Greetings, Earth kid! You've probably seen plenty of movies about aliens like me. You know...visitors from other worlds who want to attack your planet. Hey, I'm not one of those alien types. But I do know some aliens that are threatening your wild world. I'm talking about plants and animals that live all around you, but don't belong there. They aren't natives: species that have always lived in North America. They're species which are naturally found outside North America, but have now settled here. And biologists actually do call them aliens.

Alien plants and animals usually arrive in North America with help from humans. People have chosen to bring many alien species here on purpose, for food, recreation or business. Alien species have also gotten here by accident. They've hitched rides on boats and planes, in people's suitcases, in packing materials, just about anything that's transported into North America.

 

Some aliens don't survive in this new home. But others have an easy time getting settled. For them, problems from back home, like disease or predators, are often missing. So, the aliens can quickly spread and grow in number.

What's wrong with that? Sometimes nothing. Many aliens are very welcome. Examples include horses, wheat, rice, cows, chickens, rabbits, pheasants, trout, cats and dogs. But other aliens make life hard for native species. They kill them off, crowd them out, eat their food, ruin their habitat or make them sick.

Of course, aliens are just doing what they do naturally–they're not trying to be bad. Still, this kind of attack gives aliens like me a bad name! Just look at some of the aliens I tracked down with my Alien-o-matic detector. I found them hiding out in what you Earthlings call wetlands...

(Click on the picture of the alien species you want to know more about...)
Carp
Nutria
Mute Swan
Purple Loosestrife
Zebra Mussel
Starling