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Without vegetation, a site loses its natural capacity for stormwater management, filtration, and groundwater recharge. Reduced vegetative cover also affects soil health, because vegetation maintains soil structure, contributes to soil organic matter, and prevents erosion. Through evaporation, transpiration, and the uptake and storage of carbon, trees and other vegetation moderate the climate of the world and provide a breathable atmosphere. 

In the continental United States, carbon sequestration provided by urban trees alone is estimated to be about 25 million tons per year,1 which is equivalent to the carbon emitted by almost 18 million cars annually.2

Shade trees planted in parking lots reduce evaporative emissions of volatile organic compounds (VOCs)—precursors to ground-level ozone—from parked cars.3

In the Chicago area, urban trees filter an estimated 6,000 tons of air pollutants each year, providing air cleansing valued at $9.2 million.4

Once established, native plants can save time and money by reducing maintenance and resource requirements.5

Examples of Sustainable Practices

Protect and use existing vegetation
Select sites that do not include habitat for threatened or endangered species. Design the site to minimize disruption to existing habitats. Preserve trees designated as important by local, state, or federal entities. Mature trees are significant community resources because of their cultural, aesthetic, or historic relevance. Encourage a tight disturbance zone to limit construction damage to vegetation.

Use vegetation that promotes a regional identity and a sense of place
Use native and appropriate non-native plants adapted to site conditions, climate, and design intent to support biodiversity, reduced pesticide use, and water conservation. Use only non-invasive plants that are nursery grown, legally harvested, or salvaged for reuse from on- or off-site.

Use vegetation to lower energy consumption
To reduce energy consumption and costs associated with indoor energy needs, place vegetation or vegetated structures in strategic locations around buildings. To reduce urban heat island effects, use trees, green roofs, or vegetated structures (e.g., trellises) to cover non-vegetated surfaces such as walkways, roofs, or parking lots, and select vegetation-based methods to achieve stormwater management goals for the site.

Manage landscapes effectively to reduce potential damage
Control and remove invasive species to limit damage to local ecosystems. To mitigate potential fire hazards, contact local fire departments for recommendations on plant spacing, fire-resistant plant species, and fuel management practices appropriate to the local area.

[1] Nowak, DJ and DE Crane. 2002. Carbon storage and sequestration by urban trees in the USA. Environmental Pollution 116: pp. 381-89.
[2] U.S. Climate Technology Cooperation. 2007. Greenhouse Gas Equivalencies Calculator. http://www.usctcgateway.net/tool/.
[3] U.S. Environmental Protection Agency. Heat Island Effect: Trees and Vegetation. http://www.epa.gov/hiri/strategies/vegetation.html (accessed August 20, 2008).
[4] McPherson, G, DJ Nowak, and RA Rowntree. 1994. Chicago’s Urban Forest Ecosystem: Results of the Chicago Urban Forest Climate Project. Department of Agriculture, Forest Service, and Northeastern Forest Experiment Station (Gen. Tech. Rep. NE-186).
[5] U.S. Environmental Protection Agency. Landscaping with Native Plants Factsheet. http://www.epa.gov/greenacres/nativeplants/factsht.html#Why Should I (accessed August 20, 2008).