A scientist wearing a headlamp stands on the shore of a Costa Rican mountain stream holding an iridescent green tree frog in the dark. The frog has a bright white throat pouch and skin textured like moss to hide from predators. Despite this adaptation, the frog’s species, Isthmohyla calypso, would be functionally extinct by the following year.
When the scientist returned to the remote patch of cloud forest the next summer, all of the amphibians had vanished. Not only the tree frogs were gone, but also the toads and the stream frogs. The streams were eerily silent and empty. The mysterious 1993 disappearance of the amphibians would change the course of the scientist’s life and unveil a global ecological disaster.
The scientist was Karen Lips, an ecologist now working with the University of Maryland’s biology department. She has dedicated her life to the study and preservation of amphibians. She returned to the research site in the summer of 1996 to a forest devoid of amphibian life. Lips observed no obvious change to the habitat to explain the 90 percent decline of all the local frog species in such a short time span.
By the time she returned to the U.S. that September, she was ready to present an argument to the scientific community that her Costa Rica site had experienced an enigmatic amphibian decline. Enigmatic amphibian declines are mysterious mass disappearances of amphibians that occur without any obvious change to their environment. Lips had been reading reports about the mysterious disappearance of amphibian populations around the world since she was a grad student. Her research would eventually help reveal the culprit: an invasive microscopic fungus called Batrachochytrium dendrobatidis or Bd.
Bd spreads between ecosystems infecting amphibians when the fungus’s spores pass from the water into an unsuspecting amphibian’s skin. The fungus will then kill the creature over the course of two weeks by disrupting the animal’s electrolyte balance and reducing its number of lymphocyte immune cells. Once the amphibian is dead more spores grown in the dying creature will be released through the skin into the environment to infect more animals completing the pathogen’s life cycle.
Peter Jenkins is an environmental lawyer who worked with Lips to advocate for U.S. government action against Bd and its more recently discovered variant Bsal. Jenkins explained the threat Bd poses to the amphibian world by drawing a parallel to the pandemic currently being faced by humans saying Bd is "like coronavirus for amphibians but worse."
Lips witnessed the devastation wrought by Bd before she figured out what was killing her beloved amphibians. There were no frogs left to study so she would have to get creative to find the source of the decline. She compared the loss of her amphibians in southern Costa Rica to a previous mass disappearance to the north of her site and made a startling inference. Lips hypothesized that the collapse of the amphibian populations was sweeping through Central America like a wave. So, in order to gather evidence for the theory, she would have to get out in front of this wave.
Lips moved on to a new location in Panama where amphibians were still abundant called Fortuna. On her first visit, she cataloged 40 species. When she returned in December of 1996 she encountered her worst fears. The frogs were dying. Population numbers were down in many of the area’s streams and many of the frogs she and her team were finding were unhealthy or dead. Many even died in the hands of researchers.
This time however Lips and her team had bodies to examine. Eventually, scientists determined that the frogs were being killed by a microscopic fungus. Joyce Longcore, an associate research professor at the University of Maine, soon discovered the Bd fungus while studying a dead specimen from the U.S. National Zoo. Longcore and her colleagues also found the fungus on a dying frog from Australia. When taken together the data showed that Bd was decimating amphibian populations globally though more research was obviously needed.
Lips and her team continued that research over the following years. In 2004 they documented the collapse of yet another amphibian population this time in central Panama. Lips was stuck in the U.S. at the time but her graduate students diligently stepped up their efforts so they could gather as much data as possible before the epidemic wiped out the frogs.
Lips said, “It was frustrating to be trapped at school while ‘my’ frogs were dying in Panama—after all those years of work and all those transects, I would miss the actual epidemic. But I knew that while my field team documented the devastation, my responsibility was to tell everybody in the larger community what was happening and what it meant.”
In more recent years Lips has shifted her focus from fieldwork to public advocacy. In 2009 she teamed up with the Defenders of Wildlife to petition the U.S. Fish and Wildlife Service to better regulate the pet trade in order to prevent the spread of Bd in the U.S. The USFWS ultimately shelved the project after it became clear that Bd was already present in the domestic pet market and could not be blocked from the country.
However, a Bd variant able to infect salamanders known as Bsal has not been found in North America. The urging of Lips and other advocates got the USFWS to ban the import of 200 salamander species in 2016 to protect America’s salamander species from Bsal transmission. The U.S. has more native salamander species than any other nation. Lips hopes to spare them the fate of her green tree frogs.
Lips is hopeful that the pandemic will bring needed attention to and the plight of amphibians saying: "If we can prevent the next COVID we can also save the frogs [and salamanders] at the same time." In the coronavirus age, she is now championing the concept of “One Health:” that human, wildlife, and environmental health are all linked and must be managed collectively.