Lost golden toad signals mass extinction threat posed by climate change

Those who were lucky enough to see them will never forget it. For just a few days each year, Costa Rica’s elven cloud forest came alive with throngs of golden toads the length of a child’s thumb, emerging from the undergrowth to mate in swollen pools. by the rain. In this mysterious forest, clouds blanket the mountain ridges and “the trees are dwarfed and wind-sculpted, gnarled and heavily laden with moss,” said J Alan Pounds, ecologist at Monteverde Forest Reserve in Costa Rica. . “The floors are very dark and golden toadstools stood out like animal figurines. It was quite a sight.” Then in 1990, they disappeared. The golden toad was the first species for which climate change was identified as a key driver of extinction. His fate might just be the beginning.

For years, researchers have warned that the world faces both a climate crisis and a biodiversity crisis. More and more, they say they are connected.

One in 10 people are at risk of extinction

Even if warming is capped at the ambitious goal of 1.5 degrees Celsius above pre-industrial levels, the United Nations Intergovernmental Panel on Climate Change says nearly one in 10 species is at risk of extinction.

The golden toad has only been found in the highland forest of Monteverde. So when trouble hit, the species was completely wiped out.

“It was pretty clear that about 99% of the population had declined in a single year,” said Pounds, whose research into the golden toad’s demise was cited in the IPCC’s February report on climate impacts.

Climate change was barely on the research radar when Pounds arrived in Costa Rica in the early 1980s to study amphibians.

But global warming was already starting to take its toll.

After the disappearance of the golden toad, Monteverde’s harlequin frog and others, researchers compared datasets of temperature and weather patterns with those of local species.

They found not only the signature of the periodic weather phenomenon El Niño, but also trends related to climate change.

Climate trigger

The deaths occurred after unusually hot and dry periods.

Pounds and colleagues linked the declines to chytridiomycosis infection, but concluded that the disease was just the “bullet – climate change was pulling the trigger.”

“We hypothesized that climate change and the resulting extreme events were sort of loading the dice for these kinds of outbreaks,” Pounds told AFP.

It was not an isolated incident.

The expansion of the chytrid fungus globally, as well as local climate change “are implicated in the extinction of a wide range of tropical amphibians”, according to the IPCC.

The fingerprints of global warming have since been found in other disappearances.

Bramble Cay melomys, a small rodent living on a low island in the Torres Strait, was last seen in 2009.

The only endemic mammal of the Great Barrier Reef, its populations have been battered by rising sea levels, increased storm surges and tropical cyclones – all made worse by climate change.

The vegetation that provided its food dropped from 11 plant species in 1998 to just two in 2014. It was recently declared extinct.

Today, climate change is listed as a direct threat to 11,475 species assessed by the International Union for Conservation of Nature. About 5,775 are threatened with extinction.

#MeToo for cash

The main reason climate change is increasingly being cited as a threat to so many species is because its impacts are becoming increasingly evident, said Wendy Foden, head of IUCN’s climate change specialist group. .

But there is also a growing understanding of the enormous variety of effects.

Beyond extreme weather, warming can also cause species to move, change their behavior, or even have more male or female offspring.

And that’s on top of other human threats like poaching, deforestation, overfishing and pollution.

In 2019, a report by UN experts on biodiversity said that one million species could become extinct in the coming decades, raising fears that the world was entering a sixth era of mass extinction.

“It’s absolutely terrifying,” Foden said, adding that warnings of catastrophic biodiversity loss have often been ignored.

“We need a #MeToo movement for cash, a full wake up call on what we’re doing.”

Nearly 200 countries are currently locked in global biodiversity talks to try to safeguard nature, including a key milestone of 30% of the Earth’s surface protected by 2030.

But Foden said the threat of climate change means the response will have to go beyond traditional conservation.

“It can’t happen anymore, even in the most remote wilderness, climate change will affect it,” Foden said.

In some cases, people will have to choose which species to save.

Take the endangered African penguin in South Africa, which Foden wrote about for the IPCC Climate Impacts Report.

Forced to nest in the open after humans mined their nesting sites with guano, adults now have to swim ever further afield to find fish, likely due to a combination of overfishing and climate change. During this time, chicks in exposed nests may die from heat stress.

“We are at the last 7,000 breeding pairs. At this point, every penguin matters,” Foden said.

cloudless forest

In Monteverde, even the clouds have changed.

While rainfall has increased somewhat over the past 50 years, Pounds said it has become much more variable.

In the 1970s, the forest experienced about 25 dry days per year on average – in the last decade it was more like 115.

The mist that kept the forest moist during the dry season has diminished by about 70%.

Pounds said that sometimes tourists in the area stop him and ask him how to get to the cloud forest.

“And I say, ‘You’re in,'” he said.

“It often looks more like a dust forest than a cloud forest.”

The researchers also found a sharp decline in frogs, snakes and lizards and changes in bird populations. Some have moved to cooler areas, others have completely disappeared from the region.

As for the golden toad, last year a team from the Monteverde Conservation League, supported by the conservation group Re:wild, launched an expedition to search for the golden toad in its historic habitat in the Children’s Eternal Rainforest, after tantalizing rumors of sightings.

But in vain.

Meanwhile, Pounds and her colleagues continue to monitor the golden toad during the rainy season.

“We haven’t completely given up,” he said.

“But with each passing year, it seems less likely that they will reappear.”

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