Congress has passed a $30 million, five-year plan to fight nutria, a large South American relative of the muskrat blamed for destroying thousands of acres of marshes on Maryland’s Eastern Shore and in Louisiana.

The Nutria Eradication and Control Act, sponsored by Rep. Wayne Gilchrest, R-MD, authorizes Congress to spend up to $6 million a year, starting in the fiscal year that begins this October, for a coalition of state and federal agencies to battle the rodents. If funded, Maryland would get $4 million a year, and Louisiana $2 million.

The bill cleared both the House and Senate in April.

Nutria are a major cause of wetland loss on the Eastern Shore. They forage on the roots of wetland grasses, which destabilizes the soils and allows wetland areas to be eroded away.

In Blackwater National Wildlife Refuge alone, they are blamed for the loss of more than 7,000 acres of marsh habitat, with an additional 500 to 1,000 acres being lost annually. Even larger amounts of wetlands are being lost annually in other nearby areas, including Fishing Bay.

The nonnative species was brought to the Eastern Shore in 1934 to be reared as a furbearing animal, but they escaped into the wild.

Their population in Dorchester County alone is now estimated to be between 52,000 and 75,000 animals, and the animals have spread to every Maryland county on the Eastern Shore of the Chesapeake Bay.

The new legislation is a follow-up to a three-year program in which biologists determined the best techniques to get rid of the rodents, based on a successful effort in Great Britain.

The new legislation funds a ramped-up program aimed at eradicating the animals, which is to serve as a model for 15 other states with nutria problems.