Life is a pretty simple thing…from a scientific standpoint of course. As a living organism, one simply has to metabolize, grow, reproduce, and adapt to one’s environment over a period of time. See? Simple! It’s a perfectly natural process that has been working for eons. In doing so, organisms find a balance between consuming and reproducing that allows life to go on indefinitely. Sometimes though, organisms show up where they don’t belong, which can tip the scales and send environments and economies into utter chaos. For example, when a species is introduced into an unfamiliar location, it may have vast amounts of resources to consume and no natural predators to keep populations in check. The following list is comprised of just a few of the world’s worst invasive species.
There are few scenes more aesthetically pleasing than a Victorian-era brick home with a wall covered in English Ivy. It looks so romantic! Kudzu is like Ivy on steroids. In the later part of the 1800s, horticultural geniuses at the Centennial Expo in Chicago sold Kudzu (a subtropical Asian vine-plant) to Southern folk as an economically sound ornamental plant that could provide shade for their hot, sun-baked porches. Soon, Kudzu was touted as a miracle plant, able to provide a healthy, affordable protein source for grazing animals, and to act as a soil binder to help mitigate erosion. The government even stepped in, funding distribution and planting. However, as southern farmers abandoned country-life to move to big, industrialized cities, kudzu was able to grow unchecked in hot, humid locales – and kudzu vines can grow as much as a foot per day. Starting at an estimated 3 million acres of coverage in 1946, today’s (hopeful) estimates are at 7.4 million acres of sweet, southern soil, scattered, smothered and covered by kudzu. Kudzu chokes out other plants, stealing nutrients, sunlight, and space from naturally occurring foliage. Right now, the best method of control is grazing by goats and sheep.
9. Asian Citrus Psyllid
Another species hailing from Asia, this little bug has made its way to Central and South America, Mexico and the Caribbean, most sunny places from where you might procure a delicious citrus fruit. It has a fuzzy, brownish exterior and harbors a bacterium that kills citrus trees. While the insect itself produces a toxin that stunts the outward growth of new shoots where the bug feeds, the more disastrous issue is the bacteria spread by the APD to the tree causing “Huanglongbing”, or Citrus Greening Disease. There is no cure and once infected, the tree grows small, distorted, greenish fruit, which cannot be marketed or sold, and the tree eventually dies. The psyllids were discovered in Florida in 1998 and have since spread all the way to California (as of 2008). Quarantine restrictions of citrus crops have been enacted in California in an attempt to control and hopefully eradicate the problem. Consider this; over the last five years, Florida, the nation’s second largest citrus economy, has lost over $7 billion and 6,600 jobs due to this devastating invasive species. Imagine the ramifications for California, the nation’s leading citrus economy.
8. Cheatgrass (Bromus Tectorum)
Sometime in the 1800s, Cheatgrass came to North America through contaminated shipments from Euroasia. Stowing away in shipped goods is a common method of introduction for many species, and the seeds of this organism have a hearty shelf life. They can still germinate even if they’ve been in storage for up to 11 years. Cheatgrass grows very quickly and is one of the most common grassy weeds that cover disturbed ground and roadsides, and it can starve out some food crops like wheat if it infiltrates fields. It has a relatively shallow root system with an incredible propensity for sapping moisture from the soil, so much so that it deprives other plants of water. Cheatgrass also dries out early in the summer, causing lots of dry matter to collect on top of the soil; see where this is going? The result is the perfect, super-flammable tinder, and many drier locales with dense cheatgrass growth have experienced huge increases in late summer wildfire frequency, especially in the western United States. Once established, cheatgrass is hard to get under control, leaving the lands most affected extremely vulnerable to uncontrolled wildfires and soil erosion.
7. Red Imported Fire Ant
Spawned from Satan but native to South America, the RIFA is another critter that made its way around the world by sneaking into shipments and can now be found in the US, Australia, many Asian countries, and in the Caribbean. These ants are very aggressive, swarm quickly, and sting simultaneously. They do a fine job of ridding croplands of pests, but while they’re at it, they get rid everything else. Once they’re firmly established in an area, most ground-dwelling insects, worms, birds, and lizards either move out or become food for the colony. They’re omnivorous too, meaning they can interfere with crops, especially root systems, and they can withstand flooding and droughts. They are a nightmare to eradicate, and of all the countries with initiatives in place to do so, Australia is the only one to have succeeded. Other countries barely even made a dent in RIFA populations.
According to the Food and Drug Administration, the U.S. spends almost $5.8 billion annually on control measures, medical treatment, and damages of both crops and livestock. Although pesticides were useful in killing the organism themselves, the main brand used from the 1950s to the 1970s ultimately killed almost all of the other ant populations that could have competed with the RIFA and allowed for even greater RIFA expansion in the later part of the 1900s. The next time you get stung by this ant, just know it’s nothing personal. He wants to eat you AND every other living organism around you.
