October 25, 2007
Green standards coming for site development
By DEB GUENTHER
With sustainable building and greenhouse gas management practices being adopted across the nation, landscape architecture is now advancing the challenge. A new initiative will expand green standards to guide and motivate the sustainable design, construction and maintenance of landscapes.
The Sustainable Sites Initiative links research with practice to encourage site development that not only reduces environmental footprints, but also contributes to the long-term health of our communities and the planet.
According to the Environmental and Energy Study Institute, buildings produce almost half of greenhouse gas emissions in the United States. But our nation’s land practices also have significant environmental and economic impact.
From pollution to depletion of natural resources to use of non-renewable and environmentally harmful materials, our landscapes pose the same challenges as buildings. For example, turf grasses, including residential and commercial lawns and golf courses, are the single largest irrigated crop in the United States. This “crop” consumes vast amounts of water and huge amounts of nitrogen-based chemical fertilizer. According to NASA’s Ames Research Center, approximately 2.2 billion gallons of fossil fuels are used on lawns nationwide, making turf a major contributor to global warming. Additionally, the Millennium Ecosystem Assessment targets nitrogen-based chemical fertilizers as a primary global threat to water quality issues.
The Sustainable Sites Initiative grew out of a discussion in 2002 among a group of concerned landscape architects who met at the first Greenbuild International Conference and Expo in Austin, Texas. The American Society of Landscape Architects and the Lady Bird Johnson Wildflower Center agreed to spearhead efforts with a coalition of 11 stakeholder organizations to establish an industry-wide standard for sustainable land development and management practices. This year, the U.S. Green Building Council committed to use the Sustainable Sites metrics in the next iteration of its LEED rating system.
The Sustainable Sites Initiative is built upon the concept of ecosystem services, referring to the natural goods and services that landscapes provide such as water and air purification, climate regulation, food, raw material production, waste decomposition, erosion control and biological habitat. Because the natural world provides so many ecosystem services, humans often underestimate or ignore their value when making land-use decisions. The Sustainable Sites Initiative will establish a credible and authoritative basis for evaluating the performance of sites and their ecosystem services for both building and site-only projects.
The Sustainable Sites Initiative product development committee includes representatives from a broad spectrum of interests, including the U.S. Environmental Protection Agency, National Association of County and City Health Officials, National Recreation and Park Association, the U.S. Green Building Council and the Nature Conservancy, among others.
The first Sustainable Sites Initiative product will be available Nov. 1: A draft best management practices to address the land development and management industry’s approach to soil, hydrology, vegetation and materials. More than 300 organizations are reviewing the document.
The research devoted to this report has illuminated a number of strategies that can be adopted now:
• Conscious hydrology
Conventional practices often treat water as a waste product, with drainage systems quickly diverting large volumes of water to stormwater systems and eventually to streams and lakes. This contributes to increased downstream flooding, erosion, pollution and a higher water temperature that harms fish, wildlife and natural habitat.
The Sustainable Sites Initiative recommends valuing all water on a site to establish a balance that mimics the functions of the natural hydrological cycle. Precipitation, ground water and stream system recharge, potable water, rainwater, gray water and wastewater can and should be used to maximize economic, environmental and human benefits.
Keeping natural hydrological features intact has measurable value. For example, when the quality of New York City’s drinking water from the Catskill Mountains was threatened, the city compared the costs of purchasing land and restoring the Catskill’s watershed to the costs of installing an artificial filtration plant. The city determined that it would cost $6 billion to replace the natural ecosystem, and decided to purchase and protect the watershed at a much lower investment of taxpayers’ money.
• Healthy soils
Healthy soil is a combination of rich organic matter and microbes that promote strong disease- and pest-resistant plants. Maintaining healthy soil seems like common sense, however, it is often compacted during construction or removed at the start of a project only to be replaced with imported soil.
The Sustainable Sites Initiative best management practices suggest soil protection as a routine part of construction specifications, just as tree protection has become a standard over the last 20 years. Amendments, such as compost and organic fertilizer that increase biomass and improve water-holding and nutrient absorption, maximize soils’ ecological value. Also, understanding the functional characteristics of different types of soils can inform the land-use plan, placement of buildings and overall landscape design.
Soils are more effective than vegetation at holding greenhouse gases. The biomass of the root zone sequesters significantly more carbon than a tree canopy. Soil sequestration efficiently captures many of the six greenhouse gas culprits in global warming, such as methane, sulfur dioxide and nitrous oxide.
Testing a project’s embodied carbon, including soil sequestration during the construction process, can be done using a carbon calculator developed by Mithun, the Ladybird Johnson Wildflower Center and the University of Washington.
• Optimizing vegetation
Another Sustainable Sites Initiative best practice is to select and maintain vegetation that optimizes ecological function.
Trees and plants sequester or remove carbon dioxide from the atmosphere through photosynthesis and help to reduce the “urban heat island” effect by providing a natural cooling source for buildings. Each year in the United States, urban trees store 771 million tons of carbon (equivalent to the amount emitted by almost 500 million cars) and uptake an additional 25 million tons. Also, native and drought-tolerant plants conserve water, while alternatives to traditional lawns, such as planted landscapes (including green roofs and rain gardens) are superior at recharging groundwater.
• Managing materials
The Sustainable Sites Initiative targets a “zero waste site.”
Yard and landscape waste contributes about 32 million tons to the municipal waste stream, accounting for 13 percent of total waste in the United States. The waste generated by landscape development and maintenance can be significantly reduced or eliminated through on-site composting and the reuse of existing soil, rock and other organic features.
Like the natural world, human preferences follow cycles. Our trend toward sustainable landscapes harkens back to the Olmsteds’ legacy. Frederick Law Olmsted and the Olmsted brothers, known for their distinctive artistry of park systems across the United States, also applied a whole-systems method. They integrated natural systems with infrastructure, driven by the positive health benefits of outdoor spaces.
Subsequently, conventional practice compartmentalized services, and focused on the beautification of green spaces. Now the pendulum is swinging back with new knowledge and urgency to respect the interrelationship of natural and built systems, and their impact on public health.
The Sustainable Sites Initiative’s next round of study will look at the economic impact of healthy ecological systems on human well being in terms of bio-regional differences.
Landscapes have the unique ability to enhance or regenerate natural resources. From our management of soils to how we value ecological systems services to materials specifications, we can make choices that support positive economic, social and environmental outcomes. Based on the land development and management industry’s ever-increasing commitment to sustainable practices, the Sustainable Sites Initiative will become an essential professional tool helping us make intelligent decisions for a healthy future.
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