Urban Green Roofs as Wildlife Habitat

The world is rapidly urbanizing, and many previously biodiverse areas are now mostly composed of impervious surface. This loss of natural habitat causes wildlife communities to decline or become dominated by urban dweller and urban utilizer species and reduces the amount of habitat available for arthropods, migrating, and breeding birds and bats. Green roofs, roofs covered with a waterproof membrane, growing medium, and planted with vegetation, can increase green space in urban landscapes, potentially providing new habitat for wildlife. I use three different approaches to explore wildlife use of urban green roofs. I survey arthropods, an important food source for insectivores, and birds on green roofs and nearby comparable conventional (non-green) roofs in New York City. I found that arthropods were more abundant and taxonomically rich on green roofs than conventional roods and that birds were more active and species rich on green roofs than conventional roofs. In addition, I found that green roofs host more insectivorous urban avoider and utilizer bird species than conventional roofs. I also demonstrated, for the first time, that birds use green roofs as stopover habitat during migration. To further investigate the potential of green roofs arthropods as prey for insectivores, I examined the relationship between bats and their preferred prey, moths. To do this, I monitored bats and arthropods on a single large 27,316 m2 green roof. I found that moth abundance, while a relatively small proportion of green roof arthropods, correlated positively with bat activity. Finally, I investigated green roof age as a driver of bird activity and richness on small green roof plots over five years. Unexpectedly, I found that the green roof plots did not measurably increase bird activity and richness on the roofs, possibly due to the green space surrounding the roofs being of higher habitat quality than the green roof plots. While not all urban green roofs may provide the same benefits to wildlife, establishing green roofs in urban landscapes increases the amount of habitat available for wildlife and can partially mitigate the loss of habitat due to increasing urbanization