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Wherever people have gone they have taken other animals with them, whether they knew it or not. The Taíno Indians must have watched in horrified amazement as Columbus’s men hauled their desperately flailing horses ashore on San Salvador, but the equines were only the most visible and obvious of the immigrants (aside from the hairy conquistadors themselves)—hidden belowdecks and inside the barrels of rotting wheat and barley, within the wooden planks of the Santa María, even deep in the lung tissues and blood vessels of the newcomers’ own bodies, lurked a host of alien organisms poised to explode across the entirety of an unready New World.
The Columbian Exchange was a momentous ecological interaction of the Eastern and Western Hemispheres in which thousands of animals, plants, funguses and diseases were brought from Eurasia and Africa and unleashed upon the unwilling Americas (and to a much smaller extent vice versa) either by accident or design. Not since the Late Pleistocene extinction event of 10,000 years previously, during which newly arrived Siberians managed to wipe out approximately 33 of 45 genera of North American mammals over 100 pounds (46 of 58 genera in South America), had introduced species so freely run amok in such a biologically innocent Eden. The ruinous movement of nonnative species across biomes still reverberates from that fatal shore in 1492, and with today’s routine international travel, the globalized economy and the continuous upheaval of peoples due to war, famine and climate change, the challenges posed by exotic organisms has never been as acute as now.
Take a walk down a forested area in the Shenandoah Valley and observe the skeletal corpses of the mighty hemlocks crumbling away along the stream banks, victims of a tiny insect called the woolly adelgid, native to Asia. Recoil with disgust from the unsightly brown marmorated stinkbugs that squeeze their way into your cozy home every fall, another unwelcome immigrant from the Asian landmass. Curse the squalid and slovenly European starlings (Sturnus vulgaris) that shove aside native birds at your feeder, but save some invective for Mr. Eugene Scheiffelin of the American Acclimatization Society, who in 1890 released 100 representatives of this feathered plague into Central Park on the grounds that rustic America would benefit from welcoming every bird mentioned in Shakespeare; alas for cavity-dwelling natives across the continent, Hotspur, in Henry V Part 1, fatefully mutters, “Nay, I’ll have a starling shall be taught to speak nothing but ‘Mortimer.’” Why couldn’t you have used a raven, Bill?
Of the thousands of exotic creatures and pestilences that abound today in Virginia, a representative five—a bird, a mammal, an insect, and an aquatic and a terrestrial plant—will serve to illustrate the totality with which nonnative species have impacted our ecosystems. Let’s start with a massive waterfowl beloved of park-goers and melancholy romantics: the mute swan.
Introduced into North American at about the same time as the starling, the admittedly gorgeous mute swan was meant to languidly grace the palatial estates of the noveau riche. Feeling themselves to be the legitimate heirs to the European nobility, these plutocrats sought to adorn their new villas with the same art, architecture, cuisine and general décor as their Old World role models, up to and including the stately porcelain swans that paddled sedately in fountains and impoundments with regal implacability—precisely the impression their importers sought to convey about themselves to visitors.
Weighing up to 25 pounds and with an 8-foot wingspan, the mute swan is now the largest bird in the Chesapeake Bay, and routinely bullies smaller native waterfowl away from prime feeding grounds. The swans can eat up to eight pounds of eelgrass a day, yanking the plants out by the roots and ruining a vital source of nutrition for other birds, and they have no natural predators. Challenged, the cob (adult male) will puff out his snowy back feathers, raise his head high in the air, extend his wings, emit an ominous hissing sound and slowly stomp toward the dog, person or other intruder who dared breach his personal space. If cygnets are present the response is even more alarming, and the birds are immensely powerful; in 2012 a man drowned when a couple of mute swans tipped over his kayak. And yet there is strong resistance among the public to proposals to eradicate mute swans from their midst. “New York Wants to Banish a Symbol of Love” hollered the Times last winter apropos a plan to eliminate the 2,200 birds in the state. Lovely or not, the mute swan poses a genuine threat to our native ducks, geese and swans.
