As detailed in the Municipal Forest Resource Analysis done for the city of Boise in 2007 by the USDA Center for Urban Forest Research, benefits of street tree are a big ticket item, with the benefits far outweighing the initial investment. This is like a breath of fresh air in our time of budget cuts and city services trimming. Here are the facts:
- Energy Savings: By shading homes and buildings, Boise's street trees currently save $331,756 annually in energy costs. One hundred street trees in Boise provide an average of $1,426 per year in net energy savings in the form of both electricity and natural gas savings.
- CO2 reduction and avoidance: Street trees directly sequester carbon in their wood and leaves, while shade reduces demand for heating and air conditioning, further reducing CO2 emission. Citywide, Boise's current street tree population reduces atmospheric CO2 by a net of 907 tons annually. This benefit is valued at $26 per 100 trees annually.
- Air Quality Improvement: Boise's street trees improve our air quality in 5 ways: directly absorbing gaseous pollutants (ozone, nitrogen oxides, etc.,), intercepting particulate matter (dust, ash, pollen, smoke), reducing emissions from power generators by reducing energy consumption, releasing O2 through photosynthesis, transpiring water and shading surfaces (which results in lower local air temperatures, thereby reducing ozone levels). Total annual benefit from Boise's current street tree population is about $6300. Annual benefits provided by 100 shade trees are estimated at $27.
- Stormwater Runoff Reductions: Healthy trees reduce the amount of runoff and pollutant loading in receiving waters in three main ways: interception and storage of rainfall, increase soil infiltration by rainfall through root growth and decomposition, reduction of soil erosion and surface transport. Boise's street trees intercept over 19 million gallons of storm water annually, or about 827 gallons per tree on average. This results in a total annual benefit to the city of $96,238. One hundred trees provide net benefits of $414 every year.
- Property Value, Aesthetic and Other Benefits: These benefits are more difficult to translate into economic terms. Wildlife habitat, privacy, reduction of sound pollution, human comfort, well being and other such benefits are included here. Estimates given in the Municipal Forest Resource Analysis are $561,917 for Boise's current street tree population. Broken down, 100 trees can provide $2,416 annually in such benefits.
- Total Benefits: Total of all benefits of Boise's street tree population amounts to over $1,000,000. This is equivalent to about $43 per tree in gross benefits. and about $10 per tree in net benefits. Breaking this down to a manageable number, 100 street trees provide $4,300 in annual gross benefits to Boise or about $1,000 in annual benefits. These benefits will increase as our current population of street trees grows, providing greater benefits as time goes by, as long as the trees remain healthy and continue to grow.
A much larger increase in benefits is possible only if Boise increases the population of street trees. The return on increasing the city's street tree canopy is very favorable for you as a home owner and for all the residents of Boise.