Eurasian water-milfoil (Myriophyllum spicatum). [Ontario Federation of Anglers and Hunters photo]

Invasive species can be a matter of perspective

Column: Great Outdoors/James Murray

The Invasive Species Council of British Columbia says invasive species are among Canada’s greatest threats to the survival of our wild animal and plant life.

“These invaders arrive, often accidentally, from elsewhere in the world and, in the absence of natural predators, kill, crowd out or otherwise devastate native species and their ecosystems. These non-native plants and animals not only threaten to transform the wildlife, woodlands and waterways that Canadians depend on, they cost this country billions of dollars in losses to forestry, agriculture, fisheries and other industries affected by their impact.”

We’ve had a problem in many of our lakes with Eurasian water-milfoil for some time. It was introduced to the United States in the 1940s as a decoration in aquariums, likely dumped into a lake or pond and has since spread throughout North America. There are also new concerns now about the introduction of other invasive plant species such as knotweed, periwinkle and the flowering rush plant – not to mention zebra mussels. The list goes on.

A few years back there was an illegal introduction of yellow perch into a number of B.C.’s Southern Interior lakes which threatened the very nature and make-up of those drainage systems. When non-indigenous fish species are introduced into a system, they compete with resident populations for food. Consequently, some of these lakes ended up having to be poisoned-off in order to eradicate the yellow perch. Most of our Interior lakes and streams are part of much larger watershed systems. Once an invasive species becomes established in a body of water they tend to take over and then spread throughout the entire system. A lot of time and money was spent undoing the mistakes of a few ill-informed individuals who either knowingly or unintentionally broke the law.

Related: White Lake part of invasive goldfish study

One would think education would be an integral part of prevention. However, the problem is not all that simple. When wildlife biologists and other experts use words like “alien,” “exotic” and “invasive” to describe plant and animal species introduced into non-indigenous environments, it can be as much a question of perspective and semantics as anything else. After all, wildlife species have been dispersing and re-dispersing themselves throughout the world for millions of years. The only real difference between so-called “historical” introduction of species and those which have taken place in the past couple of hundred years, is the rate and scale with which they have taken place. Before human travel became widespread, plants and animals arrived on foreign shores mostly by chance. In some instances they swam across oceans, migrated across continents, drifted on the air and water currents or hitched a ride with other travellers until they hopped off in a new habitat.

Related: Help stop the spread of invasive plants in the Okanagan-Shuswap

This is certainly where semantics come in. Plant and animal species that arrive and establish themselves in an ecosystem where they did not evolve are often described as “alien” or “exotic.” Once established beyond the initial point of introduction, they are then considered “naturalized” components of their new environment. A naturalized species is only considered “invasive” when and if it displaces native species. The so-called invasive species tend to reproduce quickly, spread rapidly and compete aggressively with indigenous species, in large part, because there are usually few or no indigenous species that can or will predate on the new arrivals.

Related: Preventing invasive mussels in the Shuswap

However, these so-called alien/invasive species did not actually sit down and plot out any sort of intentional invasion of their new home and surroundings. They simply one day found themselves there and then proceeded to go about the mundane business of surviving and reproducing. A yellow perch does not know that it has been somehow transported to a new lake or stream. It just does what the species has always done.

A good example of perspective would be when humans allow cattle (a domesticated species of bovine raised to generate monetary profit) to range further and further into timbered areas which wildlife such as wolves call their home. The wolves end up predating on cattle which are grazing on their home turf. So who is the invasive species? Expecting wolves not to predate on cattle grazing in their backyard is sort of like baking up a batch of chocolate cupcakes, setting them on the kitchen table to cool and telling the dog not to touch them.

Perspective and/or semantics. The bottom line is understanding how the introduction of non-indigenous plant and animal species affect ecosystems and natural habitat – both in the short term and long term. We are all responsible for our own actions.


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