SACRAMENTO — As director of the emergency room at University of California Medical Center, Robert Derlet always wondered what made people sick.
Each summer, on hiking trips into the high Sierra, he brought that curiosity along, asking himself: Where do you get infections in the wilderness? The most obvious possibility, he believed, was the water.
Now, after 10 years of fieldwork and 4,500 miles of backpacking, Derlet knows for sure. What he has learned, after analyzing hundreds of samples dipped from backcountry lakes and streams, is that parts of the high Sierra are not nearly as pristine as they look.
Nowhere is the water dirtier, he discovered, than on U.S. Forest Service land, including wilderness areas, where beef cattle and commercial pack stock — horses and mules — graze during the summer. There, bacterial contamination was easily high enough to sicken hikers with Giardia, E. coli and other diseases. In places, slimy, pea-green algae blossomed in the bacteria-laden water.
Overall, the worst water quality he found was in the Stanislaus and Humboldt-Toiyabe national forests, north of Yosemite National Park. Elsewhere, particularly at high elevations in Yosemite, Sequoia and Kings Canyon national parks, Derlet found a striking difference: Most lakes and streams were clear as champagne and pollution-free.
That contrast has prompted Derlet and Charles Goldman, director of the University of California at Davis Tahoe Research Center, to mount a publicity campaign calling for dramatic management change in the Sierra. Cattle, they say, should be moved to lower elevations. And Forest Service areas where they now graze should be turned into national parks.
"At one time, cattle were important for developing civilization here," said Derlet. "But now, with 40 million people in California, the Sierra is not for cattle. It's for water. We need water more than Big Macs."
Anne Yost, regional rangeland program manager for the Forest Service, said her agency is doing a good job managing cattle in the Sierra. Other studies, she said, "show that we can still successfully manage livestock and maintain water quality."
A cause for conflict
This is not the first time livestock in the Sierra have caused conflict. Indeed, Yosemite and Sequoia national parks were created in part because of damage from sheep grazing.
But never before have high Sierra lakes and streams been the focus of such exhaustive water quality research, which Derlet has published in peer-reviewed scientific periodicals such as Wilderness & Environmental Medicine.
"This proves cattle are contaminating the water," said John Buckley, executive director of the nonprofit Central Sierra Environmental Resource Center. "I guarantee you many people don't realize that snowmelt water, that looks so pure, has fecal coliform and E. coli in it."
Twain Harte resident Richard Stark, 78, needs no convincing.
Five years ago, at the end of a long day of hiking, he came upon a herd of about 50 cattle at Kennedy Lake, a camping area at 7,800 feet in the Emigrant Wilderness Area, north of Yosemite.
Searching for a campsite, he and two friends stepped on mounds of manure and stumbled across a meadow pockmarked by cow hooves.
"The meadow was trampled to smithereens," Stark recalled. The air smelled like a barnyard. But the water was a bigger concern.
Some cows stood directly in the inlet stream, he said. The lake bottom was covered with bright green scum; mats of aquatic weeds crowded the water along shore.
"We were horrified," he said. "It was the absolute antithesis of a wilderness experience. We were so terrified of drinking the water that we triple-iodined it."
Sampling water for answers
All lakes harbor bacteria, but discovering what kind inhabit the high Sierra, and at what levels, is a challenge because most backcountry lakes and streams are miles from the nearest road. And microscopic organisms spoil if they get too warm.
"For us, it's logistically really, really difficult" to sample backcountry water, said the Forest Service's Yost. So the agency relies instead on studies that estimate the potential for pollution, she said.
Derlet solved the problem by devising an insulated nylon kit and procedure for keeping samples fresh, which involves rushing back to his car, icing the vials in a cooler and driving directly to a UC Davis lab.
Every year, he lugs that kit over more than 400 miles of trails, dipping his sampling tubes in some of the range's most scenic spots.
Six years ago, Derlet sampled the water in Chiquito Creek, in an area of the Ansel Adams Wilderness where cattle graze. It turned up positive for E. coli, a fecal bacterium that can cause diarrhea and abdominal pain.
"I can recall ... spots in the Sierra where tears almost want to come to your eyes, where you see cow patties right in the stream," Derlet said. "Flushing down from the Sierra, we have raw sewage."
The more he hiked, the more he realized cattle were not the only potential sources of pollution. So are people, with their sunscreen, soap and fecal waste. So are the horses and mules that carry supplies for hikers and work crews. Even wild animals and birds can foul the water.
To sort it out, Derlet sampled strategic locations. Water near campsites where hikers congregated, but not cattle, was largely free of pollution, he found. Seldom- visited streams and lakes were almost always safe for drinking.
But near horses and cattle, evidence of contamination grew. In one study, every Forest Service cattle grazing site sampled harbored E. coli. And 12 of 15 pack stock sites tested positive, two of them inside Kings Canyon National Park and one in Yosemite.
"The overriding problem is the cattle," Derlet said. "Horses are usually along the trails and controlled by a guy who theoretically will make sure they poop away from the water."
Another organism Derlet worries about is Giardia, a parasite that can cause diarrhea and vomiting.
"It may be that 20 to 40 percent of the cattle carry Giardia," Derlet said in a presentation earlier this year, citing other studies. "Each infected cow can shed enough cysts — it takes only 10 cysts to get sick — to infect the entire city of Los Angeles. That's each day. That is an incredible weapon of mass destruction."
But the Forest Service's Yost is skeptical. "For the most part, livestock aren't standing in the streams," she said. "They are grazing in the uplands. ... Where there is proper vegetation, there is filtering before any of that fecal material gets into the water."
Giardia and E. coli are invisible. But algae is not. According to Derlet, algae blooms are spreading in the Sierra, often in cattle grazing areas. And such blooms, he said, are incubators of bacteria.
"There is a close symbiotic relationship between algae and bacteria," he said. "But it's more than bacteria we worry about. It's potential algal toxins" that can cause life-threatening disease.
Is grazing too cheap?
Earlier this year, Derlet reported in the Journal of Water and Health that high Sierra grazing is a deal: Ranchers pay just $1.35 a month per cow. Sheep are a better deal: only 27 cents a month, according to the Forest Service. Overall, 15,045 sheep and 35,721 cattle grazed on national forests in the Sierra in 2009, the agency said.
Total grazing fees last year came to $168,942, just $3.33 per animal; that's less than a latte.
The Forest Service takes in so little from grazing, the U.S. Government Accountability Office has reported, that it loses millions of dollars administering the national program. "The public pays to have cows contaminate the water," said Buckley, the nonprofit director.
Again, Yost sees the issue differently. "I don't think it was ever intended to be a money-making venture," she said. "Congress sets the fee every year, and so that is outside the Forest Service's scope."
Derlet and Goldman, of the UC Davis research center, envision a solution in their proposed string of five new national parks stretching 6,000 square miles across the high Sierra. They have even named those dreams: Eureka National Park, Lake Tahoe National Park, Mokelumne National Park, John Muir National Park and Golden Trout National Park.
"This is where the water is the purest," Derlet said. "This is what needs to be protected."
Yost countered that national forests were established to provide a broad range of resources, including grass for cattle. That applies to federally designated wilderness areas, too, she added.
Though Derlet believes science is on his side, he's braced for controversy.
"I'll tell you what keeps me going," he said. "Mahatma Gandhi made this statement: 'At first they ignore you. Then they laugh at you. Then they fight you. Then you win.' "