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Invasive Species Hurting Southeast Resources

By | September 11, 2012

There are at least 135 invasive species already thriving in Southeast Alaska. Biologists are worried about several more that could have the potential to dramatically affect the region, especially in the ocean environment.

Red daisy flameweed. Devil’s paintbrush. Fox-and-cubs.

No matter what you call the plant most commonly known as orange hawkweed, you’ve probably seen it. The low-flowering, flame-colored perennial grows in dense patches along Southeast Alaska’s roads. While it adds to the picturesque, wildflower-speckled look of our road systems, the orange hawkweed is not a welcome resident in Southeast.  Neither is Japanese knotweed, reed canary grass or scotchbroom.

These plants are some of the most invasive species threatening the Southeast region. For example, the orange hawkweed releases chemicals from its roots that poison surrounding plants. A member of the sunflower family, it spreads at a rapid, almost uncontrollable pace, hurting the diversity of an area.

The Japanese knotweed also inhibits the growth of surrounding plant species.  It forms dense thickets that block the light needed by native vegetation. A little less recognizable than orange hawkweed, Japanese knotweed resembles bamboo, with cane-like stems growing as high as 10 to 12 feet, and large, heart-shaped leaves.

Matt Carlson, botanist at the Alaska National Heritage Program and Assistant Professor at the University of Alaska-Anchorage, studies invasive plant species. He’s most concerned about what could happen if knotweed continues to spread.

“Japanese knotweed develops these really thick monocultures where only the Japanese knotweed is growing and no other species can occur there,” said Carlson.  “It’s particularly bad along riparian areas, and so it can get into salmon spawning streams and affect the amount of flow that occurs along those salmon streams, and it can also affect the amount of invertebrate animals and things that would show up in fish diets when they turn into these single species cultures.”

How did they get here? Carlson said they were likely first introduced for use in gardens and as a form of erosion control, which is why you often see invasives along roadsides or beach margins.

“They got here because people were planting them and had good reasons at the time to do so,” said Carlson. “Since then, they’re expanding by people as well as by natural forces, moving down streams by wind and animals and things.”

So these single-species cultures, or monocultures, are expanding and dominating native vegetation. This in turn alters and disrupts water flow, and ultimately, affects the diets and ecosystems of our fish.

Of imminent threat to marine life in Southeast is the European green crab. It’s distinguished by three bumps between the eyes and five spines, or teeth, on each side of the shell. Like the behavior of invasive plant species, the European green crab also competes with native species in a region.

They’re aggressive predators. European green crabs eat huge quantities of native shellfish, including young Dungeness crab. Tammy Davis, invasive species project leader at the Alaska Department of Fish and Game, said it not only eats but also displaces native crab populations.

“What has been seen in other areas is, it causes shifts in native crab distribution,” said Davis. “They tend to shift around because the green crab can be aggressive, and forces native crab either deeper or into newer areas… so sort of a habitat shift.”

Having arrived in the San Francisco Bay area more than 20 years ago, the European green crab is making its way up the coast of Canada. Scientists say it could be just a year or two before the crab arrives in Southeast Alaska.

In addition to the European green crab, non-native tunicates are threatening marine life in Southeast Alaska. You might know them as sea squirts: grape-like, squishy invertebrates growing on rocks or piers. Gary Freitag, a Marine Advisory Agent and University of Alaska-Fairbanks associate professor, said there are several native tunicates in Southeast. If the non-native species spread, however, they can suffocate marine life.

“One of the biggest problems is that they can smother shellfish, for example,” said Freitag. “They actually coat them so they can’t filter feed. They can affect your resources from that standpoint. We are worried about them, for example, in Sitka coating eggs of herring. So it might kill off the population of herring if it ever spread to a point where it’s coating the bottom.”

Harming herring populations is one thing. Harming our populations of salmon, however, could be disastrous. Atlantic salmon are an invasive species putting our five native species of salmon at risk. When they escape fish farms in Washington or Canada, we see them in Southeast first. Tammy Davis said the concern with Atlantic salmon is that they could transmit diseases that our salmon aren’t prepared to fight.

“As far as concerns with Atlantic salmon, one big one is they could potentially be carrying pathogens that they are inoculated to fight, but the native species don’t have those same inoculations and so could be pretty severely affected,” said Davis. “It isn’t uncommon that if there is an escape event of Atlantic salmon, they tend to school up with Pacific salmon. And if an Atlantic salmon or two or five school up with Pacific, they could easily transmit a bacteria or a disease of some kind, or even any sort of pathogen.”

The biggest challenge with invasive species may be their unpredictability. Freitag said that for species that haven’t yet arrived in Southeast, like the European green crab, it’s difficult to know with certainty what might happen when it gets here.

“That’s the problem with invasive species,” said Freitag. “They’ve never been in the area so you have no idea what kinds of interactions are going to happen with the native populations. Sometimes they can coexist with no detrimental effects at all, sometimes they get eaten by the native species, sometimes they eat the native species. So we just don’t know what’s going to happen until it occurs. But we want to watch it because it’ll have an effect on the commercial fisheries.”

For invasive species already living in Southeast Alaska, there are many factors that could cause a dramatic spike in their proliferation.

“They seem to go through a phase where they remain in a low concentration, kind of dormant, and then all of a sudden something happens, whether it be warming of the ocean, or whatever it happens to be. And then they all of a sudden they explode everywhere,” said Freitag. “And that’s the typical profile of an invasive species. When that spreads everywhere, then it has economic impacts to our resources and that’s what we’re worried about.”

Invasive species – whether they are plants or marine life – can have dramatic effects on Southeast Alaska’s ecology.  There are state and federal agencies, like the Cooperative Extension Service, that are working to manage and raise awareness about these species before they begin hurting our economy. Gino Graziano is an invasive plant instructor at the Cooperative Extension Service, and said it’s important for the general public to have an awareness of invasives and how to prevent their spread.

“We’ve actually had quite a few findings of new invasive species to the state through citizen scientists and the public who’ve become aware of different plants that we’re on the lookout for – even insects and diseases of plants – and reported those,” said Graziano.

Scientists encourage us all to become citizen scientists – and keep our eyes open – for anything that looks like it doesn’t belong. Confirm with the Extension Service that those potential perennials you were hoping to put in your garden are not invasive. Clean your boat hull or fishing gear carefully and dispose of ballast water properly. Educate yourself and others about invasive species, before it’s too late.

Report sightings of invasive species to AlaskaInvasives.org, or call 1-877-INVASIV.

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