
Like many other freshwater wildlife species, amphibians have faced steep declines throughout California. Climate-fueled disasters are only increasing the stress on these creatures. As we saw after the recent Palisades fire, species rescue is becoming increasingly necessary. Fortunately, a team of agencies and a local university were able to rescue hundreds of endangered Tidewater Goby from a Malibu lagoon to protect them from toxic debris flows generated from the fire.
Emergency actions like this are truly important—but they should be an action of last resort. One of the best ways to improve a species’ chance of survival is, quite simply, to make sure that they don’t become too isolated. A recent study of the imperiled Sierra Nevada yellow-legged frog is pointing a way forward—and offering hope for an iconic species that was once the most common amphibian in the High Sierra.
In the 1800s, yellow-legged frog populations started to plummet following the introduction of non-native trout into the previously fishless lakes of the High Sierra. However, the species faced an even greater threat in the 1900s with the appearance of a deadly fungus, Batrachochytrium dendrobatidis, a disease that has devastated amphibian populations worldwide. The disease was catastrophic for the Sierra Nevada yellow-legged frog, leading to its disappearance from over 90% of its historic range and motivating its listing under the Endangered Species Act. The effects of climate change are an emerging concern for the remnant frog populations in the High Sierra because of changes in streamflow and snowfall, destructive wildfires, and rapidly warming temperatures.
A remarkable new study by a consortium of university and agency scientists has shown how we may be able to recover Sierra Nevada yellow-legged frogs. In their initial research, the scientists found that some lakes had remnant populations that were relatively resistant to the disease. However, these frogs were unlikely to efficiently recolonize other areas because their movements are blocked by rugged mountain terrain and waterways filled with predators from other parts of the world.
The researchers reasoned that taking a bold step—transplanting disease-resistant frogs to other lakes—could be an effective way to recover the larger population. They recently published the results of a 15-year study in which disease-resistant frogs were collected and reintroduced into a dozen lakes in Yosemite National Park. The results of the project were stunning— reintroductions were successful in many lakes, resulting in self-sustaining populations of Sierra Nevada yellow-legged frogs.
The return of the sounds of native frogs to Yosemite National Park is an undeniably powerful symbol of nature’s ability to regenerate. This innovative project also offers important management lessons that have much broader implications for wildlife conservation in a changing climate:
Recovery is possible, even for some of the most challenging conservation issues
Sierra Nevada yellow-legged frogs are a high-profile example of a California species that came dangerously close to extinction. Yet even in the country’s most populous and increasingly urbanized state, a team of scientists and resource managers has shown that well-designed actions can help to recover the most at-risk species.
As I discussed in a recent PPIC report, climate change is a particularly daunting issue for freshwater conservation since these changes greatly amplify historical environmental damage. Sierra Nevada yellow-legged frogs demonstrate that it is not too late to save these resources.
Major management interventions are generally necessary to save our freshwater species
One of the enduring myths in conservation is that nature can be relied on to “heal itself.” While natural processes are powerful and frequently have strong mechanisms to correct imbalances, our freshwater ecosystems have experienced so many changes that they are struggling (and often failing) to rebalance. Most of our waterways have been radically altered by dams, levees, diversions, contaminants, and urbanization. With the amplifying effects of climate change, many species can no longer survive in their existing habitats or easily move to more suitable habitats. As in the Sierra Nevada example, recovery therefore often depends on bold interventions such as transplantation, captive breeding, veterinary treatments, and large-scale invasive species removal.
A suite of actions is needed
Conservation issues are almost always multifaceted, so relying on a single management strategy such as improving streamflow is unlikely to be enough to recover at-risk species. This was the case in the High Sierra, where both introduced predators and disease were responsible for yellow-legged frog declines. Climate change generates an even more challenging situation, so it’s important that resource managers adopt a suite of conservation actions—a portfolio of restoration tools is a “bet-hedging” strategy to deal with future uncertainty and helps to counter multiple stressors.
The bottom line is that climate change is accelerating so fast that we cannot wait patiently for freshwater ecosystems to heal themselves. The Sierra Nevada yellow-legged frog project shows that we need to consider bold and even risky management actions to save species.
The good news is that California is a proven leader in freshwater species conservation. This is evident in other major 2024 conservation stories, including the massive Klamath River dam removal project; the reintroduction of winter-run Chinook salmon into the McCloud River; and the reconnection of the Yolo Bypass floodplain to the Sacramento River. This is a great start, and much more aggressive and widespread conservation work will be needed to protect California’s freshwater biodiversity.
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