Multiple benefits of green infrastructure and role of green infrastructure in sustainability and ecosystem services

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Human activities can negatively impact hydrologic and chemical cycles, pollute air and water, degrade soil, and reduce biodiversity. Failure to maintain basic ecosystem functions places humans at risk because of our dependence on these functions. As human populations and resource consumption increase, it becomes even more important to preserve basic ecosystem functions. Sustainability is the principle and practice of creating and maintaining the conditions under which humans and nature can exist in productive harmony to support present and future generations. Green infrastructure is one tool or approach to creating sustainable urban environments.

What are ecosystem services?

Harvesting rain water and using it to grow vegetation is an example of a provisioning service, with water being the product obtained. Photo by MWMO Staff. To enlarge,click on image.

The natural environment provides basic services required for humans and all life to survive. These ecosystem services can be divided into four basic categories or types ([1], [2], [3]).

• Supporting services are basic services needed to support all other ecosystem services. An example is primary production, which is the production of organic compounds from carbon dioxide. Plants and algae are largely responsible for primary production. Other examples of supporting services are nutrient cycling and soil formation. These services provide basic materials needed by organisms.
• Provisioning services are products obtained from ecosystems, such as food, minerals, lumber, energy, medicines, and water. It is these services that humans typically rely on for economic purposes and to improve quality of life. The concern is that in utilizing provisioning services we degrade other services.
• Regulating services ensure the continued availability of other ecosystem services. Examples include purification of air and water, waste composition, and climate regulation. Humans often stress these systems. for example, introducing too much phosphorus into a lake impairs the ability of the lake to regulate the growth of algae.
• Cultural services are unique to humans. Though not essential to survival, they are important for human well-being and development. Examples include the use of ecosystems for recreation, scientific development, and education.

Numerous studies attempt to place a dollar value on ecosystem services, though the value of these services is infinite in the sense that human survival depends on them. Costanza et al. (2014) place an annual value of 125 to 145 trillion dollars on ecosystem services, which is more than double the global GDP. The authors also estimate an annual loss of 4.3 to 20.2 trillion dollars, underscoring the negative impact humans are having on basic ecosystem functions necessary for our well-being.

Sustainability

Vegetation on the Target Center Arena green roof. Vegetation consisted of a pregrown Sedum mat supplemented with 22 species of plugs and 16 species of seed native to Minnesota’s bedrock bluff prairies. Image Courtesy of The Kestrel Design Group, Inc.

A central tenet of sustainability is that we must preserve ecosystem services necessary for humans to survive and prosper. In 1987, a World Commission on Environment and Development report (UN, 1987) defined sustainable development as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs".

A challenge is incorporating basic sustainability concepts into social and economic systems. These systems historically have not placed proper value on ecosystem services, resulting in the degradation of these services. For example, stormwater in urban areas was traditionally viewed as something that negatively impacted humans, primarily through flooding. Traditional stormwater systems were designed to discharge stormwater to the nearest receiving water as quickly as possibly. The result was a dramatic change in urban hydrology, increased flooding downstream, reduced water quality, and loss of habitat. Sustainability stresses using stormwater as a resource. Using stormwater as a resource restores some natural resource function and provides economic and social benefit. Sustainable practices achieve a balance between environmental, social, and economic factors.

Relationship of green infrastructure to ecosystem services and sustainability

Green infrastructure is an approach to managing urban wet weather impacts that mimics, restores, or maintains natural hydrology. Green infrastructure includes a wide array of practices, including infiltrating, evapotranspiring, or harvesting and using stormwater. On a regional scale, green infrastructure is the preservation or restoration of natural landscape features, such as forests, floodplains and wetlands. On the local scale, green infrastructure consists of site and neighborhood-specific practices, such as bioretention, trees, green roofs, permeable pavements and cisterns. Regional and local practices are coupled with policies such as infill and redevelopment that reduce overall imperviousness in a watershed.

