Invasive species often thrive in new environments and overrun native species because they have an unfair advantage. “Invasive species end up with about half the parasites, or diseases, they had at home,” says U.S. Geological Survey ecologist Kevin Lafferty. “Parasites are to invasive species what kryptonite is to Superman. Back on planet Krypton, kryptonite was a regulator, keeping Superman ordinary. Freed from kryptonite on earth, he gained super powers.”
Animals that have an average of 16 parasites on their home turf only bring about three of them to their new location. And only about four new parasites will adapt to attack the invading species. That makes 7 parasites?less than half of what they had at home.
For instance, barnacles in Europe keep populations of the European green crab small and rare by castrating many of the crabs. But the crab has since spread unchecked to both American coasts, as well as to South Africa, Australia and Japan, destroying native shellfish populations. It’s also true with plants: invaders quickly become weeds when they move to new locations. One solution is to import parasites from the invader’s home turf, but this can be dangerous if they also learn to feed off native populations.
A “red army” of king crabs is on the march west from Russia, heading towards the beaches of Portugal. The 12 million crabs are descended from stock brought from the Pacific Ocean by Stalin, and they’ve had a population explosion recently. The World Wildlife Fund thinks the only solution is to eat more of them, since they’re considered a delicacy.
Weather changes can turn even native species into invaders. An army of worms is slithering across northern New Mexico in response to the unusually warm weather there. Army worms travel in large numbers and can “march” long distances in search of food. Experts say they’re not dangerous, but they could turn into a slippery mess on the highways. Critters and birds all over the world are responding to global warming, so maybe we should too.
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