First, the frogs died. Then people got sick.An emerging area of research is uncovering hidden links between nature and human health.This reporting was supported by the Pulitzer Center....moreThis reporting was supported by the Pulitzer Center....moreNovember 14, 2025 at 6:00 a.m. EST9 minutes agoALTOS DE CAMPANA NATIONAL PARK, Panama — Brian Gratwicke’s lunch box was full of frogs.Kneeling on the muddy rainforest floor, the biologist opened his red Coleman cooler and scooped one up. It was a Pratt’s rocket frog — about the size of a walnut, sporting black-and-white racing stripes. Gratwicke deposited the frog in a small mesh tent, a “catio” for indoor pets to glimpse the outdoors, and encouraged it to acclimate to its transitional home.“There you go,” he told it. “Look at all that nice leaf litter.” The frog darted into the carpet of leaves, unaware it had just leaped into a high-stakes experiment.Conservation biologist Brian Gratwicke searches with his team for frogs in Altos de Campana National Park in Panama.Nate Weisenbeck, a research intern with the Panama Amphibian Rescue and Conservation Project, checks on how a pair of Pratt’s rocket frogs are acclimating to the forest.Gratwicke is a conservation biologist who leads amphibian work at the Smithsonian’s National Zoo and Conservation Biology Institute. He had flown to Panama, in the middle of rainy season, to help resurrect frog species that had vanished from the cloud forest decades ago.Whether these amphibians can strike out on their own and thrive here again is uncertain.What is becoming increasingly clear is that without them, humans are in trouble. It turns out that frogs — in biblical times regarded as a plague — are actually guardians against disease.50 Species that Save UsThis series highlights emerging research on how plants and animals protect human health – and how their disappearance is already sickening thousands of people around the world. Explore these connections in our illustrated, interactive species cards.As dozens of frog species have declined across Central America, scientists have witnessed a remarkable chain of events: With fewer tadpoles to eat mosquito larvae, rates of mosquito-borne malaria in the region have climbed, resulting in a fivefold increase in cases.The discovery of this link is part of an emerging area of research in which ecologists and economists are trying to calculate the costs of species decline.They are revealing hidden ways that thriving populations of many plants and animals — including wolves, bats, birds and trees — underpin humanity’s well-being.They are learning that without saving nature, we cannot save ourselves.The mystery of the vanishing frogsAt first, no one knew why frogs seemed to be disappearing everywhere.In Texas, some herpetologists thought egrets were eating them. In Connecticut, people accused raccoons. In Brazil, they blamed a bout of chilly weather. But the fact that so many frogs were vanishing from so many places in the early 1990s suggested something widespread but invisible was behind the decline.Karen Lips was a graduate student at the time, working with amphibians in Costa Rica, near the border with Panama. During a trip there in 1993, she couldn’t find the toads she had been studying. “Almost everything was gone,” she recalled. At first, she blamed the weather, her headlamp, her searching technique.Then she remembered a related toad species had disappeared a few hundred miles to the north. It dawned on her: Perhaps a frog-killing “wave” was sweeping from mountain to mountain.Weisenbeck works with harlequin frogs raised at the Panama Amphibian Rescue and Conservation Project in Gamboa.Lemur leaf frogs are grouped in a breeding tank with multiple males and females at the Panama Amphibian Rescue and Conservation Project.Whatever it was, she wanted to get ahead of it. She set up camp farther east, in a cloud forest in Panama. She thought she’d have many years to study the 40-odd species of frogs there. But by 1996, many of the ones she was picking up were leathery and lethargic.“Sometimes they would make one jump and it would be their last bout of energy,” recalled Lips, today an ecologist at the International Institute for Applied Systems Analysis. “They’d make a big jump to try and escape. And then they couldn’t move anymore at all, and they would just die there.”After she helped publish a photo of an infection on the frogs’ skin, herpetologists studying wild frogs in Australia and captive ones at the National Zoo realized they were all dealing with the same disease: a fungus that would be dubbed Batrachochytrium dendrobatidis, or Bd for short.The researchers swab a yellow-flecked glass frog to assess the prevalence of Bd in wild frog communities in Altos de Campana National Park.Thought to have originated in Asia or Africa, Bd may have hitched a ride on ships or planes to traverse otherwise insurmountable oceans. It now coats every continent except Antarctica (where there are no frogs).The microscopic pathogen kills by burrowing into an amphibian’s sensitive skin, blocking electrolytes and sapping muscles of their strength. Ultimately, an infected frog becomes so fatigued that its heart stops.As the fungus swept eastward through Panama, Gratwicke and his colleagues raced to rescue as many frogs as they could. They persuaded a shipping company to donate seven containers to a Smithsonian facility an hour outside Panama City. There, along the Panama Canal, they built a makeshift ark, stacking each container floor-to-ceiling with terrariums full of frogs for a captive breeding program.The Smithsonian focused on saving nine species it assessed to be in the direst state. “It’s absolute triage,” Gratwicke said. “We can’t look after 200 species.”Among those targeted for preservation was the Panamanian golden frog, a national icon and symbol of good luck that is depicted on banners and beer cans.