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Defining Our Terms: Exotics in Our Landscape

Summer 2001 Newsletter

When I was growing up, the word "exotic" evoked an image of Dorothy Lamour in a flowered sarong with an orchid in her hair.

Today, the word exotic (a.k.a. alien) evokes images of garlic mustard, purple loosestrife, gypsy moths, zebra mussels, starlings.

An exotic (or alien) is something that grows, flies, crawls, or walks where it did not naturally evolve. In its original home it evolved within an ecosystem where it lived in a balanced relationship with its neighbors and natural enemies.

Through time, many species maintained that balance, adjusting as necessary, and survived the give and take of changes in climate and habitat and competition from nearby evolving species — others dropped by the wayside and became quietly extinct.

Through time species also migrated to new spaces. Either they settled in as good neighbors, died off because they just didn't "fit in" or perhaps they settled in and made some negative impact on the neighborhood.

They're Not all bad guys

Aliens can be detrimental (invasive and destructive of native habitat and other animal species); they may be valuable food sources (under our control, such as wheat, soy, and corn); or they may be neutral (no problem).

Ironically, the unwelcome invaders are rarely pests in their native lands where their natural enemies and balanced habitat kept them in check.

Without these enemies, or without strong competitors, opportunistic aliens can spread in their new habitat with alarming abandon, out competing natives for ground space, food, sun, water supply, and/or housing.

They can destroy the very landscape that serves as their new home. Very often alien species gain a foothold because the habitat has already been disturbed or degraded — perhaps by overgrazing.

In Our Own Backyard

Garlic mustard presented us with a bumper crop this spring. Originating in Western Europe, where it was used as a medicinal herb, it is not a welcome addition to our Midwestern woods.

According to a recent article in the Chicago Tribune (May 8, 2000) garlic mustard was first documented in Long Island in 1868; however, the pungent pest has advanced most rapidly in the last 25 years.

Garlic mustard reaches its peak in early spring, robbing native woodland plants of sunlight, water and nutrients. The prolific towering plant elbows out native seedlings.

Aside from pulling the plant in the spring before it seeds, there are few ways to control it, though herbicides and controlled burning have met with some success, according to Ellen Jaquard, director of stewardship with the Indiana Nature Conservancy.

Although it is not yet time to declare a cease fire, an informal group of researchers and managers of natural areas working with Swiss researchers, has isolated several weevils that are garlic mustard's natural enemies.

These enemies are currently being tested on native American plants to make sure the weevils don't eat them too. So far, there's good news, and if it continues, according to Cornell's Bernd Blossey, "…the weevils could be introduced in the United States within a few years, pending federal approval."

Ah, ah, don't touch…and don't let it touch you. Along roadsides and at other disturbed places another alien, wild parsnip, (Pastinaca sativa L) can be found blooming in late spring or early summer.

It can be recognized by its umbrella-like clusters of pale yellow flowers, 2' to 5' tall above deeply grooved stout stems. The juice from leaves or stems is plentiful and caustic, causing slow-healing burn-like blisters in the presence of sunlight.

Gloves are a must but, if you attack the stem with a shovel, the juice can actually squirt up into your face and leave a permanent scar.

Not a New Problem

When European colonists settled along the Eastern seaboard, the geographical and ecological barriers, which had for so long virtually isolated North America, were all but eliminated.

Sailing ships with human, agricultural and livestock cargoes (all of which had some impact on the new continent) brought not only their highly visible selves but also a select group of hardy insects. (The Nature of Illinois, Fall 1993)

Honeybees were imported as early as 1622, speeding the establishment of the honeybee throughout America. Problems arose when African bees were imported to "improve" the European honeybee.

Hybridization resulted in a new highly aggressive species. Now an alien mite is threatening the vigor of the bees and the honey industry. The Hessian fly crawled in by way of the straw bedding of Hessian mercenaries during the Revolutionary War.

Today it is a pest in almost all wheat-growing regions of the country. The bedbug and oriental cockroach, first recorded in the mid-1700s, willingly made the westward trek with early pioneers.

A century later, as the population in the New World expanded, the demand grew for greater quantities and varieties of food, exotic nursery stock, livestock, and new and better plant varieties from around the world.

Each shipment and import had the potential not only for enriching life but also for introducing future problems. The march of exotics began almost unheeded — quietly stowing away or welcomed as additions to our flora and fauna.

Alien Awareness

As awareness of possible pesty imports arose in the early 1900s, federal legislation provided for the inspection and quarantine of plant material and cargoes and the control of importation of exotic animals and birds. With, unfortunately, limited success.

The gypsy moth was brought in by a scientist who wanted it for study purposes. Well, the fellow escaped from the laboratory and has created havoc throughout native forests. Even with increased awareness, accidental (and purposeful) introductions still occur and spread.

Purple loosestrife, a handsome weed, is an aggressive invader of wetlands, covering acres and acres with its colorful blossoms. It is a major problem in Illinois' few remaining wetlands, according to Dr. Rob Wiedenmann, a research scientist at the Illinois Natural History Survey's Center for Economic Entomology.

