5/16/2013 - The small boat zig-zagged slowly across Powwow Pond in Kingston earlier this month. Biologist Amy Smagula stood on the bow, a GPS in one hand and a small float in the other.
With the help of the sun and polarized sunglasses, Smagula could see right to the bottom of the shallow pond. Some lily pads were beginning to emerge. Vegetation was visible on the mucky bottom.
Smagula tossed an eight-inch-long float into the water. A small weight tied to the float kept it in place, marking clumps of milfoil. Scuba divers will descend upon Powwow Pond this month to pull up variable milfoil, one of the state’s most notorious invasive species.
Variable milfoil, which looks sort of like an evergreen, sends fuzzy-looking shoots toward the surface. The strands extend from the bottom of a lake or pond to the surface, choking out all native vegetation and aquatic life. When strands reach the surface, they form a mat, blocking out sunlight and ultimately impacting water chemistry. It spreads quickly, forming a mono culture.
“It takes up the entire water column around a lake so that there’s no more structure and diversity,” said Smagula, who spends her springs and summers surveying the state’s water bodies for a variety of invasive species.
Variable milfoil is just one invasive species wreaking havoc in the state.
New Hampshire is under attack. In some cases, the attack is imminent, but in many others, the battle is well underway. In some instances, the state is winning. In others, it’s struggling for survival, it’s battling for every inch. Invasive species are threatening New Hampshire’s waterways, its forests, its watersheds and its backyards.
“If it feels like we’re under siege at times, we are,” said Mark Ellingwood, a biologist with the state Fish and Game Department.
They come in all different shapes and sizes, but they all do the same thing: they force out native wildlife, destroy native habitat and become a nuisance.
Variable milfoil can quickly take over a lake or pond. Purple loosestrife can dominate watersheds, again pushing out native plant life. The emerald ash borer has the potential to wipe out all of the ash trees in the state. Feral hogs are not yet a big problem, but the sometimes ornery swine can destroy wetlands and trample and eat native vegetation.
“There are lots of checks and balances that evolve in nature, and when you take a species, a plant, an animal, a virus and you introduce it into a system that it was not developed in, then none of the normal checks and balances exist,” Ellingwood said. “It has the potential for that exotic to wreak havoc in a system as a consequence.”
The natural systems in this world are a function of thousands of years of evolution. If something is introduced that hasn’t evolved in the same context, then it can play by a different set of rules, and it can disrupt everything, Ellingwood said. Invasive species aren’t super species. In their own natural environments, they are a piece of that system’s biological puzzle, where checks and balances exist.
New Hampshire officials, volunteers and property owners are waging a widespread campaign to prevent, subdue, hold back and ultimately defeat invasive species, but the war is far from over.
To the forests
The Asian longhorned beetle has long struck fear in the hearts of tree lovers. The beetle could devastate New Hampshire’s hardwood species, specifically sugar maples, the marquee foliage and maple syrup species in this state.
An Asian longhorned beetle infestation in Worcester, Mass., went undetected for about a decade; once found, officials had to cut down acres and acres of hardwood trees. The one thing in New Hampshire’s favor is that Asian longhorned beetles are rather large and tend not to fly long distances. Their spread can take a little longer than other species, officials said. But there is no natural control to slow the beetles’ spread.
So it’s a waiting game.
As far as the emerald ash borer goes, the wait is over. As expected, the emerald ash borer has arrived in New Hampshire and ash species are at risk.
George Frame, senior director of forestry with the Society for the Protection of New Hampshire Forests, urged patience, but the potential devastation is considerable. Ash make up about 6 percent of the forest in New Hampshire.
“We try not to panic at these things,” Frame said. “In the areas that were hit the most heavily [by emerald ash borer], there is about a 30-percent survival rate. So if you go in in advance of the pests and wipe out the food stock, then you’re not allowing nature to develop what it needs to survive. We need to be slow and determined about things. We can’t go off all crazy.”
Frame pointed to outbreaks of other species in the past, such as the saddled prominent and the gypsy moth. Some have tested the mettle of the forest and foresters alike, but in the end, the forest has found a way to survive.
Frame expects the impact from the emerald ash borer to be felt severely in urban areas. Ash was frequently planted in urban settings to provide shade. The tree was chosen as a replacement for elm trees. That’s been the case for more than 40 years.