Green infrastructure is an important component of sustainable urban communities. Green infrastructure helps maintain ecosystem services in the following ways.

• Air quality regulation: Potential of ecosystems to capture and remove air pollutants in the lower atmosphere.
• Erosion protection: Potential of ecosystems to retain soil and to prevent erosion and landslides.
• Water flow regulation: Influence ecosystems have on the timing and magnitude of water runoff and aquifer recharge, particularly in terms of water storage potential.
• Pollination: Potential of animal vectors (bees being the dominant taxon) to transport pollen between flower parts
• Maintenance of soil structure and quality: The role ecosystems play in sustaining the soil's biological activity, physical structure, composition, diversity and productivity.
• Water purification: The role of biota in biochemical and physicochemical processes involved in the removal of wastes and pollutants from the aquatic environment
• Climate regulation: The influence ecosystems have on global climate by regulating greenhouse and climate active gases (notably carbon dioxide) from the atmosphere.

The following section provides detailed information on each of these. For more information on stormwater green infrastructure practices, link here.

It is beyond the scope of this page to describe in detail the relationship between green infrastructure, sustainability, ecosystem services, and stormwater. Some suggested references on this topic are provided below.

• Mapping green infrastructure based on ecosystem services and ecological networks: A Pan-European case study - the paper presents a methodology that can be used to identify and map GI elements at landscape level based on the notions of ecological connectivity, multi-functionality of ecosystems and maximisation of benefits both for humans and for natural conservation.
• Using the Concepts of Green Infrastructure and Ecosystem Services to Specify Leitbilder for Compact and Green Cities—The Example of the Landscape Plan of Dresden (Germany) - this study applies the concepts of green infrastructure and ecosystem services to develop a guideline for landscape planning to foster compact and green cities. The guideline was tested on the example of the landscape plan of Dresden, Germany.
• Enhancing Sustainable Communities with Green Infrastructure - this EPA documents provides a good discussion of green infrastructure and sustainable communities. The document provides strategies that support sustainable communities and green infrastructure.
• The Multifunctionality of Green Infrastructure - this report describes the different functions that GI seeks to execute and explores the scientific evidence behind its ability to perform these functions, using case studies where available. Stormwater is not a focal point of this report.
• The Value of Green Infrastructure - A Guide to Recognizing Its Economic, Environmental and Social Benefits - this guide distills key considerations involved in assessing the economic merits of green infrastructure practices. There is a chapter devoted to water-related aspects of green infrastructure.
• The Economic Benefits of Green Infrastructure
• Promoting ecosystem and human health in urban areas using Green Infrastructure: A literature review - this paper discusses the possible contributions of urban and peri-urban green space systems, or Green Infrastructure, on both ecosystem and human health
• From Multifunctionality to Multiple Ecosystem Services? A Conceptual Framework for Multifunctionality in Green Infrastructure Planning for Urban Areas - this paper explores how multifunctionality as one important principle of green infrastructure planning can be operationalized by approaches developed and tested in ecosystem services research.

Environmental benefits of green infrastructure

An increasing focus on Green Infrastructure has brought an awareness that stormwater management can provide numerous benefits beyond improving water quality and urban hydrology. Trees, for example, provide a multitude of benefits beyond stormwater management, as discussed in this article. In particular, vegetated stormwater best management practices (BMPs), including tree-based systems and other bioretention systems, offer opportunities to achieve multiple benefits, ranging from aesthetics (see, for example, this presentation by Dr. Steven Rodie from the University of Nebraska - Omaha) to ecosystem friendly designs.

Impact on pollinators

Mississippi River WMO video on plant ecology of the Mississippi River Gorge in the Twin Cities

Rainfall from the roof on this house is routed to a perennial garden containing, among other plants, goldenrod, milkweed, and purple coneflower, all of which are considered pollinator-friendly plants.

