Streets Lined with Gold
Streets Lined with Gold
By Charlie
Hall, AIB Past President
Streets
lined with gold? Not exactly, but a new report from the U.S. Forest Service's
Pacific Southwest Research Station estimates trees lining California streets
and boulevards provide benefits to municipalities and residents worth $1
billion.
One of the
six criteria that are used to evaluate cities participating in the America in
Bloom awards program each year is “urban forestry.” It sounds rather
straightforward (e.g. all the trees we have in our city), but it is
more comprehensive than that. Judges evaluate the distribution, variety, and
suitability of trees; new tree plantings; whether or not a formal urban tree
program exists; qualified tree-related personnel or access to trained
individuals; whether or not the city has a tree inventory or database;
frequency of tree surveys; tree care and maintenance programs; preservation of
heritage trees and wooded lots; and any scheduled succession tree plantings. Wow!
Another
key metric (that is often hard to quantify) involves the economic contributions
of the urban forests in a particular community. I recently came across an
excellent paper entitled "Structure, Function and Value of Street Trees in
California, USA," published in this month's issue of "Urban Forestry
and Urban Greening." It is a case study of a comprehensive inventory of
"street trees" within California and it represents one of the best
of-to-date analyses of the value of street trees I’ve seen.
Using
municipal inventories analyzed in i-Tree
Streets, a computerized tree inventory and management suite, researchers
were able to create a composite picture of not only the number of California's
street trees, but also their species, size, location and associated benefits.
With an
estimated 9.1 million trees lining California's streets and boulevards, it
averages to about one street tree for every four residents. But according to
the study, room remains for another 16 million street trees to be planted, if
resources allow.
Sometimes
it’s easy to think of trees along city streets as offering mere aesthetics, or
worse, a nuisance with falling leaves and limbs or uprooting sidewalks. But
what their study shows is that these trees have a real monetary benefit to the
municipalities and residents who care for them.
From
carbon storage ($10.32 million) and removal of air pollutants ($18.15 million)
to interception of rainfall ($41.5 million) and energy savings from both
heating and cooling ($101.15 million), California's street trees are paying big
dividends. They even bolster property values and home sale prices to the tune
of $838.94 million.
The
researchers calculated that for every $1 spent on planting or maintaining a
street tree, that tree returns, on average, $5.82 in benefits. Another important
factor is that these trees are benefiting their communities 24 hours a day, 365
days a year.
The report
also highlights trends and tree demographics. The authors say they hope this
information will guide urban foresters in future decisions regarding what trees
to plant and where. For example, while the number of street trees has increased
from 5.9 million in 1988, tree density has actually fallen from 105 to 75 trees
per mile, nearly a 30 percent drop. And while statewide species diversification
appears respectable with only one species claiming more than 10 percent
relative abundance (London planetree at 10.5 percent), individually, 39 of the
49 studied communities were over-reliant on a single species, potentially
making their urban forest susceptible to a species-specific disturbance or
pathogen.
Municipal
foresters can obviously use the data from this study to see how their trees
compare to other cities in their climate zone or in the state. It might also help
in the allocation of resources, whether it be to increase planting to address
low density or species diversification, increase pruning to manage
predominately younger trees for structure and form, or to control pests and
disease or intensively manage older trees so as to not lose them prematurely.
Of course,
we know that they provide an excellent structural background to the other
landscape amenities offered by our America in Bloom cities! So use this case
study as a tool to convince your local community to invest in trees!
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