I recall first learning about invasive flora and fauna when I volunteered with the Sierra Club who was removing Melaleuca. I was shocked that Environmentalists had put them in the Swamp area of Dade County (Miami)Florida in order to use a natural way to drain the swamps for building.
They were too efficient and grew/spread to the Everglades and other wetland areas in Dade County.

[lflank.wordpress.com]

Another environmental control was in Lake Michigan which put Coho salmon in the lake to prevent the die off on the beach of alewife fish, which effected tourism and was costly to clean up. I recall the beaches had thousands in deep piles along the shoreline which stunk in the heat of summer. .It drew tourists to fish, but we didn't eat them because of factories that dumped in the lake. My grandparents did not think it was healthy. This was in the 1960s. Apparently after that they added mussels which caused an imbalance.Here is an article I found.

[mlive.com]

Biodiversity is negatively impacted by invasive species as the invading species displace natives, outcompete and usually don’t have predators or grazers available to curb their rampage. The net effect is threatening ecosystem balance and declining biodiversity - ask a Hawaiian biologist

@gigihein We have the same problem here in the NW. I worked for the Nature Conservancy and a lot of the work involved removing invasive's as Scotch Broom (brought in by the highway Dept. to control erosion) and FoxGlove. Here on the islands we have Tansy ragwort, Bull headed Thistle, European Green Crab and on and on. Most of these invasive plants and animals were brought in by humans.

@JackPedigo we just arent good at thinking of consequences. And sometimes couldn't know an outcome. Should just assume there will be a negative consequence

@gigihein What we don't know can and is killing us. Unfortunately, we always look to finding a simple reason for problems. All our present day issues are very complicated. too complicated for the average person. The people in charge are supposed to understand consequences and act accordingly but these days they only ant power and money and don't care about consequences.

@JackPedigo i know
I am so naive. I read they put the salmon in for tourists not to est alewives that died on beach. It is almost always about money.