Minnesota works hard to keep invasive plants and animals
from becoming established, but the global economy means
the battle will never end.
By Dennis Lien
St. Paul Pioneer Press
For an enduring image of non-native species, it's tough
to beat silver carp, a large, voracious Asian fish that's
moving up the Mississippi River and can explode from the
water like an out-of-control torpedo.
But in the past century, and especially the past decade
or two, other alien invaders have left a lasting, if more
insidious, mark on Minnesota.
From Eurasian water milfoil, which crowds out native
lake plants, to zebra mussels, which foul beaches and
out compete native clams, the state finds itself under
attack from plants and animals that have established footholds
here and are resisting eradication. Other potentially
devastating threats, such as the New Zealand mud snail
and the emerald ash borer, a killer of ash trees, are
on the horizon.
They're getting here through the air, flying from other
infested places. They're reaching us by water, from easy
pathways such as the Great Lakes and the Mississippi River.
They're hitching rides on cargo in cars and trucks. They're
even coming through the mail.
The sheer speed of today's transportation systems and
an increasingly global economy that ships material from
all over the world has outpaced traditional geographical
barriers, posing problems for state regulators trying
to keep the state from being overrun.
"A lot of commodity is coming from underdeveloped
parts of the world, where there's not the greatest infrastructure
or sanitation,'' said Geir Friisoe, section manager for
plant protection at the Minnesota Department of Agriculture.
Despite those onslaughts, Minnesota is better off than
many other states, where even more non-native invaders
have become established.
One reason is our climate, which is too cold for many
species that have found new homes in places such as Florida.
"There's something good to be said for hard, hard
winters,'' Friisoe said. "It knocks down a lot of
those kinds of pests.''
Another is our location midway between the two coasts,
where invasive species often are introduced and addressed
Still another is the state's relatively early response
to invasive threats. Before many other states committed
resources to them, the Minnesota Department of Natural
Resources and the Agriculture Department were already
In 1991, the Minnesota Legislature established an Exotic
Species Program within the DNR that's responsible for
monitoring and managing harmful exotics, including animals
and aquatics. The agriculture department handles other
exotic insects and plants.
Earlier this year, the Legislature strengthened plant-protection
standards and raised the exotic species program's budget
from $1.2 million a year to $1.6 million. "I think
it was a recognition that we have more problems, higher
costs, and we need to do more to address this issue,''
said Jay Rendall, the DNR's exotic species coordinator.
"The states I talk to, they look to Minnesota as
a leader in terms of education and changing boaters' behavior,''
said Jeff Gunderson, associate director of Minnesota Sea
Grant in Duluth.
Invasive species have been with us for more than a century.
Common carp, for example, were brought here in the 19th
century as a food source. Eventually, they took over many
southern wetlands and lakes, damaging the habitat in such
famous waterfowl lakes as Heron Lake in southwestern Minnesota.
European earthworms, another one, are eating away the
floor in Minnesota forests, where native worms were eradicated
by glaciers thousands of years ago. Anglers have spread
them to northern lakes, only to discard some on land.
Once there, the worms eat the small layer of duff - or
leaf beds - on the forest floor, disrupting the forest's
ability to sustain a rich and varied system of plants.
That pace, however, has quickened in recent decades,
with more than half the state's exotic species arriving
since 1985. Examples include zebra mussels, round gobies,
and Japanese beetles.
Gypsy moths, tree defoliators that the state has battled
successfully so far, may become a much bigger problem
soon, according to Friisoe. Introduced into the United
States in the 1800s, they have been moving westward and
now infest much of Wisconsin.
"What's called the action line is moving across
Wisconsin with frightening speed,'' Friisoe said. "It
looks like gypsy moths will be arriving in Minnesota faster
than our previous expectations. I would say within five
If potential problems such as Asian carp from the south
and gypsy moths from the east aren't enough, another potentially
disruptive creature sits on our northern border. Earlier
this year, researchers found the New Zealand mud snail
in Thunder Bay, Ontario, prompting fears it could infest
Lake Superior and other inland waters.
The tiny, prolific creatures were brought to the United
States in 1987, apparently with New Zealand trout, and
have since colonized hundreds of miles of the Snake River
in Idaho and other Western rivers and streams. They have
no natural enemies and can reach densities of 300,000
a square meter.
"Because they reach such high numbers, it's difficult
to imagine they would have not have some sort of impact,''
said Billie Kerans, an associate professor of ecology
at Montana State University.
"And the thing is, they are very easily transportable,''
she added, explaining how they leapfrogged their way east.
Still another emerging problem, Rendall said, is the
commercial sale of aquatic plants and animals, particularly
in the water-garden industry.
"Most of what they sell is not native,'' Rendall
said. "It could be contaminated. You could buy a
water lily and find hydrilla in with the roots.''
A University of Minnesota report to Minnesota Sea Grant
and the DNR last year examined the problem.
The researchers ordered 681 plants from 34 aquatic plant
vendors across the United States. They said 10 percent
of purchases contained federal or state noxious weeds
and 93 percent contained plant or animal species that
weren't requested. Misidentified plants were found in
15 percent of the orders.
MINNESOTA AT FOREFRONT
With so many potential problems, people might find it
easy to get discouraged. But Gunderson said that would
be a mistake.
"There are a number of myths, and one of them is
it only takes one bad boater, one zebra mussel, one introduction,
and the game's over,'' Gunderson said. "That's not
the case at all. Every introduction isn't going to take
hold. This is something that builds up over time. If we
can change the majority of people's behavior, we feel
we can make a difference in reducing the spread of a number
of exotic species.''
Friisoe agreed, saying "99.9 percent'' of the insects
that arrive in Minnesota can't survive here.
Gunderson said a Sea Grant survey show the DNR's education
efforts have been very successful in changing behavior
and limiting new introductions of zebra mussels and Eurasian
"I think Minnesota has been on the forefront of
putting money into efforts, and it shows,'' Gunderson
Besides a bigger budget, the state has tighter regulations
than many other places.
It's against the law, for example, to possess, sell,
or import an exotic species. There's also a regulation
against transporting any aquatic plant, native or not.
Rendall said there are reasons for that.
"One, you don't have to be a biologist to follow
the rule,'' he said. "Just take it off. Two, there
are plants that are not in the state yet. It makes it
illegal to bring them here. Visitors must follow the same
rule. Three, zebra mussels can attach themselves to aquatic