Invasive Plant Species in New England
Dave Jacke is no lone wolf in his opposition to the current framing of the non-native-species issue as one demanding urgent battle to thwart an aggressive enemy. Indeed, the more I poked around, the more people I found who hold the view that our ecosystems are in a constant state of flux. Part and parcel of this view seems to be an understanding of humanity’s role in the spread of non-native species, both in regard to the actual act of disseminating the plants via horticulture and in humans’ impact on the land, which tends to create soil disturbance and therefore opportunities for non-native flora to prosper.
To better understand this view, I called Mark Davis, professor of biology at Macalester College in Saint Paul, Minnesota, and author of the book Invasion Biology, which, despite its title, is decidedly skeptical of the field as a whole. Davis is nationally known for his rebuke of the dominant us-versus-them view of invasive species. It’s a position that has at times been uncomfortable to maintain; Davis has actually received hate mail, deploring him for his contrarian position.
Like Jacke, Davis believes that our definition of “native” is flawed, and is therefore leading us down the wrong path in response to non-native species. “On some level, it’s about baselines, about what we’re used to,” he said. “Look, the New Hampshire state flower is non-native. And so is Vermont’s state insect.” (After our conversation, I fact-checked this assertion, and he’s right. The New Hampshire state flower, the purple lilac, was imported from England during the first half of the 1700s. And Vermont’s state insect, the European honeybee, was introduced to North America in the 1600s.)
Furthermore, Davis contends, the typical response to non-native species–spraying them with herbicides–only compounds the problem: “We’re doing more harm by spraying all these chemicals, which disrupt healthy soil biology and probably just make it more susceptible to opportunistic plant species.” Interestingly, this was something that Markus had noticed: In some of the areas he’d sprayed to eradicate one non-native species, another had popped up.
Both Davis and Jacke are very clear that they’re not calling for an entirely hands-off approach to invasive plant species–only that our efforts should be carefully considered and dependent on regional and even site-specific goals. “There are introduced species that are doing real harm,” Davis noted. “We shouldn’t get sidetracked by species that [represent] really just change and not harm.” He sighed. “Look, trying to re-create the forests of the past is simply not possible.”
For his part, Jacke believes we need to accept that some areas are going to become “overrun” with non-native species: “I think it’s a good idea in places to let them go nuts, so we can see how the ecosystem adapts. So we can learn.” He opened his eyes wide. “I mean, let’s be honest: We know so little about this stuff. The basic assumption we have to have is that we know nothing.”
“Okay, fine,” I said. “I get it. I know nothing.” Given all that, what did he think I should do about all the honeysuckle taking root in my woods?
Jacke didn’t hesitate for a second: “Oh, man, I don’t like that stuff. If I had it on my land, I’d be pulling it out.”
As so often happens, I’d gone seeking clarity and ended up more confused than I’d been in the first place. Are invasive plant species a threat to the region, or are they not? Should I even be calling them “invasive”? And what constitutes “native,” anyway?
I’d come to realize that there are no easy answers to these questions, and even Markus, as avid a hunter of these species as likely exists, acknowledged as much. “This thing is still in its infancy,” he told me, when I called him one winter’s evening to confess my quandary. “We don’t know how effective or ineffective we’re going to be over the long haul. If things are in check, these plants shouldn’t be impacting the ecosystem in a harmful way. But we just don’t understand all the relationships.”