| Image credit: Brooklyn Bridge Park, Brooklyn, New York.
Michael Van Valkenburgh Associates, Inc.
With rapid global population growth and increasing urban and suburban density, there is often less room for green spaces. However, further integrating different types of high-performing green spaces, or green infrastructure, into the built environment is becoming a priority.
Green infrastructure can be considered a conceptual framework for understanding the "valuable services nature provides the human environment." At the national or regional level, interconnected networks of park systems and wildlife corridors preserve ecological function, manage water, provide wildlife habitat, and create a balance between built and natural environments. At the urban level, parks and urban forestry are central to reducing energy usage costs and creating clean, temperate air. Lastly, green roofs, walls, and other techniques within or on buildings bring a range of benefits, including reduced energy consumption and dramatically decreased stormwater runoff. At all scales, green infrastructure provides real ecological, economic, and social benefits.
The benefits of green infrastructure are numerous. Green infrastructure is an effective and cost-efficient tool for absorbing and sequestering atmospheric carbon dioxide (C02). Efficient use of green infrastructure can reduce energy usage through passive heating and cooling; filter air and water pollutants; decrease solar heat gain; provide wildlife habitat; reduce the public cost of stormwater management infrastructure and provide flood control; offer food sources; and stabilize soil to prevent or reduce erosion. Green infrastructure is crucial to combating climate change, creating healthy built environments, and improving quality of life.
Center for Neighborhood Technology
Green Infrastructure Foundation
Landscape Architecture Foundation
National Association of Clean Water Agencies
Natural Resources Defense Council
Sustainable Urban Forests Coalition
Green Infrastructure, The Conservation Fund
Green Infrastructure, U.S. Environmental Protection Agency
Green Infrastructure Wiki
Green Infrastructure Strategies, Land Policy Institute
Interview with Congresswoman Donna Edwards on Green Infrastructure, ASLA
Interview with Nina-Marie Lister, Affiliate ASLA, on Ecological Urbanism, ASLA
Landscape Performance Series, Landscape Architecture Foundation
Sustainable Sites Initiative (SITES)
NYC Green Infrastructure Plan
Philadelphia Green Infrastructure Plan
"Barriers and Gateways to Green Infrastrucure," Clean Water Alliance America, 2011
"Green, Clean, and Dollar-smart: Ecosystem Restoration in Cities and Countryside," Environmental Defense Fund, 2010
"Integrating Valuation Methods to Recognize Green Infrastructure's Multiple Benefits," Center for Neighborhood Technology, 2010
"The Value of Green Infrastructure: A Guide to Recognizing Its Economic, Environmental, and Social Benefits," Center for Neighborhood Technology and American Rivers, 2010
"Green Infrastructure Data Quantification & Assessment," Center for Neighborhood Technology, 2009
"Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined Sewer Overflows," Natural Resources Defense Council, 2006
"Landscape as Infrastructure," Pierre Belanger, Landscape Journal, 2009 (subscription required)
The Floyds Fork Greenway Master Plan, Louisville, KY (Wallace Roberts & Todd, LLC)
Open Space Seattle 2100 Envisioning Seattle's Green Infrastructure for the Next Century, Seattle, Washington (Department of Landscape Architecture, University of Washington, and the Open Space Seattle 2100 Coalition)
Port Lands Estuary: Reinventing the Don River as an Agent of Urbanism, Toronto, Ontario, Canada (Michael Van Valkenburgh Associates, Inc.)
Seattle Green Factor, Seattle,Washington (City of Seattle Department of Planning and Development)
Not only are park systems opportunities for recreation, social interaction, psychological renewal, and environmental education, they are also valuable carbon sinks and wildlife habitats. Governments, organizations and communities should continue to invest in networks of parks and other open spaces as a remedy to long-term urban, suburban and regional landscape decline.
A number of states and local governments have taken steps to raise much-needed revenue to create, expand, and preserve these important open spaces. Revenue bonds, transfer of development rights, and partnerships with the private sector or non-profit organizations are just a few of the methods used to create resources for park systems.
In an effort to establish more park systems, park policy makers should consider increased multiple use trails, rails-to-trails, both "wild and scenic" and recreational river and greenways programs.