He points out that, "A single loosestrife plant can produce as many as 2.7 million seeds [a hearty competitor!] which can be carried by water and may germinate years later."

Purple loosestrife is a perfect candidate for biological control, he says, because it is a perennial, is restricted to wet and stable habitats and is not closely related to an agricultural crop or an endangered plant species.

Several species of exotic beetles have proven effective in killing the noxious weed; however, the enemies were not released until extensive testing showed that in releasing them, the researchers would not be releasing a species that would create a worse problem than the loosestrife itself.

"Realistically," Wiedenmann pointed out, "even with biological control we will never be able to call a truce in the war on insect and weed pests… there will always be new pests to challenge us." Although many pests may hopefully be brought under some control, they will not be completely eradicated.

Recent surveys indicate that at least 6,000 non-native plants have become established in the United States. Most of them are benign but hundreds cause real trouble.

Take cheat grass, for example. It has become the most common plant in the Intermountain West, wiping out much of the native sagebrush. "The spread is so rapid as to escape recording," wrote Aldo Leopold in 1941. "One simply woke one fine spring to find the range dominated by a new weed."

Not Just Weeds

In 1890 about 60 starlings were set free in Central Park in NYC. The next year another 40 were set free. Originally a native of the British Isles, these birds were imported to fulfill one man's desire to introduce all the birds mentioned in Shakespeare's plays to the New World.

A romantic, poetic idea: however, today millions upon millions of starlings have since spread all across the country. A particularly aggressive bird, the starling—-which travels in large, noisy flocks — often steals the nests of native birds and out competes them for territory.

High on the list of harmful species is the wild pig, introduced into California by Spanish explorers and settlers in the 1700s. In 1924, hunters added the European boar. Today, interbred, they inhabit 49 out of 58 counties in California.

Why are they so "successful"? Because they breed faster than any other large hoofed animal; they eat everything, denuding vineyards, destroying vegetable gardens, uprooting tidy lawns and golf courses and the best hillsides for grazing; they chew plastic pipes and turn beautiful sections of streams into mud pits. (Well, they act just like pigs! )

Well intentioned but misguided professionals and fishermen have dumped "good" game fish into streams and lakes throughout the country, upsetting the natural balance of the waters. And the native fish suffer, diminish, and may even disappear.

Not half a century ago white tail deer were nearly extirpated from Illinois. "Good management practices" and habitat changes have turned Bambi into something of a pest. Now sharp shooters (as well as sport hunters) are welcomed into our fields, towns, and city gardens.

In the Opinion of Some Experts

O.W. Wilson, eminent entomologist from Harvard University points to exotic or alien species as the second most serious danger to biodiversity after habitat loss.

David Quammen, journalist also writes about habitat fragmentation and loss in a Harper's Magazine interview with the late David Jablonski, University of Chicago paleontologist. Jablonski describes the five, catastrophic extinctions over the last 600 million years.

"The Ordovician extinction, 439 million years ago, entailed the disappearance of roughly 85% of marine animal species — and that was before there were any animals on land.

"The Devonian extinction, 367 million years ago, almost as severe.

"The Permian extinction, 245 million years ago, the worst ever, claiming 95 percent of all known animal species and therefore almost wiping out the animal kingdom altogether.

"The Triassic, 208 million years ago, not quite as bad as the Permian, and most recently the Cretaceous extinction, which ended the age of dinosaurs as well as marine reptiles, mammals, and the ammonites totaling about 76 percent of all species."

In between these massive events, extinctions continued, but at a much slower pace… known as the background rate, infrequent enough to be counterbalanced by the evolution of new species.

Jablonski posits that the time between impoverishment and return to ecological fullness to be roughly 5 to 10 million years. Jablonski adds that the consensus among many conscientious biologists is that we're headed into another mass extinction. Habitat loss and fragmentation of habitat appears to be the main culprit.

We Are Aliens Too!

We should not forget that we are aliens too. We pave the landscape with malls and roads and parking lots. We pollute our rivers, our streams, our air. We introduce other alien species that may be problematic and we do not always practice good land management.

Not being as dumb as a garlic mustard plant or as mindless as a wild pig in California, we aliens, individually and in groups, have the choice to be good neighbors, balancing our needs with the needs of the land.

In a rain forest on Maui, Robert Devine, author of Alien Invasion, met a teenage stewardship volunteer who said it best: The rain forest is more than just a place to hike or the watershed for his town. The rain forest in part of who he is, part of where he belongs. "That's why," he said, "I'm taking care of it."

Gloves, as well as arm and leg protection should be a part of every weed pulling session since some plant juices contain known carcinogens.

Sources for additional reading:

• Quammen, David: Song of the Dodo
• Wild Thoughts from Wild Place; and Harper's Magazine, Oct. 1998
• Stein, Sara: Noah's Garden, Restoring the Ecology in our Own Back Yards
• Devine, Robert: Alien Invasion, America's Battle with Non-Native Animals and Plants.

—Jean Gray