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THE SUSTAINABLE SITES INITIATIVE: Two Botanic Gardens partnering toward sustainable Landscapes

Volume 6 Number 2 - July 2009

Adapted by Ray Mims, USBG for the Sustainable Sites Initiative


The Lady Bird Johnson Wildflower Center in Austin Texas and the United States Botanic Garden in Washington DC have partnered with the American Society of Landscape Architects (ASLA) for the last three years developing the Sustainable Sites Initiative. Working with a large diverse group of supporting organizations, this initiative has developed a set voluntary guidelines and benchmarks that will reduce the environmental impact of designed landscapes.

Botanic Gardens are in an excellent position to understand the use of ‘green’ techniques and all three partners have been aware of the gaps in current ‘green building’ technologies. Through the last decade there has been substantial increase in sustainability awareness and in the number of standards for sustainable structures or ‘green buildings’. In ten years the United States Green Building Council (USGBC) has seen thousands of buildings certified through LEED®, tens of thousands of professionals become LEED certified and the building industry transformed. Green Globes, the Green Building Initiative and countless global organizations continue to challenge the way structures are designed, built and maintained. However, despite this tremendous growth, there were no comprehensive guidelines to create and measure sustainable landscapes. Yet landscapes have great potential to do environmental good and counter previous environmental damage. As a result of this, the Lady Bird Johnson Wildflower Center, ASLA, and the USBG joined forces to insure this vital piece of the built environment is not overlooked. Working with a diverse group of stakeholder organizations the Sustainable Sites Initiative began concentrating on the hydrology, materials (use and waste), soil, vegetation and human health as related to a constructed landscape. Analyzing these site components through the lens of ecosystem services should help shape the guidelines to promote not only ecologically sensitive design, construction and maintenance, but landscapes that are also ecologically regenerative.

Ecosystem services are the collective resources and assets provided by the natural world and are the foundation of human existence. Temperature mitigation, climate control, clean water, clean air, carbon (greenhouse gas) storage are only a few ecosystem services that are crucial, yet these services and the natural world that provides them are underestimated or simply ignored throughout land-use decisions. As these have begun to diminish or disappear, we have made attempts to replicate them. However the difficulty, expense and futility of attempting to replicate these services has become apparent.

A central message of the Sustainable Sites Initiative is that a landscape - any landscape - whether the site of a large housing development, a shopping mall, a park, an abandoned rail yard, or even one home, holds the potential both to improve and to regenerate the services provided by natural ecosystems. With careful consideration through the planning, design, construction and maintenance of landscapes, the natural world should be viewed not as a hindrance, but a resource. Landscapes can assist in the efficient use of resources as well improving air and water quality, reduce the urban heat island effect and sequester carbon, along with many other ecosystem services.

The Sustainable Sites Initiative is therefore creating guidelines to conserve, protect and restore resources, reduce pollution and improve the quality of life and long-term health of both communities and the environment.

Using appropriate plants

Vegetation and soil can help reduce the amount of carbon dioxide, a greenhouse gas, in the atmosphere by capturing and storing it. Studies indicate that in the United States, urban trees capture up to 25 million tons of carbon each year. However, appropriate plant use in landscapes is very important. Approximately 85 percent of the invasive woody plant species in the U.S. were introduced for landscape or ornamental use and approximately 5,000 plant species have escaped into natural ecosystems, resulting in millions of dollars in control costs (Pimentel et al., 2005). Through competition with native plant species, invasive species are a threat to native flora and fauna. Correctly using vegetation can also reduce costs associated with urban heat islands and protect plant and animal biodiversity. Strategically planted vegetation can reduce the energy spent for cooling buildings by up to one quarter. In New York City alone, a study found that trees provided an annual climate-moderating benefit of $27.8 million, or $47.63 per tree. Studies by American Forests (2001) found that tree canopy reduces residential home cooling costs, saving an average of between $11 per household per year in Portland, Oregon, and $28 per household per year in Atlanta, Georgia. Multiplied across the region, this household benefit can add up: in the Atlanta region, savings in home cooling costs amount to $2.8 million per year.

Managing soils

Soils compacted during landscape modifications and construction lose the ability to absorb storm water and to supply plant roots with air and water. Over time, soil fertility and health is destroyed by the use of herbicides, pesticides and chemical fertilizers – all of which are currently accepted landscaping practices. Natural organic products and the use of onsite composting can limit and remediate soil damage by mimicking natural nutrient cycles.

Waste management

Retaining and recycling land-clearing materials, construction waste and maintenance debris lowers the cost of waste disposal and could reduce the need for new purchased materials and soil amendments such as compost and mulch. In 2007, approximately 33 million tons of yard waste and landscape trimmings entered the municipal waste stream, representing 13% of total municipal waste in the United States (U.S. Environmental Protection Agency, 2007a). Sustainable Sites will emphasis turning waste into a resource. Sustainable landscapes will greatly reduce waste from construction as well as from landscaping materials and ‘green’ waste, decreasing the pressure on landfills.