It is clear that pollinators, both vertebrates and invertebrates, are in decline (see [4], [5], [6], [7], [8]). Vegetated stormwater BMPs can be designed to be pollinator-friendly. The following sections provide numerous links to information that can be used in designing and implementing pollinator-friendly stormwater BMPs.

Pollinator friendly plants

• Minnesota Stormwater Manual
• Metro Blooms: Planting for Pollinators: How Raingardens Can Help
• The Xerces Society for Invertebrate Conservation: Pollinator plants - Great Lakes Region
• Pollinator Partnership: Ecoregional Planting Guides
• United States Department of Agriculture - Forest Service: Attracting Pollinators to Your Garden Using Native Plants
• National Wildlife Federation: Plants for Pollinators: A Collection of Favorites
• Deeproot: Want Pollinators? Plant Trees
• Native Seed Mix Design for Roadsides: Minnesota Department of Transportation

Pollinator friendly practices

Although much of the information on these pages is general, many of the practices can be incorporated into vegetated stormwater BMPs.

• United States Department of Agriculture - Forest Service: Pollinator Friendly Practices
• North American Pollinator Protection Campaign: Pollinator Friendly Practices
• Institute for Agriculture and Trade Policy: A landowner’s guide to pollinator-friendly practices

Case studies

• Andover Pollinator Awareness Project
• Penn State Extension
• Penn State University: Pollinator Garden Certification

Other links

• NEW!!! The Environmental Quality Board recently released a Minnesota State Agency Pollinator Report. The Report includes three specific goals in areas where state agencies have the greatest potential to reduce stress on pollinators.
• The Board of Water and Soil Resources has a Pollinator Plan that includes why pollinator populations and habitat restoration matter, current protection and restoration efforts, native seed mixes, a fact sheet and a solar site pollinator habitat assessment form.
• The Xerces Society: Targeted for gardeners, this site contains much useful general information on pollinators and managing for pollinators
• Pollinator Friendly Alliance
• Board of Water and Soil Resources Pollinator Toolbox

Carbon sequestration

Carbon sequestration is the capture and long-term storage of carbon from atmospheric carbon dioxide. Sequestration occurs in plants and soil. Carbon sequestration is often discussed in the context of climate mitigation, but there are numerous benefits to increased carbon (organic matter) content in soils, including improved soil structure, infiltration through soil, nutrient retention and cycling, and pollutant attenuation.

The primary mechanism of carbon sequestration is through enhanced vegetative growth. Nowak and Crane (2002) estimated that, in 2002, urban trees stored 700 million tonnes of carbon with a gross carbon sequestration rate of 22.8 million tonnes of carbon per year. They estimated the average urban forest carbon storage density was 25.1 tonnes of carbon per hectare, compared with 53.5 tonnes of carbon per hectare in forest stands. This illustrates that urban forests store considerable carbon, but also that there may be opportunities for further increases in carbon storage.

Management activities can promote carbon sequestration in urban soils. Examples include leaving grass clippings and growing perennial gardens (see [9], [10]). Practices that promote deep rooting of vegetation establish stable carbon forms that extend deeply into the soil.

Jo (2001) presents the following strategies for green infrastructure practices that promote carbon sequestration in urban settings.

• Available growing space and planting potential could be increased by locating parking lots and above-ground utility lines below ground.
• Multi-layered plantings, in which herb, shrub, and tree layers overlap, would increase C storage and uptake per unit area, andmaintain amulti-aged tree structure to promote continuous C uptake over time.
• Ordinances should be amended to increase greenspace area in urban lands.
• Tree species that have high growth rates, even under adverse urban growing conditions, should be planted. Broad-leaved tree species have higher growth rates than conifers and shrubs.
• Natural lands, in which C storage and uptake per unit area are significant, should be conserved.

Brown et al. (2011) present strategies for minimizing the carbon footprint of urban areas. An important stratgey is better utilizing organic wastes generated within the urban landscape, including land application of organic waste.

