People seem to think that toying with an ecosystem is like cooking.
I'm not entirely making this up. This stuff happens.
This can and mostly likely will spiral further out of control...
When I think of non-native species I usually think of animals, but the problems are just as severe with plants, if not worse. A fantastic example is Kudzu (sounds like the plant's rapper name, no?).
This ambitious vine was introduced into the southern areas of the United States in the 1800s because of claims that its strong roots were good for controlling erosion. Kudzu, which is originally from Asia, turns out to absolutely adore the climate in the South. It can grow up to 1 foot per day while it chokes the area's native plants. And because it's from out of town, it has no natural pests or predators that can keep it in check. It just grows... and grows... and grows.
Part of what makes us human is testing our limits and exploring our surroundings. That's great. But we really have to quit thinking that ecosystems are made of play-doh. They're not toys; you can't play with them. You can't shape them into something else. Ecosystems are more like porcelain. Don't touch! You'll break it, and they don't make super glue that works on the ecosystem level yet.
If you want to continue to nerd out (and I know you want to), you can check out the U.S. list of non-native species: invasivespeciesinfo.gov You're welcome!