Urban Wetland Restoration: Creating Room to Grow
While walking in a large city, one may encounter fish and wildlife, remnants of the city’s past, in unusual places. Instead of cliffs or tree hollows, peregrine falcons now nest on skyscrapers and bridges in New York City. A few salmon and steelhead trout still return to streams in San Francisco. A great blue heron nesting colony can be found near the developed shores of Seattle’s Ship Canal. These are just a few examples of urban wildlife that continue to survive and adapt in cities throughout the country.
These species, though adaptable, depend on small pockets of tranquil habitat that remain within the urban setting, such as parks, backyards and, in more recent times, urban restoration sites.
Habitat loss is one of the leading causes of the overall decline in plant and animal populations. More than 1,300 species are listed as threatened or endangered under the Endangered Species Act. Species loss is often greatest in the most highly developed areas, such as urban centers and their surrounding suburbs. Despite significant habitat loss and reduced biodiversity in cities, however, many wildlife species persist, thanks in part to these new urban restoration efforts.
Such efforts are growing nationwide in both private and public arenas. With increasing awareness about global climate change, people are beginning to recognize the important role the natural world plays in their daily lives. With that awareness comes a renewed sense of responsibility and the desire to improve habitat.
Wetlands often serve as transitional zones between upland areas and aquatic environments such as lakes, rivers or streams; however, they can also exist as isolated pockets in forests, fields and urban areas. Wetlands serve as breeding grounds, foraging areas or migration corridors for a variety of invertebrate, fish, amphibian, bird and mammal species. Wetland vegetation in riparian and shoreline areas creates shade to help keep water cool and is used as cover by birds, fish and other aquatic species. Woody debris such as snags and downed trees are common in wetlands and provide shelter and nesting areas for birds and mammals.
As a transitional ecosystem, wetlands serve a variety of functions. They play a key role in hydrologic processes, feeding lakes and streams, recharging groundwater aquifers and providing stormwater retention and erosion control. During heavy precipitation events, wetlands help to control flooding and can retain up to 1.5 million gallons of water per acre, according to the U.S. Environmental Protection Agency (EPA), releasing it slowly over time to connected aquatic systems such as lakes and streams. The natural ability of wetlands to reduce flooding helps protect the integrity of habitat structures in aquatic environments, such as fish spawning beds, which are often washed away by fast-moving storm flow.
Wetlands also serve an important function in the cycling and storage of nutrients such as nitrogen, carbon, sulfur, iron and manganese, converting them into forms that can be absorbed through plant roots and making them available to other organisms higher up the food chain. Wetlands also improve water quality. Soils and plants in wetlands provide natural filtration, removing contaminants from surface water and groundwater. Chemicals such as chlorinated compounds and hydrocarbons can be removed naturally in wetland systems through absorption, degradation or volatilization.
Early losses were primarily associated with the drainage and reclamation of land for agricultural purposes. Settlers believed that wetlands created “swamp vapors” and caused fevers and illness because they provided breeding grounds for mosquitoes, vectors of malaria and dengue fever; therefore, wetland drainage was encouraged. Settlers drained much of the land in Virginia and the Carolinas, for example. Later, as industrialization consolidated populations into urban centers, such as in Chicago and Miami, wetlands were drained to increase the land available for development. Lands along rivers and bays within developing cities were desirable locations for manufacturing and processing operations because they provided easy access to open water, which was essential for transporting goods. It was against this backdrop that “wetlands” became synonymous with “wastelands” — land that needed to be converted to a useful purpose.
As a result, many urban waterways have been engineered to make them more suitable for industrial, commercial and transportation activities, leading to an almost complete wetland loss in many urban areas. The dramatic reduction in wetland acreage nationwide has translated into losses of important habitat areas and other wetland benefits, as evidenced by declining fish and wildlife populations, increased flooding during storm events and declining water quality in rivers, lakes and bays.
Under the Clean Water Act, the protection of remaining wetlands is handled through federal, state and local regulations designed to prevent further losses and mitigate for unavoidable damages to wetlands. Individual states build on the federal policies and often implement additional regulations that are more stringent than federal policies. Local jurisdictions, such as counties and cities, can also enforce wetlands regulations through their authority over land-use management.
A major component of federal wetlands regulations is mitigation, whereby proposed projects must first attempt to avoid and minimize their impact on wetlands, and any unavoidable impact must be addressed during the permitting process (see sidebar). Permitted wetland losses must be offset through mitigation efforts. Parties applying for wetland permits must demonstrate that they have made every practicable attempt to avoid wetland impacts before mitigation will be considered.
Since the implementation of the Clean Water Act and wetlands mitigation practices, mitigation has generally focused on the property where the proposed impact will occur, adhering to the practice of keeping the mitigation activities onsite. Furthermore, federal guidelines generally call for “in-kind” mitigation, meaning that the newly created or restored wetland be of the same class or type — generally based on position in the landscape, water regime and vegetation type — as the original, affected wetland. Though well-intentioned, in many instances, these mitigation policies lead to the creation of small, low-functioning wetlands, stifled by poor hydrology, invasive species infestations or other factors. According to the Interstate Technology and Regulatory Council, only 30 to 50 percent of wetland mitigation projects are considered successful. Thus, these mitigation projects often fail to meet their goals of replacing the acreage and functions lost when the original wetland was affected. All is not lost, however, as urban restoration is on the rise and is beginning to help create and restore wetland habitats within urban areas.
Moreover, the presence of urban wetlands offers opportunities for people to learn about and enjoy natural areas close to home, which elevates the social value placed on them. After walking along Whatcom Creek in Bellingham, Wash., for example, and seeing salmon swim up the stream, people become aware of the other species that share their home.
Efforts to restore wetlands in urban areas around the country are on the rise. For example, the Duwamish River in Seattle, Wash., is a wetlands ecosystem that was altered to accommodate shipping in the early 1900s. Located on Puget Sound, the Lower Duwamish Waterway once comprised hundreds of acres of wetlands and marsh habitat. To better serve the needs of a growing city, the river channel was straightened and dredged, and the surrounding wetlands area was drained and filled, eliminating 98 percent of the existing tidal flats, marshes and swamps.
The Passaic River in New Jersey faced a similar situation. According to the Hudson River Foundation, 80 percent of the New York/New Jersey estuary complex, of which the Passaic River is part, has been filled in or dredged for urban and industrial purposes.
Current plans and efforts to restore both of these areas are focusing on creating intertidal, estuarine and other wetlands habitats that will benefit resident and migratory fish, birds and terrestrial wildlife. For example, the Hamm Creek Estuary Restoration Project, a collaborative effort between public and private groups, was initiated to restore this tributary of the Duwamish Estuary. The project restored part of the salt marsh, freshwater wetlands and stream channel, returning one portion of this historical river system to salmon, birds and other wildlife. In the New York/New Jersey Harbor system, the Harbor Estuary Program has identified impacted wetlands areas in eight watersheds for restoration.
Wetland restoration efforts will play an important role in the survival and recovery of wildlife in urban areas. These efforts have to involve both cooperation and collaboration of stakeholders, including local governments, private landowners, scientists and the local community. Each piece of urban habitat connected to another, like pearls on a string, creates critical sanctuary for the peregrine falcon, salmon, trout, the great blue heron, and every other species trying to survive in our nation’s cities and suburbs.