Incoming! The World’s 10 Worst Invasive Species

The introduction of non-native species of plants and animals to a new ecosystem almost always results in environmental stress, degradation and sometimes even disaster. These 10 invasive species are infamous for the destruction they have caused, even when introduced with the best of intentions.



Invasive_1b(images via: Free Republic, JJ Anthony and Cynical-C)

Kudzu… its name may sound like that of a Japanese movie monster and this pretty ornamental vine does indeed originate in Japan (and southeast China) – and has caused extensive destruction to boot. The only plant on this list, kudzu earns a place in the annals of misguided attempts to introduce foreign species because it was one of the first such invaders to be noted, publicized and controlled. Well, attempted to be controlled at least… tell that to the owner of the house above.

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Kudzu was first displayed in the United States at the Philadelphia Centennial Exposition in 1876, where it was extolled as a hardy, fast-growing ground cover that could help inhibit soil erosion. The first two attributes proved only too true as within 50 years kudzu had earned new nicknames: “the vine that ate the South” and The Green Menace. Today kudzu runs rampant throughout the states of the old Confederacy and beyond, as far north as New Jersey. Pockets of wild kudzu have recently been found in coastal Oregon, which is the last thing west coast farmers want to hear.



Invasive_2b(images via: Othmar Vohringer and Colin Ewington)

“The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting.” So wrote Australian farmer Thomas Austin in 1859, shortly after he freed 24 grey rabbits to, well, do what rabbits do best. By the end of the century the rabbit population had exploded to the point where Australia’s native plants, animals, even the soil itself were on the brink of collapse.

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Australia’s Council for Scientific and Industrial Research began testing the effectiveness of the Myxomatosis virus against feral rabbits in late 1937 – rabbits are seen above drinking at a government-dug water hole on Wardang Island in 1938. By 1950 the virus was deemed safe to use against rabbits and within 2 years the population had dropped from an estimated 600 million to “only” 100 million.



Invasive_3b(images via: Robert Hayden and Nature-Search)

New York City, 1890… a prominent drug manufacturer and Shakespeare lover named Eugene Schieffelin walked to Central Park and released 60 European Starlings he had just taken delivery of. Next year he did the same thing, this time with 40 birds – the reason being, he wanted to bring to the USA every bird the Bard mentioned in his plays. Isn’t that precious? Knowing how noisy, aggressive and omnipresent starlings are today, one has to wonder if Schieffelin may have sampled his own wares just a mite. Today starlings are blamed for agricultural losses of up to $800 million annually in the United States, as well as being implicated in a number of deadly plane crashes.

Invasive_3x(image via: He and Fi)

Starlings are gregarious birds that congregate in flocks of up to a million or more. From afar the intricate swirling of an airborne flock can be fascinating; from beneath, not so much. The flock above appears to be giving the finger to those who object to their presence in North America.

Burmese Pythons


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Snakes on a plane? Old news. Snakes on a plain? Bad news – when the plains are in Florida. Authorities in the Sunshine State estimate that more than 30,000 Burmese Pythons infest Everglades National Park and that number is growing as the scaly invaders have very few predators. Alligators up to five feet long have been found inside the bellies of captured pythons, as have a wide variety of native endangered species who have no defense against the scaly serpents.

Invasive_4x(image via: A View From My Balcony)

Global warming may prove a boon for the wily wrigglers, allowing them to spread throughout the American southeast. Voracious and fearless predators, Burmese pythons can grow up to 20 feet in length and eat pretty much anything that gets too close. Sadly, not kudzu.

Cane Toads


Invasive_5b(images via: The Guardian, Invasive Species Weblog and Flatrock)

You’d think Australia would have learned a thing or two about introducing non-native species from the rabbit fiasco but noooo… at around the time myxomatosis virii were being tested as a way to control the rampant rabbits, cane toads were being freed into the sugar cane plantations of Queensland to control insect pests. By mid-1937 over 60,000 young toads had been released to eat insects – which they didn’t, because the sugar cane fields didn’t provide enough protection for the toads. Not that they needed it; cane toads excrete a potent toxin from their skin that usually kills any other creature that is ignorant enough to attack and eat them. Predators in the Americas (including southern Texas) have adapted to deal with the toads, those in Australia have not.

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Cane toads can grow up to 15 inches long (from snout to vent) and will eat most anything around, dead or alive. Toadzilla indeed! While only 0.5% of cane toad tadpoles (which are also toxic) survive to breeding age, the warty amphibians are so fertile that the low survival rate doesn’t much matter. Just like rabbits… poisonous rabbits.

Snakehead Fish


Invasive_6a(images via: National Geographic, SwittersB and MIT Sea Grant)

From Toadzilla to “Fishzilla”, which is what National Geographic dubbed the Northern Snakehead. Once snakeheads infest a pond or lake, they will devour anything else they can find – then, they are able to breathe air for up to 4 days as they crawl across land to find a new body of water. Authorities have been known to poison entire lakes just to kill any snakeheads lurking within.

