The ecologist who dared love Yosemite's frogs
Once called the "antichrist of trout," Roland Knapp has traversed the High Sierra for 30 years to save its native frog. Now, birds, snakes and bears are feasting on frogs.
Ecologist Roland Knapp describes himself 30 years ago as “young, ambitious and crazy.” Starting in 1995, Knapp led the first effort to find out exactly what was living in each of the 7,000 lakes of California’s Sierra Nevada, an endeavor that required hiking across 3,000 square miles of high-altitude terrain.
His team confirmed a disheartening situation: Yosemite’s native frogs only live in fish-free lakes.
Fish are recent arrivals to this glacier-carved landscape, First, European colonists packed them in on mules 150 years ago. Then, beginning in the 1950s, they were flown in by airplane to boost recreational fishing.
Knapp began to push for removing fish from High Sierra lakes, a not-so-new idea that was met with disregard by some and outrage by others.
Why remove fish? Because the fish were eating all the frogs. The Sierra Nevada mountain yellow-legged frog was on a trajectory toward extinction.
By 2007, Yosemite National Park began removing fish from a few lakes. Scientists soon noticed that not only did the lakes become alive with frogs, but life on land around the lakes changed as well. When given a chance to thrive, the frog feeds a panoply of animals, from bears to birds to snakes, in an ecosystem balanced precariously among ice, snow and floods for up to nine months a year.
Knapp’s determination is responsible for saving the frog from extinction, not once, but twice: First, from non-native fish, then from a deadly fungus. Now, he’s hoping his work can help save other amphibians across the world.
“To see this recovery playing out in real time after all the work that had to be done to lay the foundation, after all the challenges we faced after the first frog reintroductions, it truly is mind-blowing,” Knapp said as he described a recent trip to the high country. “It’s unreal to look into that frog’s eyes and think what a crazy path it’s been. And you think, ‘Welcome home, frog.’”
Oh, and what a frog! Early explorers described seeing hundreds basking on high country lakeshores. It croaks not while on land, but sings underwater, silent to our ears. The sound it makes above water is another marvel, documented by naturalist Joseph Grinnell in 1911:
There are a great number of apparently full-grown frogs around the shores of the lakes. The conspicuous thing about them is their extreme wariness. They jump into the water and dive quickly into the deepest holes within reach, when one is yet fully 10 yards from them. There is thus a shower of frogs in advance of a person as he walks along the beach. They must have some nimble and persistent enemy.
— Rocky Basin Lakes, Joseph Grinnell, field notes written on August, 21, 1911
Hike, discover, recover … repeat
Knapp recruited 50 others to conduct that first survey of the Sierra Nevada’s thousands of water bodies, including lakes, ponds, marshes and meadows — an unprecedented endeavor that spanned from northern Yosemite National Park to southern Sequioa National Park. They found 1,800 lakes big enough to support frogs, but only 330 — those that were fishless — contained frogs.
Knapp and his team went to work expanding that number, lobbying to remove fish from lakes and successfully reintroducing frogs. Simultaneously, in the late 1990s, a devastating fungus began killing off 90 percent of the population. Undeterred, they hiked and surveyed again, discovering fungus-resistant frogs. They reintroduced them again, carrying frogs on their backs across a vast high-altitude landscape. Helicopters helped out at times.
Knapp’s recent paper in Nature Communications, which made worldwide news last fall, outlined a 15-year study of lakes where both chytrid fungus and fungus-resistant frogs are coexisting. Chytrid fungus has decimated amphibians across the world, leading to at least 90 extinctions. The study shows reintroductions could be used as a model to save other species.
An ecosystem ripples alive as birds flock to fish-free lakes
With the yellow-legged frog’s slow recovery, the surrounding ecosystem rippled with surprising changes. Several birds flock to fish-free, frog-filled lakes. Some birds eat the frogs. Others eat the bugs that are no longer devoured by the fish.
Frogs eat bugs, too, but not every last bug.
“It’s eating things but it’s not wiping them out,” Knapp said. “The fish wipe them out. … [In fish-stocked lakes], the fish have eaten all the larger prey. All of the mayflies, the backswimmers, dragonflies, damselflies, all of the frogs. Now, rosy finches are eating those mayflies, filling their stomachs and flying the mayflies back to their nests and fledglings.”