As urbanization continues, it's critical for communities to plan for and develop park systems that can be an integral part of the urban fabric. Green infrastructure of special natural, scenic and cultural significance should be protected and preserved. In rural areas, existing parks should be rehabilitated to protect vanishing landscapes.
City Parks Alliance
Natural Recreation and Park Association
Project for Public Spaces
Trust for Public Land
Urban Greenspaces Institute
"E.O. Wilson's Love Letter to Parks," The Dirt blog
City of Toronto Parks, Forestry and Recreation Department
High Performance Landscape Guidelines, NYC Department of Parks and Recreation
National Parks, United Kingdom
New York City Department of Parks and Recreation
U.S. Park Service
“The Central Park Effect,” Appleseed / Central Park Conservancy
"Financing Parks: A Borrowing Guide," Project for Public Spaces
“Measuring the Economic Value of a City Park System,” Center for City Park Excellence, Trust for Public Land, 2009
“Philadelphia Park Value Report,” Center for City Park Excellence, Trust for Public Land, 2008
“How Much Value Does the City of Philadelphia Receive from its Park and Recreation System?” The Trust for Public Land’s Center for City Park Excellence, June 2008
"Public / Private Partnerships," Project for Public Spaces
“White Paper: Quantifying the Greenhouse Gas Benefits of Urban Parks,” Center for City Park Excellence, Trust for Public Land, 2008
“How Cities Use Parks for Green Infrastructure,” American Planning Association
"Quantifying the Greenhouse Gas Benefits of Parks," Trust for Public Land, 2008
Brooklyn Bridge Park, Brooklyn, New York (Michael Van Valkenburgh Associates)
Bryant Park, New York, NY (OLIN)
Buffalo Bayou Promenade, Houston, Texas (SWA Group)
High Line Park, New York, NY (James Corner Field Operations + Diller, Scofidio, Renfro)
HtO, Toronto, Ontario, Canada (Janet Rosenberg + Associates (JRA), Claude Cormier Architectes Paysagistes, and Hariri Pontarini Acrhitects)
Lagoon Park: Living at the Edge of Wilderness, Santa Barbara, California (Van Atta Associates, Inc.)
The Lurie Garden, Millennium Park, Chicago, Illinois (Gustafson Guthrie Nichol Ltd)
Orange County Great Park Comprehensive Master Plan "A Vision for the Great Park of the 21st Century", Irvine, California
(Ken Smith Workshop West and Mia Lehrer + Associates)
"Red Ribbon" Tang He River Park, Qinhuangdao City, Hebei, China (Kongjian Yu / Turenscape)
Teardrop Park, New York, NY (Michael Van Valkenburgh Associates, Inc.)
From Industrial Wasteland to Community Park, ASLA
Revitalizing Communities with Parks, ASLA
Wildlife Habitat and Corridors
An array of independent and uncoordinated land use decisions often leads to a "landscape mosaic" comprised of fragmented wildlife habitats. Habitat modification also leads to changes in diversity within most ecosystems. Instead, comprehensive land-use planning and design should promote the enhancement, protection, and management of landscapes that support wildlife. The integration of land-use planning and design with wildlife habitat protection can strengthen ecosystem biodiversity.
The future of wildlife and wildlife habitat in wild, rural, suburban and urban settings depend on an environmentally responsible strategy of land management that emphasizes a mix of spaces for people and wildlife. The use of ecological information in the design process can create a more positive union between land use and the natural environment, and increase public awareness of wildlife, wildlife habitats, and their value to human welfare. Wildlife and wildlife habitat values should be considered early in the development process.
