THE NATIONAL Park Service says it has found a rare ecological jewel just 50 miles southeast of Washington on Maryland's Eastern Shore. Its centerpiece is the Blackwater River, part of a wintering ground for thousands of migratory waterfowl. The Park Service says it is one of only three rivers in the continental United States that are still wild from beginning to end and largely untouched by man-made development. The Blackwater and its watershed need National Park Service protection, officials say, perhaps as the country's first national river park.

Large acquisitions of land would be needed, along with a change in existing federal authority. There would be new regulations and new restrictions on usage within the park. In all, a new national park sounds like an exciting and welcome distinction for the Chesapeake Bay region. But the proposal has been greeted with anything but enthusiasm by local landowners and elected officials who feel that the effort is unnecessary. Their hesitation has a certain basis. The area does seem to have considerable protection already.

The existing Blackwater National Wildlife Refuge was created in 1930. That put about 15,600 acres of the river, its shallow pools and its marshes under jurisdiction of the federal government's Fish and Wildlife Service, a branch of the U.S. Department of the Interior. Hunting and fishing are allowed, but nothing that would alter the ecology of the refuge is permitted. Do Fish and Wildlife Service officials feel that additional protection for the river is needed? Their answer is no.

A Maryland law, designed to help clean up the Chesapeake Bay, also protects much of the river's watershed from intensive development. And the region's governments -- in Maryland, Virginia, and the District -- are taking additional steps to preserve and restore the fragile life of the bay area. Their goal, announced in a recently adopted pact, is to reduce pollution and to lessen man-made influence on wildlife migration in and around the bay.

That seems to indicate that the Blackwater area already enjoys more protection than most of the country's remaining wild areas. A burden remains on the National Park Service to demonstrate that more regulation and protection are necessary.