Karen Lips was a grad student when she came face to face with a mass extinction for the first time. It was the early 1990s, and she was doing research on frogs in the mountains of Costa Rica. At the beginning, they were everywhere. And then, poof: “I came back one year and there were no frogs,” she remembers. Puzzled, she explored other sites—and started turning up corpses. An area that had thrummed with amphibian life had morphed into a graveyard.
Over the course of the next few years, Lips and her colleagues would identify the troubling cause of death: a fungus called Batrachochytrium dendrobatidis, or Bd for short, growing all over their bodies. That’s a problem because amphibians drink and even breathe by absorbing water and oxygen directly through their skin. Bd, which belongs to a phylum of fungi called chytrids, interferes with that, messing with blood chemistry and leading to organ failure. Since Lips helped discover it, Bd has caused the collapse or extinction of over 200 amphibian species around the world—the most devastating wildlife disease ever recorded.
So when fire salamanders started dying in a nature preserve in the Netherlands a few years ago, researchers there thought it had to be Bd. The salamanders were covered in lesions, typical of a skin-infecting chytrid fungus. But when An Martel, a veterinarian at Ghent University in Belgium, ran a DNA test on the pathogen, it came up negative for Bd. She had discovered a new chytrid. In experiments it only infected salamanders, so she and her colleagues named it Batrachochytrium salamandrivorans, or Bsal, and reported its existence in a Science paper last October.
Bsal appears to be native to Asia, where it lives in relative harmony with salamander species that have had millions of years to evolve ways of dealing with it. But nearly 50 percent of the world’s salamander species live half a world away, in North America. As far as anyone can tell, they’ve never seen Bsal before—which means no resistance.
That could mean real trouble if they ever meet. “From the moment [Bsal] was described, I’ve been in a bit of a blind panic about it,” says Brian Gratwicke, a biologist who leads the amphibian efforts at the Smithsonian Conservation Biology Institute in Washington, DC. Salamanders are a vital link in the food chain of many forests, devouring insects on the forest floor and being eaten in turn by larger mammals, birds, and snakes. A disease that took salamanders out of the equation could allow insect populations to explode. More insects munching on fallen leaves and dead trees speeds up the decay process, releasing plants’ carbon into the atmosphere at a faster rate—not good in the era of climate change. The loss of North America’s salamanders “could really spiral,” says Tiffany Yap, a graduate student in environmental science at UCLA.
The good news is that Bsal doesn’t appear to have reached North America—yet. But without some serious policy changes, it’s only a matter of time. Ninety-nine percent of the salamanders imported to the US as pets come from ports in Asia, and 91 percent are Asian species thought to be potential carriers of Bsal, Yap and colleagues write in a paper published today in Science. Even worse, the five US ports where the majority of foreign salamanders arrive—Los Angeles, Tampa, New York, Atlanta, and San Francisco—are all in or near areas with lots and lots of native salamander species. If even one infected salamander escapes (or is released) into the wild, it could decimate wild populations before anyone even has the chance to notice. That’s why Yap and her co-authors call for the US to immediately ban live salamander imports, at least until scientists and policy makers can figure out ways to screen for Bsal and keep it from spreading.
Scientists never had the chance to do that with Bd. By the time they found it, it had spread to species after species, ecosystem after ecosystem, country after country. It was already too late to bring infected populations back from collapse. Bsal, on the other hand, hasn't yet begun to rampage. “We get a second chance at this,” Lips says. “Can we do better?”
Maybe. The US Fish and Wildlife Service and other regulatory agencies are taking amphibian scientists’ dire warnings very seriously. With Bd, “we wasted years debating whether population declines were actually happening. This time around there’s no debate,” Lips says. The bad news is that if Bsal does manage to slip into North America, there’s no way to turn back the clock. Salamanders are so shy that finding and treating them in the field is so difficult as to be futile. Trying to stop the spread of Bsal once it starts infecting North American salamanders “would be like trying to put out a forest fire by blowing on it,” Gratwicke says.
He should know, since that’s essentially what he’s trying to do in at the Smithsonian’s amphibian rescue lab in Panama. There, Gratwicke and his colleagues are rearing isolated populations of several species of frog threatened by Bd, with the hopes that one day they can release them back into Bd-free ecosystems. (When that might be is anybody’s guess.) They’ve also run several experiments on treating the fungus by introducing beneficial bacteria onto frogs’ skin, but Gratwicke is the first admit that they will likely never find a silver-bullet cure. He’s a natural optimist, he says, but seeing history threaten to repeat itself with North American salamanders is almost too much to bear. “It is my greatest hope that we can stop [Bsal] from coming into this country,” he says.
Yap is also trying to look on the bright side, at least for now. “It seems like we’ve caught it early,” she says. “Bd was described in 1998, and it took over seven years for there to be any kind of conservation plan to address it. Maybe if we had acted earlier, it might be a different story.”
Lips, now a professor at the University of Maryland, isn’t as hopeful. Having seen Bd wreak havoc right under her nose, she says, “personally, I don’t have a lot of confidence that we’re going to be able to stop [Bsal]." It might already be too late. “We already know it’s in the [pet] trade”—that’s probably how it got to Europe—“and every year we’ve been importing hundreds of thousands of salamanders. What’s the chance that an infected salamander has already been introduced to the US? Probably pretty high.”
Amphibian scientists have been on the front lines of the sixth extinction for decades, so they know what it looks like—so subtle as to be undetectable, until suddenly it explodes right before your eyes. It came for the frogs. Sooner or later, it will come for the salamanders. At least this time, they have the chance to get ready.
