The first species I have researched is a fungal disease called Endothia parasitica or Chestnut Blight. It was accidentally brought to a zoologist park in New York by a Chinese chestnut. There is no known method of combating these fungi so it has spread throughout the United States. These fungi would affect any animals that rely on eating chestnuts.
The second species I’ve researched is a relation to the beaver called the nutria. This animal was purposely introduced in the United States to stimulate the fur industry. When the fur industry failed, there was a surplus of these animals because they have no natural enemies. Nutria have severely damaged marsh vegetation which causes conversion of heavy vegetation to open water, thereby removing nesting or over wintering habitat for many birds, and eliminating habitat critical to the juvenile stages of important commercial species such as shrimp, crabs, oysters, many species of young fishes, and others.
Finally, I have researched a flower called the purple-loose-strife. No flowering plant in the Northeast has caused as much concern as the European, marsh-loving Purple-Loose-strife. Crowding out other wetland species with its tenacious root system, Purple Loose-strife is changing the face of many of our freshwater marshes, by turning them into biologically unproductive monocultures. The sometimes vast magenta flowerbeds attract bees and butterflies to their blossoms, but offer no sustenance to higher life-forms. Efforts to control the species by pulling it up have been fruitless. Introducing European beetles that feed exclusively on this plant may prove the best defense.