~
“When God invented the hog,” a friend of my father’s once observed, “He could’ve stopped right there. Bacon, ham, sausage, chops, ribs … the hog’s got it all.” Indeed. But when loosed into the wild those docile pink or mottled porkers become in a couple of generations lean, hairy, canny usurpers of your local woodland wildlife. With vicious tusks, surly temperaments and an insatiable appetite for the eggs of such ground nesters as quail, grouse and turkeys, feral hogs are equally fond of the mast—acorns and other tree fruit—that our bears depend on prior to hibernation. They can triple their population in a little over a year and have no natural predators that have evolved with them, as the nearest pig-like native is the doughty javelina of the desert Southwest.
While feral hogs have been with us for some time (those selfsame conquistadors doubtless offloaded swine in that Caribbean beach), in Virginia they are at the northern end of their acquired range, and currently we only have around 3,500 in total, a drop in the slop bucket compared to Texas’s population of five million. This means that we still have time to annihilate the problem before it becomes unmanageable, a sure bet if left alone for a sufficient time. Voracious and clever, feral hogs pose a menace to native woodlands as their rooting behavior churns up the forest floor in just such a way as to allow colonization by other exotic pests such as kudzu and Japanese honeysuckle. DGIF permits hogs to be killed any and every way possible, but their nocturnal preferences and innate caution coupled with an outstanding sense of smell make them challenging game to say the least.
~
Drive down I-95 on a summer afternoon anywhere from Maine to Florida and in unmanaged fields you’re likely to see burgeoning groves of a 15-foot shrub with dense branches housing abundant leaves of a somehow sickly shade of dusty gray-green. The autumn olive, native to East Asia, was brought here in the 1830s for the usual reasons—ornament and erosion control—and like much else has taken off explosively, utilizing some handy traits that propel its success while hindering that of others. Nitrogen-fixing root nodules allow it to exploit even the poorest soils so long as they’re relatively dry and sunny, and each shrub can produce up to 200,000 seeds per year. Burning or cutting autumn olive are the worst ways to control it, as both approaches encourage ravenous regrowth that is even denser and hardier (Virginia DCR recommends glyphosate herbicide application). With entire pastures being engulfed by these supremely adaptable woody bushes in a matter of a few years and native plants that wildlife depend upon paying the price, landowners should take steps to eradicate autumn olive whenever and wherever it raises its sallow shoots.
~
In 2002 arborists were alerted to a puzzling decline of the ash trees shading the streets of Detroit. Eventually an entomologist in Slovakia, of all places, identified the culprit as the emerald ash borer, a bright metallic green splinter of a bug about half an inch long and another native of East Asia. Thought to have tagged along in foreign ash wood used to support crates during transatlantic shipping, the emerald ash borer poses an urgent threat to the entire Fraxinus genus, that colorfully-named (green, black, white, blue, etc.) collection of hardwoods that provides important benefits to wildlife. Ash seeds are eaten by waterfowl, upland game birds, songbirds and small mammals, while deer and beaver browse the leaves. Cavity-dwellers such as woodpeckers, wood ducks, kestrels and screech owls nest in larger ash trees. Ashes growing in riparian areas stabilize stream banks and provide important shade for cold-loving trout—all the more important now that the woolly adelgid has wiped out most of our hemlocks.
While the emerald ash borer is spreading throughout the Midwest and upper South at the rate of about 12 miles yearly, the wide-ranging transportation of firewood in our hyper-connected culture has allowed the pest to establish colonies far from its original point of invasion. Ash trees are killed by the feeding larvae, which tunnel meandering paths of destruction just under the bark, eventually stifling the flow of nutrients and girdling the tree. Without native predators to stymy its spread, researchers are looking to three species of parasitic, non-stinging wasps that hunt the ash borer in its native land to put the quietus on its booming population … ideally before the rest of our ashes follow the tens of millions already killed.
~
Bringing in nonnative control organisms to combat nonnative invasives is an uneasy solution at best—even the careful laboratory testing that precedes such releases is often conducted in a rush in order to get the corrective element out into the woods and eliminating the exotic pest. Our final infamous exotic is also being fought with enemies imported from its homeland, local herbivores being uninterested in this unappetizing specimen.
