As watersheds are deforested, floodplains are constrained, stormwater is directed through pipes, and rivers are channelized, many ecological services are severely impaired. Flooding becomes more frequent, extreme, and expensive; the recreational benefits of surface creeks are lost; habitat is degraded; water quality is impaired; and wastewater treatment facilities may be overburdened.
Ecosystem services like water purification, flood control, recreational amenities, and climate stabilization are particularly valuable when provided to thousands of people in urban or rural areas. By recognizing such ecosystem services, it is possible to create economic and social incentives to preserve and restore them. They can be recognized as core features of an ecological infrastructure that meshes seamlessly with existing urban infrastructure.
The most critical part of the ecological infrastructure is the movement of water, stormwater, and wastewater throughout the city. The urban hydrological cycle begins with water captured and purified in nearby watersheds. Recent studies suggest that the water purification services provided by National Forest lands near urban centers rival timber harvests in economic value.
Ecological approaches to stormwater management treat rainwater as an important resource to be held on-site as long as possible. When residential and commercial developments employ permeable paving (e.g. paving tiles), rooftop rainwater catchment systems, or water-retaining eco-roofs, they allow water to infiltrate on-site, often after one or more uses. Neighborhood-scale gathering and infiltration of stormwater can be accomplished with bioswales (gentle drainage trenches planted with water-purifying vegetation) and retention ponds. Stream and wetland restoration, tree planting, and landscaping can all slow the flow of water, helping to smooth a storm's spike of rainfall into a gradual release lasting several days.
When stormwater management is properly integrated into the ecological infrastructure of a town or city, it can mitigate flooding and improve the quality of water entering local waterways. The flow of water through the city can be celebrated through a decentralized system of open spaces, restored creeks and wetlands, swales, and retention ponds. Such a system, combined with an emphasis on
Treepeople, in Los Angeles, has developed a series of rigorous design standards, engineering analyses, and cost-benefit studies for ecological stormwater management. They are now retrofitting homes and schools throughout Los Angeles, with very rapid payback on investment from improved water quality, stormwater retention and filtration, and the cooling effects of trees. They have developed an extraordinary collaboration with dozens of Los Angeles area bureaus and agencies, Trans-Agency Resources for Environmental and Economic Sustainability (T.R.E.E.S.), which is completely transforming the city's water and stormwater infrastructure.
Technologies like constructed wetlands and living machines extend ecological infrastructure to wastewater treatment. They rely on the inherent capacity of complex aquatic ecosystems to purify water, are cost-effective, and have been used successfully to treat sewage, refinery wastewater, dairy wastes, brewery waste, and many other wastestreams. They provide water of exceptional quality to downstream ecosystems.
Other pieces of the ecological infrastructure include urban forests and plantings which create favorable microclimates and purify the air; areas of restored habitat in parks and open spaces which form pearls in a Wildlife Corridor meeting up with regional systems of connected wildlands; and fire control services obtained by mimicking the effects of natural fires. Ecological infrastructure embodies the hope that cities and towns may function as ecosystems, purifying their own wastes, providing their own energy, metabolizing their own materials, and providing excellent habitat for human and other species.
Create an ecological infrastructure for cities and towns that partially replaces materials, energy, and engineering with the self-organizing intelligence of living systems.
Examples of this pattern in action:
A Living Machine is an effective and economical system for biological treatment of high strength industrial wastewater and sewage. Finished water from a Living Machine is clean enough for re-use applications such as irrigation or toilet flush water. Living Machines incorporate and accelerate the processes nature uses to purify water. With the help of sunlight and a managed environment, a diversity of organisms including bacteria, plants, snails, and fish break down and digest organic pollutants. Depending on the climate, Living Machines can be housed in a protective greenhouse, under light shelter or in the open air.
Noted landscape architect Cornelia Oberlander, ASLA, designed an extensive greenroof on top of the Liberty Square Building in downtown Vancouver, British Columbia (Landscape Architecture Magazine, May 1998). This application is a prime example of the purely aesthetic benefits provided by the welcome visual relief for the many high-rise office views. Blue and green fescues and kinnikinnick, a native ground cover, are planted to represent the local Fraser River flowing through the mountains. Although this greenroof is installed with a low-intensity irrigation system, it does not require fertilization or cutting. The grasses are raked at the end of the winter (Landscape Architecture Magazine, May 1998).
A bioswale is a drainage canal that diverts runoff water from the sewer into a natural area where native wetland plants help absorb and recycle it. Plants like grasses and rushes are commonly found in bioswales because they help to trap the water and force it to absorb, rather than flowing through the bioswale to the other side.
Organizations whose work incorporate this pattern:
Honachefsky, William B. Ecologically Based Municipal Planning. Lewis Publishers. Boca Raton, FL. 1999.
Matilsky, Barbara C. Fragile Ecologies: Contemporary Artists' Interpretations. Rizzoli Books. New York, NY. 1992.
Whole Earth Review, . Modern Landscape Ecology (Special Issue). Whole Earth Review. San Rafael, CA. Summer 1998.