Amphibious Assault
Scientists debate what's causing Sierra frogs and toads to vanish

by Mark Grossi
The Fresno Bee- July 16, 2001


Roland Knapp hauls a 90-pound backpack through thick chaparral in 95-degree heat, avoids the rattlesnakes and braves bug-infested backcountry for weeks at a time.

He does it so he can snorkel in cold, murky mountain bogs, ponds and lakes filled with slimy, little critters. Since 1995, Knapp has been wearing himself out, living most summers without Starbucks or indoor plumbing.
This guy is serious about frogs and toads.

Knapp, a University of California research biologist, and his crews have been combing lakes and ponds in Yosemite, Sequoia and Kings Canyon national parks for the past six years. When they finish, they estimate they will have surveyed almost 7,000 bodies of water for amphibians, fish and their habitat.

His marathon summers, covering 1.5 million acres of national parks east of Fresno, are aimed at answering troubling questions about the mysterious decline of Sierra frogs and toads.

Underwritten the past couple summers by a $250,000 Yosemite Fund grant, Knapp should complete the job next year.

"That’s more than half of the water bodies in the Sierra," Knapp says. "We need to know what’s there now so we can begin to understand what we need to protect the native species of frogs and toads."

He has come to believe non-native fish -- specifically trout planted in lakes -- could be eating populations of frog and toad tadpoles. He acknowledges that the decline also could be caused by predation from other animals, disease, pesticides, ultraviolet radiation and global warming. It could be a combination of factors.

Bottom line, nobody knows why frogs and toads are disappearing, which opens the door for differing theories and professional disagreements. Dueling science, as some put it. A disagreement exists over the Sierra amphibian decline.

Knapp believes fish could be a major cause of the decline, while a U.S. Geological Survey biologist is more inclined toward pesticide contamination, probably from San Joaquin Valley agriculture.

No matter what the major causes are, scientists agree that the Sierra amphibian decline is part of a worldwide loss of frogs and toads.

Many believe the downturn in these sensitive creatures could be a prelude to environmental problems that might one day threaten human life.

Amphibians respire through the skin and lungs, making them susceptible to subtle changes in the environment. Those changes, such as global warming or depletion of the ozone layer, could cause oceans to rise, disease to increase and life expectancy to plummet.

People around the world are paying more attention to frogs and toads.
"It’s a consistent decline for amphibians," Knapp says. "That’s why a complete survey of these bodies of water will be so important 100 years from now when people look back and try to figure out what has happened."

Knapp’s work has already influenced a controversial state Department of Fish and Game decision to suspend fish stocking in 25% of Sierra lakes this year in an attempt to strike a balance between fish and frogs.
Other research confirms fish as a possible "smoking gun" in the Sierra amphibian decline, but another expert, USGS research biologist Gary Fellers, disagrees.

Fellers, who is based at Point Reyes National Seashore, says he admires Knapp’s work, but says pesticides are a more likely candidate to be a primary cause.

Fellers and two other scientists wrote a study published this month demonstrating that pesticide chemicals found in high Sierra amphibians are affecting nerve functions, causing the same fatal symptoms that affect insects killed in farm fields with the chemicals.

"The observed declines could well be caused by contaminants," Fellers says. "The data for the impact of fish are not as compelling. Both Roland and I have documented declines that point to fish as a problem. I don't believe that fish are the primary cause of the declines, in part because we see declines in areas that have no fish, and have never had fish."

On the other hand, Knapp doubts Fellers’ pesticide theory. He wonders why toads and frogs co-exist with modern agriculture on the Valley floor where many tons of pesticides are used each year. Why aren’t pesticides wiping out Valley frogs and toads, too? And, does the wind really carry the pesticides to the Sierra crest?

Both scientists, however, say they are more interested in reversing the trend than earning the bragging rights as the one who discovered the primary cause. Both believe that many questions should be investigated.

Knapp and his crews investigate with nets, vials, waders, fins and other equipment, walking to every body of water shown on detailed, USGS topographic maps. The idea is to describe the habitat and conditions of many species at every single body of water to provide a baseline of knowledge.

"I’ve been doing this since I was 30, " says Knapp, now 36. "I usually weigh about 170 at the start of summer and lose 15 pounds. We try to stay out 10 to 15 days at a time."

At times, his crews will start an expedition at 4,000 feet in Sequoia-Kings Canyon National Parks and wind up at 12,000 feet two days later. Along with hip waders, a dry suit, gill nets and other equipment, they carry small transmitters, which they attach around a frog’s body.

"They fit very well, actually, "Knapp says. "They have small batteries that can transmit for about 30 days. "

He collects fish, zooplankton and amphibians as well as other creatures. Knapp and his teams also note the lake’s dimensions and characteristics. Last year, they encountered 400 unmapped bodies of water, ranging from small meadow bogs to lakes.

Heavy glaciation left thousands of lakes in the central and southern Sierra over the past 3 million years, ending about 10,000 years ago. Glaciers deepened canyons and created waterfalls on many waterways, so fish could not return to the higher elevations. But frogs and toads did.

Fish began appearing in the high Sierra during the 1800s when European settlers put them in streams and lakes for anglers. Stocking or planting was continued in the 1900s by the Fish and Game Department, though national parks stopped fish planting in the 1970s to protect native species, such as amphibians.

Now, recreational fishing attracts millions of people, says California Trout Inc., a conservation group for anglers. Officials say many fishing enthusiasts are worried about the state stopping trout planting in some Sierra lakes as a result of research done by Knapp and others.

"I believe our stance is to give them room to try to investigate further the real culprits in the amphibian decline, but also try to protect the fisheries," says Brett Matzke, public lands director of CalTrout. "I do believe that trout introduced species are a part of the problem, but we have problems when they seem to be the scapegoat."

State officials are also interested in preserving the fisheries, says Ed Pert, fishery science adviser to the Fish and Game director. A number of state biologists have been looking at the problem for the past three years, he says.

"We’re trying to see if our stocking program has been managed right," Pert says. "If we’re stocking in a place where the fish population is sustaining itself year to year, the fish will be stunted because of the competition when planted fish are added."

Stocking has been stopped at such places, but it has also been stopped in some other lakes that are known to support frogs or toads. Anglers have told the state officials that they're going too far, and environmentalists don't feel the state has gone far enough.

Officials say fishing shouldn’t be affected this summer or next. Pert says state wildlife officials hope their efforts will open places where the amphibians can avoid the threat of fish, yet allow fisheries to thrive in other places.

Another fishing group, Trout Unlimited, says the state is taking a sound approach so far. Steve Trafton, state policy coordinator, says this isn’t the end of recreational fishing by a long shot.

"My worry is that if we did nothing now that the frogs become listed under the Endangered Species Act," he says. "Then you wind up with a federal agency with a mission to recover frogs."

The Center for Biological Diversity in late May filed a federal lawsuit to force protection for two high Sierra amphibians, the Yosemite toad and the mountain yellow-legged frog.

Knapp doesn’t see himself as an enemy of anglers, though he supports the idea of removing all the fish in some backcountry lakes where there is little recreation and frog populations are suffering. He agrees with a Kings Canyon National Park project to remove fish from 11 lakes this summer.
But Knapp also loves to fly fish. It’s one of the reasons he's so interested in the aquatic life in the Sierra.

"I’ve published far more papers on trout than on amphibians," he says.
"But how much fish removal do you need? How many frogs do you need? How do we maintain amphibians in Yosemite? We need to work on those questions."