Purple loosestrife is an invasive wetlands weed from Europe, where it traditionally was used to treat everything from dysentery to ulcers. An herbaceous perennial that can reach nearly seven feet in height and produce over two million grainy seeds annually, purple loosestrife crowds out native wetlands flora such as cattails with such vigor that entire marsh ecosystems are negatively impacted. Such is the density of loosestrife stands that natives ranging from rails to muskrats, spotted turtles to bullfrogs, are muscled out of their own habitat. Bugs from the old country—two leaf beetles and three weevils—have been introduced and are proving to be successful at defoliating loosestrife, a positive note indeed so long as the necessarily imperfect science of fighting exotics with exotics maintains its edgy ecological balance.
~
Businesses catering to lawn ornamentation and erosion control, the shamefully unregulated international pet trade, agribusiness and the all-pervasive juggernaut of global commerce all share the blame for the escalating cavalcade of alien beings barging into our midst. And the problem certainly goes both ways; in Europe our introduced bullfrog and gray squirrel are seen as the foreign menaces they are there.
In May of 2014 an international group of scientists published a study in the journal PLOS | Biology arguing for a new method of classifying exotic species, a calculation of ascending harm ranging from Minimal to Maximum that seeks to better inform lawmakers and regulators of the magnitude of economic and ecological injury of a given invasive. This sensible approach would put the impacts of these foreign armies front and center, with any luck sparking the kind of funding decisions and agency actions that are needed to address this multifaceted dilemma. Without a forthright and consistent approach, these hardened generalists from overseas will continue to exploit our hapless natives to the full extent of their powers until, like Columbus, they have made our world their own.
~
SIDEBAR: The feral housecat, while not a species that DGIF is charged with managing, is after humans the reigning king of harmful exotic species. The 84 million pet cats and from 30 to 80 million feral cats in the US have recently been estimated to kill an astounding 2.4 billion birds each and every year, and an even more absurd 12.3 billion small mammals along with around 650 million reptiles and amphibians. The most pampered housecats are semi-feral at heart in a way that dogs cannot be. Even stuffed with gourmet chow, a young and healthy housecat let outside will quickly assume the predatory habits of its ancestors, killing not from hunger but from instinct. Cat owners must keep their pets indoors or closely supervised when visiting the yard, or assume their share of the blame for these horrifying statistics.
The Columbian Exchange was a momentous ecological interaction of the Eastern and Western Hemispheres in which thousands of animals, plants, funguses and diseases were brought from Eurasia and Africa and unleashed upon the unwilling Americas (and to a much smaller extent vice versa) either by accident or design. Not since the Late Pleistocene extinction event of 10,000 years previously, during which newly arrived Siberians managed to wipe out approximately 33 of 45 genera of North American mammals over 100 pounds (46 of 58 genera in South America), had introduced species so freely run amok in such a biologically innocent Eden. The ruinous movement of nonnative species across biomes still reverberates from that fatal shore in 1492, and with today’s routine international travel, the globalized economy and the continuous upheaval of peoples due to war, famine and climate change, the challenges posed by exotic organisms has never been as acute as now.
Take a walk down a forested area in the Shenandoah Valley and observe the skeletal corpses of the mighty hemlocks crumbling away along the stream banks, victims of a tiny insect called the woolly adelgid, native to Asia. Recoil with disgust from the unsightly brown marmorated stinkbugs that squeeze their way into your cozy home every fall, another unwelcome immigrant from the Asian landmass. Curse the squalid and slovenly European starlings (Sturnus vulgaris) that shove aside native birds at your feeder, but save some invective for Mr. Eugene Scheiffelin of the American Acclimatization Society, who in 1890 released 100 representatives of this feathered plague into Central Park on the grounds that rustic America would benefit from welcoming every bird mentioned in Shakespeare; alas for cavity-dwelling natives across the continent, Hotspur, in Henry V Part 1, fatefully mutters, “Nay, I’ll have a starling shall be taught to speak nothing but ‘Mortimer.’” Why couldn’t you have used a raven, Bill?
