What is an invasive species?

Water hyacinth (Eichhornia crassipes) David Sanger / Getty Images

Invasive species can mean a lot of things, from fungus to feral pigs and European starlings to kudzu vines. Basically, it's anything brought to a place, either by humans or nature, that didn't originate there. They aren't always a problem, but many times they can wreak havoc on the local ecosystem. Learn all about these invaders today.

If you dig the topic, read "How Invasive Species Work."