6. Zebra Mussels
Hiding in the ballast water on a trans-oceanic voyage sounds like the plot line of some epic story, but for this fingernail-sized mussel, it was just the beginning of its reign of terror. This mini-monster was detected in Canadian waters north of Detroit, Michigan in the late 80s, and has since spread to the southern United States. While they efficiently clean pollutants from waters by filtration, they’ve pushed many species in the Great Lakes to the edge of extinction by stealing their food and overwhelming their habitat. They’re known for their sharp-edged shells and many swimmers have come away from once pleasurable swimming locations with cut up feet. However, the real issue with zebra mussels is their dense growth pattern; they form thick, crusty layers on any substrate and commonly clog or destroy underwater pipelines and equipment including those used for municipal water supplies or hydroelectricity. Their numbers and clusters on water treatment equipment have even led to restricted water usage in drought-stricken areas of the southern states. Though reports vary, studies indicate that the U.S. spends between $270 and $500 million annually to try to control the invasion and repair damage to facilities that utilize water infected by the infamous zebra mussel.
One fine day in the early 80s, some do-gooder (most likely in Florida) got tired of his aquarium and thought, “Instead of selling my terrifying, non-native devil-fish to some other fish lover, I’ll just dump this thing in the wild! It’ll be fine!” It wasn’t fine…this showy, venomous fish reproduced at such an astonishing pace that it currently exists in greater population densities in locations where it has been introduced than in its native habitat, the Indo-Pacific. This is partially due to the fact that the lionfish has almost no predators in its new-found home on the East coast of the US and in the Caribbean Sea, and partially because this fish can reproduce every month of the entire year.
The lionfish is one of very few aquarium fish to make a home in waters where it was unnaturally introduced, which is kind of an admirable feat, until you realize that the lionfish is utterly destroying coral reef biodiversity. Reefs represent a fragile balance between prey and predator, and lionfish are incredibly aggressive and efficient predators. A single fish living on a reef can reportedly eradicate up to 79% of juvenile fish. Unfortunately, experts agree that attempting to control the lionfish population by catch and kill is the best we can do as eradication is basically out of the question.
4. Burmese Python
Another issue stemming from the release of an unwanted pet into the wild, Burmese Pythons are taking over Florida. In the Everglades especially, these gigantic snakes are growing, breeding, and eating way too much of the local animal population. Humans and alligators are the only boss-fights they encounter, because how could any other animal fight a giant snake? The fact that they mature quickly and live for a long time (up to 20 years), and can eat just about anything, or eat very infrequently, makes them particularly good at establishing populations. As the budding population of Burmese pythons was observed, a very significant decline in native animal species was also witnessed. Because it’s nearly impossible to locate or capture them in the wild, eradication efforts have proven relatively fruitless. However, the ‘powers that be’ have created new laws restricting the import of new pythons to the US or any release of snakes into the wild.
3. Black Rats
A germ in the gut of a flea on a rat in a ship on its way to your country! It’s almost like a Mother Goose rhyme. And when the flea bites you, it regurgitates bacteria into your skin, you get Bubonic Plague and die. Or at least that’s how it’s happened many times over throughout history, most notably during the Black Plague which killed a third of the population of Europe in the mid-1300s. The rats likely arrived in Europe via ships going between Asia and Constantinople. However, the bacteria that causes the plague hits animals too, not just humans. Certain species of ferret and prairie dog in the U.S. are affected to the point of endangerment. Black rats are also incredibly destructive to many environments, killing eggs, eating baby animals and a variety of insects, ruining crops, and causing general chaos in most locations where they have few natural predators…which brings us to our next species…
2. House Cats
Didn’t see this one coming, did you? That sweet little kitten you just got isn’t really from around here. While it has long been thought that cats were originally domesticated in Egypt, new evidence has shown that domestication may have begun in the Middle East several thousand years earlier than previously known. Wherever it began, think of the ramifications. Through the ages, man has toted the domesticated cat all over the world, and today cats are the most common household pet, living everywhere humans do. This is because of the companionship people find with the domestic cat, and its much-valued ability to keep human domiciles rodent-free. Carnivorous and relatively aggressive predators, when a cat chases a mouse or bug, we often get the sensation that we’re seeing eons of genetic memory filtering into little Fluffy. However, cats breed quickly, and without population control measures, stray cat populations can build up quickly, and while they’re not terribly destructive (minus their impact on populations of small mammals and birds), they do carry several human diseases and some cultures see them as a nuisance. Many communities spend large amounts of money on catch-neuter-release programs for feral cats, while others spend fortunes on animal shelters and adopt-a-pet campaigns.
If ever there was an invasive species crossing the landscape and wreaking havoc on the earth, it’s people. The human population has spiraled out of control with no end in sight. At the beginning of the 1800s, the earth’s population was at one billion, a mere century later, the population is at seven billion. With relatively long life spans and a voracious appetite for non-renewable resources, the human race is fast approaching its “best if used by” date. Many countries are already strained under the burden of overpopulation, suffering from water shortages, famine, illness, and crime. The human race is also capable of amazing destruction: the ruination of the rainforest, the extinction of many species and fragile eco-systems, and vast islands of trash floating in the ocean, just to name a few. Here’s some interesting food for thought; as a species aware of and trying to control the spread and destruction of other invasive species, what are we doing to curb our own?