Numerous stormwater activities can promote carbon sequestration. These include use of bioretention, tree trench/tree box, green roofs, and constructed wetland practices to treat stormwater runoff, improving soils and turf, and disconnecting impervious surfaces. Note that some stormwater practices, such as bioretention and green roofs, may export carbon, particularly in the first years after establishment. In addition, construction and maintenance of stormwater control practices leads to carbon emissions that can offset carbon sequestration. Moore and Hunt (2013) state "Despite accounting for sequestration by vegetation in these systems, only stormwater wetlands and grassed swales were predicted to store more carbon than what was released through construction and maintenance".

Additional information on stormwater management and carbon sequestration can be found in the following articles and reports.

• Carbon Sequestration Potential of Extensive Green Roofs
• Ecosystem service provision by stormwater wetlands and ponds – A means for evaluation?
• Assessing Soil Carbon Sequestration in Turfgrass Systems Using Long-Term Soil Testing Data
• The capacity of roadside vegetated filter strips and swales to sequester carbon

Maintaining ecosystem functions

pollination, carbon storage, hydrology, pollutant management

Enhanced biodiversity

The National Wildlife Federation defines biodiversity as the variety of life. Biodiversity can be considered at many levels, ranging from individual species to communities, landscapes, and ecosystems.

Biodiversity is important to ecosystem health, which in turn allows ecosystems to deliver services that humans require. Some of the benefits of enhanced biodiversity include the following.

• Provides for an array of foods and materials
• Provides medicines
• Enhances the delivery of ecosystem services, such as purifying air and water
• Provides resilience to ecosystems, which allows them to withstand disturbances (e.g. fires, diseases)
• Provides aesthetic and recreational value for humans

Biodiversity almost always decreases in human-impacted ecosystems, including urban landscapes. The primary reason for this is loss, fragmentation, or degradation of habitat. The loss of native vegetation and wildlife often promotes the spread of invasive species, which may further degrade or eliminate habitat. Aronson et al. (2014) studied bird and plant diversity in cities around the earth and observed the density of bird and plant species (the number of species per square kilometer) declined substantially: only 8% of native bird and 25% of native plant species were currently present compared with estimates of non-urban density of species. Additional information on impacts of urban landscapes on biodiversity can be found in these articles and reports.

Sustainable communities

Sustainable communities are places that balance their economic assets, natural resources, and social priorities so that residents' diverse needs can be met now and in the future.

Communities want to protect their water quality while also getting the greatest possible benefit out of every investment they make. Many are conserving, restoring, or enhancing natural areas while incorporating green infrastructure practices, such as trees, rain gardens, green roofs and other practices. These green infrastructure practices mimic natural systems into developed areas to manage rainwater where it falls. Green infrastructure practices are an integral component of sustainable communities because they can help communities protect the environment and human health while providing other social and economic benefits, allowing communities to achieve more for their money. Using green infrastructure practices strategies to reduce stormwater runoff can strengthen efforts to preserve open space and natural areas and encourage development in existing communities. These practices help make neighborhood streets and greenways pleasant and safe for walking and biking and reinforce a sense of place. Integrating green infrastructure and sustainable communities encourages collaboration in development decision and promotes green building practices.

Sustainable communities that fully integrate green infrastructure approaches use community design to help simultaneously achieve environmental, economic, and social goals. These goals include improving water quality, revitalizing neighborhoods, reducing flood risk, and providing recreational areas that encourage physical activity. Community planners can enhance these and other benefits by selecting the types and locations of green infrastructure practices that best support their goals.

To learn more about sustainable communities and green infrastructure, including how to develop a Sustainable Communities and Green Infrastructure Plan, read the EPA's report on Enhancing Sustainable Communities with Green Infrastructure.

