Invaders threaten Alaska species

Posted: Friday, November 28, 2003

Ecosystems across the globe are facing challenges from foreign species that compete with local fauna and flora, sometimes with devastating effects.

These "invasive species" are no strangers to Alaska, coming here in the ballast of ships or otherwise stowing away aboard boats, ships, planes and automobiles, even, in the case of diseases, aboard animals, according to a study just released by the Union of Concerned Scientists, based in Cambridge, Mass.

While cold winters and the months of long nights have helped guard the state against the kinds of onslaughts that have occurred in warmer climes, the 16-page report, "Invasive Species Alaska," does detail that indigenous life forms are facing threats from invaders on land, sea and in the air.

Human activities are a primary cause.

According to the study, invasive species pose "a significant threat to nearly half of the native U.S. species currently listed under the federal Endangered Species Act."

The costs of preventing, monitoring and controlling invasive species, and the cost of damage to crops, fisheries, forests and other resources are huge, the report said. The economic impact of invasive plants alone is estimated to be about $13 billion a year nationally.

While native and non-native species in Alaska's vast landscape have not been well catalogued, literally dozens of harmful non-native organisms, including plants, animals and microbes, are known to have arrived from Outside, the report said. Among other things, they can defoliate forests, decimate seabird colonies and kill fish.

Listed as being of greatest concern in Alaska were the Norway rat, two species of pigeon and starling, two fish species Atlantic salmon and northern pike at least eight insects, including the larch sawfly, strawberry root weevil and western tent caterpillar, at least 11 of the 170 non-native land plant species known to have established themselves in Alaska, at least six aquatic plant species and seven aquatic invertebrate species, including a soft-shell clam, the rope grass hydroid and the boring sponge.

The report said there is debate over which species actually should be labeled non-native, and which should be considered truly harmful. For instance, Alaska once had a subspecies of bison that went extinct long ago, but another was introduced. Some introduced game species are valuable economically, so the distinctions "are somewhat subjective" for some species, the report acknowledged.

"In general, however, there is broad consensus among Alaska's experts on the seriousness of the risk posed by many of these species," the report said.

Some intentional introductions have proved disastrous. Foxes loosed on 450 Alaska islands for fur trapping and farming, as well as creatures introduced as fox food, have devastated native bird populations and disrupted island ecosystems, according to studies cited in the report.

Sometimes species are introduced by accident. The Norway rat came ashore in the Aleutians from a Japanese shipwreck in 1780. Ten years later, an Aleutian island was named Rat Island. Since then, the rats have invaded some 30 islands and some coastal areas. By some estimates, so-called "rat spills" may be more damaging than oil spills.

Here on the Kenai Peninsula, northern pike, a fish native in northern Alaska, was introduced into local waters "by unknown individuals, presumably for sport fishing," the report said. These predatory creatures are invading lake and stream systems around Southcentral Alaska consuming salmon fry.

Hundreds of thousands of Atlantic salmon raised on farms in British Columbia and Washington State have escaped to the ocean, according to the report. Some have reached waters near Ketchikan and Yakutat and as far north as the Bering Sea. Scientists have found pen-reared Atlantic salmon in fresh water, where it was originally believed they would not venture, the report said.

In the mid-1990s, an insect called the amber-marked Birch Leaf Minor was accidentally introduced into the Anchorage bowl where it had no natural enemies. Larvae defoliated more than 30,000 acres in 2002 and has been found in the Matanuska-Susitna Valley and even as far north as Fairbanks.

Not yet considered to be invading Alaska, but nevertheless a known threat off British Columbia, is the European green crab. Scientists are tracking the species' progress north because the crab successfully competes with Dungeness and other shellfish.

As for dealing with the problem, the U.S. Fish and Wildlife Service and the Alaska Department of Fish and Game are engaged in efforts to manager or eradicate some invasive species. One such effort is focusing on removing Norway rats from some 20 islands.

Elsewhere, the Prince William Sound Regional Citizen's Advisory Council and other agencies have been studying ballast water invasive-species transport in the Port of Valdez and other Alaska ports.

The report concludes that invasive species are a growing problem in Alaska, and threaten the state's rare and unusual animals and plants. They impact the functioning of whole ecosystems, the report said.

The report can be found at the Union of Concerned Scientists' website: www.ucsusa.org.



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