Of the thousands of exotic creatures and pestilences that abound today in Virginia, a representative five—a bird, a mammal, an insect, and an aquatic and a terrestrial plant—will serve to illustrate the totality with which nonnative species have impacted our ecosystems. Let’s start with a massive waterfowl beloved of park-goers and melancholy romantics: the mute swan.
Introduced into North American at about the same time as the starling, the admittedly gorgeous mute swan was meant to languidly grace the palatial estates of the noveau riche. Feeling themselves to be the legitimate heirs to the European nobility, these plutocrats sought to adorn their new villas with the same art, architecture, cuisine and general décor as their Old World role models, up to and including the stately porcelain swans that paddled sedately in fountains and impoundments with regal implacability—precisely the impression their importers sought to convey about themselves to visitors.
Weighing up to 25 pounds and with an 8-foot wingspan, the mute swan is now the largest bird in the Chesapeake Bay, and routinely bullies smaller native waterfowl away from prime feeding grounds. The swans can eat up to eight pounds of eelgrass a day, yanking the plants out by the roots and ruining a vital source of nutrition for other birds, and they have no natural predators. Challenged, the cob (adult male) will puff out his snowy back feathers, raise his head high in the air, extend his wings, emit an ominous hissing sound and slowly stomp toward the dog, person or other intruder who dared breach his personal space. If cygnets are present the response is even more alarming, and the birds are immensely powerful; in 2012 a man drowned when a couple of mute swans tipped over his kayak. And yet there is strong resistance among the public to proposals to eradicate mute swans from their midst. “New York Wants to Banish a Symbol of Love” hollered the Times last winter apropos a plan to eliminate the 2,200 birds in the state. Lovely or not, the mute swan poses a genuine threat to our native ducks, geese and swans.
~
“When God invented the hog,” a friend of my father’s once observed, “He could’ve stopped right there. Bacon, ham, sausage, chops, ribs … the hog’s got it all.” Indeed. But when loosed into the wild those docile pink or mottled porkers become in a couple of generations lean, hairy, canny usurpers of your local woodland wildlife. With vicious tusks, surly temperaments and an insatiable appetite for the eggs of such ground nesters as quail, grouse and turkeys, feral hogs are equally fond of the mast—acorns and other tree fruit—that our bears depend on prior to hibernation. They can triple their population in a little over a year and have no natural predators that have evolved with them, as the nearest pig-like native is the doughty javelina of the desert Southwest.
While feral hogs have been with us for some time (those selfsame conquistadors doubtless offloaded swine in that Caribbean beach), in Virginia they are at the northern end of their acquired range, and currently we only have around 3,500 in total, a drop in the slop bucket compared to Texas’s population of five million. This means that we still have time to annihilate the problem before it becomes unmanageable, a sure bet if left alone for a sufficient time. Voracious and clever, feral hogs pose a menace to native woodlands as their rooting behavior churns up the forest floor in just such a way as to allow colonization by other exotic pests such as kudzu and Japanese honeysuckle. DGIF permits hogs to be killed any and every way possible, but their nocturnal preferences and innate caution coupled with an outstanding sense of smell make them challenging game to say the least.
~
Drive down I-95 on a summer afternoon anywhere from Maine to Florida and in unmanaged fields you’re likely to see burgeoning groves of a 15-foot shrub with dense branches housing abundant leaves of a somehow sickly shade of dusty gray-green. The autumn olive, native to East Asia, was brought here in the 1830s for the usual reasons—ornament and erosion control—and like much else has taken off explosively, utilizing some handy traits that propel its success while hindering that of others. Nitrogen-fixing root nodules allow it to exploit even the poorest soils so long as they’re relatively dry and sunny, and each shrub can produce up to 200,000 seeds per year. Burning or cutting autumn olive are the worst ways to control it, as both approaches encourage ravenous regrowth that is even denser and hardier (Virginia DCR recommends glyphosate herbicide application). With entire pastures being engulfed by these supremely adaptable woody bushes in a matter of a few years and native plants that wildlife depend upon paying the price, landowners should take steps to eradicate autumn olive whenever and wherever it raises its sallow shoots.
