Protecting the urban forest

Winnipeg’s canopy of trees, its urban forest, is in a slow decline. Last year, approximately 6,600 trees were lost, either due to disease, decay or for development purposes and about 4,000 of them were on private land. The city planted 1,500 trees on public land — boulevards and parks.

On the plus side, there are an estimated eight million trees in Winnipeg, so from a bird’s perspective there’s still a lot of leafy greenery. The Dutch elm disease program has held down the annual toll of that scourge; the program is testament to the value of a dedicated, sustained and well-funded strategy — those losses are replaced one for one on public property. The elm and its majestic canopy holds a special place in the city’s landscape psyche.

That same story will not be written about Winnipeg’s and Manitoba’s ash trees. Winnipeg’s estimated 280,000 ash trees are now the dominant species on the city’s boulevards and in its parks. The emerald ash borer, which has decimated ash trees in Eastern Canada and the United States, is expected to make its voracious appearance in Manitoba shortly. (Traps are being set by the city and the Canadian Food Inspection Agency to detect its arrival — the borer can live in a tree for two years before noticeable symptoms appear so it may actually be here now.) But there is no good defence against the bug, except to remove the infected trees and hope its march is halted, although experience proves otherwise.

The only meaningful response to the infestation will be to cull the diseased trees and replant. That means protecting the urban forest will require more money for planting.

Winnipeg’s forestry branch has only recently seen its budget approach meaningful levels. This year, some $8.68 million goes to planting, pruning and removing, $3.68 million of which is dedicated to the elms alone. Of the $5 million set aside for all other tree business, $800,000 is spent on replanting. To replant one tree for every one lost, that allotment would have to double. In 2011, the projection for the tree-planting budget is to rise to almost $2 million, but many more trees will be cut down because there will be more money to do that, as well.

And the cutting and replanting may lose ground on maintaining a healthy forest in Winnipeg if the speedy ash borer makes its appearance.

There are many reasons why the trees in Winnipeg have fallen so vulnerable to disease and infestation. Outside of the elm program, tree replanting has not been high on the priority list — until recently, in fact, there has not been an inventory taken to know how many of which kinds of trees are in what state across the city. Emphasis is put on pruning and cutting trees to defend the health of the urban forest, and to keep property and people safe.

But the forestry branch is still trying to describe exactly how much of the urban forest is dead and dying. Further, there is no program to encourage or help fund replanting on private property, where most of the loss occurs. That is something Winnipeggers ought to think about, that city councillors should consider once the real toll of dying trees is known.

The emerald ash borer arrived in North America eight years ago, and for at least two years its appearance in Winnipeg has been thought imminent. The city is only now considering a mass public education campaign about the dangers of transporting wood, particularly firewood, and wood products across borders — human transport of the borer rapidly increases its spread — and how to detect the visible symptoms of infection.

Past planning errors, such as monoculture planting, have made Winnipeg’s leafy canopy vulnerable. The emerald ash borer is simply the latest threat that is having its way with an urban forest. The battle against Dutch elm disease is a success, and is a model to follow in that it shows the value of vigilance and dedication.

As city council ramps up spending on taking down diseased trees, it must aim to replace them, one for one, with a new tree planted.

Republished from Winnipeg Free Press July 2, 2010

Comments are closed.