Chris Riley, Dan Herms, and Mary Gardiner recently published a paper as part of a special issue of Urban Forestry and Urban Greening titled: Exotic trees contribute to urban forest diversity and ecosystem services in inner-city Cleveland, OH.
This study highlights the importance of vacant land to the urban forest – these sites had three times as many trees as residential sites! The majority of trees found on vacant land are exotic and naturally regenerated. This weedy forest, such as the tree-of-heaven individuals which have sprouted up alongside the abandoned building in the photo below are not traditionally thought to provide any benefits in their invaded ecosystems. But, in inner-city Cleveland exotic trees are providing many ecosystem services such as energy cost reduction, pollution removal and increased storm water infiltration. How the presence of these species influences the biodiversity of tree-dwelling herbivores and their predators in vacant lots is currently being investigated by Chris Riley.