National Wildlife Federation
Natural Capital Project
UK Green Building Council Biodiversity Task Force
Urban Biodiversity, United Nations Environment Program (UNEP)
Wildlife Habitat Council
"Biophilia: An 'Innate Emotional Affilation with Nature,'" The Dirt blog
"Better Crossing Design Can Reduce Collisions Between Wildlife and People," The Dirt blog
"Designing for the Full Range of Biodiversity," The Dirt blog
Interview with Carolyn Fraser, Author of Rewilding the World: Dispatches from the Conservation Revolution, ASLA
"Legacy of the Cold War: Germany's Green Belt," The Dirt blog
"Recreating Wildlife Habitat in Cities," The Dirt blog
"Restoring the Balance Between People and Nature Through Wildlife Habitat Design," The Dirt blog
"Taking Nature to the City," The Dirt blog
Wildlife Habitat Resources, Natural Resources Conservation Service, U.S. Department of Agriculture
Conservation Buffers: Design Guidelines for Buffers, Corridors, and Greenways, U.S. Department of Agriculture, National Agroforestry Center
Cambridgeshire County Council Green Infrastructure Strategy
"Climate Disruption and Biodiversity," Stuart Pimm. Current Biology, 2009
"The 'Habitat Backbone" as Strategy to Conserve Pioneer Species in Dynamic Port Habitats: Lessons from the Natterjack Toad in the Port of Antwerp," Robbert Snep and Fabrice Ottburg. Landscape Ecology, 2007
“Biodiversity and Green Infrastructure in Urban Landscapes: The Importance of Urban Green Spaces,” Ulf G. Sandstrom, VDM Verlag, 2008
“The Ecological City: Preserving and Restoring Urban Biodiversity,” Rowan A. Rowntree, Rutherford H. Platt, Pamela C. Muick, University of Massachusetts Press, 1994
Fresh Kills Park, New York
Shelby Farms Park Conservancy
Trees create a sense of balance in dense building environments. Trees and plants mitigate carbon dioxide emissions, create animal habitat, and filter and absorb stormwater runoff. Not only are trees beneficial to the environment and humans’ health, in urban areas, they can offer economic benefits, including increased property values.
Federal, state, and local policies are needed regarding the appropriate use of native, indigenous, noxious, and invasive tree and plant species. Plant and tree professionals, advocacy groups, and government agencies can facilitate sound plant selection and planting practices. Native plant communities of a region provide the strongest cues to the unique identity of a place, and generally require less maintenance and irrigation. Both design and scientific approaches are needed to create a healthy growing environment.
New federal legislation recognizes the many benefits of urban forestry. The Energy Conservation Through Trees Act, authored by Congresswoman Doris Matsui (CA) of Sacramento, would establish a grant program with electricity providers to plant shade trees to insulate residential buildings and minimize home heating and cooling costs. The legislation would require an education and information campaign to encourage residents to maintain their shade trees over a long term; require monitoring and reporting of tree survival, growth, overall health, and estimated savings; and require tree recipients to provide stewardship and care of the trees. Also, Congressman Ed Perlmutter (CO) has authored the Green Energy Resources for Energy Efficient Neighborhoods (GREEN) Act, which, among other things, would require the use of tree canopy coverage, site planning, green roofs, and other green infrastructure techniques, in certain Department of Housing and Urban Development (HUD) units as a way to create more energy efficient homes for HUD residents.
Urban forestry benefits include:
- CO2 Sequestration: The net rate of carbon sequestered by urban trees in the continental United States in 2005 is estimated to have been around 24 million tons per year (88.5 million tons CO2), while current total carbon storage in urban trees in the continental United States is approximately 700 million tons of carbon.
- Lower heating and cooling energy costs: Lawrence Berkeley National Laboratory and Sacramento Municipal Utility District found that trees placed around houses to shade windows yielded between 7 and 47 percent energy savings. Trees planted in the west and southwest of buildings yielded the highest savings. Furthermore, a 20 percent tree canopy could result in cooling savings of 8-18 percent and heating savings of 2 to 8 percent.
- Reduced air pollution: Urban trees in the U.S. removed 784,000 tons of air pollutants with a value of $3.8 billion.
- Cooler air temperature: Peak air temperatures in tree groves are 9 degrees cooler than open areas without trees. Suburban areas with mature trees are 4 to 6ºF (2 to 3ºC) cooler than new suburbs without trees.
- Sustainable Stormwater Management: Evergreens and conifers in Sacramento were found to intercept over 35 percent of the rainfall that hit them.
- Higher Property values: The value of residential properties with the trees and vegetation are 3 to 10 percent higher than properties without.
- Cost-efficiency: Cities were recorded as spending $15-65 per tree, but received total net environmental benefits ranging from $30-90 per tree.
