A new study by American Forests has found that Southeast Michigan—defined as Wayne, Macomb, Monroe, Washtenaw, Jackson, Ingham, Livingston, Genesee, and Oakland counties—has suffered from a net decline in green infrastructure from 1991 to 2002. During that period, open space in the nine counties declined by 10% while urban areas increased by 21% during that time. Tree cover, which is directly tied to environmental quality as it can help reduce the need for expensive infrastructures to manage air and water resources, increased by just 2% in the region while tree canopies in the watersheds of important area rivers decreased. All counties in the study, with the exception of Livingston, lost a significant amount of open space.
The study further documents that from 1990 to 2000 land in Southeast Michigan developed three times faster than population increased, with tree cover in three watersheds—Ecorse, St. Claire, and Rogue—declining significantly between 1991 and 2002. As a result, storm water runoff has increased while air and water quality has decreased. It is estimated that the costs of addressing just problems with the regions sewer system to better handle storm water and sewage will cost the region $14 to $26 billion over the next 30 years. As development has moved from the city of Detroit to surrounding suburbs, 4,600 acres (66,000 lots) of previously-developed land is now vacant within the city of Detroit.