TWELVE
A WARNING FROM THE GOLDEN TOAD

In our story we are yet to meet a single species that has definitely become extinct because of climate change. In the regions where it is likely to have occurred, such as New Guinea’s forests and coral reefs, there’s been no biologist on hand to document the event. In contrast, there are many researchers at the Monteverde Cloud Forest Preserve in Costa Rica, Central America, where the Golden Toad Laboratory for Conservation is located.

Soon after our fragile planet passed through the climatic magic gate of 1976, abrupt and strange events were observed by the ecologists who spend their lives working in these pristine forests.

During the winter dry season of 1987, the frogs that live in the mossy rainforests one and a half kilometres above the sea began to disappear. Thirty of the fifty species known to inhabit the 30-square-kilometre study site vanished. Among them was a spectacular toad the colour of spun gold. The golden toad lived only on the upper slopes of the mountain. At certain times of the year crowds of the brilliant males gathered around puddles on the forest floor to mate.

The golden toad was discovered and named in 1966, although the Indians knew about it long before. They have myths about a mysterious golden frog that is very difficult to find, but should anyone search the mountains for long enough to find one they will obtain great happiness. Their stories tell of one man who found the frog but let it go because he found happiness too painful to bear. Another released the creature because he didn’t recognise happiness when he had it.

Only the males are golden; the females are mottled black, yellow and scarlet. For much of the year it’s a secretive creature, spending its time in burrows amid the mossy roots of the woodland. Then, as the dry season gives way to the wet in April–May, it appears above ground en masse, for just a few days or weeks. With such a short time to reproduce, the males fight with each other for top spot and take every opportunity to mate—even if it’s only with a field worker’s boot.

In her book In Search of the Golden Frog, amphibian expert Marty Crump tells us what it was like to see the creature in its mating frenzy:

I trudge uphill…through cloud forest, then through gnarled elfin forest…At the next bend I see one of the most incredible sights I’ve ever seen. There, congregated around several small pools at the bases of dwarfed, windswept trees, are over one hundred Day-Glo golden orange toads poised like statues, dazzling jewels against the dark brown mud.

On 15 April 1987 Crump made a note in her field diary that was to have historic significance:

We see a large orange blob with legs flailing in all directions: a writhing mass of toad flesh. Closer examination reveals three males, each struggling to gain access to the female in the middle. Forty-two brilliant orange splotches poised around the pool are unmated males, alert to any movement and ready to pounce. Another fifty-seven unmated males are scattered nearby. In total we find 133 toads in the neighbourhood of this kitchen sink-sized pool.

On 20 April:

Breeding seems to be over. I found the last female four days ago, and gradually the males have returned to their underground retreats. Every day the ground is drier and the pools contain less water. Today’s observations are discouraging. Most of the pools have dried completely, leaving behind desiccated eggs already covered in mold. Unfortunately, the dry weather conditions of El Niño are still affecting this part of Costa Rica.

As if they knew the fate of their eggs, the toads attempted to breed again in May. This was, as far as the world knows, the last great toad orgy ever to occur. Despite the fact that 43,500 eggs were deposited in the ten pools Crump studied, only twenty-nine tadpoles survived for longer than a week, because the pools once again quickly dried.

The following year Crump was back at Monteverde for the breeding season, but this time things were different. After a long search, on 21 May she located a single male. By June, and still searching, Crump was worried: ‘the forest seems sterile and depressing without the bright orange splashes of colour…I don’t understand what’s happening. Why haven’t we found a few hopeful males, checking out the pools in anticipation?’

A year was to pass before, on 15 May 1989, a solitary male was again sighted. As it was sitting just three metres from where Crump made her sighting twelve months earlier, it was almost certainly the same toad.

For the second year running he held a lonely vigil, waiting for the arrival of his fellows. He was, as far as we know, the last of his species. The golden toad has not been seen since.

Other species at Monteverde were also affected. Two species of lizard vanished entirely. Today, the mountain’s rainforests continue to be stripped of their jewels, with many reptiles, frogs and other fauna becoming rarer by the year. While still verdant enough to justify its name, the Monteverde Cloud Forest Preserve is beginning to resemble a crown that has lost its brightest gems.

Researchers began to study the records of temperature and rainfall. Eventually, in 1999, they announced that they had solved the mystery of the disappearance of the golden toad.

Ever since Earth passed through its first climatic magic gate in 1976, there were more and more mistless days each dry season on Monteverde, until they had joined into runs of mistless days. By the dry season of 1987, the number of consecutive mistless days had passed some critical threshold. Mist, you see, brings vital moisture. Its absence caused catastrophic changes.

Why, the researchers wanted to know, had the mist left Monteverde? Beginning in 1976 the bottom of the cloud mass had risen until it was above the level of the forest. The change had been driven by the abrupt rise in sea surface temperatures in the central western Pacific. A hot ocean had heated the air, elevating the condensation point for moisture. By 1987 the rising cloud-line was, on many days, above the mossy forest altogether, bringing shade but no mist. The golden toad has porous skin, and it likes to wander in daylight hours. It was exquisitely vulnerable to the new drier climate.

It’s always devastating when you witness the extinction of a species. You are seeing the dismantling of ecosystems and irreparable genetic loss. It takes hundreds of thousands of years for such species to evolve.

The golden toad is the first documented victim of global warming. We killed it with our reckless use of coal-fired electricity and our huge cars, just as surely as if we had flattened its forest with bulldozers.

Since 1976 many researchers have observed amphibian species vanish before their eyes without being able to determine the cause. New studies indicate that climate change is responsible for these disappearances too.

In the late 1970s, a remarkable creature known as the gastric brooding frog disappeared from the mossy forests of southeastern Queensland. When it was first discovered in 1973 this brown, medium-sized frog astonished a researcher who looked into a female’s open mouth—to observe a miniature frog sitting on her tongue! Not just the frog— scientists around the world were open-mouthed too.

The species is not a cannibal. It has bizarre breeding habits. The female swallows her fertilised eggs, and the tadpoles develop in her stomach until they metamorphose into frogs, which she then regurgitates into the world.

Australia’s gastric brooding frog nurtured its tadpoles in its stomach, which it somehow transformed from an organ of digestion into a brood chamber. The species may well be Australia’s first victim of climate change.

When this novel method of reproduction was announced, some medical researchers understandably got excited. How did the frog transform its stomach from an acid-filled digesting device into a nursery? The answer might help doctors treat a variety of stomach complaints. Alas, they were unable to carry out many experiments, for in 1979—six years after humans learned of its existence—the gastric brooding frog vanished, and with it went another inhabitant of the same streams, the day frog. Neither has been seen since.

In the early 1990s, frogs began to disappear en masse from the rainforests of northern Queensland. Today some sixteen frog species (13 per cent of Australia’s total amphibian fauna), have experienced falls in numbers. The decreases in rainfall experienced in eastern Australia over the past few decades cannot have been good for frogs. At least in the case of the gastric brooder and day frog, climate change is the most likely cause of their disappearance.

Now almost a third of the world’s 6000-odd species of amphibians is threatened with extinction. Some scientists believe shallower breeding ponds—due to El Niño-like conditions—may be to blame. Fungal diseases are also contributing to the extinctions, and climate change is altering conditions in such a way that the fungus is flourishing.

Climate change seems to be the hidden cause of this wave of amphibian extinction.