ENVIRO NOTES: Take care with trees

Last July, my environmental column outlined the many benefits we derive from growing trees in our neighbourhoods.

A subsequent column set out some of the related environmental problems which arise from concentration of our population in vast cities, concrete jungles lacking greenery.

Modern technology offers a way to ameliorate this situation and put dollar signs on the costs of action or inaction.

A novel computer program, i-Tree Eco, uses field data which can be collected in any community from either a complete inventory or from random plots to describe forest structure and, by hourly recordings of air-borne pollutant and meteorological data, to quantify environmental effects imparted by the trees.

These effects include removal of particulates from the air, carbon sequestration, oxygen discharge, shading effects and pollen counts.

The i-Tree Eco program can be applied at will to a single tree, a park or a whole municipality. It derives from the Urban Forest Effects computer model, developed jointly by the U. S. Forest Service and many academic and industrial collaborators.

One such data set indicated that Vancouver’s loss of trees between 1972 and 2000 resulted in the discharge of some 963 million cubic feet of contaminated stormwater directly to streams.

To ameliorate such events in future,  Vancouver plans to plant an additional 150,000 trees by 2020.

Although the case for trees is strong, choice of species is a vital consideration.

Trees such as Douglas-fir, western red cedar or redwoods, which may grow to 100 metres, are, obviously, not suitable everywhere.

Cottonwoods, with their surficial roots, can cause heaving damage to sidewalks, thus making for dangerously uneven footing.

Deciduous trees will have no foliage through winter, and thus are preferred for the south side of buildings where they will provide shade in summer but allow sunlight to pass through in winter. These are just some characteristics to be kept in mind when developing a tree plan.

White Rock has an Integrated Stormwater Management Plan, an Environmental Strategic Plan and is linked to the provincial Trees for Tomorrow initiative.

Surrey, with a commendable ratio of 4.5ha of green area for every 1,000 people, has a Park Natural Area Strategic Management Plan, a Shade Tree Strategic Management Plan, an Ecosystem Management Strategy and is working on a Biodiversity Conservation Strategy.

Obviously, both cities have trees and the environment in their sights but no specific urban tree management plan.

While both have tree-preservation bylaws in place, neither enforces it rigorously, and penalties for infringement are hardly deterrents.

Dr. Roy Strang writes monthly on the environment for the Peace Arch News.

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