Birds known to be attracted to fishless Sierra Nevada lakes include:
Gray-crowned rosy-finch
Clark’s nutcracker
American dipper.
Animals observed preying on mountain yellow-legged frogs:
black bear
coyote
Brewer's blackbird
Clark's nutcracker
American robin
Swainson's hawk
Sierra garter snake
western terrestrial garter snake
The High Sierra lakes are often compared to jewels or mirrors, perfectly reflecting magenta sunsets, cobalt skies and creamy granite peaks. Glaciated cirques catch snowmelt like glass bowls. If the lakes are connected at all to other water bodies, it’s only through steep, tumbling waterfalls.
When the lakes are alive with frogs, these “mirrors” dissipate. Frogs connect the water with the land to form a single ecosystem that thrives.
“It wasn’t until King’s Canyon National Park that I watched the Clark’s nutcrackers feeding on frogs that I realized the obvious: What we do to the aquatic, we do to the terrestrial, whether we want to or not,” Knapp said.
“If we can restore the lake and its aliveness, we can connect the aquatic with the terrestrial. It took three years of that inventory work when I finally made the connection between the aquatic and terrestrial. I was literally struck by a knowledge lightning bolt.”
What drives these fish to behave so ravenously?
Fish and frogs coexist fine in other ecosystems. But we must remember Yosemite’s unforgiveable snow and ice, the enormous miracle that life exists at all in this granite landscape from 10,000 to 14,000 feet. Unlike many other amphibians that prefer warm, shallow waters, breeding and maturing in one summer, the mountain yellow-legged frog has adapted to cold water, maturing slowly, preferring deep lakes, where it spends one or two winters as a tadpole. However, as the top layers of these lakes freeze in winter, the tadpoles share their ever-shrinking environment with starving fish.
“That’s the adaptation that allowed them to colonize the High Sierra, but that’s the same adaptation that makes them so vulnerable to non-native trout,” Knapp said. “In the winter, they both refuge in the deepest parts of these lakes.”
“I’m not satisfied with words like ‘impossible.’”
Decades ago, the notion of removing trout from stunning alpine lakes frequented by recreational anglers did not abide without controversy. Heated public meetings ensued. Knapp was called the “antichrist of trout.”
“Early on, when that issue first hit the newspapers, I was called a lot of names,” Knapp recalled. “It wasn’t very pleasant. It was clear to me that it was part of the process. [However], protection and restoration are the highest mandates in national parks. I was in a position to propose solutions. I had to be the one to propose them first.”
When Knapp first showed state and federal agencies his research demonstrating that native frogs and non-native fish don’t coexist in High Sierra lakes, so the frog faced near extinction, he was told, essentially, “Well, that’s too bad.”
“I was imagining what the future might be,” Knapp said. “Is there a way that this impact might be reversible? If the science does in fact show that trout are widespread to the point of wiping [yellow-legged frogs] off the face of the earth …
“I’m a scientist. I’m not satisfied with words like ‘impossible.’ I’m not satisfied with, ‘What’s done is done,’ or ‘We just need to learn to live with it.’ I want to know is there in fact a way around the problem that we have just described in excruciating detail.”
Turns out, likely due to genetic variation, the bigger the frog population when the fungus arrives, the more likely some frogs will survive. So the initial efforts to remove fish, restock the frogs and boost their populations likely helped the frogs avoid total annihilation by chytrid fungus.
“We all began collaborating on fish removal projects”
The “what’s done is done” attitude came to a screeching halt when Sierra Nevada mountain yellow-legged frog was listed as federally endangered in 2014. The government agencies, all with different mandates, some conflicting, finally woke up and came to the table to find solutions.
Now, an effort that spans two national parks to remove fish and restore amphibians has become the most ambitious mountain lake and aquatic system restoration initiative in the world.
Knapp, ever inspired by Grinnel’s “shower of frogs” quote more than 100 years ago, began to see it in real life.
“They were removing brook trout and seeing frogs recovering,” Knapp said. “And we were saying to ourselves, ‘Holy cow, you should see the frogs.’”