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The Giant Snakehead grows up to 3 feet long and is said to be the most aggressive of them all – of course. One was recently caught in Leeds, England, which caused quite a stir as they are native to East Asian waters.

Eastern Grey Squirrels



Invasive_7a2(images via: CBC News and The Guardian)

It would be wrong to underestimate cute, fluffy Eastern Grey Squirrels, isn’t that right, Australians? In this case the location is Great Britain and the victims are the smaller, cuter, native Red Squirrels who find they can’t compete with their larger, more aggressive North American cousins. The greys also carry a deadly virus that only affects the native reds. Various “save the squirrels” movements have sprung up in England and none other than HRH Prince Charles has come out vocally for the eradication of the pesky greys by any and all means.

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Under British law, the Eastern Grey Squirrel is considered to be “vermin”. The few remaining reds (such as the one above) live in isolated pockets of habitat mainly in Scotland and the Lake District in England. As for the greys, the British media is promoting ways to catch, kill, cook and eat them. “Squirrels have no fat and the flesh is sweet,” according to Lard Redesdale, shown above enjoying a squirrel snack with his family.

Killer Bees

Invasive_8(images via: All-Florida Bee Removal and BBC)

Africanized Honey Bees have been the poster children for invasive species for some time now. The product of an experiment that sought to improve the viability of European honey bees in tropical regions, so-called Killer Bees trace their origin to São Paulo State in southeastern of Brazil. In 1957, 26 Tanzanian queen bees were released accidentally by a replacement bee-keeper. The queens then mated with native drones and the resulting hybrid bees proved more than a match for their meeker European cousins. By 2007 AHBs were found in the New Orleans area and in 2009 hives were discovered in southern Utah. A similar relentless spread is taking place in South America.

Invasive_8x(images via: Nippon Cinema, LA West Vector and Stroke Of Midnight)

The threat from Africanized Bees has spawned a host of creature feature flicks led off by 1974’s Killer Bees, followed by The Swarm from 1978 and then spreading across the globe with Die Bienen (Germany) and Kira Bi (Japan). Save your money folks, most of the bee movies are B-movies that sting to high heaven.

Asian Carp


Invasive_9bb(images via: Fishing Fury, WKMS and Air America)

Holy carp! Asian or Silver Carp can grow to humongous sizes (over 100 pounds!) but at a cost of a shattered ecosystem. Originally imported to clear algae from catfish ponds in the southern USA, flooding allowed some carp to escape into the Mississippi River and its tributaries where they quickly became MANY carp. One possible silver ining to this fishy dark cloud is that in China, silver carp are considered a delicacy and have become rare due to over-fishing. Fishermen in the U.S. Midwest have begun catching silver carp, processing them and shipping them back to China. This is one marine pest that could end up padding more than a few pockets if commercial fishing could be expanded to a large “scale”.

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“As God is my witness, I never thought fish could fly.” Guess again, Nessman, reports of carp leaping through the air and knocking fishermen and boaters senseless are rising like a helicopter loaded with live turkeys. It seems that carp are easily startled by the sound of boat engines and will leap before they look, so to speak. On the bright side, if one can avoid being clobbered it’s possible to catch a few fish without ever baiting a hook.

Rat Island

Invasive_10a(images via: Old Dirt, Alaska Science Forum and ABC News)

Rats have infested 90 percent of the world’s islands and are blamed for up to 60 percent of recorded extinctions of island birds and reptiles. A classic case is Rat Island in Alaska’s Aleutian Island chain. Norway Rats escaping from a shipwrecked Japanese boat in 1780 quickly decimated the seabird population of the treeless, uninhabited island. Their descendants survive today on mis-adventuresome birds and marine life stranded in the shore’s intertidal zone. Rat Island is notable because it’s a test case in the U.S. governments battle to reclaim an entire habitat from an invasive species. In 2008 packets of rat poison were scattered across Rat Island’s 11 square miles and then, in June of 2009, biologists tentatively declared Rat Island rat free. Is a name change in the offing? Is “R Diddy” taken?

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Norway Rats are picky eaters as well, according to Art Sowls, a biologist with the Alaska Maritime National Wildlife Refuge. States Sowls, “A lot of the birds you find, the only parts the rats eat are the eyeballs and the brains.” Nice. As if rats aren’t bad enough, Alaska’s dealing with invasive zombie rats. We’re definitely going to need more poison.

As the world continues to shrink in relative terms, it’s only “natural” that the rate of species invasions will rise in consequence. By attempting to reverse the tide are we fighting an un-winnable battle? Perhaps – continental drift and varying sea levels have been bringing once-separate species into contact with one another for hundreds of millions of years. Maybe we can’t emerge victorious in the war but by winning a few battles here and there we can at least preserve better lives for both Man and beasts.