Living (green) streets

A living street is new type of street that is narrower and has less pavement than existing streets. Reducing the width of existing streets reduces construction costs and allows room for the installation of trees and rainwater gardens to treat stormwater. Where there is a need, bike trails and sidewalks are installed to provide for safe pedestrian and bike movement. Living streets are designed for cars, people and the environment. Rainwater gardens and street trees remove pollutants from stormwater before the water enters area lakes, helping to improve lake quality. Narrower streets and street trees also slow traffic, creating a safe environment for everyone. In 2012, the City of Maplewood partnered with the Ramsey Washington Metro Watershed District to install a living streets demonstration project. For more detailed information about the project, go to the Ramsey Washington Metro Watershed District web site.

A green street is a stormwater management approach that incorporates vegetation, soil and engineered systems such as pavement to slow, filter and cleanse stormwater runoff from impervious surfaces such as streets and sidewalks. Green streets are designed to capture rainwater at its source, where rain falls.

Green streets protect water quality in rivers and streams by removing up to 90 percent of pollutants. They replenish groundwater supplies, absorb carbon, improve air quality and neighborhood aethestics, and provide green connections between parks and open space. Vegetated curb extensions improve pedestrian and bicycle safety and calm traffic. For information on green streets can be found on the EPA's web site

One principle of green infrastructure involves reducing and treating stormwater close to its source. Green streets provide a source control for a main contributor of stormwater runoff and pollutant load. In addition, green infrastructure practices complement street facility upgrades, street aesthetic improvements, and urban tree canopy efforts that also make use of the right-of-way and allow it to achieve multiple goals and benefits.

Green streets can incorporate a wide variety of design elements including street trees, permeable pavements, bioretention and swales. Successful application of green techniques will encourage soil and vegetation contact and infiltration and retention of stormwater. Bioretention is a versatile green street strategy. Bioretention practices can be tree boxes taking runoff from the street, as well as planter boxes or curb extensions. Permeable Pavement systems have an aggregate base which provides structural support, runoff storage and pollutant removal through filtering and adsorption. Tree trenches and tree boxes reduce stormwater runoff, help to reduce the urban heat island effect, improves air quality and urban aesthetics.

Watch a video, produced by the EPA on the benefits of Green Streets

Climate adaptation

carbon storage,

References

• Aronson, M.F.J., F. A. La Sorte, C. H. Nilon, M. Katti, M. A. Goddard, C. A. Lepczyk, P. S. Warren, N. S. G. Williams, S. Cilliers, B. Clarkson, C. Dobbs, R. Dolan, M. Hedblom, S. Klotz, J. L. Kooijmans, I. Kühn, I. MacGregor-Fors, M. McDonnell, U. Mörtberg, P. Pyšek, S. Siebert, J. Sushinsky, P. Werner, and M. Winter, 2014. A global analysis of the impacts of urbanization on bird and plant diversity reveals key anthropogenic drivers. Proceedings of the Royal Society B. Volume 281, Issue 1780.
• Brown, S., E. Miltner, C. Cogger. 2011. Carbon Sequestration Potential in Urban Soils. In Carbon Sequestration in Urban Ecosystems. Editors: Rattan Lal, Bruce Augustin. Springer Nature.
• Costanza, Robert, Rudolf de Groot, Paul Sutton, Sander van der Ploeg, Sharolyn J. Anderson, Ida Kubiszewski, Stephen Farber, and R. Kerry Turner. 2014. Changes in the global value of ecosystem services. Global Environmental Change. 26:152-158.
• Jo, Hyun-Kil. 2001. Impacts of urban greenspace on offsetting carbon emissions for middle Korea. Journal of Environmental Management (2002) 64, 115–126.
• Moore, T.L.C., W.F. Hunt. 2013. Predicting the carbon footprint of urban stormwater infrastructure. Ecological Engineering Volume 58, September 2013, Pages 44-51.
• Nowak, D.J. and D.E. Crane. 2002. Carbon storage and sequestration by urban trees in the USA. Environmental Pollution. 116:3:381-389.