A beautiful old sycamore tree lives next to the Conservancy’s newly opened Emerald Necklace Visitor and Volunteer Center in the Back Bay Fens. The tree’s diamater at breast height, or DBH, looks to be about four and a half feet. How much is this tree worth, in dollar value, to the City of Boston? To answer this question, the Leadership Team plugged a few pieces of data into the Tree Benefits calculator at www.treebenefits.com.
Zip code: 02115
Tree species: Sycamore, American
DBH in inches: 45 (the maximum possible input)
What land-use type is this tree nearest? Park or other vacant land
What did we learn? This 45 inch American sycamore provides overall benefits of $295 every year.
Your 45 inch American sycamore will intercept 7,538 gallons of stormwater runoff this year.
Urban stormwater runoff (or “non-point source pollution”) washes chemicals (oil, gasoline, salts, etc.) and litter from surfaces such as roadways and parking lots into streams, wetlands, rivers and oceans. The more impervious the surface (e.g., concrete, asphalt, rooftops), the more quickly pollutants are washed into our community waterways. Drinking water, aquatic life and the health of our entire ecosystem can be adversely effected by this process.
Trees act as mini-reservoirs, controlling runoff at the source. Trees reduce runoff by:
- Intercepting and holding rain on leaves, branches and bark
- Increasing infiltration and storage of rainwater through the tree’s root system
- Reducing soil erosion by slowing rainfall before it strikes the soil
Located in front of a park or other vacant land, this 45 inch American sycamore will raise the property value by $48 this year.
Trees in front of single family homes have a greater property value benefit than those in front of multi-family homes, parks or commercial properties. Real estate agents have long known that trees can increase the “curb appeal” of properties thereby increasing sale prices. Research has verified this by showing that home buyers are willing to pay more for properties with ample versus few or no trees.
This model uses a tree’s Leaf Surface Area (LSA) to determine increases in property values. That’s a researcher’s way of saying that a home with more trees (and more LSA) tends to have a higher value than one with fewer trees (and lower LSA). The values shown are annual and accumulate incrementally over time because each tree typically adds more leaf surface area each growing season. The amount of that increase depends on the type of tree – some add more, some less.
The 45 inch American sycamore you selected will add 199 square feet of LSA this year. In subsequent years it will add more, and the property value will increase accordingly.
Your 45 inch American sycamore will conserve 271 Kilowatt/hours of electricity for cooling and reduce consumption of oil or natural gas by 80 therm(s).
Trees modify climate and conserve building energy use in three principal 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.
Air quality benefits of your 45 inch American sycamore:
Air pollution is a serious health threat that causes asthma, coughing, headaches, respiratory and heart disease, and cancer. Over 150 million people live in areas where ozone levels violate federal air quality standards; more than 100 million people are impacted when dust and other particulate levels are considered “unhealthy.” We now know that the urban forest can mitigate the health effects of pollution by:
- 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 which reduces the production of ozone
- Reducing energy use and subsequent pollutant emissions from power plants
It should be noted that trees themselves emit biogenic volatile organic compounds (BVOCs) which can contribute to ground-level ozone production. This may negate the positive impact the tree has on ozone mitigation for some high emitting species (e.g. Willow Oak or Sweetgum). However, the sum total of the tree’s environmental benefits always trumps this negative.
This year your 45 inch American sycamore tree will reduce atmospheric carbon by 1,594 pounds.
How significant is this number? Most car owners of an “average” car (mid-sized sedan) drive 12,000 miles generating about 11,000 pounds of CO2 every year. A flight from New York to Los Angeles adds 1,400 pounds of CO2 per passenger. Trees can have an impact by reducing atmospheric carbon in two primary ways (see figure at left):
- They sequester (“lock up”) CO2 in their roots, trunks, stems and leaves while they grow, and in wood products after they are harvested.
- Trees near buildings can reduce heating and air conditioning demands, thereby reducing emissions associated with power production.
Combating climate change will take a worldwide, multifaceted approach, but by planting a tree in a strategic location, driving fewer miles, or replacing business trips with conference calls, it’s easy to see how we can each reduce our individual carbon “footprints.”