– There’s not much anyone can tell Barry Sorensen about Idaho’s Big Desert that he doesn’t know. Sorensen, 72, and his brother have been running cattle in this sere landscape all their lives, and they’ve weathered every calamity man and nature have thrown at them — until this drought came along.

Sitting in a rustic cabin where he spends many months looking after his cattle, Sorensen’s voice was tinged with defeat. “To be honest with you,” he said, “I think our way of life is pretty much going to be over in 10 years.”

Yearslong drought has pummeled millions of acres of federal rangeland in the West into dust, leaving a devastating swath from the Rockies to the Pacific. Add to that climate change, invasive plants and wildfire seasons that are longer and more severe, and conditions have reached a breaking point in many Western regions. The land can no longer support both livestock and wildlife.

“All these issues — it’s changing the landscape of the West, dramatically,” said Ken Wixon, who grazes 4,000 ewes and lambs on federal land in the Snake River Plain. For public lands ranchers like him who depend on federal acreage to sustain their animals, the mood ranges from brooding to surrender.

The situation was spelled out in stark terms by the Bureau of Land Management. It told the ranchers what they already knew: Unless something changes, the days of business as usual on the 154 million acres of federal grazing land are over. This drought-stressed range can no longer sustain livestock, the letter warned. Better plan to reduce herd numbers by at least 30 percent for the spring turnout.

“I knew it was coming,” Sorensen said.

Sorensen’s grazing allotment is so compromised that he was forced to make multiple adjustments. He waited 2½ weeks longer than usual before turning out his cows and calves on federal pastures, and then released only half his herd. The rest he kept on his ranch, feeding them hay from his own fields.

Conditions could easily grow worse. Livestock shares the range with wildlife, including the greater sage grouse, a species dependent on sagebrush and native grasslands to survive. The grouse population has plummeted by 93 percent in the past 50 years, and its habitat has shrunk to one-quarter of its former 240,000-square-mile range.

If the federal government grants endangered species protection to the grouse next year, ranching on federal land will be cut back even more. In some regions, public lands ranching might end altogether.

The problem for livestock and wildlife alike is that the drought has been merciless on all plants in the West. Last week 60 percent of the 11 Western states were experiencing some degree of serious drought.

Climate change has altered weather patterns so much that vegetation in some regions is transforming from abundant sagebrush, grass and forbs to a new landscape of weeds and cheat grass — fast-burning fuels that propel wildfire and destroy rangeland.

In southern New Mexico, the transformation has gone one step further — from sagebrush to weeds to sand-blown desert — and biologists say the pattern is likely to be repeated across the West. If that happens, the economics of cattle ranching will unravel.

Public lands grazing is a remnant of Washington’s interest in settling the West. Ranchers pay a fee, far below market rate, for each mother cow and calf they turn out to graze on federal acreage. If public land is not available, ranchers could find private property to graze their animals, paying as much as 16 times more than on federal ground.

Critics have little sympathy. They say the operations are highly subsidized by taxpayers and are secondary to the goal of preserving native ecosystems. Grazing receipts in fiscal year 2013 were $12.2 million, while the program cost the government $48.2 million to operate. Fees are based on range conditions that existed in 1966, and the monthly charge of $1.35 for a cow and calf hasn’t significantly changed in 50 years.

Ranchers argue that they are stewards of the land and that they make improvements that benefit deer, birds and other wildlife as well as improve water quality. “Without ranchers functioning, the landscape ceases to function,” rancher Shane Rosenkrance said.

But biologists and conservation groups say historic overgrazing caused wholesale changes to the landscape and fostered the growth of cheat grass — which has fanned wildfires. And, they say, when ranchers allow cattle to trample streams and riverbeds, crucial riparian areas can be destroyed.

The sage grouse is particularly vulnerable to sagebrush loss. Cattle grazing reduces forbs and grasses the birds use for protection and cover, leaving them exposed to predators.

Alarmed Western state governors, fearful that an endangered species listing could also mean the end of energy, mining and other commercial activities on federal land, are scrambling to protect the birds and their breeding grounds.

Some environmental groups, such as Western Watersheds Project, can’t envision any science-based plan to preserve sage grouse habitat that would allow sheep and cattle grazing. “A lot of ranchers will probably see it as a game changer,” said Travis Bruner, the executive director.

Sorensen does. “I think it’s inevitable” that the sage grouse will push cattle off the range, he said. When that happens, it will trigger a cascade of ruinous changes, he said. “All of this ground is going to go to hell. There won’t be any cattle to eat the grass. That grass will burn. Then there will be no sage grouse left.”