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Invasive Species

An invasive species is a plant or animal that is foreign to an ecosystem. During the past two centuries, invasive species have significantly changed the Great Lakes ecosystem. These changes have greatly affected the economy, health, and well being of the people that rely on the system for food, water, and recreation. Once established, it is extremely difficult to control their spread.

Animal species

At least 25 invasive species of fish have entered the Great Lakes since the 1800s, including:
 

Plant species

The Great Lakes have also been troubled by fast-growing invasive plants, that displace the native plants that support wildlife habitat and prevent erosion. These include:
  • common reed
  • reed canary grass
  • purple loosestrife
  • curly pondweed
  • Eurasian milfoil
  • frogbit
  • non-native cattail

Prevention Measures

Ballast Water Regulation

Ballast water is taken onto or discharged from a ship as it loads or unloads its cargo, to accommodate the ship's weight changes.

Thirty percent of invasive species in the Great Lakes have been introduced through ship ballast water. In the early 1990s, the U.S. Coast Guard began requiring ships to exchange their ballast water, or seal their ballast tanks for the duration of their stay. The Coast Guard later used their success in the Great Lakes to develop a ballast management program for the entire nation. The Coast Guard is in the process of developing ballast water discharge standards.

Preventing Potential Invaders

Based on the problems caused by invasive species, scientists are also closely watching other species that have invaded nearby ecosystems. Asian carp are of particular concern because they have been found in nearby waterways that eventually connect to the Great Lakes. In 2004, EPA and other state and local agencies began construction of a permanent electric barrier to prevent the fish from entering Lake Michigan.

EPA is also studying how existing invasive species have become established in the Great Lakes. These studies will help develop new techniques to predict future invasions.