It happens all the time. A plant or animal is introduced into a new habitat with intent or inadvertently. Without a control - a natural predator, the new species soon dominates the landscape (i.e. european starlings, brazilian pepper trees, starbucks). Often the solution is to bring in another exotic species to control this new "invasive exotic". Water Hyacinth is a floating plant that was accidentally introduced into Florida back in the late 1800's. It spreads through seeds and rhizomes (the nutritional storage portion of the plant) and can create impenetrable mats of vegetation. Although this purple-flowered plant has been part of the Florida landscape for well over 130 years, Water Hyacinth was not a problem until excessive levels of nitrates and phosphates (used on agricultural lands) got into the watershed.
During the 60's the problem became a nightmare as the pollutant loving plant spread through out the lakes and canals of south Florida and choked off water ways, slowing flows, blocking out light and causing many native species to struggle to adapt to this changing environment.
So what could possibly control Water Hyacinth? What eats it? How about an herbivore of colossal proportions? Hippos! The federal government developed plans to introduce an exotic species to Florida that not only has never lived in the new world but is one of the top killers of humans in their native Africa. Eventually they thought better of this plan and resorted to heavy doses of herbicides which I'm sure had no deleterious effects on non-target species (he said with heavy doses of sarcasm).
While the plant is considered "well managed" by the state today and used in the production of biogas, there are still areas where the plants dominate the waterways. I took these in Port Charlotte. It's hard to tell there is water below!