Sources: “Reducing Urban Heat Islands: Compendium of Strategies.Trees and Vegetation,” U.S. Environmental Protection Agency
Alliance for Community Trees
Arbor Day Foundation
Human Dimensions of Urban Forestry and Urban Greening, College of Forest Resources, University of Washington
National Urban and Community Forestry Advisory Council
United Nations Environment Program
Urban Horticultural Institute, Cornell University
Yale University School of Forestry and Environmental Studies
Urban Tree Planting Programs
Green Miami (Increase tree cover to 30 percent by 2017)
Grow Greener Boston (100,000 new trees by 2020)
Leading to a Greener London (Two million trees by 2025)
Million Trees NYC (Part of PlaNYC)
Million Trees L.A. (Target is one million new trees)
Plant a Billion Trees The Nature Conservancy
TreeBaltimore (Double tree cover from 20 percent to 40 percent within 30 years)
United Nations Environment Program (UNEP) One Billion Tree Campaign
"A New Way to Plant Urban Trees," The Dirt blog
Benefits of NYC's Urban Forest, MillionTreesNYC
Urban and Community Forestry, United States Forest Service
U.K. Forestry Commission
Reducing the Urban Heat Island Effect (City of Chicago Government)
Urban Heat Island Mitigation Strategies (U.S. Environmental Protection Agency)
"Sustaining America's Urban Trees and Forests," U.S. Forest Service, 2010
“Reducing Urban Heat Islands: Compendium of Strategies.Trees and Vegetation,” U.S. Environmental Protection Agency
"Restoration ecology processes to advance natural landscape design," Steven N. Handel, Rutgers University
“More in Store: Research on City Trees and Retail,” Kathleen L. Wolf, International Society of Arboriculture, April 2009
“Strip Malls, City Trees, and Community Values,” Kathleen L. Wolf, Agriculture and Urban Forestry, January 2009
"Urban Heat Island Mitigation Strategies Can Improve New York City’s Environment: Research on the Impact of Mitigation Strategies," Sustainable South Bronx / Columbia University Earth Institute, October 2008
“City of Indianapolis, Indiana: Municipal Forest Resource Analysis,” Paula J. Peper, E. Gregory McPherson, James R. Simpson, Kelaine E. Vargas, and Qingfu Xiao, April 2008
“Los Angeles One Million Tree Canopy Cover Assessment Final Report,” Greg McPherson, Jim Simpson, Qingfu Xiao, and Chelsea Wu, March 2007
"Assessing Urban Forest Effects and Values: New York City's Urban Forest," U.S. Forest Service and Ufore, 2007
"Projected Urban Growth (2000-2050) and Its Estimated Impact on US Forest Resource," Journal of Forestry, 2005
"The Effects of Urban Trees on Air Quality," U.S. Forest Service, 2002
"Evaluating Street Tree Microclimates in New York," Urban Horticulture Institute, Department of Floriculture and Ornamental Horticulture, Cornell University
Green roofs can help regulate a building’s internal temperature, reduce stormwater runoff, and mitigate the urban heat island effect. Green roofs offer significant economic benefits, including a longer roof life and heating and cooling energy savings. Green roofs also provide an opportunity for urban food production, and increasing urban biodiversity. If well-designed and cared for, green roofs can expose people to the psychological benefits of nature.
Green roofs benefits include:
- Energy savings: A typical 2-3 story building could experience 15-25 percent savings in summertime energy costs.
- Lower air temperatures: A modeling study found that adding green roofs to 50 percent of the available surfaces in downtown Toronto would cool the entire city by 0.2 to 1.4°F (0.1 to 0.8°C).
- More efficient stormwater management: Green roofs can catch 40-60 percent of stormwater, reducing flow into a city’s sewers
- Lower long-term maintenance costs: Green roofs can extend a roof’s lifespan by two or three times. According to Sustainable South Bronx, on a 90 degree day a green roof is about 80°F, while a black roof is 175°F, causing substantial wear and tear.
- Cost-efficiency: A University of Michigan study showed that a 21,000 sq. ft. USD 464,000 green roof will save USD 200,000 over its lifetime. “Nearly two-thirds of these savings would come from reduced energy needs for the building with the green roof.”
Sources: “Reducing Urban Heat Islands: Compendium of Strategies, Green Roofs,” U.S. Environmental Protection Agency and Sustainable South Bronx
Green walls include most of the benefits of green roofs, but also:
- Reduced air temperatures: Temperatures behind green walls can be reduced by as much as 10 degree celsius.
- Reduced Noise Pollution: Green walls can help reduce sound reflection
- Cost-efficiency: Through shading, green walls can lower temperatures in summer and reduce energy costs by 23 percent.
