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Purple Loosestrife. Photo by Bet Zimmerman.  

Intentional introductions of bully plants, animals and insects can have devastating consequences. More...

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The Curse of Unintended Consequences – Part II

When my husband Doug does something disastrous, I often ask “What were you thinking?”  He often replies “It seemed like a good idea at the time!” or “How could I have known?”  These same questions and rationale apply to intentional introductions of non-native species.  Those who brought these creatures into a new ecosystem all had their reasons.  Here are just a few examples of the many bully birds, plants, fish, insects and more that well meaning people have welcomed to our shores, with devastating consequences.

Bighead Carp.
How would you like to get hit in the head by a flying carp? It can happen to boaters on water bodies infested with this invasive species.  This is a photo of a bighead carp, which does not normally jump when frightened. Image from Asiancarp.org

In 1890 and 1891, the Acclimatization Society of North America decided to introduce all the birds mentioned in Shakespeare's works.  About 60-100 European Starlings were released into Central Park, NY.  Now they number 200,000,000.  By the late 1940s, starlings had spread to nearly all of the U.S. states and Canadian provinces.  Today, they are the most numerous bird in the U.S.  These bold scavengers will eat just about anything, especially fruits like strawberries, blueberries and grapes, and livestock feed.  In an hour, flocks of tens of thousands of birds can wipe out wild berries that would have sustained native birds for the entire winter.  To top if off, these invaders aggressively compete with beneficial native cavity nesters like bluebirds and woodpeckers.

Purple Loosestrife was widely admired for its striking, purple spikes (now blooming along roadsides near you), and valued for medicinal purposes. This European native was introduced to the northeastern U.S. and Canada in the 1800's.  Since then, it has sprawled westward to Minnesota and southward to Virginia.  It is still widely sold in states where it is not banned.  One mature plant can produce an estimated 250,000 to 2,000,000 seeds in one year, and seed survival is high.   This beautiful monster can overrun wetlands thousands of acres in size.  It can completely fill in open water habitat.  It eventually chokes out native plants.  Often, those plants provided food, nesting material and cover for wildlife, some of which were already struggling to survive due to loss of wetland habitat.  

Several species (bighead, grass, silver and black carp) of Asian Carp were imported to the U.S. to control algae and manage water quality in catfish aquaculture in the 1960s and 70s.  In the 1990s, some escaped from southern fish farms during floods. Others were stocked in lakes or reservoirs that connected to streams. They rapidly expanded their territory and now pose a threat to the Great Lakes ecosystem. Asian carp can weight up to 100 lbs., grow four feet long and live 30 years.  They are extremely prolific, and ravenous, eating up to 40% of their body weight in plankton daily.  The carp compete aggressively with native fish, which impacts the fishing industry. They are also dangerous when they leap out of the water and wallop boats and boaters.  (See video of a CNN reporter getting pummeled.)  Stocking grass carp as a biological control against nuisance aquatic plants in ponds and lakes continues to this day.

Multicolored Asian Lady Beetles were introduced by the U.S. Dept. of Agriculture as a biological control from 1978-1982.  They will dine on more than 50 species of agricultural/landscape pests such as aphids and scales.  Unfortunately, they also relish ripening peaches, apples, grapes and other fruits.  Because of their habit of swarming homes while looking for a place to overwinter, they can become a household nuisance.  When disturbed, they reflexively ooze out a stinky yellow-orange liquid that can permanently stain fabric and walls.  Unlike other lady beetles, they can bite and cause welts, and an allergic reaction in some people. No insecticides are currently labeled for their control.

Some of these consequences from introductions were due to ignorance.  It is not possible to foresee everything.  Some were errors.  Others resulted from a focus on immediate benefits versus long term ramifications. All of these invasive aliens have negatively impacted the complex food web and various habitats. In the process, they can drive native species to the brink of extinction, and damage the economy as well.  The human race has had plenty of opportunities to learn from these experiences. The question that remains is “When will we ever learn?” 

Also see Part I and Part III
Originally published in the Villager newspapers on August 1, 2008

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