Why Sustainable Sites?
While standards exist for sustainable structures—“green buildings”—there are no standards to guide those who want to create sustainable landscapes as there are for green buildings. Yet landscapes have great potential for both environmental good and severe environmental damage. For example:
Greenhouse gas emissions. Vegetation helps reduce the amount of carbon dioxide, a greenhouse gas, in the atmosphere by capturing and storing it for use in producing roots, leaves and bark. In the United States, urban trees capture up to 25 million tons of carbon each year.1
Urban Climate. Urban trees reduce the urban heat island effect and provide windbreaks. A study of five U.S. cities found that the presence of urban trees can result in substantial annual energy savings--$553,000 per year in Berkeley, CA and $187,000 in Cheyenne, WY.2
Biodiversity. Well-designed landscapes promote biodiversity
with a mix of native species and ecologically appropriate non-native species.
Approximately 85% of the invasive woody plant species in the U.S. were introduced
for landscape or ornamental use,3 
and
approximately 5,000 plant species are estimated to have escaped to natural
ecosystems.4 Purple
loosestrife (Lythrum salicaria), for example, was introduced as an
ornamental plant in the U.S. and has since rapidly and aggressively spread
to 48 states, resulting in control costs of almost $45 million per year nationwide.5 Through
competition with native plant species, invasive species such as purple loosestrife
are a threat to native flora and fauna.
Water waste. Native plants and water-conserving landscapes reduce the use of scarce water resources. The turf grasses used in residential and commercial lawns and golf courses are the single largest irrigated crop in America in terms of surface area, covering an area the size of the state of Mississippi. On average, each U.S. citizen uses 200 gallons of water per day in order to maintain this “crop.”
Water pollution. The U.S. Fish and Wildlife Service reported that “homeowners use up to 10 times more chemical pesticides per acre on their lawns than farmers use on crops.”6 Careful plant selection and organic soil additions reduce the use of pesticides and fertilizers that can contaminate water. Good design and techniques like rain gardens or swales reduce runoff. 1995 EPA data showed that urban runoff contributed to damaging more than 26,000 river and stream miles. In addition, the National Water Quality Inventory: 2000 Report to Congress identified urban runoff as one of the leading sources of water quality impairment in surface waters.7
Yard waste. Composting leaves and grass is good for the soil, yet leaves and grass comprise as much as 18 percent of landfill volume, with another seven percent consisting of rock, soil and woody landscape waste. In Texas alone, it costs $150 million a year to dispose of this yard waste.8
Public health. Studies show that the visual effect of flowers and plants are good for people. Nursing homes in Texas that incorporated more plants and animals into residents’ daily lives noted a marked decrease in behavior incidents, bedsores and restraints.9 A Chicago study links tree and grass cover to fewer property crimes, fewer violent crimes, stronger ties among neighbors, more frequent use of common neighborhood spaces and a greater sense of safety.10
Energy consumption. Using local, sustainable materials takes less of a toll on our energy supply. The energy demands to produce and transport materials (embodied energy) can account for up 15 percent of a building’s energy use over its entire lifespan.11