How Trees Work for Us
Updated: Apr 22, 2020
Do you know how much carbon dioxide (a greenhouse gas) your trees are keeping out of the atmosphere?
Carbon dioxide (CO2) is a naturally occurring chemical compound composed of two oxygen atoms bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in the Earth’s atmosphere as a gas (Wikipedia).
CO2 is released into the atmosphere naturally, and through human activities like the burning of fossil fuels. Scientific concensus is that increasing concentrations of CO2 in the atmosphere since the industrial era are contributing to significant, and dangerous, changes in climate (see www.climateottawa.ca).
CO2 is also removed from the atmosphere by plant photosynthesis and by the exchange of carbon dioxide between the atmosphere and the oceans. Growing plants remove CO2 and store it as carbon in plant biomass, and release the oxygen back into the atmosphere.
The biggest Bur Oaks in our neighbourhood each remove 1,119 kg (2,462 lbs) of CO2 per year (see calculation methods at iTrees). There are 50 Bur Oaks in Champlain Park 50 cm or more in diameter, the measure used by the City of Ottawa to distinguish a “distinctive” tree. Taking into account our detailed survey of these trees (including their location and diameter) we estimate that these “Champlain Oaks” alone remove 40,284 kg (88,632 lbs) of CO2 from the atmosphere EVERY YEAR. Each of the big maples in the neighbourhood also remove 568 kg of CO2 from the atmosphere each year.
Is that a lot? Well, yes and no. It is clear that only dramatic changes in the amount of CO2 released by people and corporations into the atmosphere, and removed by plants and oceans (carbon sinks) will save the planet from massive climatic changes. The threat is real, and it is daunting. The Champlain Oaks are working for us, however. The trees remove every year the equivalent of emmissions by 3.7 “average” car owners. They lock up atmospheric carbon in their roots, trunks, stems and leaves. By shading our homes and streets they also reduce heating and air conditioning demands on the electrical power grid totalling 11,304 kilowatt/hours. The leaves snatch dust and smoke from the air, thereby absorbing pollutants like ozone, nitrogen dioxide and sulfur dioxide (Bur Oaks are particularly good at this). The 50 Champlain Oaks intercept yearly 33,652 liters of stormwater runoff that would otherwise erode the soil and pollute our drinking water.
The contribution of trees to property values is subject to more personal and variable considerations. There is little doubt, however, that people that live in this neighbourhood like their trees and that others are attracted to the neighbourhood in part because of the big trees that grace our streets and backyards. Some attempts to quantify this contribution use a measure of leaf surface area to determine increases in property values, reflecting what real estate agents know — home buyers are willing to pay more for properties with ample trees and views of large trees. Other estimates, including the method used by professional foresters, are based on the cost to supply and install a replacement tree.
The grandmother Bur Oak cut down on Northwestern Avenue earlier this year had an appraised value of $11,940. While this does not in my view reflect the true loss to community heritage suffered, extension of this appraisal to the 50 Champlain Oaks would give an appraised value in the order of $430,000. To give perspective, this is more than the average house price in Ottawa ($338,000 as of February, 2011). There are, of course, many other fine trees in our neighourhood that contribute to the “curb appeal” of Champlain Park. The various species of maple, red oak, American basswood, spruce, pine, black walnut, cedar, ash and various other tree species documented in Champlain Park (see a forthcoming post) create an Urban Forest we can be proud of and must fight to protect. An upcoming exhibit at the Bytown Museum on the history of Ottawa’s urban forest will give us all a chance to identify actions relevant to the situation today based on lessons of the past.
This combines well with a new survey on our neighbhourhood’s views and practices related to environmental issues, sponsored by the Environment Committee of the Champlain Park Community Association. The on-line survey provides an opportunity for us to assess where we are really at, and plan to make Champlain Park the greenest neighbourhood around.