For frogs, it's essentially doomsday. Here's what's killing them.

Starting in the 1980s, scientists noted an incredibly rapid decline in frog populations across almost all corners of the globe. Streams that once teemed with tadpoles mysteriously emptied. Warm nights once filled with the chorus of "ribbits" were suddenly devoid of any frog song.

Let's zoom into just one of hundreds of frog dissapearance. A few decades ago, the Sierra Nevada yellow-legged frog was the most abundant amphibian in the high lakes of the Sierra Nevada mountain range, including Yosemite National Park, in California. Their population has plummeted by 95%, according to the National Park Service.

In Sept. 2016, a frog named 'Toughie' died in a botanical garden in Atlanta. His demise marked the extinction of the entire Rabbs’ fringe-limbed tree frog species, as far as scientists know. These unique frogs were capable of gliding by spreading their enormous fully webbed hands and feet during descent. At least 90 species of amphibians have gone extinct in recent years.

Photo: Rabb's Fringe-limbed Treefrog, Brian Gratwicke via Wikimedia Commons

Despite having existed on the planet for hundreds of millions of years, more than 500 species have been seriously affected, if not wiped out entirely. An estimated 124 species' populations have dropped by over 90%, according to a groundbreaking study in Science, that found at least 300 more species have experienced significant declines. The study stated that the majority of species and populations were still in decline.

The United States Department of Agriculture states that one-third of amphibian species are at risk of extinction (imagine if that were the case for mammals!). They face a combination of multiple threats including habitat loss, disease, invasive species, overexploitation, climate change, and chemical pollution.

Although they've evolved to survive, frogs are clearly not thriving in the so-called Anthropocene. Climate change is a threat. In 2022, the UN said that the golden toad (pictured) was one of two species for which the climate crisis was implicated as a key driver of extinction, driving "extreme droughts" that wiped out its moist habitat. But so far, this isn't the key contributor to the mass extinction.

A study published in Nature found that frogs can be affected by the weedkiller atrazine, as well as commonly used phosphate fertilizers. These chemicals trigger a domino effect of environmental harm that can lead to a boom in algae growth. While this is unfortunate, it's not the largest contributor either.

Most species of frogs have evolved to blend into and thrive in specific environments. But with the expansion of human activities and deforestation, particularly in the Amazon, which hosts hundreds of amazing species, many species' ancient lifestyle is being fatally disrupted. While a major threat, habitat loss isn't the main cause of the frog apocalypse either.

Known as BD for short, this devastating fungus thrives in cool, moist conditions, which means larger frogs and frogs that live in cool environments have been the most affected. It has been silently massacring groups of frogs since around the late 1970s, though scientists didn't realize it was the primary cause of the frogpocalypse until the late 1990s.

Given the brutal outbreak of the fungus, it’s now being called "the most deadly pathogen known to science," according to Wendy Palen, a frog scientist at Simon Fraser University. Indeed, this doomsday fungus has condemned more species to extinction than any other known pathogen.

Image: Dr Alex Hyatt, CSIRO, via Wikimedia Commons

BD works primarily by eating away at the skin of amphibians and triggering fatal heart attacks, as part of a disease called chytridiomycosis. The fungus spreads easily in water and can wipe out entire groups. Once it has established itself in a new environment, it’s nearly impossible to remove.

The popular HBO show focuses on a post-apocalyptic world where a fungus wipes out large portions of the population (and also turns them into zombies). It's kind of like that, minus the zombie part. But in the real world, another fungal disease, white-nose syndrome, is devastating the bat populations of the US and Canada.

A genetic study conducted by Imperial College London suggests that BD originated in Asia. But in the 20th century, as global trade boomed, it gradually spread to five other continents, decimating populations not used to the disease. According to the New York Times, it was likely spread via the pet amphibian trade, and it still hasn't reached New Guinea.. but if it did, it would be devastating.

Frogs are both predators and prey. Without tadpoles to consume algae, it can grow out of control. Without frogs to eat insects, some bothersome and potentially harmful species may become more common. At the same time, birds and other predators who enjoy a tasty meal of frog legs have to seek alternatives.

Frogs have been struggling, but scientists in Switzerland have found a fairly simple solution to aiding populations: digging ponds. In one experiment of pond digging, of the eight endangered species in the area, 52% increased their regional populations and 32% were stabilized. However, this doesn't necessarily address the deadly fungus.

While the 2019 Science study was far from encouraging, it did contain a glimmer of hope. Though most frog species are still declining, 12% are showing signs of recovery and the decimation indeed peeked in the 1980s in most areas. This could be because natural selection is favoring animals resistant to the fungus.

While combating the fungus might be too much, you can do your part and help provide some shelter to weary amphibians. It's often as simple as digging a small pond, creating toad abodes or other spaces where amphibians can finally rest and live in peace.

Science has finally caught up with the fungus and is managing to prevent it from decimating other amphibians. When a similar fungus targeting salamanders was discovered in Belgium, many feared the worst. However, researchers identified it quickly and implemented barriers to halt its spread.