A deadly fungus identified in 2013 could devastate native salamander populations in North America unless U.S. officials make an immediate effort to halt salamander importation, according to an urgent new report published today in the journal Science.
San Francisco State University biologist Vance Vredenburg, his graduate student Tiffany Yap and their colleagues at the University of California, Berkeley and the University of California, Los Angeles say the southeastern United States (particularly the southern extent of the Appalachian Mountain range and its southern neighboring region), the Pacific Northwest and the Sierra Nevada, and the central highlands of Mexico are at the highest risk for salamander declines and extinctions if the fatal Batrachochytrium salamandrivorans (Bsal) fungus makes its way into those regions.
Salamanders are popular worldwide as pets, and frequently traded across borders. That has scientists worried that the fungus could spread from Asia, where it likely originated, to other parts of the globe. Vredenburg and his coauthors on the study are asking the U.S. Fish and Wildlife Service to place an immediate ban on live salamander imports to the U.S. until there is a plan in place to detect and prevent the spread of Bsal. Although the ban has been supported by key scientists for some time, including in a prominent op-ed in the New York Times last year, the government has been slow to act.
"This is an imminent threat, and a place where policy could have a very positive effect," Vredenburg said. "We actually have a decent chance of preventing a major catastrophe."
Salamanders are one of the most abundant vertebrate animals in many North American ecosystems and play a number of key ecological roles. "They are very important predators of insects, but also an important part of the food chain," noted Vredenburg, an associate professor of biology.
Bsal likely originated in Asian species of salamander that are traded as popular pets around the world. When the fungus made its way into Europe through the pet trade, it caused a 96 percent fatality rate among the European salamander species that it infected. It was also fatal to American salamanders exposed to the fungus in the lab.
The blue-tailed fire-bellied newt (Cynops cyanurus), the Japanese fire-bellied newt (Cynops pyrrhogaster), and the Tam Dao or Vietnamese salamander (Paramesotriton deloustali) are thought to be the main carriers of Bsal. Alarmingly, 91 percent of pet salamanders imported to North America come from either the Cynops or Paramesotriton groups.
"We've made specific predictions, on the ground, of where North American species are most vulnerable to Bsal," said Vredenburg. "And the places that have the highest amount of trade in these salamanders happen to be in those high-risk areas."
To map out high-risk regions of Bsal infection in North America, the research team looked at habitats where the fungus might thrive, based on its Asian carrier locations, along with data on how many different species might be threatened in those areas and the location of major U.S. ports of entry for salamander trade between 2010 and 2014.
Vredenburg fears that the salamanders might be on the verge of an ecological crisis that is all too familiar to him. For more than a decade he has studied the impact of a similarly deadly fungus called Batrachochytrium dendrobatidis (Bd). More than 200 species of amphibians have gone extinct or are near to extinction as a result of Bd infection, making it the most devastating infectious wildlife disease ever recorded.
"I have seen the effects of Bd on frogs, to the point where I've seen tens of thousands of animals die in the wild in pristine areas, here in California, right in front of my eyes," Vredenburg said. "It is just an unbelievable sight to see all these dead animals."
The heartbreaking work might have a silver lining, he said, if it can be used to save the salamanders from a similar plight.
"One of the things that I find remarkable about this is that unlike when we first figured out what was going on with Bd, no one could even imagine that one pathogen could cause so much damage across all these different species, because we had never seen anything like that ever before," Vredenburg said. "What's encouraging about this time, with Bsal, is that the scientific community figured it out really quickly, and we can learn a lesson from the past."
Vredenburg is the co-founder of AmphibiaWeb, an online database of information on amphibian biology that receives 7.3 million queries each year. Salamanders are astonishing animals, he said, ranging from species that live 35 feet up in the trees to others that roll into balls and hurl themselves off cliffs to escape predators. The familiar California slender salamanders, found all over Northern California, are one of the groups most threatened by Bsal infection.
"They're incredibly diverse, they've been around for tens of millions of years, and the thought of losing them because of human error, humans moving pathogens around by accident, is just a terrible thought," Vredenburg said. "And it's preventable."
"Averting a North American biodiversity crisis" by Tiffany A. Yap, Michelle S. Koo, Richard F. Ambrose David B. Wake and Vance Vredenburg was published July 31 in Science.