Water use

Lowering the use of potable water in landscapes is another goal of the Sustainable Sites Initiative. Irrigation of current (unsustainable) landscapes accounts for more than a third of residential water use—more than 7 billion gallons per day nationwide (U.S. Environmental Protection Agency, 2007b). On average, a U.S. citizen uses 200 gallons of water daily to maintain turf grass lawn. Turf grasses on residential and commercial lawns, golf courses and other landscapes is the single largest irrigated crop in America. Furthermore, one quarter to half of the electricity used by U.S. cities goes to treat municipal water and wastewater. To make matters worse, up to half of landscape irrigation water may be wasted as a result of evaporation, wind, improper system design and overwatering. While storm water runoff from impervious surfaces is a major pollutant in urban and suburban watersheds, the capture and use of such water runoff can save money and benefit the environment. Therefore a sustainable landscape minimizes, if not eliminates, the use of potable water for irrigation and promotes the reuse of storm water and the use of regionally appropriate plants.

Reducing pollution

Healthy landscapes with functioning ecosystems filter airborne contaminants, an issue in areas with high automobile emissions. According to the Environmental Protection Agency, lawn mowers, blowers and other landscape maintenance tools contribute more than 5% of total U.S. air pollution. Careful design of landscapes can reduce our reliance on single cycle engines for maintenance. Sustainable landscapes can also help convert airborne pollutants into clean air as they grow and develop.

Reduction or elimination of the reliance on chemicals is an important factor in sustainable maintenance practices. A National Research Academy of Sciences study found that more pesticides are used on suburban lawns and gardens than for agricultural use. Not only do these chemicals contribute to water pollution, they require substantial inputs of energy in their manufacture. Heavy use of pesticides increases exposure to these chemicals, which are also carried by rainwater into streams and rivers. Sustainable landscapes require little or no chemical fertilizer, herbicides and pesticides, reducing toxic pollutants that find their way into waterways and groundwater.

Human well-being

Research indicates that encounters with nature - a green view from an office window, a lunchtime stroll through a nearby park, well-tended landscapes around schools - restore the ability to concentrate, calm feelings of anxiety and reduce aggression (Ulrich, 1986). In addition, a Chicago study links tree and grass cover to fewer property crimes, fewer violent crimes, stronger ties amongst neighbours, more frequent use of common neighbourhood spaces and a greater sense of safety. Low-income communities in urban areas are disproportionately denied the benefits of safe open spaces for physical activity in parks and schools and disproportionately suffer from obesity-related diseases. The epidemic of obesity, inactivity, and related diseases such as diabetes is shortening children’s lives, destroying the quality of their lives, and costing the United States over $100 billion each year (Pratt et al., 2000).

Long-term vision

Although led by the Wildflower Center, the USBG, and ASLA, a tremendous amount of work has been done by experts from the Environmental Protection Agency’s GreenScapes Program and Office of Water, the National Recreation and Parks Association, the American Society of Civil Engineers’ Environment and Water Resources Institute, the National Association of County and City Health Officials, The Nature Conservancy’s Global Invasive Species Initiative, the Center for Sustainable Development at the University of Texas at Austin, American Planning Association and the U.S. Green Building Council.

The initiative is expanding beyond LEED (Leadership in Energy and Environmental Design) by focusing efforts on improving landscape or site components of sustainable design. The Initiative uses ecosystem services as a framework to illustrate how sustainable sites can improve the quality of life in our communities. The standards and guidelines are based on extensive research with leading practitioners of sustainable approaches and aim to establish science-based parameters for evaluating the sustainability of landscapes during design, construction and maintenance. The Initiative will provide sustainability principles for any site, with or without buildings, which will be protected, developed or redeveloped for public or private purposes, extending standards to new markets and bringing increased relevance to landscape architects, civil engineers, contractors, and land managers, as well as the large project portfolios they design, construct and maintain.. Examples include parks, corporate campuses, utility corridors and streetscapes. The U.S. Green Building Council (USGBC), a stakeholder in the Initiative, anticipates incorporating the Sustainable Sites Initiative standards and guidelines into future iterations of the LEED, but this ‘green landscape’ tool can serve as a stand-alone tool for developers, landscape architects, civil engineers, planners, landscape designers, landscape contractors and land managers.

For more information and to learn about the pilot project phase and get involved, visit


Pimental, D., Zniga, R. and Morrison, D. 2005. Update on the environmental and economic costs associated with alien invasive species in the United States. Ecological Economics 52: 273-288.

Pratt, M., Macera, C.A. and Wang, G. 2000. Higher direct medical costs associated with physical inactivity. Physician and Sportsmedicine 28 (10): 63-70.

Regional Ecosystem Analysis for the Willamette/Lower Columbia Region of Northwestern Oregon and Southwestern Washington State. American Forests, October 2001.

Ulrich, R.S. 1986. Human responses to vegetation and landscapes. Landscape and Urban Planning 13: 29-44.

Urban Ecosystem Analysis: Atlanta Metro Area: Calculating the Value of Nature. American Forests, August 2001.

U.S. Environmental Protection Agency, 2007a. Municipal solid waste generation, recycling and disposal in the United States: Facts and figures for 2007.

U.S. Environmental Protection Agency, 2007b. Outdoor water use in the United States, EPA-832-F-06-005 (Department of the Interior, 2007).

Ray Mims
Conservation Horticulture & Sustainability
United States Botanic Garden
245 First Street SW
District Of Columbia 20024