Ash wood is used to make ax handles, baseball bats and shovel handles, and it makes excellent firewood.It’s also used in basket making and is a key wetland tree species that provides shade and soil-holding capabilities.
Hemlocks are under attack as well, and have been for several years now. The hemlock woolly adelgid, which can occur in concert with the elongate hemlock scale, has been wreaking havoc on hemlock species for the past six or seven years. The invasive pest is now into the five southern counties in New Hampshire, and it’s moving north. But Frame said there does appear to be a temperature barrier for the woolly adelgid. That does bring in the concern of climate change, which could raise that temperature barrier in the Granite State. When teamed with the elongate scale, the hemlock woolly adelgid can kill a tree in just a few years.
The woolly adelgid was discovered in Virginia and worked its way north through the Blue Ridge Mountains, the mid-Atlantic states and New England, Frame said.
The loss of hemlocks would be catastrophic. Hemlocks are a winter yarding tree. Deer and other animals congregate beneath the limbs of hemlocks for shelter from the snow and cold. Losing the tree could have measurable impacts on a number of species that rely on them for some thermal benefit. There isn’t an economically viable treatment to eliminate the pest, since hemlocks span tens of thousands of acres in the state, Frame said.
There is a local balsam woolly adelgid, which makes New Hampshire home and looks much like the hemlock woolly adelgid, but trees have had time to build up a resistance.
“So while it is here, it’s not devastating,” Frame said.
People can find woolly adelgids on the underside of hemlock twigs. They look like little white tufts. The fluff acts as a sort of protection for the bugs, which are often transported from tree to tree by birds.
“There is no resistance in the northern trees,” Frame said.
In some cases, officials have been able to bring in a type of beetle that eats the hemlock woolly adelgid. It’s a beetle that is a natural predator of the bug but not a native inhabitant of New Hampshire.
Similarly, there is some talk about bringing in a species of predatory wasp that would eat the larvae of the emerald ash borer. Biologists are looking for natural controls, Frame said.
“But of course, if you’re bringing in natural controls from the place where the bug came from, then you can end up with two invasive pests instead of just the one you’re trying to get rid of.
“There is just a lot more that we don’t know than we know,” Frame said.
Frame said it doesn’t make any sense to cut down all the ash in advance of the ash borer.
“We’ll lose some but maybe some will have a natural resistance,” Frame said. “If we just panic and cut them all … then we’ve lost the opportunity for those trees that can adapt to do that.”
Natural selection provides an opportunity for species to have wide genetic backgrounds. Some may be able to resist. Those that do survive would propagate and pass on their genetic proclivity, Frame said.
In the face of threats, plant species have three options: adapt, migrate or die. Frame would prefer trees be allowed to adapt, since they can’t migrate. That said, it doesn’t always work out. Frame mentioned that a fungus all but wiped out the butternut tree in New Hampshire. It wasn’t a commercially important tree but it did produce tasty nuts. The tree is essentially gone from the state, following in the footsteps of the American elm and the American chestnut, two important species that have succumbed to blight and disease.
Biologists are currently working to develop a blight-resistant strain of the American chestnut. Chestnut trees still sprout from stumps but by the time they reach three to four inches in diameter, blight takes hold. Biologists are using genetic material from the American chestnut and the Chinese chestnut to create a tree that can stand up to the blight.
“All that can happen because we’ve got enough viable material to do it with, but if we cut everything in advance of the bugs, it’s taking the opportunity for the future scientists who may be able to find a way to get around it. Let nature work its way,” Frame said.
Protecting backyards and farmland
It takes constant vigilance to keep invasive species at bay.
“We’re constantly trying to look at what’s on its way here and how we can adjust,” said Douglas Cygan, invasives species coordinator for the state Department of Agriculture. “We’re constantly battling.”
It’s about helping people understand how their actions can impact, positively and negatively, the spread of invasive species. Take Japanese knotweed. Just last year, Cygan covered 200 highway miles applying herbicides to invasive species, particularly Japanese knotweed, which can grow to about 6 feet tall.
“They have a negative and adverse impact on the natural ecological succession to plant communities that occur in natural wildlife areas,” Cygan said.
