Did you know?
According to one study, in 1991 trees in the Chicago area removed as much as 234 tons of particulate matter, 210 tons of ozone, 93 tons of sulfur dioxide, and 17 tons of carbon monoxide from the air.1
A study of five US cities found that urban trees can contribute to substantial annual energy savings. For example, annual cooling and heating savings from shading and windbreak benefits reached $553,000 in Berkeley, CA, and $187,000 in Cheyenne, WY.2
Purple loosestrife (Lythrum salicaria) was introduced as an ornamental plant in the US and has since rapidly and aggressively spread to 48 states, resulting in control costs of almost $45 million per year nationwide.3 Purple loosestrife is an invasive species which crowds out native plant species.
Vegetation
Plants provide a livable atmosphere and moderate climate by regulating the earth’s oxygen/carbon dioxide balance and filtering pollutants from air and water. During photosynthesis, plants take in carbon dioxide, water and light to produce carbohydrates, a food for growth, and oxygen. Vegetation (along with soil biota) can convert and recycle human waste by processing, removing, transforming and storing pollutants from air and water. For example, plants can filter gaseous pollutants from the air by absorption through leaf stomata and bark pores.
Current Vegetation Practices
Disturbing or removing vegetation causes a site to lose valuable
ecosystem services such as climate regulation, protection of soil health, provision
of habitat for wildlife and pollinators and filtration of pollutants from water
and air. This also can restrict the capacity of the landscape to intercept
and infiltrate water which in turn manages stormwater, recharges groundwater
and filters water. 
Current
practices that impair plant health also affect soil health, as vegetation maintains
soil structure, prevents erosion and contributes to organic matter in the soil. Vegetation
also provides the shade and evapotranspiration that cool buildings and save
on energy costs. Research
in New York City indicates that a single tree provides $5.60 in benefits for
every $1 spent on its care.4
Invasive species in landscape design jeopardize native wildlife species. Approximately 85 percent of the invasive woody plant species in the US were introduced for landscape or ornamental5 and approximately 5,000 plant species are estimated to have escaped to natural ecosystems.6
Examples of Sustainable Vegetation Practices
Protect and conserve existing vegetation. Incorporate healthy native or non-invasive vegetation currently existing on the site into the site design. Encourage a tight disturbance zone to limit construction damage to vegetation.
Eliminate the use of invasive plants. An invasive species is defined as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.”
Specify plants from local growers to reduce energy use and other negative environmental impacts of shipping and ensure that plants are adapted to local environmental conditions.
Minimize the amount of time that plants are stored on-site before planting. If plants or on-site transplants must be stored on-site, store them in ways that prevent stress and disease post-planting. Provide adequate water, heal-in root balls and apply nutrients, if needed.