~
In 2002 arborists were alerted to a puzzling decline of the ash trees shading the streets of Detroit. Eventually an entomologist in Slovakia, of all places, identified the culprit as the emerald ash borer, a bright metallic green splinter of a bug about half an inch long and another native of East Asia. Thought to have tagged along in foreign ash wood used to support crates during transatlantic shipping, the emerald ash borer poses an urgent threat to the entire Fraxinus genus, that colorfully-named (green, black, white, blue, etc.) collection of hardwoods that provides important benefits to wildlife. Ash seeds are eaten by waterfowl, upland game birds, songbirds and small mammals, while deer and beaver browse the leaves. Cavity-dwellers such as woodpeckers, wood ducks, kestrels and screech owls nest in larger ash trees. Ashes growing in riparian areas stabilize stream banks and provide important shade for cold-loving trout—all the more important now that the woolly adelgid has wiped out most of our hemlocks.
While the emerald ash borer is spreading throughout the Midwest and upper South at the rate of about 12 miles yearly, the wide-ranging transportation of firewood in our hyper-connected culture has allowed the pest to establish colonies far from its original point of invasion. Ash trees are killed by the feeding larvae, which tunnel meandering paths of destruction just under the bark, eventually stifling the flow of nutrients and girdling the tree. Without native predators to stymy its spread, researchers are looking to three species of parasitic, non-stinging wasps that hunt the ash borer in its native land to put the quietus on its booming population … ideally before the rest of our ashes follow the tens of millions already killed.
~
Bringing in nonnative control organisms to combat nonnative invasives is an uneasy solution at best—even the careful laboratory testing that precedes such releases is often conducted in a rush in order to get the corrective element out into the woods and eliminating the exotic pest. Our final infamous exotic is also being fought with enemies imported from its homeland, local herbivores being uninterested in this unappetizing specimen.
Purple loosestrife is an invasive wetlands weed from Europe, where it traditionally was used to treat everything from dysentery to ulcers. An herbaceous perennial that can reach nearly seven feet in height and produce over two million grainy seeds annually, purple loosestrife crowds out native wetlands flora such as cattails with such vigor that entire marsh ecosystems are negatively impacted. Such is the density of loosestrife stands that natives ranging from rails to muskrats, spotted turtles to bullfrogs, are muscled out of their own habitat. Bugs from the old country—two leaf beetles and three weevils—have been introduced and are proving to be successful at defoliating loosestrife, a positive note indeed so long as the necessarily imperfect science of fighting exotics with exotics maintains its edgy ecological balance.
~
Businesses catering to lawn ornamentation and erosion control, the shamefully unregulated international pet trade, agribusiness and the all-pervasive juggernaut of global commerce all share the blame for the escalating cavalcade of alien beings barging into our midst. And the problem certainly goes both ways; in Europe our introduced bullfrog and gray squirrel are seen as the foreign menaces they are there.
In May of 2014 an international group of scientists published a study in the journal PLOS | Biology arguing for a new method of classifying exotic species, a calculation of ascending harm ranging from Minimal to Maximum that seeks to better inform lawmakers and regulators of the magnitude of economic and ecological injury of a given invasive. This sensible approach would put the impacts of these foreign armies front and center, with any luck sparking the kind of funding decisions and agency actions that are needed to address this multifaceted dilemma. Without a forthright and consistent approach, these hardened generalists from overseas will continue to exploit our hapless natives to the full extent of their powers until, like Columbus, they have made our world their own.
~
SIDEBAR: The feral housecat, while not a species that DGIF is charged with managing, is after humans the reigning king of harmful exotic species. The 84 million pet cats and from 30 to 80 million feral cats in the US have recently been estimated to kill an astounding 2.4 billion birds each and every year, and an even more absurd 12.3 billion small mammals along with around 650 million reptiles and amphibians. The most pampered housecats are semi-feral at heart in a way that dogs cannot be. Even stuffed with gourmet chow, a young and healthy housecat let outside will quickly assume the predatory habits of its ancestors, killing not from hunger but from instinct. Cat owners must keep their pets indoors or closely supervised when visiting the yard, or assume their share of the blame for these horrifying statistics.
