As if Winnipeg’s urban forest didn’t have enough trouble with Dutch elm disease, now our canopy of trees is threatened by the emerald ash borer.

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This article was published 15/12/2017 (1501 days ago), so information in it may no longer be current.


As if Winnipeg’s urban forest didn’t have enough trouble with Dutch elm disease, now our canopy of trees is threatened by the emerald ash borer.

Native to China, the borer is an invasive species in Manitoba which could destroy all of the city’s 350,000 ash trees within 10 years. The Canada Food Inspection Agency says infested trees die within two to three years, but heavily infested trees can die in as little as one year.

CANADIAN FOOD INSPECTION AGENCY</p><p>The emerald ash borer is killing our ash trees.</p></p>


The emerald ash borer is killing our ash trees.

As reported earlier this week, according to city forester Martha Barwinsky, "Our canopy is at risk... When we look at the percentage of elm and ash on boulevards and parks, we have 60 per cent of our canopy."

Winnipeggers take our many shady streets for granted, but the comfort and beauty provided by boulevard trees took decades worth of investment. Without those trees, our streets become more intense heat sinks, the sidewalk-level climate is subject to more extremes and we lose a huge chunk of biodiversity. The total value of all boulevard and park trees is an estimated $437 million.

The emerald ash borer has been found in 31 U.S. states. It was first detected in Canada in 2002 in Windsor, Ont., but it has spread rapidly from there. In North America, it has few natural enemies — and the ash trees here have little resistance to it.

The Emerald Ashborer Information Network says the bug has killed hundreds of millions of ash trees in North America and "cost municipalities, property owners, nursery operators and forest products industries hundreds of millions of dollars."

The ability to catch their presence is limited, though in the United States, Department of Agriculture scientists have developed a green prism trap system for detecting emerald ash borer infestations.

The City of Winnipeg should continue to look at options for detecting and controlling the ash borer, in addition to the work it is already doing to protect our elm trees.

And given the backlog in combating Dutch elm disease, more money for these efforts is both needed and justified.

The city is strapped for cash, as evidenced by the recently announced hikes in parking rates and bus fares. But an ounce of prevention is worth a pound of cure. Money spent protecting what we have will be less expensive than trying to reforest everything from scratch.

And given the infestation will likely not be limited to the city, the province should move to support protecting our canopy, as well.

It may be that we can’t save the ash trees, but we should still have an aggressive reforesting plan in place for areas likely to be hit hard by the loss.

This kind of infrastructure can’t be rushed; it takes careful forethought and decades of favourable growing conditions.

We may well be best off to start thinking that way, as we save the trees we can. Going forward, what species (or, better, mix of species, to avoid monoculture) are best suited to our climate? How long does it take them to become fully established? And how would they interact with our existing flora and fauna?

One thing so far is clear: absent naturally occurring predators and resistant trees, the emerald ash borer is here to stay — and it’s very likely our ash trees are not.