“It’s a huge weight of responsibility on our shoulders,” Gratwicke said. “Because if we screw this up, we screw it up for an entire species.”This year, the researchers also brought into captivity a population of Pratt’s rocket frogs that had disappeared in the national park but survived elsewhere, possibly because they had developed some immunity to the fungus. Gratwicke and his colleagues were relocating two dozen of those potentially resistant frogs to Altos de Campana. After two weeks, the researchers would unzip them from the tents, with the hope that the transplanted frogs might help repopulate the park.Globally, frog populations have crashed as a result of Bd. The fungus has affected more than 500 amphibian species, decimating at least 90 to the point where they are thought to be extinct in the wild. For the researchers watching it all unfold over the past three decades, it was clear a frog apocalypse was underway. The fungus, along with climate change and habitat loss, has made amphibians the most vulnerable group of vertebrates on Earth.Lips began studying the cascading effects of these massive losses. She found algae thrived in spots where there were no tadpoles to eat it. Snake populations, meanwhile, dwindled with fewer adult frogs to eat.When describing this upheaval in a call with other scientists, she piqued the interest of Michael Springborn, an environmental economist at the University of California at Davis. “I’d heard a little bit about Bd,” he recalled, “but I was embarrassed to learn that I didn’t really understand how impactful that had been.” The two decided to work together.Lemur leaf frogs are among the lab-raised specimens at the Panama Amphibian Rescue and Conservation Project.With statistical tools more commonly used in economics, they mapped the frog die-offs and spread of the fungus county-by-county across Costa Rica and Panama.Then they compared that spread to county-level health records of malaria in humans. They found a striking pattern: a fivefold spike in malaria cases after the fungus arrived and the frogs died. Lips, Springborn and their colleagues published the discovery in 2022 in the journal Environmental Research Letters.The region’s tapered shape, bound on either side by the Caribbean and the Pacific, allowed them to track the spread of the disease in detail. “We got lucky in a sense that there’s this … narrow strip where you had Bd arguably channeled through,” Springborn said.Some herpetologists, Lips said, would be content to stay in their lane and just “count the frogs.” But she anticipated that “if we could link it to people, maybe we could get more traction. Maybe people would care.”Biologists have long documented ways in which people benefit from nature — what, in academic circles, are called “ecosystem services.” Bees pollinate crops, trees suck heat-trapping carbon dioxide out of the air, and coral reefs guard coastal communities from storms and foster fish for food.But the interdisciplinary effort to uncover the relationship between biodiversity and human health — an approach dubbed “One Health” — is just beginning to tease out even deeper connections.The researchers are working toward the release of Panamanian golden frogs, an icon of the country.In the United States, researchers have shown that a collapse of insect-eating bat populations prompted farmers to use more pesticide on crops, which in turn led to a higher human infant mortality rate.Around the Great Lakes, the reemergence of gray wolves has had the surprising effect of keeping motorists safe. The canines prowl along roads while hunting, spooking deer from crossing and reducing collisions with cars.Also in North America, invasive emerald ash borers devastated ash trees, contributing to elevated temperatures and an increase in cardiovascular and respiratory deaths.India may have witnessed the most astounding ecological breakdown of them all. After vultures experienced a mass die-off, the livestock carcasses they once scavenged piled up. Packs of feral dogs took the place of vultures, resulting in a rise in deaths from rabies.Eyal Frank, a University of Chicago economist who helped connect the dots in the bat and vulture case studies, said we often don’t realize how crucial a plant or animal is to our well-being until it is gone.“Why preserve biodiversity?” Frank said. “We might not realize now that this species is important. But we might realize in the future that it’s important.”By 2012, the frog-killing fungus had conquered Panama, reaching its easternmost point, the Darién Gap.A remote and roadless jungle, the area is known as a treacherous stretch for migrants trying to make their way from North to South America. The resident population is small and mostly made up of Indigenous tribes.Jando Mejia, from the seminomadic Wounaan people, figures he was bitten when he was visiting his mother there in 2023. When a mosquito latched onto his skin and sucked his blood, it must have dropped a single-celled parasite called a plasmodium into his body.Within days the parasite began wreaking havoc, invading and multiplying within his red blood cells. His eyes and tongue turned yellow. His head felt like it was splitting open with pain.