On a visit to the Galapagos Islands a number of years ago, I quickly became used to the daily “shoe dunk in the bucket” ritual. Traveling from island to island on a boat, we made sure our shoes hadn’t picked up dirt and seeds from the islands we had visited so that we didn’t transport plants to the next island. We had seen the effects of invasive alien plants and animals on the fragile ecology of the islands, and we didn’t want to contribute to the problem unknowingly.
I remembered the Galapagos shoe dunk ritual the first time I came across one of those signs about zebra mussels and Eurasian milfoil posted at many boat ramps in Vermont and New Hampshire. Instead of rinsing my shoes in a bucket, I was being asked to take part in another, similar, ritual. Now I make sure that my kayak or canoe doesn’t have any plant material stuck to it, or any water caught in it, before I leave the ramp and head off to another body of water.
Different rituals, worlds apart, but both serve the same purpose: controlling the spread of invasive plants and animals.
What makes plants or animals “invasive” and what do they have to do with northern New England? Plants or animals are considered “invasive” if they are a) not native to the area in which they are growing, and b) cause economic or environmental harm or harm to human health. Sometimes invasive species are introduced by people, either intentionally or unintentionally. In other situations, they migrate on their own or are carried by other animals. Not all non-native plants and animals are considered invasive – only those that are harmful to the environment or people.
Zebra mussels and Eurasian milfoil are two of the invasive species that pose a threat to New England lakes and rivers. On a kayak trip to a shallow part of Lake Champlain, I developed a special stroke to try to keep the thick growth of Eurasian milfoil from clinging to my paddle. A feathery, fern-like plant that grows on the bottom in shallow areas, its dense mats are more than just a nuisance for kayakers. It also displaces native plants and provides little food value to wildlife. Eurasian milfoil is found in many ponds and lakes in Vermont, including those that feed into the Connecticut River, such as Lake Fairlee and Lake Morey. Because it can grow from stem fragments, it is easily spread between bodies of water by plant parts stuck on boats and boat trailers.
Later on that kayak trip, I saw rocks covered with clumps of small, striped mussels. Zebra mussels came to Lake Champlain in 1993, likely spread as free-floating larvae in boat ballast and bait water or as adults stuck to boats. While they are not yet in the Connecticut River watershed, they have been found in Lake Bomoseen, and could easily be transported to the Connecticut River via boats that have been used in Lake Champlain. The zebra mussel is the only freshwater mollusk that attaches itself to solid objects. Because they can live in a wide range of habitats, eat everything, and reproduce rapidly and prolifically, they are quickly out-competing native mollusks. It’s not just other mollusks that feel the impact of zebra mussels. Water facilities, fish hatcheries, and industrial plants have spent over $5 million to keep zebra mussels from clogging intake pipes.
Invasive species are land dwellers as well as water dwellers. Gypsy moths were imported in the 1860s from France by E. Leopold Trouvelot who tried unsuccessfully to start silk production in Massachusetts. The moths escaped from his backyard and have since spread to many parts of the country, including Vermont and New Hampshire. In their periodic outbreaks, gypsy moths cause widespread defoliation and damage to New England forests.
Another common invasive plant in Vermont and New Hampshire is purple loosestrife, a native of Europe that was probably brought to North America by immigrants who appreciated its attractive spikes of purple flowers. Unfortunately, in wetlands, it quickly takes over and out-competes native plants such as cattails and sedges. Because purple loosestrife isn’t a useful food for wildlife, animals of wetland areas are affected by its presence. It spreads by seeds and plant and root fragments transported by water, and is also still sold by many nurseries for use in gardens.
Just as when I was in the Galapagos Islands, I want to avoid spreading invasive plants and animals in New England. I’m careful to make sure my boat isn’t carrying any unwanted hitchhikers when I travel from place to place, and I restrain myself from bringing home a bouquet of those pretty purple flowers blooming near where I launch my kayak.