Ecosystem Services

Stormwater wetlands provide a variety of ecosystem services, defined as the benefits people obtain from ecosystems. The services provided by stormwater wetlands range from removing pollutants in runoff to providing importatn habitat for insects that prey upon mosquitoes. Find out more about these beneficial services in the following sections.

• Water Quality
• Flood Control
• Carbon Sequestration
• Biodiversity
• Recreation
• Education

Water Quality- Stormwater wetlands employ a combination of physical, chemical, and biological processes to remove pollutants carried by stormwater runoff.  These pollutants include sediment, metals, motor oil, pathogens and excess nutrients.  Wetland plants help to slow incoming runoff, allowing sediment and other particles to fall out of suspension and settle in the wetland.  Plants may also directly take up nitrogen and phosphorus in runoff to fuel their own growth.  Bacteria living in association with wetland plants and sediment are especially important in providing water treatment services.  Bacteria break down hydrocarbons such as oil and remove excess nitrogen from the water through a process called denitrification.  By providing this service, stormwater wetlands help protect downstream aquatic ecosystems for use by wildlife and people alike.     

Flood Control- Impervious surfaces such as roads and rooftops increase both the volume and velocity of surface runoff, which leads to more frequent flash flooding in urban areas.  Stormwater wetlands are designed to store a portion of this surface runoff and release it slowly over a period of 2 to 5 days.  By regulating the hydrology of urban runoff, stormwater wetlands can help reduce frequent small floods and reduce erosion in stream channels caused by high runoff velocities.  

Carbon Sequestration- Concerns over global climate change have increased the societal value of ecosystems that sequester, or store, carbon over long periods of time. Wetlands provide an ideal environment for carbon sequestration. Wetland plants remove carbon dioxide (CO2), an important greenhouse gas, from the atmosphere through photosynthesis as they are growing. When the plants die, some of the carbon they captured over their lifetime is released back to the atmosphere through decay. However, some carbon is incorporated into wetland sediments, the low oxygen environment of which slows decomposition processes, and is stored long-term in the wetland. Since the runoff entering stormwater wetlands is enriched with nutrients from the urban landscape, these constructed ecosystems can support a productive plant community with the potential to accumulate large quantities of carbon over time. It should be noted that the same saturated, anaerobic soil conditions that contribute to carbon storage in wetlands also promote methane (CH4) generation by bacteria living in wetland sediments. CH4 is a potent greenhouse gas, though the quantity produced in stormwater wetlands has not been measured.

Biodiversity- Stormwater wetlands can provide important habitat for plants, insects, amphibians, birds, and other animals that is otherwise lacking most urban landscapes. Through such habitat provision, stormwater wetlands can contribute to the biologic diversity in urban and suburban areas. Biodiversity is an important part of most ecosystems as it underpins the provision of many other ecosystem services. For instance, diverse plant and benthic macroinvertebrate communities may improve nutrient cycling and removal in stormwater wetlands and have increased resilience against disturbances such as drought or disease. Stormwater wetlands can support a diverse community of aquatic insects and fish that prey upon mosquito larvae, providing an important pest control service.

Recreation- Stormwater wetlands can provide a place for community members to participate in recreational activities. Many wetland plants produce colorful flowers that attract dragonflies and birds, making stormwater wetlands an ideal place to observe wildlife within urban and suburban areas. Walking trails and boardwalks can be installed in stormwater wetlands treating runoff from neighborhoods or parks to provide community members a place to stroll and enjoy the aesthetic component of these constructed ecosystems.  

Education- Stormwater wetlands can also be utilized as educational amenities. Like their naturally-occurring counterparts, stormwater wetlands are complex ecological systems and provide a site for hands-on learning. For example, a stormwater wetland installed at the Smithfield-Selma High School in Smithfield, NC has been integrated into the school’s environmental science program, where students collect water quality data, identify wetland flora and fauna, and learn about wetland functions and processes. Educational signs can be placed at any stormwater wetland to inform the public about the beneficial suite of services these ecosystems provide.