“I couldn’t taste food,” he said. “I lost my appetite, and I felt dizzy and weak. I couldn’t do anything.”Mejia, 23, believes he contracted malaria in eastern Panama.Mejia was at that point staying with his sister in central Panama. Her house is on concrete stilts to deter snakes and other wildlife, but its plywood walls and open-air windows provide little protection from buzzing mosquitos. Smoke wafts from spiral-shaped repellents to keep the insects away. Nearby, vendors in the village sell golden frog figurines.His sister set up a bed for him on the floor. His mother made the journey from the Darién Gap to help. “I was in bed for a week,” he said. “I could hardly remember anything.”Even after the worst of the symptoms subsided, it was weeks before he had enough strength to return to his $15-a-day job on a farm growing coffee and plantains.“He wasn’t normal,” his sister, Chanita Mejia, recalled. “Even climbing a small hill was hard. He felt tired.”By the time he could go back to work, he had lost out on a month of income.Telbinia Toscon, a traditional craftswoman in the Embera village, lost her mother to malaria.Frogs are a recurring image in Panamanian crafts.No single case of malaria can be attributed to the wave of frog deaths. And other factors, too, may have contributed to the rise in cases. José Ricardo Rovira, a mosquito researcher at Indicasat, a Panamanian institute, noted that paths made by migrants crisscrossing the Darién have further enabled the spread of malaria-carrying mosquitos.But Springborn, Lips and their colleagues estimate there were tens of thousands of additional cases of the disease in Panama and Costa Rica in the decade following the amphibian decline. Although it’s difficult to estimate, that increase in cases would have led to “a handful” of additional deaths each year, Springborn said.Rovira knows how debilitating the disease can be. He vividly remembers the fever and chills he experienced after twice contracting malaria while setting mosquito traps in the Darién.He said he doesn’t fear malaria, but has learned to respect it. Now 75, he appreciates he must be cautious. “I’m not going out to the field much anymore,” he said.Working to restore the frogsOn Gratwicke’s recent Panama trip, after depositing the Pratt’s rocket frogs in their tent, he turned to the question of how much Bd was still out there.He bounded down a series of waterfalls on a rumbling creek, sweeping his flashlight along the muddy embankment. The light caught a glint of yellow. It was a Panama rocket frog, a related species. True to its name, it shot off after being spotted. The hunt was on.With a stick, Gratwicke prodded the fugitive frog into the water. “Just wait, he’ll come up,” he said leaning over the stream. The birdlike chirps of rocket frogs used to fill this gully, he explained. Now, save for the rush of the water, it was mostly silent.“Oh, I got it!” Gratwicke yelped after reaching his gloved hands into the stream. Pulling out a long cotton swab, he dabbed the frogs’ feet, thighs and belly before letting it go. (Lab tests on the swabs would later reveal that Bd was on a third of the frogs plucked from the water that day.)Gratwicke and his team listen to frog calls while walking through Altos de Campana National Park.Conservation scientists Julie Dogger, Oliver Granucci and Orlando Garces check on tadpole development in Altos de Campana National Park. Next stop was the encampment of a crowned tree frog. This chocolate brown frog had been bred in a Smithsonian lab, and after two weeks acclimating to the forest, it was ready for release — into a still perilous place.Nate Weisenbeck, Gratwicke’s colleague from the Smithsonian, reached up and unlatched the front of a mesh cube nailed to a tree teetering on the mountainside.“This is a pilot,” Gratwicke said. “Because it’s the first time this has ever been done, you can’t really predict all the ways in which things can go wrong.”The researchers are trying to set their frogs up with the best shot at survival, but don’t know if they will succumb to the fungus or other predators. (The work is supported financially by the Bezos Earth Fund, a philanthropic initiative of Washington Post owner Jeff Bezos, as well as the Cheyenne Mountain Zoo, Zoo New England and the Panamanian government.)Weisenbeck had installed a variety of possible shelters for the frog to choose next: a hollow stalk of bamboo, a stack of black plastic pots, a wooden birdhouse.When the researchers came back about six hours later, wearing headlamps to navigate the pitch-black jungle at night, all those potential homes were empty.Weisenbeck unfurled a six-pronged antenna on a device that beeped to indicate whether he was homing in on the tracker tied to the frog’s back.A metamorphosing lemur leaf frog tadpole hangs on the edge of Dogger’s net. A crowned tree frog wears a radio transmitter to enable tracking within the national park.He circled the tree: beep… beep…He was careful with his feet, so as not to inadvertently step on a frog. The device grew louder. Beep… Beep…He twisted to prevent the antenna from getting tangled in the vegetation. BEEP… BEEP… BEEP…“Well done, Nate,” Gratwicke said. Weisenbeck bent down to capture one last photo of his frog, resting on a cigar plant about 30 feet from the tree.“Yeah, this could be the last time we see him,” Weisenbeck said. “He’s wild.”Two variable harlequin frogs at the Panama Amphibian Rescue and Conservation Project in Gamboa.About this storyThis article is part of The Washington Post’s “Species That Save Us” series, highlighting hidden links between nature and human health. Photos and video by Melina Mara. Design and development by Hailey Haymond. Editing by Marisa Bellack, Juliet Eilperin, John Farrell, Dominique Hildebrand and Joe Moore. Copy editing by Mike Cirelli.

An emerging area of research is uncovering hidden links between nature and human health.