partnership forms to combat invasive plant species in N.H.

Each of the 4,000-plus invasive plants in the United States is beautiful in its own way. The flowers of the purple loosestrife have pink-lavender petals surrounding small, yellow centers. Phragmites have tall stalks that sway gently in wetland breezes. Some honeysuckle species have bell-shaped flowers that produce sweet, edible nectar.

But, when these plants pop up in areas where they don’t belong, they are both aggressive and destructive. On the Seacoast, invasives threaten to completely alter the region’s ecology, rendering habitat unlivable for many native species.

“In short, they decrease biodiversity,” said Ted Deers, of the N.H. Coastal Program.
Deers was on hand at the Great Bay Discovery Center in Greenland on May 20 to help launch the Coastal Watershed Invasive Plant Partnership. CWIPP, as it has come to be known, consists of 11 state and federal agencies and nonprofit conservation groups that have come together to protect the coastal watershed’s ecology against destructive invasive plants. 

That watershed consists of 42 towns in Strafford and Rockingham counties and is home to more than 130 rare species, some of which cannot be found anywhere else in the state, according to Thomas Burack, commissioner of the N.H. Department of Environmental Services. The watershed’s native species provide ecosystem services such as clean air, shade, flood protection and water filtration, as well as recreational opportunities and beautiful scenery.

“All of these are put at risk due to the threat of invasive species,” Burack said.

Although similar groups exist in the western United States and elsewhere in the world, CWIPP represents the first partnerships of its kind in New England.

“The signatories are coming together to formalize our common goals for invasive species management for the next five years,” Burack said.

By bringing a diverse collection of groups and agencies together, CWIPP will share a number of resources for technical assistance, research and finances. But the partnership faces a number of significant hurdles. Burack noted that climate change will likely exacerbate the problem of invasive species. As New Hampshire’s climate gets warmer, species that could not grow here in the past will begin to find the area hospitable. 

“In many ways, this is a new arena for all of us,” Burack said. “The challenges we face are huge.”

The origins of invasive plant species in North America stretch back to the mid- to late- 18th century, when European settlers brought nonnative plants across the ocean for landscaping, food and medicinal purposes. It didn’t take long for these plants to spread and form large populations in the wild.

“Over a short period of time, people started noticing that these nonnative plants started escaping cultivation,” said Doug Cygan, invasive species coordinator for the N.H. Department of Agriculture.

Today, more than 4,000 plant species have become invasive in the United States, taking over more than 100,000 acres of American soil. Most of the natural predators and pathogens that keep invasive populations in check in their native lands are not present in the United States, which allows them to proliferate at a dangerously rapid pace.

“Invasive plants are so adaptable to most any type of environment that they can produce different attributes to the plant that allow them to survive,” Cygan said. “Native species typically cannot do that.”

Invasive plants produce offspring in higher numbers and can survive through a longer growing season than native species, Cygan added. Purple loosestrife, for example, disperses between 4.5 and 6.5 million seeds per year.

“These seeds can remain dormant for long periods of time, just waiting for the opportunity to germinate and come out,” Cygan said.

If it seems like green foliage started appearing early on the Seacoast this spring, it is largely because of invasive species like honeysuckle, which begins foliating earlier than native species and thrives longer in the fall. Honeysuckle grows faster and taller than native plants and eventually pushes them off the soil.

Invasive species represent the second most common cause of losing endangered species in the United States, the top cause being development. The alien plants are also harmful to insects, animals and, in some cases, humans. Garlic mustard plants, for example, contain chemicals that are harmful to butterflies. Giant hogweed, which has appeared in Dover, can cause painful blisters if it contacts human skin. Invasives also impact water quality by contributing to erosion. According to Cygan, a 2001 study revealed that the United States spent an average of $138 billion per year on dealing with invasives.

To illustrate the variety of invasive species that have become prevalent in the Great Bay Estuary, Cygan collected samples prior to the ceremony on May 20. Searching within one mile of the Great Bay Discovery Center, he found samples of Morrow’s honeysuckle, autumn olive, Japanese knotweed, Japanese barberry, European barberry, glossy buckthorn, Norway maple, burning bush and Oriental bittersweet.

Despite the daunting extent of this alien plant invasion, Cygan believes we have the power to do something about it.

Methods for combating invasive plants vary depending on the species. For some species, herbicides are effective. Stem injection guns have been developed to deliver herbicides into the hollow canes of plants, preventing re-growth.

For other species, mowing is a more practical defense. Michael Morrison, president of an invasive plant control company called Swamp Inc., demonstrated several machines that are used to eradicate certain species. His equipment includes a dump carrier, a wetland excavator and a skid steer machine with a powerful, hydraulic mower. 

To deal with purple loosestrife, one of the most common invasives in the state, Cygan released tens of thousands of leaf-eating Galerucella beetles in the late 1990s. Although he had not released any of the insects within 10 miles of the Discovery Center, a withered patch of loosestrife showed evidence of their presence. Many of the plants were covered with shotgun-like holes where beetles had chewed at the leaves. Plucking a small stalk from the patch, Cygan quickly located two mating beetles. Although leaf-eating beetles will not kill off purple loosestrife completely, they stunt the species’ growth enough to allow native plants to establish themselves and drive the intruders out, Cygan said.

Dave Burdick, a research associate professor of marine ecology and restoration at the University of New Hampshire, took guests at the May 20 ceremony on a short tour of other invasives around the Great Bay Estuary, including Oriental bittersweet, multiflora rose and honeysuckle.

Closer to the water, Burdick pointed out a stretch of nonnative Phragmites australis, also known as the common reed. The tall perennial grass towers over the estuary, reaching 10 feet or more into the air. This common wetland invader demonstrates the prevalence of nonnative species in the coastal watershed.

Representatives from all the agencies involved in CWIPP signed an official agreement on May 20. Fittingly, the 11 signatories used a pen custom made from a Phragmite stem (“Phragwrites” are manufactured by Dave Kellam, of the N.H. Estuaries Project). The partners have already mapped invasive plants on more than 2,000 acres in the coastal watershed, storing the information in an electronic database. They will now work with landowners, municipalities and state and federal land managers to control invasive species and restore native habitats.

CWIPP signatories included the N.H. Coastal Program, the N.H. Fish and Game Department, the N.H. Department of Agriculture, the N.H. Department of Transportation, the N.H. Department of Resources and Economic Development, the Rockingham County Conservation District, the U.S. Forest Service, the Natural Resources Conservation Service, the Nature Conservancy, the Great Bay National Estuarine Research Reserve, and the UNH Cooperative Extension.

Tom Burack called the signing a historic occasion. Now the work begins.