Japanese knotweed, which develops a woody and belligerent root system and looks somewhat like bamboo, doesn’t spread effectively here through its natural reproductive process. Instead, its primary vector for spread is when fragments are spread by people who mow the plants. Cygan said the tiniest piece of a plant has the potential to turn into a new plant. When stands aren’t mowed, Cygan said they typically don’t spread much at all.
“It thinks it’s going to die, and the response is to send out more shoots,” Cygan said. “So if you have a few square feet of it and you mow it down, it will exponentially grow. ... So just mowing along roadways, it’s actually creating more of a problem.”
Cygan said municipalities often run into issues with knotweed. Look along the side of the highway or a local road — there is a good chance you’ll spot Japanese knotweed, and potentially, not much else in places. Homeowners often take top soil that already has knotweed present for a garden or other purposes. Inadvertently, they are spreading the invasive plant.
Instead, Cygan suggested allowing the plant to grow back and then, after it flowers, applying an herbicide. If it’s applied correctly, it can knock out an entire stand in one application. The timing is key. Apply too early and the herbicide won’t be as effective. But after the plant has flowered, the plant’s energy is traveling back down through its stock to the roots. Hit it with the herbicide then, and it will carry the herbicide right into the roots. People can purchase an injection tool that allows them to explicitly target the knotweed alone rather than spraying and killing everything that gets in the way. People can also use tarps to prevent the sunlight from getting to knotweed plants.
Since 2004, nurseries in New Hampshire have been prohibited from selling and distributing invasive species, such as Japanese knotweed. That includes species like the Norway maple and the burning bush, species many people have grown accustomed to.
Cygan sees progress. In the last 10 years or so, each year, he gets more requests for invasive plant presentations from municipalities and environmental groups. Cygan spends this time of year meeting with property owners, municipalities and stakeholders to discuss control measures. Several municipalities are working to control invasive species, including Laconia and Amherst.
Beyond simply outlawing the sale of invasive species, officials promote alternative native species that can fit people’s landscaping needs. Invasive species like the Norway maple and Japanese barberry can be replaced with other trees that won’t impact the rest of the ecosystem negatively. The Japanese barberry provides a fantastic deer tick habitat, making it all the more important to rid the landscape of it.
“People love the burning bush, but boy is it hard to get rid of,” said Lyn Lombard of the Piscataquog Land Conservancy. “You watch for the little shoots for years. For 10 years, I would pull them out. Now I think I’ve gained control.”
Sometimes people are amazed at some of the seemingly ordinary plants that make the state’s invasive species list, Lombard said. Technically, people can’t transport something, once so innocuous, as bringing their neighbor a wreath made of bittersweet. Bittersweet is an invasive vine that can choke out even large trees, Lombard said.
“The key is not to buy plants from other states,” Lombard said.
Lombard mentioned a couple native maple varieties, as well as the European beech tree.
“There are tons of replacement plants for all of these, all these invasives,” Lombard said. “People aren’t worried about it until it gets into your yard. When it starts taking over their yard or their pastures or their garden, that’s when people start worrying.”
Preserving natural wetlands and some success
Purple loosestrife got the ball rolling for watershed associations. Years ago, people noticed the plant, with its characteristic purple flowers, were filling up wetlands “like crazy,” displacing native animals and plants along the way, Lombard said. In some cases, loosestrife grows so thickly it can impact the flow of water.
Lombard got involved initially with a plot to raise beetles that would eat the loosestrife. Officials and volunteers would dig up some loosestrife plants, enclose them in a pot with nets and release beetles into the pot. Then they’d let the loosestrife grow, and when it was a couple feet tall, they’d release the beetles in a field of loosestrife — by that time, the 10 beetles they released into each pot had reproduced to 500 beetles.
“It was amazing how well it worked,” Lombard said. “Beetles never traveled more than a mile, and they never ate anything else.”
Beetles held down the loosestrife, which is often present along roadways. Lombard conceded officials will never entirely get rid of the loosestrife. But they would see a 6-foot plant reduced to 2 feet.
Invasive species come in all shapes and sizes, but none bigger than feral hogs, the largest invasive species on this country. It’s not a severe problem just yet, but the presence of a limited number of feral hogs in New Hampshire has biologists and property owners on high alert.
Wild pigs cause major damage in the southern part of the country and could do the same in the Granite State. The theory is that feral hogs escaped from a game farm in New Hampshire and have been reproducing in the wild. They would compete with many native species for food. A couple years ago, officials estimated there were between 100 and 200 feral pigs in this state.
