Each year on February 15, Canada celebrates the inauguration of its national flag, which has featured the iconic maple leaf since 1965. But while we honour maple trees as symbols of Canada, we put them at unnecessary risk. Imagine the day that North America’s maple trees start dying like ash trees, that are already being killed by the invasive emerald ash borer (it kills over 99% of ash trees). It would mark the end of fall colours, maple syrup, many of our street trees – and really a way of life in eastern Canada. It sounds hyperbolic, but this is a very real potential future if the invasive Asian longhorned beetle establishes in North America – most of the forests of southern Ontario, Quebec, and swaths of the maritimes would become unrecognizable, as the dominant forest tree disappears.
This scenario isn’t just speculation. Asian longhorned beetle has been found in various parts of North America, and was present in the Greater Toronto Area between 2003-2006, and again in 2013. The latter was probably a second introduction that has now been eradicated. It begs the question: why does this dangerous pest keep showing up in North America? The answer: it usually gets imported in wood boxes and palettes. It’s a problem that should have been dealt with in 2009 when a new international standard for the treatment of wood products (ISPM 15) was fully implemented. But research since then has shown that the infestation rate of wood packaging was only reduced by half. An estimated 13,000 shipments contaminated with live wood-boring insects could still enter the US every year. That’s a lot of pests, any one of which could be devastating to the forest industry, parks, and our street trees. Canada is probably not much better off.
We have the solution
The Cary Institute, which is a US-based research center, is promoting “Tree-SMART Trade” which aims to keep tree killing insects and pathogens from crossing borders, as well as improving detection and response programs. Measures can be as simple as enforcing adequate penalties for violations (i.e. there should be a cost for putting forests at risk). The policy measures being promoted through Tree-SMART Trade in the US make sense for Canada too, according to Anne Bell, director of conservation and education with Ontario Nature.
The up-front cost of preventing invasive species more than pays for itself, since we already spend a lot of money managing and responding to invasive species. Prevention is not only far more cost effective, it also shifts the cost of invasive species away from municipalities, conservation authorities, home owners, and tax payers, and back to corporations that are importing the goods and making profits. And the costs, particularly to municipalities, are large – estimated at over half a billion dollars for emerald ash borer in Canadian urban areas alone. We could expect the cost of an Asian longhorned beetle invasion to be much higher. If you’re in the US you can sign a petition for legislative action on this problem organized by the Cary Institute, and here is the petition for Canada.
The many faces of invasive pests
The arrival of the emerald ash borer in Ontario in 2002 has been a wake-up call for how destructive invasive forest insects can be, but Canada has a long history with tree pest and pathogen invasions. Among the earliest was larch sawfly, which was found in Quebec in 1882 and within decades wiped out most of Canada’s tamarack forest. Because the sawfly overwinters in the soil the only place tamaracks have survived is in areas where the soil is wet or seasonally flooded – we think of tamarack as a tree of wetlands and shorelines, but once it was a common tree in upland forests.
Beech bark disease was imported to Nova Scotia in the late 1800’s, where it killed and deformed most beech trees and started working west and south through the range of beech. It has been killing trees in Ontario for several decades and recently reached Muskoka. The only hope for beech is resistant trees (1-4% of trees have resistance).
Most people have heard of Dutch elm disease and chestnut blight, which eliminated major tree species from our forests in the early-mid 20th century. Again the main hope is resistant trees, but finding resistance in the remnant trees has been a challenge. The University of Guelph Arboretum is working on a project to collect cuttings from resistant elms in Ontario and interbreed them. Butternut canker has killed most of our butternut trees. Gypsy moth and white pine blister rust damage and kill trees every year.
Unfortunately we’re only in the middle of a deluge of tree-killing invasive species – there’s a long list of potential future invaders, and many that are already in North America and spreading. Some of the most imminent threats to Ontario include thousand cankers disease (which kills walnuts and butternuts), oak wilt, Asian longhorned beetle, and hemlock woolly adelgid (which is probably now established in Ontario).
The invasive species problem is a climate change problem
Invasive species exacerbate climate change by destabilizing ecosystems, killing millions of mature trees, and releasing vast amounts of carbon dioxide. In the United States alone invasive species kill enough trees to release six million tons of CO2, equal to the emissions of five million cars. If Asian longhorned beetle establishes I expect this would increase significantly. Since simple measures would go a long way towards controlling the spread of invasive species, this is low-hanging fruit for addressing climate change.
Changing the end game
We can still honour the Canadian flag without irony each February 15, and it’s famous sugar maple leaf. But if we want a future where we still have urban forests and real maple syrup, where Gatineau, Algonquin, and countless other parks aren’t filled with the skeletons of dead trees, we need to take this problem seriously. It will require more action at the federal level, and ideally international cooperation. The good news is it will save us money, and protect all our tree species, not just maples. But I have yet to see this get the attention it deserves as a critical environmental and economic issue. I look forward to the day I can once again simply celebrate the inauguration of Canada’s national flag, and not worry about the functional extinction of Canada’s national symbol. We’ve had our iconic flag for 56 years – will we still have maple forests in another half century? I don’t want to be one of the last generations that remembers Canada’s famous fall colours.
Learn more
Nonnative forest insects and pathogens in the United States: Impacts and policy options
Increasing forest loss worldwide from invasive pests requires new trade regulations