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Great Lakes Article:

Aliens all over / Nothing natural about this
Minneapolis Star Tribune
Published June 17, 2004

Alas, the Great Lakes are not the only portion of the American environment under severe threat from invasive animals and plants. Wander almost anywhere in this country and you'll hear scientists and resource managers call mankind's shuffling of the world's biota a top-level threat to ecological balance.

In the northern Rocky Mountains, alien grasses and woody weeds are driving out the native plants on which elk depend for food. In the Grand Canyon, insatiably thirsty tamarisk is crowding out native vegetation. Along the Louisiana coast, South American nutria (picture a 15-pound, water-loving gerbil) are destroying vast tracts of coastal marshland, and not incidentally making New Orleans more vulnerable to hurricane.

Minnesotans are familiar with examples closer to home: the lakes clotted with Eurasian watermilfoil, the marshes given over to purple loosestrife, the buckthorn spreading everywhere, the angler-abandoned earthworms that are radically changing soil conditions in the boreal forests.

These are complicated problems with many causes. Some invasions are driven by accident; in the West, crews fighting forest fires are a major factor in spreading noxious weeds via seeds that cling to boots and tires. Some result from ignorance; a midwestern angler who loves to fish for northern pike carries a bucketful to a stream near his Colorado cabin, never expecting they'll exterminate the native cutthroat trout. Intentional or inadvertent releases from agricultural confinement, as with nutria and Asian carp, are heavy contributors.

Reversing these invasions is almost always costly and hardly ever completely successful. Science continues to demonstrate that natural balances are even more complicated than we thought, that it's far harder to put an ecosystem back the way it was, even approximately, than to protect it from invasion in the first place. This is why it is so critically important for researchers and regulators to invest more heavily in preventive measures than postinvasion responses.

It's also important for them to educate a public that has difficulty drawing clear distinctions between stocking the Great Lakes with salmon, on the one hand, and allowing them to be colonized by invasive Asian carp, on the other.

It's not just a matter of humans preferring one kind of fish to another. Not all exotic species are invasive or noxious; the pollution-resistant Japanese ginkgo trees planted across the United States since the early 1900s have not crowded out the maples and oaks. Nor is it possible for globe-traveling humans to completely avoid carrying organisms from one environment to another. But the oft-voiced notion that all of this transfer is essentially natural -- no different from birds ingesting seeds in one meadow and depositing them in another, many miles away -- must be discounted.

Sometimes we humans promote invasions unwittingly, and for this we can be forgiven. But the biggest problems we've been causing result not from ignorance or happenstance, but from negligent and even willful acts.

We know or ought to know better than to dump an aquarium in a local pond, to stock northerns in a mountain stream, to jettison ballast water from a foreign port. That awareness gives us an ability, and also the obligation, to avoid promoting these destructive invasions whenever we can. Doing otherwise is not only irresponsible but also, when you stop to think about it, against our better nature.


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