Herbicides for Invasive Species
By Sean Beckett, Program Director
Herbicide is a dirty word among many who care deeply about the protection of nature. Understandable, considering that many of our worst environmental disasters have come from the nozzles of chemical sprayers.
Yet herbicide has become an indispensable part of the stewardship toolkit for countless organizations contending with invasive species. And a quiet part of the toolkit, too. The “H-word” is so taboo among many in the environmentalist public that it is difficult to have a conversation about the nuance and complexity of herbicide use in the context of ecological restoration. It’s time to start that conversation.
This fall, try to find a leaf that hasn’t been bitten, rolled up, infected, hollowed, or otherwise consumed by bug or beast. If you’re searching among Vermont’s 1,500-plus native plants, this will be a futile endeavor. A chewed leaf is proof of the entanglements within an ecosystem —
specialist insects have evolved to eat that plant, and the plant has coevolved defenses to persist and resist herbivory. Counterintuitively — and to the chagrin of native plant gardeners — a battered and haggard floral tapestry at the end of summer is proof of a rich and interconnected
landscape.
Now wander over to some knotweed or barberry, and you’ll be equally challenged to find a single leaf that has experienced any significant herbivory. Species like these were plucked from different environments around the globe, and left their burdens of coevolved pests and pathogens behind, half-a-world away. Here they thrive, untouchable by the local food web. Where they proliferate, a once-complex system is replaced by a plant monoculture as ecologically empty as a corn field.
About ten years ago, a few roots of Japanese Knotweed (its official name; we just call it knotweed) floated to the shores of NBNC and established in the fertile soils. The knotweed quickly spread along the river, outcompeting and replacing nearly every other herb and shrub in its wake.
Invasive species are one of the top causes of biodiversity collapse globally and in Vermont. As nature’s stewards, we are responsible for enabling healthy and resilient ecosystems. Given centuries, knotweed may slowly find its place in the ecosystem (apples, dandelions, and a handful of other introduced species have managed this), but the urgency and severity of biodiversity loss is too great to wait for knotweed to accrue its own local herbivores and pathogens.
With great effort and thousands of hours invested by technicians and volunteers, we’ve become knotweed’s only herbivore, removing it by hand, by shovel, and by scythe, week after week, year after year, acre after acre. (And yes, we even eat some of it!) In places that receive our most deliberate attention, we’ve seen shrubs reestablish (most of which we planted), but these grow amid a lawn of persistent knotweed sprouts poised to reclaim the area the moment our focus shifts.
A decade of effort has taught us that eradicating knotweed by hand is impossible, expensive, and deeply unsustainable — so much of our experience in nature by the riverside is now defined by an antagonistic relationship with knotweed. Our mission is “Connecting People with
the Natural World,” yet many of our volunteers’ experiences with plants are about killing them.
But our floodplain ecosystem is too ecologically and socially important for us to give up here. So to restore our floodplain ecosystem, and our capacity to connect people with nature, we’re adding herbicide to our toolkit. Over the next year, we’ll be working with trained, licensed teams from the Northwoods Stewardship Center and the Intervale Conservation Nursery to administer two rounds of herbicide treatment to our most intractable knotweed patches. The plan has been well-researched and approved by state wetland ecologists. All that’s left, the hardest part, is to invite you to learn with us how to weigh the potential risks and uncertainties of herbicide use against the certain and devastating reality of floodplain biodiversity loss. To us, the balance is clear: the future of our watershed depends on us taking action.
Earlier this summer, an NBNC forest ecology class visited a five-acre forest patch near the interstate that was lush, diverse, complex, and
even magical. If I were a bird, I thought, I’d live here. Ten years ago, we learned, this was a broken landscape of high tree canopies shading
a monoculture of invasive barberry — a forest in name, but not in function. As we witnessed the dramatic results of glyphosate herbicide use
here, we discussed invasive species in the past tense, and reflected on the rare and profound feeling we shared in that moment: hope.
Note: We welcome your thoughtful responses to this tricky topic. Please reach out to Sean@NorthBranchNatureCenter.org.
