Amphibians matter to humans more than we tend to realize. The number of amphibian species around the world has been plummeting at an incredibly rapid rate in recent decades, and this decline poses a serious threat.

Hundreds of amphibian species have declined and disappeared in the past few decades, making them some of the hardest-hit victims of a broader mass extinction that's wiping out many kinds of wildlife. These extinctions are due to many factors, including herbicides, habitat loss, invasive species and general pollution — but much of the problem is due to the chytrid fungus Batrachochytrium dendrobatidis (Bd). This fungus causes a disease called chytridiomycosis, which has caused mass die-offs of frogs, toads and salamanders for the past 50 years.

Chytridiomycosis is now responsible for "the greatest recorded loss of biodiversity attributable to a disease," according to a major study published March 29 in the journal Science. Conducted by a team of 41 scientists, the study marks the first worldwide analysis of the outbreak, and it reveals that Bd has pushed more than 500 amphibians toward extinction, representing 6.5 percent of all known amphibian species. At least 90 of those species are confirmed or presumed to be extinct in the wild, while the others have all declined by more than 90 percent.

"We knew that frogs were dying all around the world, but no one had gone back to the start and actually assessed what the impact was," lead author Benjamin Scheele, an ecologist at Australian National University, tells The New York Times. "It rewrote our understanding of what disease could do to wildlife," Scheele tells The Atlantic. Wendy Palen, a biologist at Simon Fraser University who co-wrote a commentary on the new study, says Bd is now "the most deadly pathogen known to science."

The Bd fungus most likely originated in East Asia, according to a 2018 study, and its spread is probably assisted by humans. As more people not only travel around the world, but also transport more plants and animals all over the planet, this fungus enjoys growing opportunities to attack new amphibian populations.

The canary in the coal mine

A common rocket frog (Colostethus panamensis) against a white background The common rocket frog (Colostethus panamensis) is an endemic species to Panama harmed by the chytrid fungus. (Photo: Brian Gratwicke/Wikimedia Commons)

This crisis matters for many reasons. Not only have we lost "some really amazing species," as Scheele tells the BBC, but these losses pose an increasing threat to more than just amphibians. A major decline in amphibian diversity can cause a major decline in the health and sustainability of ecosystems as a whole, and a deteriorating ecosystem means the deterioration of the quality of human life. Amphibians can help us in numerous ways — from assessing the general health of our ecosystems, to pest control, water filtration and medical research.

One of their greatest contributions is their role as "bioindicators" — markers that allow scientists to clearly identify the need for biological examination. Amphibian Ark reports that because of their incredibly thin skin, amphibians are much more susceptible to disease.

If an area has a large number of amphibians that exhibit signs of disease, it's clear the area isn't as healthy as it should be. Scientists follow the health of amphibians to pinpoint locations that suffer from negative environmental factors. By observing these factors, scientists can determine which areas demand attention and where they should conduct their studies.

Shenandoah salamander The Shenandoah salamander is an endangered species that exists only in Virginia's Shenandoah National Park. About half of all salamander species on Earth are now considered threatened with extinction. (Photo: Brian Gratwicke/Flickr)

In addition, amphibians are an integral part of the circle of life, as they consume many mosquitoes and other insects while also serving as prey for larger animals.

Because of amphibians' appetites for mosquitoes, they're able to help reduce the spread of mosquito-borne illnesses such as malaria. Keeping insect populations in check can also help protect crops that might otherwise be destroyed by pests. Amphibian Ark notes that areas in which a significant amphibian decline has occurred, the number of insects that pose disease- or crop-related threats has risen.

A 2014 study found that even though many fish eat mosquitoes, salamanders are helpful in mitigating mosquito populations in ephemeral wetlands where fish are unable to survive. Another 2014 study found that salamanders, thanks to their taste for leaf-chewing insects on forest floors, can even help fight climate change.

Amphibians also offer important contributions to keeping our water clean. For example, tadpoles are able to help maintain clean water by feeding on the algae that would otherwise cause contamination if left uneaten, Save the Frogs reports.

Medical benefits

red-eyed tree frog on leaf A red-eyed tree frog on a leaf. (Photo: Aleksey Stemmer/Shutterstock)

According to Amphibian Ark, chemical compounds secreted from the skin of frogs can be slightly modified to help treat a variety of diseases such as Alzheimer’s and cancer. The chemical compounds can also be useful in treating depression and seizure disorders, and can even be effective as a stimulant for heart attack victims.

The Australian red-eyed tree frog and its relatives possess chemical compounds that can be used as prevention for HIV. Due to the organic chemical compounds that exist within frogs, we are able to make advancements in medicine that might otherwise be impossible.

Amphibians broaden our research abilities by allowing us to learn more about our bodies and our environment — giving us the means to sustain many aspects of human life and the world in which we thrive.

For guidance on how you can get involved in the struggle to save amphibians, check out these suggestions from Amphibian Ark.

Editor's note: This article has been updated since it was originally published in July 2016.

Why the loss of amphibians matters
Amphibians are reliable indicators of changes in ecosystems and are valuable in medical research.