A government biologist and a hydrologist, who both retired this year from the Bureau of Land Management, said their conclusions that the proposed new rules might adversely affect water quality and wildlife, including endangered species, were excised and replaced with language justifying less stringent regulations favored by cattle ranchers.

Grazing regulations, which affect 160 million acres of public land in the Western U.S., set the conditions under which ranchers may use that land, and guide government managers in determining how many cattle may graze, where and for how long without harming natural resources.

The original draft of the environmental analysis warned that the new rules would have a "significant adverse impact" on wildlife, but that phrase was removed. The bureau now concludes that the grazing regulations are "beneficial to animals."

Eliminated from the final draft was another conclusion that read: "The Proposed Action will have a slow, long-term adverse impact on wildlife and biological diversity in general."

Also removed was language saying how a number of the rule changes could adversely affect endangered species.

"This is a whitewash. They took all of our science and reversed it 180 degrees," said Erick Campbell, a former BLM state biologist in Nevada and a 30-year bureau employee who retired this year. He was the author of sections of the report pertaining to the effect on wildlife and threatened and endangered species.

"They rewrote everything," Campbell said in an interview this week. "It's a crime."

Campbell and the other retired bureau scientist who criticized the rules were among more than a dozen BLM specialists who contributed to the environmental impact statement. Others who worked on the original draft could not be reached or did not return calls seeking comment.

A bureau official acknowledged that changes were made in the analysis and said they were part of a standard editing and review process. Ranchers hailed the regulations as a signal of new openness from the administration.

"We're hopeful that some of the provisions will strengthen the public lands grazing industry and give our members certainty in their business," said Jenni Beck of the National Cattlemen's Beef Assn. "We are encouraged that this [environmental impact statement] demonstrates the benefits of grazing on public lands."

Livestock graze on public land in 11 Western states, including 8 million acres in California. The vast acreage is needed to support a comparatively small number of livestock because in the arid region topsoil is thin and grass is generally sparse.

About 2% of the nation's beef is produced from cattle on public lands.

The new rules, published Friday by the BLM, a division of the Department of Interior, ensures ranchers expanded access to public land and requires federal land managers to conduct protracted studies before taking action to limit that access.

The rules reverse a long-standing agency policy that gave BLM experts the authority to quickly determine whether livestock grazing was inflicting damage.

The regulations also eliminate the agency's obligation to seek public input on some grazing decisions. Public comment will be allowed but not required.

In recent years, concerns about the condition of much Western grazing land has been heightened by drought, which has denuded pastures in the most arid areas, causing bureau managers to close some pastures and prompting ranchers to sell their herds.

The new rules mark a departure from grazing regulations adopted in 1995 under President Clinton and Interior Secretary Bruce Babbitt. Those regulations reflected the view of range scientists that a legacy of overgrazing in the West had degraded scarce water resources, damaged native plant communities and imperiled wildlife.

Babbitt ordered the bureau to establish standards that spelled out when public lands were open for grazing, and for the first time required range specialists to assess each pasture to ensure it held enough vegetation to support wildlife and livestock. It was the first time in about 50 years that the federal government had tried sweeping overhauls of how Western ranchers operated on public lands.

By 1994, studies from scientists at the Department of the Interior and the Department of Agriculture convinced government land managers that livestock grazing was the most pervasive threat to plant and animals in the arid West.

Some conservation groups seized on the studies to mount a campaign to eliminate grazing on public land altogether, prompting a backlash that accused environmentalists of engaging in "rural cleansing" that would drive families off the land, some of whom had been there since the 19th century.

This week, environmentalists were sharply critical of the new rules.

"It's an explicit rollback," said Thomas Lustig, staff lawyer for the National Wildlife Federation in Boulder, Colo. "What [Interior Secretary Gale A. Norton] did was take Babbitt's regs and found parts where they could put a hurdle in to undermine the reforms."

Bureau officials said the new rules represented a step forward in improving its management of livestock grazing on federal land.

Bud Cribley, the agency's manager for rangeland resources, said the report was written by a number of specialists from different offices within the BLM. When it was finished, in November 2003, the agency believed it "needed a lot of work," Cribley said.

"We disagreed with the impact analysis that was originally put forward. There were definitely changes made in the area of impact analysis. We adjusted it.

"The draft that we published we felt adequately addressed the impacts. We felt the changes we did make were based on good science."

Most of the changes came in sections analyzing projected impact of the rules on fisheries, plant and animal health as well as water quality and quantity.

Bill Brookes, a former hydrologist with the bureau who assessed the regulations' effect on water resources, said in the original draft the proposed rule change was "an abrogation of [the agency's] responsibility under the Clean Water Act."

"Everything I wrote was totally rewritten and watered down," Brookes said in an interview Thursday.

"Everything in the report that was purported to be negative was watered down. Instead of saying, in the long term, this will create problems, it now says, in the long term, grazing is the best thing since sliced bread."

Brookes said work that the bureau's original specialists required more than a year and a half to finish was changed in a matter of weeks. He and Campbell said officials in Washington said the document did not support the new rules so they called in a new team to redo it.

According to the agency officials, the new grazing regulations were meant to give land managers and ranchers more flexibility in making decisions about whether to allow grazing on a particular parcel.

Though an array of conservation and environmental groups decried the new rules, Cribley said changes were minor but necessary.

"We don't look at this as a significant change from the current regulations," he said. "This is fine-tuning and making adjustment in existing rules. We came out with some significant changes in the grazing rule in '95, and we have been implementing changes since that time. We needed to make corrections after almost 10 years of experience."