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.
Iām republishing this popular story from last year, when I had far fewer subscribers. Enjoy. šø
Ecologist Roland Knapp describes himself 30 years ago as āyoung, ambitious, and crazy.ā Starting in 1995, Knapp led the first effort to find out exactly what was living in each of the 7,000 lakes of Californiaās Sierra Nevada, an endeavor that required hiking across 3,000 square miles of high-altitude terrain.
His team confirmed a disheartening situation: Yosemiteās 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.
Knappās determination is responsible for saving the frog from extinction, not once, but twice: First, from non-native fish, then from a deadly fungus. Now, heās hoping his work can help save other amphibians across the world.
āTo 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,ā Knapp said as he described a recent trip to the high country. āItās unreal to look into that frogās eyes and think what a crazy path itās been. And you think, āWelcome home, frog.āā
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.
ā Rocky Basin Lakes, Joseph Grinnell, field notes written on August, 21, 1911
Hike, discover, recover ā¦ repeat
Knapp recruited 50 others to conduct that first survey of the Sierra Nevadaās thousands of water bodies, including lakes, ponds, marshes, and meadows ā an unprecedented endeavor that spanned from northern Yosemite National Park to southern Sequoia National Park. They found 1,800 lakes big enough to support frogs, but only 330 ā those that were fishless ā 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.
Knappās 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 frogās 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.
āItās eating things, but itās not wiping them out,ā Knapp said. āThe fish wipe them out. ā¦ [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.ā
Birds known to be attracted to fishless Sierra Nevada lakes include:
Gray-crowned rosy-finch
Clarkās 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, itās only through steep, tumbling waterfalls.
When the lakes are alive with frogs, these āmirrorsā dissipate. Frogs connect the water with the land to form a single ecosystem that thrives.
āIt wasnāt until Kingās Canyon National Park that I watched the Clarkās 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,ā Knapp said.
āIf 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.ā
What drives these fish to behave so ravenously?
Fish and frogs coexist fine in other ecosystems. But we must remember Yosemiteās unforgivable 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.
āThatās the adaptation that allowed them to colonize the High Sierra, but thatās the same adaptation that makes them so vulnerable to non-native trout,ā Knapp said. āIn the winter, they both refuge in the deepest parts of these lakes.ā
āIām not satisfied with words like āimpossible.āā
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 āantichrist of trout.ā
āEarly on, when that issue first hit the newspapers, I was called a lot of names,ā Knapp recalled. āIt wasnāt 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.ā
When Knapp first showed state and federal agencies his research demonstrating that native frogs and non-native fish donāt coexist in High Sierra lakes, so the frog faced near extinction, he was told, essentially, āWell, thatās too bad.ā
āI was imagining what the future might be,ā Knapp said. āIs 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 ā¦
āIām a scientist. Iām not satisfied with words like āimpossible.ā Iām not satisfied with, āWhatās done is done,ā or āWe just need to learn to live with it.ā I want to know, is there in fact a way around the problem that we have just described in excruciating detail?ā
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.
āWe all began collaborating on fish removal projectsā
The āwhatās done is doneā attitude came to a screeching halt when the 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 Grinnellās āshower of frogsā quote more than 100 years ago, began to see it in real life.
āThey were removing brook trout and seeing frogs recovering,ā Knapp said. āAnd we were saying to ourselves, āHoly cow, you should see the frogs.āā
Crazy young scientist recruits more crazy young scientists
Iāve spent some time in the High Country and, to me, an incredibly impressive part of this story is Knappās first big step: surveying those 7,000 water bodies across the High Sierra.
āPartly 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,ā Knapp said. āWe came together as a very effective team of people who had a similar vision, who understood the role each of us could play.
āIt 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.
āSurveying 7,000 lakes was not going to happen with Roland running around the Sierra Nevada by himself. It took people saying, āI want to be part of that crazy, I want to see how far we can push this boundary.āā
āHow could a human-caused problem not have a human solution, right?ā
A surprising thing to come out of my conversation with Knapp is where he lives.
āSo, youāre in Santa Barbara?ā I started the conversation.
āNo, I live in Lee Vining,ā 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 youāre an ecologist with a knack for saving frogs.
āWhen I finished my PhD, I thought to myself, āCan I accomplish what I want to accomplish as a professor?āā Knapp said. āI 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.
āI wasnāt 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.ā
Imagining how hard it was to save these frogs, Iād 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 āmountainsā theyād climbed.
āSo how did you maintain hope?ā I asked.
āHow could a human-caused problem not have a human solution, right?ā Knapp said. āWe just need to bring that passion and energy to the table and get the solutions on the ground.ā
āFrog recovery didnāt just happen. It happened because a lot of people spent the better part of their adult lives studying, working conscientiously toward a solution. Itās not just beating your head against the wall; Itās moving through the wall.ā
āWe 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.
āDespair to me means doing nothing. Hope drives progress in making the world a better place.ā
Recap: How to save a frog species ā 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, DONāT 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
More stories from Earth Hope about Yosemite:
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About Earth Hope
Earth Hope is a solutions-based journalism project that highlights environmental success stories to inspire action. Iām Amanda Royal, a former newspaper reporter and current eco-news junkie. Read more about this project and what inspired it. I aggregate news under my āhopeful headlines,ā conduct original reporting and interviews, and share occasional personal narratives. Visit earthhope.substack.com for more stories. To understand why I write about hope, please read āAs I went down in the river to pray ā¦ā.
How much kismet are we enjoying right now. Is it called kismet? Like when two people who are far apart end up focused on the same thing at the same time. My post that dropped today is about frogs. Lol. Canāt wait to read this later this evening.
What a fantastic story and so engagingly told. It's interesting that, by getting to know the anglers and not treating them as the enemy, the restoration eventually succeeded.