The same holds true for coyotes. First reported in South Carolina as recently as 1978, coyotes now inhabit the entire state. Another statewide species is the feral hog. Studies indicate that more than 150,000 wild pigs now inhabit the state. And who among us hasn’t performed the fire ant “dance” after accidently stepping on a telltale mound?
“Invasive species” can be a somewhat confusing, catchall phrase that covers a wide range of plants and animals that are not native to a specific region and that usually reproduce and spread to the point of causing damage to their new environment. You might think that all four species noted above are invaders from other countries, but you would be wrong. The armadillo and fire ants are, which makes them “exotic” or “alien” species, but the coyote and feral hogs are not. The armadillo and fire ants are native to Central America and South America, while coyotes are native to the United States and have simply extended their range. The feral hogs descended in part from their escaped domesticated ancestors.
Nine-banded armadillos are found throughout the southeastern United States, but their range is still expanding northward. They were first discovered in South Carolina in the late 1990s. Thought to be limited to the Lowcountry due to the Upstate’s cold winters, armadillos nonetheless began to move north and east. Today they can be found across the entire state. They are voracious eaters that dig up quite a bit of land, including flower beds and lawns, in their nocturnal search for insects and grubs. Armadillos are the only animal besides man that can be infected with the bacteria that causes leprosy, but cases of humans contracting leprosy from armadillos are extremely rare.
Prior to the 18th century, coyotes were mainly restricted to Mexico and central North America. Since then, they have dramatically expanded their range and can now be found across the entire United States as well as Canada. They are quite adaptive and can even be found in highly urbanized areas like New York City. Coyotes were first seen in South Carolina in 1978; within 20 years they could be found statewide and are now here to stay. They are wily, mostly solitary predators that can adapt their diet to what food sources are available. While many suburbanites think coyotes feed mainly on house pets, studies indicate they prefer rodents, deer (another now-urbanized species), rabbits, roadkill, and garbage. Efforts to control or eliminate coyote populations are varied and in almost all cases do not work.
Red fire ants were first discovered in South Carolina in the 1960s. It is believed that they originated in ornamental nursery plants near Seneca, South Carolina. Given how difficult fire ants are to control, a valiant and subsequently successful effort was made by entomologists at nearby Clemson University to eradicate this first outbreak. Unfortunately, fire ants were later discovered in the Charleston area and have continued to spread throughout the state, now in every county.
As our world shrinks through international commerce, and as the environment changes, the issue of invasive species has become front and center in our efforts to protect our native land. And while we tend to focus on visible animals like fire ants and armadillos, the actual number of invasive species is quite extensive and not just confined to the animal kingdom. An estimated 100 million acres in the United States are now impacted by invasive plant species. Perhaps the most visible of all invasive species is the kudzu plant. First introduced to the United States in 1876 to control soil erosion, this Japanese native soon broke free of its intended agricultural use and is now ubiquitous throughout the southern United States, swallowing trees, buildings, and anything else standing in its path.
A more recent example of a species entering our state is the beautiful but dangerous lionfish. Native to the Pacific Ocean, lionfish first appeared off South Carolina’s shores around 2001 and are now well-established off the East Coast. The list of invasive species even includes that Bradford pear growing in your front yard. Scientists estimate that more than 50,000 non-native species may be in the United States alone. Of that number, approximately 4,300 are considered invasive. (Not all exotic species are invasive. Remember, crops, such as potatoes and wheat, are not native to the United States.)
How did these creatures come to invade our lands? The causes are as varied as the number of species. Some animals, like the starling, have been around for so long and are so common that people are often surprised to learn that they were introduced into the United States from Europe in 1890. A group of New York Shakespearean enthusiasts lead by Eugene Schieffelin had an intriguing idea. They thought they would introduce some of the bird species named in Shakespeare’s various works into New York City, so in 1890 they released about 100 starlings into Central Park. European starlings are now one of the common birds in North America, with an estimated population of 200 million.
Both lionfish and the much-publicized invasion of Burmese pythons into Florida’s Everglades are believed to have resulted from the release of unwanted pets. Many others hitch rides on ships and planes and agricultural products, including nursery plants.
There are other examples of good intentions gone bad with respect to invasive species. Some people blame a single landowner in Victoria, Australia, with one of the worst international ecological disasters on record. In 1859 he imported 24 wild rabbits from England for the purpose of hunting. By the 1920s, the rabbit population in Australia had grown to an estimated 10 billion. They destroyed two million acres of Victoria’s floral lands and began spreading across the entire continent. The country went to incredible measures to stop the spread, at one point building the world’s longest fence, stretching 1,138 miles vertically down the entire western side of the continent. Over the years various rabbit-specific diseases (viruses and toxins) were introduced. Other non-native species, including red foxes and domestic cats, were also introduced, but the rabbits have so far resisted these efforts and are still a problem today. The impact of rabbits on the Australian environment has been disastrous.
