Benefits of Urban Forests 

Trees are a defining characteristic of Ann Arbor that make the city a desirable place to visit, work, do business, and live. Ann Arbor’s public trees (trees growing along city streets and in mowed parks) are a valuable resource that provide annual benefits worth $4.6 million, or about $97 per tree (Source: Calculated Public Tree Values and Benefits for the City of Ann Arbor (pdf)).  The City’s public trees reduce energy demand, offset carbon dioxide emissions, improve air quality, mitigate stormwater run-off, and provide other benefits associated with aesthetics, increased property values, and quality of life.

How does the community benefit from ONE tree?

To demonstrate the value trees in our urban environment, consider the benefits generated by a typical tree in Ann Arbor. A single 16-inch diameter sugar maple planted on a single family residential lot provides $149 in benefits every year (National Tree Benefit Calculator).

Lower energy costs

An individual sugar maple tree conserves 98 kilowatt-hours of electricity for cooling and reduces consumption of natural gas by 35 therms. Trees modify and conserve building energy use in three principle ways:

• Shading reduces the amount of heat absorbed and stored by buildings.
• Evapotranspiration converts liquid water to water vapor and cools the air by using solar energy that would otherwise result in heating of the air.
• Tree canopies slow down winds thereby reducing the amount of heat lost from a home, especially where conductivity is high (e.g., glass windows).

Strategically placed trees can increase home energy efficiency.  In summer, trees shading east and west walls keep buildings cooler. In winter, allowing the sun to strike the southern side of a building can warm interior spaces. If southern walls are shaded by dense evergreen trees there may be a resultant increase in winter heating costs.

Higher property values

Research shows homebuyers will pay more for a property with mature trees than for a property with few or no trees. This analysis is based on the tree's leaf surface area, and the property value benefit will increase as the tree grows. 

Value of ONE tree: $14.10

Value of all Ann Arbor Public Trees: $519,895

Stormwater run-off is the most prevalent water quality problem in the nation. One sugar maple tree can intercept 1763 gallons of stormwater run-off each year. Together, Ann Arbor's public trees intercept 65 million gallons of stormwater. Trees in the urban environment decrease the quantity of stormwater run-off and improve the quality of run-off that eventually reaches local lakes, streams, and reservoirs.

• The urban forest canopy, along with tree branches, bark, and mosses, captures and stores precipitation, delaying the onset of peak flows and reducing the total amount of run-off that reaches urban waterways via the storm drain system.
• Trees slow down stormwater run-off and promote groundwater infiltration.
• Trees take up water through their root systems and release it to the atmosphere through evapotranspiration, facilitating greater water storage potential in soils and increasing the amount of time before rainfall becomes run-off.
• Tree roots take up nutrients and potentially harmful chemicals from stormwater run-off. Pollutants are filtered out as water moves through the ground.

Healthier air

• Absorbing pollutants like ozone, nitrogen dioxide and sulfur dioxide through leaves
• Intercepting particulate matter like dust, ash and smoke
• Releasing oxygen through photosynthesis
• Lowering air temperatures, reducing the production of ozone
• Reducing energy use and subsequent pollutant emissions from power plants

Reduced carbon dioxide levels