Swine, which weigh between 75 and 250 pounds, are extremely adaptable and are perhaps the most reproductive large mammals on the globe. As early as six months old, pigs can reproduce and can give birth to anywhere from three to 13 piglets at a time. They can reproduce more than twice per year, officials said.
“As devastating an impact as pigs can have, it’s not a foregone conclusion that wherever you put them, they’ll have the same impact,” Ellingwood said.
Maybe the winters are severe enough in New Hampshire that feral pigs won’t take hold as strongly as they have elsewhere, particularly in the South.
“Maybe it can hold some of the species at bay in ways they wouldn’t otherwise be held,” Ellingwood said.
Wild pigs are still in their infancy in the Northeast. Officials are doing everything they can to prevent the spread of feral hogs in New Hampshire.
“We’re in a position to nip this in the bud,” Ellingwood said. “In southern places, like Texas, the Gulf Coast, they’re well beyond that point.”
“We don’t want them on our landscape,” Ellingwood said. “We’d like them to be gone. They haven’t exploded in terms of population in ways we might have expected. There seems to be some resistance.”
Pigs consume pretty much all forms of plant material, much of which — acorns, berries and beech nuts — other species are dependent on. About 90 percent of their diet is a vegetable diet, though they will also eat insects, frogs, salamanders and earthworms, as well as eggs from ground-nesting birds, like turkey and grouse. Wild pigs could impact deer populations and other animals that consume acorns and berries. Reports also indicated feral swine have been known to attack and eat deer fawns.
Pigs can have a big impact on the ground. They turn over soil aggressively, a behavior called rooting. Their rooting behavior can cause destruction in the soil from 6 inches to 2 feet deep. Rooting can be a big issue in wetlands, where pigs can easily pull out roots and tubers. They also create wallows where they can bask in the mud, leading to contamination in the wetlands.
Foiling variable milfoil
In some places, notably the Ohio area, variable milfoil is an endangered species. But not in New England. New Hampshire’s acidic waters make for fantastic habitat for milfoil, at the expense of native vegetation and aquatic life. Eurasian milfoil, which is a bigger issue than variable milfoil in other surrounding states, is not particularly common in New Hampshire aside from the western border of the state.
Powwow Pond is hardly overrun with variable milfoil, but the plant’s spread can happen quickly, particularly if people aren’t taking precautions and if officials aren’t taking proactive steps. To handle milfoil infestations, officials use a variety of tactics, including herbicides and physical removal. Milfoil is most often spread by boaters, who transport fragments from one waterbody to another, unknowingly, on the bottom of their boats.
At first, anglers might appreciate the presence of variable milfoil. It provides structure where there might otherwise be none. It provides a place for game fish, such as bass and pike, to ambush prey. But soon, if nothing is done, milfoil just keeps spreading, choking out life along the way, Smagula said.
“It’s like a corn field on land, where it’s just all the same thing, plant after plant after plant,” Smagula said.
Ultimately, milfoil decreases oxygen. It makes it much more difficult for predators to find prey. It can change the water chemistry. All of that can lead to economic issues — specifically a reduction in shorefront property values. Variable milfoil can grow in water as much as 15 feet deep.
Preventing aquatic invasive species’ spread is simple, but not easy. Boaters are the prime culprit. Fragments of plants get chopped up in propellers and stuck on boats and trailers. They can take hold in the next waterbody a boater visits.
Many aquatic plants spread in a single water body by breaking off. As pieces of plants float away, they take root elsewhere. It’s a common way for native and invasive species alike to spread. Only a few aquatic species use seeds to spread. Boaters not only transport species like milfoil from pond to pond, but they can also increase spread as they inadvertently chop off pieces.
A partnership between DES and the New Hampshire Lakes Association has helped carry out a campaign to educate boaters — specifically to clean off the bottom of their boats and propellers when they get out of the water. The slogan is “If it’s green, it’s mean.” DES provides grant money to help put staff members at various public access sites, Smagula said.
On the lookout
It’s fanwort and variable milfoil that have gotten the attention of users and residents at Beaver Lake in Derry. Fanwort is similar to milfoil in that it roots on the bottom and creates a canopy on the top.
