Intro | Profile | Ecosystem Assessment
Condition: Fair to Poor
Capacity: Deteriorating
Urban ecosystems are dominated by human activities and the built environment, but they contain vital green spaces that confer many important services. These range from removing air pollution and absorbing runoff to producing food through urban agriculture. Urban forests, parks, and yards also soften the urban experience and provide invaluable recreation and relaxation. The science of urban ecosystems is new and there is no comprehensive data showing urban ecosystem trends on a global basis. However, more localized data show that loss of urban tree cover, and the consequent decline of urban green spaces, is a widespread problem. The rapid growth in urban populations worldwide adds to the mounting stress on urban ecosystems. Continued decline in the green elements of urban ecosystems will erode the other values — economic, educational, and cultural that cities offer. Urban population increases heighten the need to incorporate the care of city green spaces as a key element in urban planning.
Changes in Tree Cover in the Baltimore-Washington Corridor, 1973-97
Overall tree cover has declined steadily in the rapidly growing Baltimore-Washington, D.C., urban corridor in the eastern United States. Urban and suburban expansion, as well as diminishing budgets for urban tree care, have shrunk tree cover from 51% of the land area in 1973 to 37% in 1997. Land with heavy tree cover (less than 50% wooded) declined by one-third, while land with little or no tree cover increased by nearly 60%.
Source note: Data are from the companion book, World Resources 2000-2001: Ecosystems and People: The Fraying Web of Life and from Pilot Analysis of Global Ecosystems: Agroecosystems (World Resources Institute, 2000).
For comprehensive data about the world's ecosystems and their current conditions and trends, visit EarthTrends at www.EarthTrends.wri.org.
The Value of Ecosystems
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