One of the ongoing aims of the TRNWR is removing “invasive species” from the refuge. The term I prefer is “introduced species” because, if you look into the history of the animals or plants labeled that way, you’ll find that people either brought those organisms into a new environment because it seemed like a good idea at the time, or they altered the environment in a way that made it easy for foreign species to move from their original habitat to a new, vulnerable one. Nutria, canary grass, and bullfrogs are examples.
So-called invasive species don’t take the initiative to invade a la War of the Worlds; they get introduced by human action and then they thrive and take over. But sometimes there’s the lingering question: Why do they succeed? After all, if the native organisms in an environment have an established ecosystem where everybody is adjusted, how is it possible for interlopers to outdo them?
Usually the break-out of invasives is attributed to lack of predators, or to human interventions such as clear-cutting or industrial-style farming that so disrupt the environment that niches of opportunity are created for invaders. But science writer Carl Zimmer reported in the NY Times last week about a study recently published that looked at big-picture situations such as invasion on both ends of the Suez Canal connecting the Indian Ocean and the Mediterranean Sea. It came up with an additional hypothesis.
Ecologists Jason Fridley and Dov Sax found that many species have successfully moved from the Indian Ocean to the Mediterranean, but not so much the other way around. They concluded it is evidence for the hypothesis that some regions of the world — like the Indian Ocean or East Asia — are “incubators” for evolution. Organisms from these old, highly-diverse environments have had a lot of practice adapting to many situations whereas organisms in the younger, less-diverse Mediterranean Sea are not as versatile. In other words, some species have had so much evolutionary experience they are better at the game than others.
Actually, Charles Darwin observed this and mentioned it in The Origin of Species. This recent study is perhaps the best one so far to get data to test Darwin’s notion.
I’ve taken an interest in this not just to quibble about terminology but because I think it’s important for us Volunteer Naturalists at the Tualatin River Refuge to provide the right perspective about the “invasive species” problem to the kids we interact with. Once again, as with so many problems we face these days, it’s human ignorance and shortsightedness that have created this environmental problem. Perhaps we can excuse our forebearers for lack of knowledge, but there’s no excuse now. We know everything’s connected, and we have no more room for error.