JEFFERSON CITY–Some invasive plants and animals come in ships from halfway around the globe. Others leapfrog from one watershed to the next in bait buckets. Occasionally they arrive in pickup trucks under cover of darkness. The National Invasive Species Council (NISC) wants to get all Americans involved in stopping them.
Invasive plants and animals are in the news more than ever today. Despite the flood of information, the nature of the threat sometimes seems vague and distant. To increase popular awareness of hos invasive exotics threaten the nation’s economy, ecology and culture, NISC has designated Feb. 26 through March 3 National Invasive Species Awareness Week. Learn how you can reduce the threat from invasive species at http://bit.ly/ywWuoa.
Missouri’s location astride several transcontinental transportation arteries and the nation’s largest river systems puts the Show-Me State squarely in the middle of invasive species issues. The problem is not new. The common carp, originally native to Eurasia, has been in the United States since the 1800s, about the same time that kudzu arrived from Japan. Dozens of other species that we now think of as part of the Show-Me State’s native flora and fauna actually are naturalized inhabitants. Most of them get along reasonably well with the natives. A few cause problems, however.
The zebra mussel is a prime example of a troublemaker. This thumbnail-sized freshwater mollusk also originated in Eurasia. It arrived in the Great Lakes in the 1980s in the ballast tanks of cargo ships. Since then, it has spread to several states, including Missouri. Zebra mussels are so prolific that they choke out native mussels, damage boats, docks and marine engines and block water intakes of municipal and commercial utilities.
Kudzu is another good example of a destructive invader. It didn’t sneak into the country the way the zebra mussel did. The Japanese government proudly escorted the vining plant into the United States for its debut at the Centennial Exposition in Philadelphia. It was touted for its value as a forage plant and widely promoted for erosion control.
Kudzu liked its new home so well that it took off at a gallop southward and westward and has only slowed down where cold or drought made it feel unwelcome. Along the way, it bushwhacked unsuspecting native plants, including trees.
Those two stories neatly bookend the larger tale of invasive species in America. Introducing organisms into new areas, whether deliberately or by mistake, is one of the world’s most powerful lessons about unintended consequences.
Missouri’s catalog of invasive plants and animals is too extensive to list. Species of primary concern at the moment include the following.
• The Asian longhorn beetle, emerald ash borer and gypsy moth are destructive forest pests.
• The walnut twig beetle spreads thousand-cankers disease, which threatens Missouri’s multi-million dollar black-walnut industry.
• Feral hogs damage wildlife habitat and agricultural crops and carry diseases that affect livestock and humans.
• The bighead, black and silver carp could drastically alter the food chain of lakes and streams with consequences that remain uncertain.
• Bush and Japanese honeysuckle choke out native vegetation, reducing biological diversity and degrading wildlife habitat.
• Canadian thistle arrived here before the revolutionary war and degrades the value of pastures. Several other invasive, exotic thistle species cause similar problems.
• The Chinese mystery snail, originally an aquarium specimen, is elbowing aside native snail species in urban streams statewide.
• Various crayfish have displaced native crayfish species in at least 21 Missouri watersheds. Some of these were introduced through interstate bait trade. Others became invasive when introduced into watersheds adjacent to their natural ranges.
• Sericea lespedeza was introduced into the United States in hopes of improving pastures and providing food for wildlife but turned out to be highly invasive and destructive to native grasslands.
• Spotted knapweed, garlic mustard, Chinese yam, Japanese knotweed, Johnson grass, purple loosestrife and several other herbaceous plants are displacing native plants, causing agricultural damage and reducing the biological diversity of Missouri’s wildlands.
It can be difficult to get excited about the abstract concept of “biodiversity.” You might wonder why it matters if Missouri has 50 plant species or 50,000. Aren’t they all green?
Diversity is important for two reasons—stability and utility.
First stability. Natural communities with lots of species are stable, because no single factor, such as disease, drought or parasites, can take out many of the components. In contrast, communities with only a handful of species are vulnerable to collapse, because adverse factors that affect a handful of species can eliminate a large portion of the remaining plants or animals. Such collapses can affect things people depend on, including food and wood products. Even more vulnerable are fish and wildlife, which are at the heart of outdoor traditions that have shaped and continue to sustain the American character.
Then there is utility. What use are diverse natural communities? Think of Missouri’s thousands of plant and animal species as items in a huge toolbox for dealing with future problems, such as how to feed ourselves or treat diseases. You don’t know which tools are useful until you need them. Plants and animals that seem unimportant sometimes turn out to have traits—such as drought tolerance or medicinal value—that would be tragic to lose. Cancer drugs, drought-resistant crops and industrial chemicals are among the benefits we already have derived from nature. Do we want to have invasive species randomly tossing tools out of our toolbox?
Changes caused by invasive species can even affect cherished cultural traditions. Take hunting. How would the loss of acorn-producing oak trees due to a gypsy moth infestation affect deer and turkey numbers? Or fishing. No one knows yet how Asian carp or zebra mussels will alter the food chains of infested lakes and streams. How will those changes affect sport fish, such as bass, catfish and crappie, or commercial fishing on Missouri’s big rivers? Clearly, everyone has a stake in keeping invasive species out of Missouri.
The Missouri Department of Conservation has information about invasive species prevention and control at mdc.mo.gov/node/4086. Once at this site, search “invasive species.”