Stopping invaders is tough
The Enterprise — Tyler Murphy
Honeysuckle shrubbery is so common in parts of the New York that many people don’t realize it’s a damaging invasive species brought into the country more than a hundred years ago. Honeysuckle is a limited source of food for native species and grows quickly on forest floors, blocking out the light that other ground-level, indigenous, woodland plants need.
NEW SCOTLAND — As people have become more connected in the last century so, too, have nature’s once-isolated ecosystems, causing unprecedented and sometimes disastrous consequences.
The threat and damage caused by invasive species has received more attention in the last decade, with state, national, and local governments launching awareness and control campaigns to stem the tide.
Several times a year, staff at the John Boyd Thacher and Thompson’s Lake state parks organize events aimed at eliminating and controlling invasive species.
In the beginning of July, an Invasive Species Strike Team from the New York State Office of Parks, Recreation and Historical Preservation visited Thacher Park to remove a specific plant — the European buckthorn, which was pushing out indigenous competitors and blocking the scenic view of the Helderberg escarpment.
Some of the most damaging foreign species, and the most difficult to remove, are resilient and fast-growing invasive plants.
“New Research indicates they have more of an ecological impact,” said backyard habitat specialist Laurel Tormey Cole comparing invasive plants to other invasive species, such as insects and wildlife. Tormey Cole works at Thompson’s Lake State Park were she helps coordinate and control invasive species.
“Invasive plants have a pretty big impact. It’s been going on a long time,” added Nancy Engel, the nature center’s director.
“Buckthorn and honeysuckle are the biggest problems. They’ll fill in any space and squeeze out other life and they’re not edible,” she said.
The two species of plants have overwhelmed the Albany area and relentlessly intruded into Thacher and Thompson’s Lake parks. Buckthorn is a small tree bearing darkened berries while Honeysuckle is a shrub bearing red berries. Both plants cause similar damage by quickly growing below the treetops of forests, blocking out the light that ground-level, indigenous, woodland, plants need to survive. The invasive plants are much less edible to local insects and wildlife, and they take over an ecological niche once filled by local growths that provided better food and shelter.
The team at Thacher removed buckthorn by the roots from trails and cliffs but the park, like much of the eastern United States, remains largely overrun by it.
Both buckthorn and honeysuckle were brought to North America more than a hundred years ago, when they were often used as decorations and planted as shrubbery. They have since spread to several states, including New York, and have become predominant in many locations.
As with many invasive species, neglectful or ignorant human activity spreads them and the damage they cause is often associated with their replacement of native life, which other local species also depended on.
As an example, Tormey Cole pointed to another local invasive species, the black swallow wort. The stalk plant likes to grow in open areas. The plant’s ideal environment directly competes with the native milkweed, which is the main source of food for monarch caterpillars. As black swallow wort becomes more prevalent in an area, monarch butterflies, and any other animal’s relying on the milkweed, become less prevalent.
“The really bad thing invasive species do is destroy biological diversity,” said Tormey Cole.
Since animals, insects, and plants in one region have evolved together for several thousands, if not millions, of years, those life forms develop an intricate web of dependent relationships with each other, like the monarch butterfly and milkweed, explained Tormey Cole. The caterpillars’ biology is unaccustomed to the foreign black swallow wort, meaning they are unable to eat it and survive.
Invasive species also tend to have few natural predators or competitors to keep them in check.
“Where this thing is from originally — there is an environment, or animals, or insects that kept it in check. Those aren’t here,” explained Tormey Cole.
Citing recent work by entomologist Douglas W. Tallamy, Tormey Cole said native plants could support four times more insects than invasive plants. To say it another way: A location overrun by invasive plants would see an average 75-percent drop in the area’s insect biomass.
Insects are a staple of most ecosystems and larger creatures, such as birds, depend on them as a nutritious and plentiful source of food. Baby birds are especially vulnerable to a loss of insects, noted Tormey Cole.
Even the presence of invasive species can cause damage, by putting more pressure on native plants and animals to sustain their own ecosystems. Tormey Cole said it was not uncommon to find native plants being overrun by native insects because they are more fiercely competing for the remaining indigenous growths.
A success story at Thompson’s Lake was the removal of the invasive Purple loosestrife, a flowering wetland plant that grows in shallow water. The invasive plant competes with the native cattail plant. Unlike the purple loosetrife the cattail has a heavier stalk, which supports more weight, such as a red-winged blackbird’s nest.
Besides depriving native animals of shelter, the purple loosetrife also decomposes more slowly in water, causing it to alter the precious balance of chemicals in lakes and ponds. If enough of the invasive plants were to die and decompose, it could change the water quality and cause more hardships for aquatic life.
With the help of volunteers and the release of a non-native beetle to help eat and destroy the purple loosestrife, it was eradicated from the shores of Thompson’s Lake.
Another species being removed from the parks is garlic mustard. The green plant is common and out-competes several species of native wildflowers.
“A few years ago, we started clearing out the Indian Ladder Trail and volunteers would come back with like 10 bags full of the stuff,” recalled Tormey Cole. “Not anymore though. We still go out every year but the bags are fewer, Last time, someone came back with just one bag full. And you can see the wildflowers coming back in along the trail now,” she said.
Though there are some success stories, as a whole, the fight against most invasive species is bleak, admits Tormey Cole.
While both Tormey Cole and Engel said park staff, environmentalists, and eco-friendly community members could probably keep certain types of species out of focused areas, the notion of eliminating them completely or finding a permanent solution to the problem, seemed optimistically daunting, if not impossible. In some cases, removing the invasive species causes more harm than good. Others are so common their presence has practically been accepted, like the honeysuckle and buckthorn.
Engel also noted Japanese barberry as an example of a very difficult invasive plant to remove, because it often survives unless its roots are completely dug out. She said barberry, like other invasive plants, often requires herbicide to eliminate.
“Barberry is very difficult to remove. First it’s covered with thorns and it has a huge root network,” said Engel. “Every piece of it can break off and it’s a new plant.”
One invasive pest at Thompson’s Lake, zebra mussels, are likely to only get worse, since there’s no practical way to remove them. The fast multiplying mussels often cling to the bottom of boats, or any other item submerged for a period of time, and are transported to other bodies of water.
“They’re in the lake and you can’t get rid of them,” said Engel. “Pretty much, there’s nothing to do about it.”
Besides threatening water ecosystems the mussels’ shells are also sharp enough to cut bathers’ and boaters’ skin.
“It breaks my heart to know that there’s really nothing we can do about it. It’ll only get worse in the next few years,” said Tormey Cole. “The best way — the only way — to avoid the impact of invasive species is to make sure people never introduce them in the first place.”