This fall, an intrepid and hardy bunch of volunteers descended on backyards across the island, from Oak Bluffs to Chilmark. Armed with loppers and spading forks, they set out to conquer an all-too-familiar foe: invasive plants that threaten the island’s ecosystems. This team is BiodiversityWorks’ Invasive Plant Brigade, an offshoot of our popular Natural Neighbors backyard habitat program, and they had one goal in mind: giving native plants a fighting chance.
What is an invasive species? The phrase means different things to different people, and what a gardener might call invasive is often different from how an ecologist would use the word. For some, “invasive” simply means “unwanted.” But the definition ecologists use involves two ecologically important criteria.
First, an invasive organism must be non-native to a given region. For the Vineyard, native species are defined as those that occurred here prior to European settlement. As their names suggest, many of our invasive plants originated in different parts of the globe, such as Oriental bittersweet (native to Asia), Japanese barberry, and Norway maple (originating in Europe). However, even species that are native to the U.S. can be considered invasive when transported from one region to another. For example black locust, native to the southern Appalachians, is often deemed invasive in the Northeast.
Second, the non-native species must cause harm in some way, either to the environment, to the economy, or to human health. While many of our non-native plants are relatively benign, such as common dandelion or common plantain, invasive plants typically grow aggressively and spread rapidly. Some, such as garlic mustard or tree-of-heaven, even produce chemicals that inhibit the growth of nearby plants. Furthermore, because the insects best adapted for feeding on invasive plants mostly live on the plant’s continent of origin, non-native plants face reduced pressure from herbivores, giving them an additional competitive advantage. These traits allow them to out-compete and displace native species.
Why does this matter? In the case of plants, which are the basis of the food chain, this disruption to the ecosystem can have cascading effects on insects, birds, and other fauna. For example, most caterpillar species are plant specialists, meaning that they feed on a limited range of species. No native plants? No caterpillars. No caterpillars? No food for birds to feed their young. No moths? No bats, which provide crucial ecosystem services by keeping populations of pest insects in check.
Because our native animals co-evolved with our native plants, they often don’t recognize exotic species as food. (One example is Japanese barberry, largely ignored by deer.) Furthermore, even when animals do eat exotic plants, such as when birds consume berries of autumn olive or non-native honeysuckles, these foods are often less nutritious than the native species they displaced, meaning that the birds have less fuel to survive cold weather or long migrations.
Consider what’s at stake: On the island, dry, sandy soils deposited at the terminus of the glacier during the last ice age support unique habitats such as pitch pine barrens, scrub oak shrublands, coastal heathlands (dominated by plants in the blueberry family), and sandplain grasslands. These globally rare “sand barrens” ecosystems occur in few other places on Earth, and are home to numerous rare species. Once these habitats are colonized by invasives, these ecosystems and their associated species are at risk of vanishing forever.
But also consider this: the Invasive Plant Brigade is founded on the principle that many hands make short work. Similar to a community barnraising during agrarian times, or a spinning bee during colonial days, what might take a homeowner days to accomplish alone is reduced to a few hours with the help of our volunteers. Amidst a national mental health crisis, wars abroad, political polarization at home, and environmental chaos wrought by a changing climate, working alongside others toward a common end can lessen our sense of isolation. Accomplishing a small, tangible goal on the corner of the earth that we steward can be a powerful antidote to despair.
But does it make a difference? Invasive species management is often a daunting task, and it may well be impossible to permanently eradicate well-established invasives such as Oriental bittersweet or autumn olive from the island’s woods and fields. What we can do, however, is create small oases of native habitat in backyards and conservation lands across the island. Together, this patchwork of habitat “islands” can provide the space and connectivity that our native species need to survive. You could call it saving the world, one backyard at a time.
Need help managing invasive plants in your backyard? To join our free Natural Neighbors program, complete the survey at https://biodiversityworksmv.org/programs-projects/natural-neighbors/.
Ready to volunteer with the Invasive Plant Brigade? Contact Rich Couse at firstname.lastname@example.org to join our email list.