5 Invasive Species That Might Conquer the World

European Rabbits

Ah, bunnies. They're so adorable, aren't they? Unless you're a homeowner or farmer, that is. Those cute, fuzzy little critters are ruining land all over the world, causing soil erosion through their overgrazing and burrowing. They also nibble on people's landscaping and flowers, and negatively impact native species by damaging fragile ecosystems.

European rabbits are native only to Southern Europe and Northern Africa. But over time, they've been introduced to almost every continent. And wherever they've been introduced, they quickly proceeded to, well, breed like rabbits. For example, a mere 24 were released in Australia in 1859 by an English farmer who thought they'd provide "a touch of home, in addition to a spot of hunting" [source: WebEcoist]. Today, rabbits have contributed to the extinction of nearly an eighth of Australia's mammal species, ruined the country's soil and caused millions of dollars annually in agricultural damage [source: Environmental Graffiti].

Australians did try to eradicate their rabbit population in 1950 by introducing the Myxoma virus to their mainland. A biological control agent, this virus causes Myxomatosis, a disease fatal in nearly every rabbit that contracts it. Five hundred million rabbits died, but the 100 million that remained developed a resistance to the disease [source: WebEcoist]. And now, the bunnies' numbers are again on the rise [source: Zukerman].

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