise urban settings as tall as 19 stories, it has been found that green roofs can attract beneficial insects, birds, bees and butterflies.  A recent list of the bee species recorded from green roofs (worldwide) highlights both the diversity of species, but also the (expected) bias towards small ground-nesting species (Hofmann and Renner, 2017). Rooftop greenery complements wild areas by providing stepping stones for songbirds, migratory birds and other wildlife facing shortages of natural habitat. Bats have also been reported to be more active over green roofs due to the foraging opportunities these roofs provide. Research at the Javits Center green roof in New York, NY, has shown a correlation between higher numbers of certain insects on the roof, particularly moths, with an increased amount of bat foraging activity. 
Green roofs also serve as a green wall, filtering pollutants and carbon dioxide out of the air, helping to lower rates of diseases such as asthma. They can also filter pollutants and heavy metals out of rainwater.