Ack-ack-ack-invasion

The words we use matter.

At ACTWS 2019 this past weekend, I heard many speakers talk about the white-tailed deer northward range expansion as “invasion.” But species naturally expand and contract their ranges in response to many factors from predation, to climate, to rainfall, to human land use… It’s a natural process that has taken place for millennia, and we see the results of past range movements through both the current distribution of species and through historic hunting/trapping records (for near-time) or the fossil record (for deep-time). We know it’s happened before because we have evidence of this happening—plants and animals moved south to escape progressing glaciers during the last ice age—and northward again as glaciers retreated.

However, the term “invasion” has a qualitatively negative undertone. It makes you think of something foreign like Mars Attacks. It evokes a type of xenophobia.

You don’t think of a benign butterfly invasion, you think of killer bees. Like there’s some kind of danger involved and you should be fearful of what the impacts will be.

Invasive species are those that have been introduced to an area outside their natural range. That can be house cats that have become feral. Rats that hitched a ride on shipping vessels. Even garden plants that could take over a natural ecosystem – like purple loosetrife or English ivy. They were purposely (as in the case of garden plants) or inadvertently (like in the case of stow-away rats) brought to areas outside where they would naturally occur.

Introduced species are invaders. They may come into ecosystems that do not have predators for them, they may outcompete native species or be overly effective at feeding. Examples include escaped farmed Atlantic salmon, rabbits in Australia, and many many more.

So we may not want mountain pine beetle to be expanding their range northward in response to climate change. We may not want white-tailed deer to move northward. But it’s still a natural process. So then why is it that we don’t want that?

Is it because we are fearful of change? Even when change is good, we seem to fear change.

In the case of range changes, is this dislike of change because we are comparing what we see to some past baseline? The problems of baselines are that they shift from generation to generation, and you could be focusing on a baseline that is no longer ecologically possible.

Or could it be because we are using terms laden with negative value, hence biasing our reaction to the process of natural range expansions or contractions?

Maybe it’s a combination of all three—fear of change, shifting baselines and negativity bias—but it seems that indeed, words do matter.