Invasive Plant Species in New England
Lo and behold, she was right.
When Dave Jacke has a strong opinion on something, which is often, he speaks loudly–yells, really–then leans forward from the waist and punctuates his point with this exclamation: “WHAT THE HELL?” As in: “People say ‘native’ and ‘non-native’ as if they were scientifically valid terms. But no quote-unquote ‘native map’ has no date on it.” He leaned forward: “WHAT THE HELL?”
And: “If we’re going to start calling these plants ‘invaders,’ and not take ownership for our own human behavior …” He leaned forward: “WHAT THE HELL?”
Finally: “Black locust is illegal to plant here, yet we’re importing pressure-treated lumber from the Southeast and polluting our soils.” He leaned forward: “WHAT THE HELL?”
I’d found Jacke through my friend Ben Falk, who runs a permaculture design school called Whole Systems Design in Vermont’s Mad River Valley. Permaculture has a complex and somewhat malleable definition, but at its essence is based on the interconnectedness of natural and human ecosystems; it seeks to foster a philosophy of working in accordance with nature, rather than attempting to control nature for humancentric purposes. Falk encouraged me to speak with Jacke in part because of his knowledge of the region’s plant species, in part because he’s the co-author of two books on the subject of permaculture, and in part, I suspect, because he knew that Jacke’s stance on invasive species would be well articulated, well researched, and passionate in the extreme.
All of which was true. Within minutes of meeting Jacke at the door of his second-floor apartment in Greenfield, Massachusetts, he was challenging the very foundation on which the basis of our battle against invasive species is waged: that there is any scientific basis for our determination regarding what is native to the region.
To make his point, Jacke pulled up the National Oceanic and Atmospheric Administration’s pollen viewer, an interactive online map that lets the user select a species, then a time frame. Click on “enter,” and you can watch species drift across hundreds and thousands of years, carried by unidentified vectors.
“Check this out,” he said, as he typed in Castanea dentata, the Latin name for the American chestnut, a tree species that has largely been lost from New England owing to blight. It’s a loss that has been much bemoaned, and restoration efforts are ongoing. Castanea dentata, it should be said, is considered native to the Northeast.
Except that it’s not, really. At least not according to NOAA, which has the species first appearing in New England about 3,000 years ago, on a march northward from its origins in the Deep South via the mid-Atlantic region. Now, 3,000 years is a very long time, and Jacke’s not claiming any differently. Rather, he’s making what seems to me a quite valid point: Without an agreed-upon definition of “native,” how are we to determine which species meet that definition and which don’t? Furthermore, our forest ecology isn’t static, and many species that we now consider “native” were, in fact, once invasive.
Except in Jacke’s view, the word “invasive” isn’t right, either, because it ascribes human intent to species that are simply trying to do what plants do best: survive and propagate. “Where do human values come into the equation?” he asked. “The word ‘invasive’ has values implied. Besides, if we’re going to start calling all these plants ‘invaders’ and not take ownership for our own behavior …” He leaned forward, and I knew what was coming next.
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.”