Sources: “Living Walls: A Way to Green the Environment” Susan Loh, Australian Council of Built Environment Design Professionals, August 2008
Green Roofs for Healthy Cities
Center for Green Roof Research, Pennsylvania State University
International Green Roof Association
"Despite Economy, Green Roofs Bloom," The Dirt blog
"Green Roofs Reduce the Urban Heat Island Effect," The Dirt blog
"Majora Carter on Green Community Infrastructure," The Dirt blog
"Philadelphia's Cutting-edge Green Infrastructure Plan," The Dirt blog
"Scaling up Green Infrastructure," The Dirt blog
"Taking Nature to the City," The Dirt blog
“By-Law to Require and Govern the Construction of Green Roofs in Toronto,” Chief Building Official and Executive Director, Toronto Building and Chief Planner and Executive Director, City Planning, March 2009
Reducing Environmental Heat Islands: Green Roofs (U.S. Environmental Protection Agency)
Report on the Environmental Benefits and Costs of Green Roof Technology (City of Toronto Government, Canada)
"Gray to Green: Jumpstarting Private Sector Investment in Green Stormwater Infrastructure" Green Economy Taskforce, Sustainable Business Network of Greater Philadelphia, 2009
“What is a Green Roof?” How Stuff Works
“Urban Heat Island Mitigation Can Improve NYC’s Environment: Research on the Impacts of Mitigation Strategies,” Sustainable South Bronx, October 2008
“Reforesting the Built Environment: A Practical Feasibility Case Study in Christchurch,” K.J. Mulligan and S.C. Page, 2008
“Sound Transmission Loss of Green Roofs,” Maureen Connelly and Murray Hodgson, 2008
“Reducing Urban Heat Islands: Compendium of Strategies, Green Roofs”, U.S. Environmental Protection Agency
"Introduction to Green Walls Technology, Benefits and Design," Green Roofs for Healthy Cities, September 2008
“Living Walls: A Way to Green the Built Environment,” Susan Loh, Australian Council of Built Environment Design Professionals, August 2008
“Quantifying Evaporation and Transpirational Water Losses from Green Roofs and Green Roof Media Capacity for Neutralizing Acid Rain,” Robert Berghage, Al Jarrett, David Beattie, Kathleen Kelley, Shazia Husain, Farzaneh Rezai, Bret Long, Ayako Negassi, Robert Cameron, and William Hunt, 2007
"When Does Green Infrastructure Make Sense? Comparing Conventional Systems with Green Infrastructure," Water Environment Research Foundation, June 2007
“Green Roofs in the New York Metropolitan Region: Research Report,” Cynthia Rosenzweig, Stuart Gaffin, and Lily Parshall (editors), Columbia University Center for Climate Change Research and NASA Goddard Institute for Space Studies, 2006
“Mitigating New York City’s Heat Island with Urban Forestry, Living Roofs, and Light Surfaces,” New York State Energy Research and Development Authority, October 2006
“Living Architecture Monitor, Fall 2008,” Green Roofs for Healthy Cities
“Green Roof Systems: A Guide to the Planning, Design and Construction of Building Over Structure,” Susan Weiler and Katrin Scholz-Barth, Wiley, 2005
ASLA Headquarters Green Roof, Washington, D.C. (Michael Van Valkenburgh & Associates, Inc.)
California Academy of Sciences, San Francisco, CA (SWA Group, Sausalito, CA)
Changi Airport Terminal 3 Interior Landscape, Singapore (Tierra Design (S) Pte Ltd.)
Chicago City Hall Green Roof, Chicago, Illinois (Conservation Design Forum)
Corporate Headquarters, San Francisco, CA (OLIN)
Gannett/USA Today Headquarters, McLean, Virginia (Michael Vergason Landscape Architects, Ltd.)
Macallen Building, South Boston, MA (Landworks Studio, Inc.)
Nueva School, Hillsborough, California (Andrea Cochran Landscape Architects)
Museo del Acero Horno3, Monterrey, Mexico (Surfacedesign Inc.+ Harari arquitectos)
Rooftop Haven for Urban Agriculture, Chicago, Illinois (Hoerr Schaudt Landscape Architects)
Washington Mutual Center Roof Garden, Seattle, Washington (Phillips Farevaag Smallenberg)
Leveraging the Landscape to Manage Water, ASLA
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