Invasive Species

Invasive species - plants, animals, or organisms introduced into an area where they are not native, and where they cause harm- have big impacts on wildlife. How big? In the US, about 42% of the species listed as threatened or endangered under the Endangered Species Act are at risk primarily because of predation or competition with invasive species, which are the second largest threat to biodiversity after habitat loss.

These newcomers wreak havoc by changing, degrading, or displacing native habitat. They may bring disease, and compete directly with wildlife for living space as well as food.

Invasive species move around the world in many ways:

  • Aquatic organisms can hitchhike by attaching themselves to ships, or even to trash in the water
  • The shipping industry unwittingly transports critters, too, like insects that get into wood products or even wooden shipping pallets.
  • Invasive species can move into the wild from homes, such as ornamental plants that wind up in the wild when tossed out with the trash, or aquarium fish and pet snakes let loose by owners who no longer want them.


Invasive Species and the Great Lakes

The Great Lakes, one of the greatest freshwater resources on Earth, is changing dramatically because of more than 160 invasive species that are tearing the fabric of the food web. The invaders include

  • the sea lamprey
  • the Eurasian ruffe
  • the zebra mussel
  • the spiny water flea

Many invasive species have arrived in the Great Lakes by way of ballast water released from ships. Others were released by people dumping aquariums or accidentally letting go of bait fish. The sea lamprey alone, which was first noted in Lake Ontario in the 1830s, not only alters habitat, but is a very aggressive fish, out-competing native fish for prey.

Invasive Species in the Chesapeake Bay: Nutria
This South American rodent, introduced by the fur industry in the 1940s, has destroyed 7,000-8,000 acres of refuge marshland in the Chesapeake Bay region, impacting all the wildlife that calls those wetlands home. They feed on the roots of marsh plants, and are so prolific that their impacts are huge. State and local government and private organizations are working together to discover the best eradication program.

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