Monday, August 10, 2009

Durham Street Tree Inventory/Canopy Analysis

By Alex Johnson, Durham Urban Forestry Manager

The following article appears in the August 2009 FHNA newsletter...

Trees provide a lot to us as residents of Durham.  Just what it is they do for us is sometimes hard to assign a value to.  This makes it hard to justify spending the money needed to maintain an urban tree canopy, especially when other issues clamor for scarce resources.

The good news is that there is a way to estimate the value of an urban forest.  Thanks to a partnership between the Davey Resource Group and the US Forest Service, there is a suite of software called i-Tree that works in conjunction with a set of tools developed specifically for inventorying and evaluating the value, condition, and canopy density of an urban forest.

Last year, the city of Durham received a grant from the NC Department of Environment and Natural Resources to conduct a survey of Durham’s street trees. This involves taking a random sample of street segments amounting to 3% of the city’s overall “grid.”

Starting this past May, volunteers have come forward to be trained in collecting data along roadside rights-of-way.  Since then, they have been counting, measuring, identifying, and evaluating the health and maintenance needs of trees on city property as well as taking note of places where trees are absent but could be planted were there resources available to do so.  When all of the data come in, we will be able to provide the city with the following information:

·       Species composition of the urban forest

·       Age/condition distribution of city trees

·       % canopy coverage citywide

·       Number of vacant planting sites

·       Number of trees in need of maintenance

·       Benefits of city trees

o   Stormwater runoff

o   Air quality / carbon sequestration

o   Energy conservation / cooling

The overall “cost/benefit” analysis will provide proof that having and maintaining urban trees is a wise investment.  Many thanks to the volunteers that have come forward from Forest Hills to help out!  There is still much more to do, so if you are interested in participating, please contact me directly: Alex Johnson, Urban Forestry Manager, at or 560-4197, extension 275.

Note from FHNA President:  Four Forest Hills residents have volunteered and assisted Alex Johnson in the Durham tree survey:  Barbara Braatz, Carsten Rist (featured above), Norris Cotton, and Tracy Mancini