Crazy young scientist recruits more crazy young scientists
I’ve spent some time in the High Country and, to me, an incredibly impressive part of this story is Knapp’s first big step: Surveying those 7,000 water bodies across the High Sierra.
“Partly because I was a crazy, 25-year-old, ambitious, driven person, I was able to effect change at a large scale but I did it with a lot of people who shared the same concerns,” Knapp said. “We came together as a very effective team of people who had a similar vision, who understood the role each of us could play.
“It often takes that one person to stick their neck out and raise the first cry. We can get on the same path and achieve this objective together.
“Surveying 7,000 lakes was not going to happen with Roland running around the Sierra Nevada by himself. It took people saying, ‘I want to be part of that crazy, I want to see how far we can push this boundary.’”
“How could a human-caused problem not have a human solution, right?”
A surprising thing to come out of my conversation with Knapp is where he lives.
“So, you’re in Santa Barbara?” I started the conversation.
“No, I live in Lee Vining,” Knapp said.
With a population of 656 people, Lee Vining sits right outside the eastern border of Yosemite National Park and is very remote (the main highway east to the rest of California is closed six months of the year due to snow).
As it turns out, Lee Vining is a perfect place to live if you’re an ecologist with a knack for saving frogs.
“When I finished my PhD, I thought to myself, ‘Can I accomplish what I want to accomplish as a professor?’” Knapp said. “I would live at least several hundred miles away from the Sierra Nevada. Those were going to be controversial issues, especially when it came to fish removal.
“I wasn’t going to make progress on those issues as a professor. I was going to make progress if those people, those managers [of the state and federal agencies], were my neighbors and my friends. That has made all the difference.”
Imagining how hard it was to save these frogs, I’d pictured biologists panting at high altitude to carry them to beautiful, remote lakes. Such trips are often accompanied by dehydration, altitude fatigue, sunburn and chapped lips. But after speaking with Knapp for a while, I understood more deeply the “mountains” they’d climbed.
“So how did you maintain hope?” I asked.
“How could a human-caused problem not have a human solution, right?” Knapp said. “We just need to bring that passion and energy to the table and get the solutions on the ground.”
“Frog recovery didn’t just happen. It happened because a lot of people spent the better part of their adult lives studying, working conscientiously toward a solution. It’s not just beating your head against the wall; It’s moving through the wall.”
“We will encounter adversity no matter what we do. You can sit there and accept adversity and cry about it and moan about it or you can do something about it.
“Despair to me means doing nothing. Hope drives progress in making the world a better place.”
Recap: How to save a frog species — twice. Ten simple but not-so-easy steps.
Survey 7,000 high country lakes and discover remaining frogs only live in fish-free lakes.
DARE TO DREAM
Change the mindset of a few state and federal agencies’ about native frogs and non-native trout while staying on friendly terms with angler groups. A dash of neighborliness helps your chances.
Eliminate invasive trout from a few dozen lakes. Gillnets will do.
Transplant frogs from old fish-free lakes into new fish-free lakes. Just a few hikes above 10,000 feet carrying heavy sacks full of frogs will do. Helicopters can help.
Watch populations boom.
When 99 percent of populations die of chytrid fungus, DON’T LOSE HOPE.
Hike to the lakes again. Find frog populations that are immune to chytrid fungus.
Transplant fungus-resistant frogs to lakes where they died out.
Watch showers of frogs from the lakesides.
Further reading:
History of fish stocking in Yosemite
California frog reintroduction is rare victory against fungal pandemic
Aquarium of the Pacific aids recovery of mountain yellow-legged frog
USA Today: 'The lakes are alive again': These frogs are back from near extinction
National Park Service EIS: Restoration of Native Species in High Elevation Aquatic Ecosystems
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Earth Hope is a solutions-based journalism project that highlights environmental success stories from around the globe, because hope is the foundation of progress. I’m Amanda Royal, a former newspaper reporter and current eco-news junkie. Read more about this project and what inspired it.
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What a heart-warming story! I so need these reasons for hope amid our current difficulties. Thank you.
This is fantastic. I have a friend named Mark Wanner who has been working for years to save the Hellbender. So I know the kind of driven that gets things done and a little about the sheer number of people who have to get involved. It’s fantastic to hear about this stunning frog success in Sierra-Nevada.