As of now, the lake does not have either species in it, and people would like to keep it that way.
“If you look at the lakes around us, they all have some sort of exotic species,” said Rob Tompkins, chairman of the board of the Beaver Lake Improvement Association.
The New Hampshire Lakes Association’s lake host program puts trained employees at public access points on lakes and ponds. Lake hosts are trained to spot a variety of invasives.
“I think the Beaver Lake Improvement Association was extremely proactive in making our users and waterfront owners aware of what exotics were and how to keep them out of the lake,” Tompkins said. “That started maybe 20 years ago or more.”
People enjoy kayaking, boating, fishing and swimming on Beaver Lake. The lake has a state-run boat ramp and a busy town beach. Tompkins said people understand what’s at stake when it comes to invasives.
“It’s sort of a miracle,” Tompkins said. “All of the boats that come to our lake have the potential to bring exotics with them.”
The lake hosts program puts a lake host at Beaver Lake for 50 hours per week, and the lake’s volunteer program has a volunteer watching for another eight to 10 hours each week. The lake’s weed watcher program consists of volunteers who paddle the lake on a kayak on the hunt for invasives.
“People have been inspired and they’ve been educated,” Tompkins said. “I think it comes from so many years of battering people over the head with it.”
Smagula coordinates a volunteer weed watcher program at a number of lakes and ponds in New Hampshire in an effort to stay on top of emerging invasive infestations.
One thing is true across the invasive species spectrum: the earlier an infestation is discovered, the better.
In terms of aquatic invasives, DES relies partly on volunteer monitors who are well-versed in what should and shouldn’t be in a water body. About 90 percent of the calls Smagula fields come from volunteers.
Tompkins said the relatively shallow Beaver Lake would make for prime milfoil habitat.
“The last thing we want is to be cocky,” Tompkins said. “We don’t want to rest on our laurels. We’ve been lucky. We have to be vigilant. It could happen today.”
Keeping threats at bay
The list of aquatic threats isn’t getting smaller in the Granite State.
The water chestnut, a cousin to the stir-fry ingredient, exists solely in the Nashua River at this time. But its potential impact has officials’ attention. Smagula said biologists have begun to see water chestnuts’ spiny, wooden seeds on boats and trailers. They’ll also stick to water fowl, which will transport them. The seeds will survive for eight to 10 years waiting to sprout.
“Like a ticking time bomb,” Smagula said.
Water chestnuts can form a floating mass that can extend for miles along a river. The sheer weight of the mass has caused dam failures. The floating mass prevents sunlight from reaching beneath the surface, again, impacting a water body’s food web.
Hydrilla is on the horizon as well. New Hampshire doesn’t have it yet, but it is spreading rapidly through Massachusetts, Maine and Connecticut. Hydrilla can grow in 25 feet of water and it grows extremely thick.
“It’s way worse than milfoil,” Smagula said.
Hydrilla can spread via boaters, but also via waterfowl, which eat the root tubers on the hydrilla plant.
Biologists are also on the lookout for the zebra mussel, the Asian clam and the spiny water flea.
The spiny water flea can cause problems with plankton growth in a lake or a pond. The flea eats much of the small microscopic life in a water body, competing with small bait fish.
“Every different invasive, we have a different approach, but we triage in the same way,” Smagula said. “We go out and assess the infestation.”
Once an infestation has taken hold, officials employ a variety of techniques. If a milfoil infestation is small enough, simply pulling up plants may suffice. If it’s bigger, officials will use a combination of methods. They might use a net to cover plants to prevent spread. They may hit infestations with a controlled herbicide and then physically remove any survivors.
Biologists will try a few methods to stunt its growth before physically removing it. Whenever using herbicides, the idea is to kill the invasive plant, but to keep the native plants, which can be challenging.
There needs to be a balance, officials say. As Frame said, it makes little sense to wipe out a species, such as ash, proactively in order to stop the spread of an invasive pest. But if people do nothing to at least slow the progress of invasives, the results could be catastrophic.
If people just stopped worrying about invasive species and let nature figure it out, Ellingwood guessed that nature would ultimately evolve, but “the end result might not be what we’d like it to be. Species that are currently here might be gone as a result of the competition. Perhaps we could reach a steady state, but maybe it would be an undesirable one, one that maybe is not what nature had in mind.”