We humans sure do like to organize things into categories. One of those category partitions is “belongs” and “doesn’t belong”.
More often than not, the things we point at and say belong are the familiar things, and the ones we like. Something that’s new or different, that comes from the other shore or the other side… we feel differently about those things. Sometimes we call them “exotic” — things we like the look of and want around, at least a little, with some controls put in place.
If “exotic” is the nice term we use for things that don’t belong, then “alien” is the word we use when our hackles are up. If something is considered “alien” that’s a pretty good indication we want it gone, or at least want to fence it up so it doesn’t spread out any farther.
When we’re talking about biology and ecosystems, the word we usually use is “invasive”. As in, an “alien” species is “invasive”. It’s a loaded word, and immediately makes us think of associated military terms and tactics of war, so perhaps it’s no wonder invasive species get such a bad rap.
Ken Thompson’s book “Where Do Camels Belong? Why Invasive Species Aren’t All Bad” is an interesting read on the topic of what makes a species invasive, and reflects a lot of changing ideas about ecosystem biodiversity. He argues that, most of the time, our war against invasive species is misplaced, unnecessary and, often, futile battles that can do as much environmental damage to the so-called native species as the invaders.
There are some species that really have wreaked havoc in some places. The brown tree snake’s arrival in Guam devastated the bird population. We did a show way back with Will Stolzenburg about the truly epic efforts humans have launched around the world to protect fragile island ecosystems from arriving rat populations. But we’re not very good at differentiating genuinely problematic invasive species from the species that are merely migrants. And even when we can definitively point at a species and say “YOU, you’re a problem for sure”, there often isn’t a lot we can do to unscrew that pooch.
Change is hard, especially with a guilty conscience. Knowing it was human arrival that triggered some of these seeming ecological catastrophes makes it hard to turn away and let the ecosystem sort itself out. Often, visible invasive species can be a symptom of human impact and how we’ve changed the environment: if a new species can adapt better to the way we’ve changed the world around us, then it will probably flourish as we flourish.
Ken Thompson’s book reminds us to look beyond our assumptions for actual evidence of harm, to remember that plants and animals have always migrated to new ranges and territories, and to consider that ecologies and environmental systems often work on a much longer timescale than our individual human lives. Sometimes things get thrown out of whack for a while when a new species shows up and makes a splash. But, he argues, the ecosystem will often balance itself again after a time, and things settle down into a new normal.
There may be a cost to invasive species, but there’s also a very real cost to trying to eradicate them. There’s also a risk of stamping out assisted migration strategies that could save endangered species before we’ve had a chance to see if they’re worthwhile. And if we’re going to talk rhetoric about invasive species, we should remember that a lot of the plants and animals we take for granted as being “native”, or just nice to have around, also come from somewhere else. If we’re going to cherry pick which species to wage war against, and which to invite into our gardens, we should at least be aware we’re doing it.
More reading about invasive species and whether or not they’re as bad as we think they are:
- Opinion: It’s Time to Stop Thinking That All Non-Native Species Are Evil at National Geographic, by Emma Marris.
- Patterns In Nature: Some Thoughts on Invasive Species by William Graham, marine biologist
- Don’t Sweat the Invasion at Slate, by Rebecca Tuhus-Dubrow
- Ecologists: Time To End Invasive-Species persecution at Wired, by Brandon Keim
- Rat Island: Predators in Paradise and the World’s Greatest Wildlife Rescue by William Stolzenburg
Featured photo of purple loosestrife in Ottawa by Jamie McCaffrey.