As published in The Erin Advocate
Invasive species of plants and animals not only threaten local biodiversity, but create a costly burden for our society. The damage to agriculture and forestry, plus the costs of suppressing the invaders is estimated at $138 billion in the US. And with fears of biological attacks, it has also become a Homeland Security issue.
For humans – perhaps the most invasive of all species – the effort to control relatively new arrivals is often a losing battle. It is simply impossible to allocate enough resources to reverse these forces of nature. Ironically, we have in some ways unleashed them upon ourselves, by clearing land, moving species away from natural predators and accelerating climate change.
Some biologists argue that the tumultuous conditions created by globalization, human population growth and climate change have made the division between native and non-native seem irrelevant. Indeed, most of our food crops and livestock are not native to North America, and farming has been a prime destroyer of biodiversity. So it is more important than ever to defend the healthy native ecosystems that we still have.
"It is about picking your battles," said Rod Krick, a Natural Heritage Ecologist with Credit Valley Conservation (CVC), at a recent seminar on invasive species. CVC has made major efforts to control invasives on its own land and to educate private landowners about the threats.
"There are some that are so widespread that there is no feasible way to control them. The ones we can do something about, we focus on them, and on areas that still have a lot of native biodiversity."
One invader that has become virtually native is reed canary grass, a tall, perennial bunchgrass, up to 2.5 m in height, imported from Europe about 1850. It has been used as a landscaping ornamental, for hay and as a livestock forage crop. It creates single-species stands, crowding out other wetland species.
"While still considered invasive in our region, it is so widespread and so integrated into our wetland flora that management is all but impossible now," said Krick. The same approach has to be taken with certain species of fish – common carp and northern pike are considered invaders in the upper Credit River, but getting rid of them is considered unrealistic.
"This does not mean they are not invasive though, or that we accept them," said Krick. "Complete control may not be possible, but in some situations we can ‘manage’ them to acceptable levels."
Speaking in Erin recently, Don MacIver, Mayor of Amaranth Township and a senior climate change scientist with Environment Canada, said that once CO2 levels double, the conditions for good forest biodiversity that now exist near Windsor will be up north of Sault Ste. Marie.
"There is a tremendous migration that is expected in terms of forest species northward as the climate warms. What happens to the native tree species? They are under threat, they are growing outside their climatic optimum, and as a consequence they are subject to disease and infestation from invasive species. It's not surprising, we see the Ash Borer here today...there are many more that will come in from the United States and elsewhere, and it is going to be very difficult to maintain native tree species in this area."
The Emerald Ash Borer attacks and kills healthy ash trees. The Canadian Food Inspection agency has urged Wellington County residents not to move firewood away from source areas, to limit the infestation.
MacIver said that with proper land use controls (restriction of development), it may be possible to reverse the decline in biodiversity by 2020, and even restore it to the level it was at prior to European settlement, by the end of this century.
"Climate change has the opportunity to re-establish the original baseline of 1792, but it won't be with native tree species. It will be a combination of native and new. You have the ability right now to grow Washington DC species here in Ontario. The climate has changed, but we haven't caught up to it. We're still out there planting native tree species.
"You have the opportunity to bring in new species. That's called planned adaptation, assisted migration. It means sitting down with the community and deciding how you want that community to look."
Credit Valley Conservation is studying the impact of climate change and planning for adaptation, but has not yet changed its tree planting practices.
"We aren’t necessarily looking at new species to bring here that may be better adapted," said Krick.
"The most recent literature says assisted migration is generally not recommended by scientists and practitioners at this point in time. Any work done in this area has to be conducted carefully and within a rigorous experimental framework, as we don't want to be introducing problem species and this would include non-natives. Rather as a first step we are looking at creating better connections between natural areas that will allow species to move more freely to ‘assist’ with more natural migration."
The Ministry of Natural Resources is conducting experiments on the success of trees planted outside their normal ranges. While the areas being planted by conservation authorities would not immediately have a major impact on the forest population, they may be able to establish seed production areas for future climates, according to Barb Boysen of the Forest Gene Conservation Association.
"Though southern sources may suffer initially under the more extreme northern conditions, within decades they might prove to be better adapted than local sources," she said. "If we waited decades to bring southern sources north, they may be too maladapted in their changed local climate to produce seed.
"Strategic action requires understanding that forests are a diverse mosaic of species and local populations of those species, which are genetically adapted to local conditions. As these conditions change, local forests may not have the genetic capacity to adapt. And there is evidence that the climate is changing faster than natural migration rates."
