The Monticello field office of the U.S. Bureau of Land Management on Monday released its long-term plan for 1.8 million acres of public property in San Juan County and parts of Grand County, home to thousands of ancient Indian relics in one of the nation's most significant archaeological regions.

The updated plan for southeastern Utah corrals more than 600,000 acres that used to be open to untamed off-highway vehicle use, now under management as a 2,000-mile trail system.

The plan also converts archaeological sites once protected as "areas of critical environmental concern" to "special recreation-management areas, " a designation that experts fear will invite more visitors and perhaps cause more damage to irreplaceable ruins.

Field office manager Tom Heinlein pointed out that about 394,000 acres are closed to any type of mechanized travel, including bicycles. He said a new enforcement plan for protecting the ruins and a travel map are in the works.

Seven special recreation-management areas on 560,000 acres are meant to focus activities, limit conflicts and protect resources, he said.

"As we begin to implement the plan's decisions," Heinlein said in a statement, "there will be ample opportunities for our partners and interested people to assist us with our on-the-ground efforts."

But, conservationists say, eliminating special protection for Cedar Mesa, Dark Canyon and Butler Wash -- home to some of the nation's most famous archaeological treasures -- is a bad idea.

The BLM's plan carves the Cedar Mesa recreation area into zones with specific rules for visitors. The Moon House ruin -- which used to be a little-known Anasazi relic but now is easy to find, thanks to the Internet -- would be subject to limits on how many people could be there at any one time and would restrict access to some areas.

A ranger is stationed at Cedar Mesa during the spring and fall, when most visitors arrive.

The Monticello plan is the last of six resource-management plans covering 11 million acres of southern and eastern Utah public lands crafted under a deadline set by the Bush administration.

The BLM has found 35.7 miles of the Colorado and San Juan rivers, as well as a portion of Dark Canyon, suitable for recommendation to Congress for inclusion in the National Wild and Scenic Rivers System. Oil and gas drilling will be allowed on 1.3 million acres, most of that with some restrictions. Before the plan was written, there were no restrictions.