The official town beetle of Plainfield, New Hampshire, is the cobblestone tiger beetle – which is listed as a threatened species but has found a home in the town.
Plainfield’s town mussel (and it does have a town mussel, which most towns can’t say) is the dwarf wedgemussel, a freshwater mussel that is on the federal endangered species list.
The town flower is Jesup’s milk vetch. It’s a purple flower in the pea family, and not only is it on the federal endangered species list but also the Plainfield population of the flower is one of only three populations on the entire planet (the other two are nearby).
In the late 1980s, Plainfield celebrated its official species with a song, a parade entry, and T-shirts. Clearly, Plainfield is a special place – not just because so many rare species are found there but because of the zeal with which the town celebrates them.
Plainfield is at the heart of a 15- to 20-mile stretch of the Connecticut River where these three rare species, and many others less rare, are found. The area is variously defined as starting at the mouth of the Ompompanoosuc River (in Norwich, Vermont) and ending at the Weathersfield Bow; or the stretch of river bracketed by the Wilder Dam and the Bellows Falls Dam.
About 15 years ago, this area was kind-of, sort-of known as the “Connecticut River Rapids Macrosite.” But that was only a nickname used by The Nature Conservancy, New Hampshire chapter and the U.S. Fish & Wildlife Service. Nobody calls it that any more. Well, except maybe out of habit.
“It was just a way of bookmarking that part of the river,” says Adair Mulligan, communications director for the Connecticut River Joint Commissions.
“There are several rare species and habitat types all packed into a small area,” says Mark Zankel, director of conservation programs for The Nature Conservancy, New Hampshire chapter, including floodplain forest, riverside seeps, rocky outcroppings, and cobble beaches. The main forces at work, he explains, are some calcium-rich bedrock and annual scouring by the Connecticut River, both by high flows in spring and ice in winter.
“The ice scouring gets rid of the woody plants,” says Bob Popp, botanist for the Vermont Nongame and Natural Heritage Program. This means that the rivershore grasslands are perpetually kept in an early stage of succession to forest.
Mid-river islands are home to two other habitats: cobblestone beaches and floodplain forests.
Zankel explains that the upstream side of these islands is like an arrowhead point covered with cobble and gravel. These cobble points are scraped clear of woody plants by ice scour and may extend 100 feet downstream from the point, beyond which first shrubs and then floodplain forest take over.
Those cobble points are habitat for the cobblestone tiger beetle, a brown beetle that is listed as threatened in both New Hampshire and Vermont.
The floodplain forest that occupies the highest parts of these islands was once also found on the river banks. But in most places, these forests of butternuts and silver maples, carpeted with ostrich ferns, have long since been cleared for farm fields.
Along the banks on the Vermont side grow obedience plant (a large mint with snapdragon-like flowers), Siberian chives, Great St. Johnswort (a large, native relative of the depression remedy), and false sticky asphodel (a tiny lily).
But the ice scouring that makes life possible for these rare plants also makes their turf appealing to invasive plants. “These floodplain forests are a Who’s Who of invasive species,” says Zankel. Floodwaters bring in the seeds and roots of invasive plants to areas freshly disturbed by ice scouring. At one time, the flooding and ice scouring might have been so severe that only the plants and animals conditioned to the habitat could thrive there. But today, it’s suspected, the dams on the river and its tributaries have tamed the river enough to open the door to invasive species.
One of the toughest new threats to the area’s natural communities is the black swallowwort, a vine that has put down roots near the Jesup’s milk vetch populations. “It’s one of the nastiest things we’ve ever had to deal with,” says Popp of the vine. “It spreads by rhizomes but also by seeds. It’s in the milkweed family, and its seeds blow everywhere. We tried weed-whacking it, and it didn’t do a darn thing.”
In New Hampshire, The Nature Conservancy is both cutting back the plants and going back to collect the flowerheads and seedpods. Eradicating the plants is impossible, Zankel says. “You would have to eliminate them from the entire upstream Connecticut River watershed.”
But even in its slightly altered state, this stretch of the Connecticut River is worth treasuring. Says Zankel: “It’s one of those little biological gems that few people know about.”