The economic and environmental impact caused by invasive species is enormous. Back in 2005, the U.S. Fish and Wildlife Service estimated that the economic impact associated with invasive species in the United States was approximately $120 billion per year. One example cited by the FWS involved Florida’s Burmese pythons. These voracious predators are known to eat almost anything, including wood storks and Key Largo woodrats, both federally protected species. The service states that from 1999 to 2009, federal and state agencies spent a total of more than $100 million on Key Largo woodrat and wood stork recovery.
The negative impact of an invasive species on the health and economy of a new environment can be enormous. As noted above, the populations of some invasive species will often explode. Why? In its native environment a species evolves along with predators, diseases, and other environmental factors that keep population growth in check. When these factors are removed in a new environment, its numbers will almost always increase. These large population numbers can have severe, negative impacts.
The following are a few examples:
Zebra mussels — a small mollusk native to fresh waters in Russia and Ukraine. They most likely arrived in the Great Lakes in the 1980s, living in the ballast water of ships entering the United States from Europe. They spread rapidly throughout the Great Lakes and into the Mississippi River basin. They are now established in Texas, Colorado, Utah, Nevada, and California. They negatively impact ecosystems in a variety of ways. Most notably, power plants spend millions of dollars removing zebra mussels from clogged water intakes. It is estimated that affected power plants have spent more than $3 billion on zebra mussel control and removal. Zebra mussels have not been found in South Carolina.
Nutria — a semi-aquatic rodent native to South America. They are not only considered an invasive species in the United States, but they have also expanded their range to almost every continent on earth. They reach sexual maturity in just a few months, reproduce up to three times a year, and produce large litters. Nutria have caused environmental catastrophes throughout the world by destroying infrastructure and crops. Their economic impact on these environments is too high to estimate. Nutria have yet to be confirmed in South Carolina, even though they have been found in coastal counties south of Savannah, Georgia, and the coastal plain of North Carolina. Their arrival is only a matter of time.
Wild hogs — the descendants of introduced wild boar, escaped domestic pigs, and hybrids of the two. The U.S. Department of Agriculture’s National Wildlife Research Center estimates the number of feral pigs in the continental United States to be between 5 and 6 million animals in at least 35 states. The South Carolina Wild Hog Taskforce reports that the annual economic loss due to damages and control costs of wild hogs in the United States is around $1.5 billion.
Bradford pear — beginning in the 1960s, homeowners and parks departments thought they had found the perfect ornamental tree. Bradford pears bloom in the spring, and their leaves turn a deep garnet color in the fall. They were planted throughout the East, South, and Midwest for decades. This once admired tree is now considered an invasive species, which grows even in poor conditions, spreads quickly, and crowds out native plants and trees. The S.C. Forestry Commission is not only asking that you not plant Bradford pears, they also encourage cutting down every Bradford pear tree on your property. They ask that you consider replacing these invasives with native alternatives such as serviceberry, fringe tree, tupelo, or dogwood.
Is there an answer to controlling or eliminating the spread of invasive species? On a local or personal level you can take steps to help. The Nature Conservancy lists several initiatives, including avoiding purchasing invasive plants or replacing invasive plants in your yard or garden. Thoroughly clean your boat before transporting it to a different body of water. The S.C. Department of Natural Resources reports that since 1981 about $22 million of federal, state, and local funds have been spent to control aquatic invasive plants in our public waterways, many of these introduced on boat propellers. Don’t release aquarium fish and plants, live bait, or other exotic animals into the wild. Volunteer at your local park, refuge, or other wildlife area to help remove invasive species.
Unfortunately, some of the most infamous global invasions, like the zebra mussel or nutria, will probably not ever be completely controlled or eradicated. Sadly, they are here to stay and their impact on the environment and economy will be ongoing. Or, to use a terrible pun, in most instances the cat is long out of the bag.
Satch Krantz, former president and CEO of Riverbanks Zoo and Garden whose career there spanned 44 years, led the zoo to national prominence. He received the R. Marlin Perkins award from the Association of Zoos and Aquariums, the highest recognition for zoo professionals, as well as The Order Of The Palmetto, the highest civilian honor in South Carolina.