Life
Page 32
A Warning from the Golden Toad
2005
When the chicha has been drunk, the night grows late and dark, and the fires die down to burning embers, the wisest old man of the tribe tells…of a beautiful miraculous golden frog that dwells in the forests of these mystical mountains. According to the legends, this frog is ever so shy and retiring and can only be found after arduous trials and patient search in the dark woods on fog-shrouded slopes and frigid peaks…The reward for the finder of this marvellous creature is sublime. Anyone who spies the glittering brilliance of the frog is at first astounded by its beauty and overwhelmed with the excitement and joy of discovery; almost simultaneously he may experience great fear. The story continues that any man who finds the legendary frog finds happiness…One story tells of a man who found the frog, captured it, but then let it go because he did not recognise happiness when he had it; another released the frog because he found happiness too painful.
J. SAVAGE, ON THE TRAIL OF THE GOLDEN FROG, 1970
UP TO THIS point in our narrative, not a single species is definitely known to have 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, the Monteverde Cloud Forest Preserve in Costa Rica, wherein is situated the Golden Toad Laboratory for Conservation, is blessed with an abundance of researchers. 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 conducting detailed field studies in these pristine forests.
Although the lion did not lie down with the lamb anywhere in the observable world after 1976, at Monteverde the keel-billed toucan (Ramphastos sulphuratus) did nest alongside the resplendent quetzal (Pharomachrus moccino)—which in the eyes of rainforest ecologists was as serious a prognostication of impending doom as any biblical omen.
The keel-billed toucan is a lowland bird and its abrupt intrusion into the misty realm of the brilliant red and green quetzal, which is the spiritual protector of the Maya, was a sign of changing conditions high on the mountain. The quetzal can still be seen on Monteverde, but it is not as common as it once was, in part because the keel-billed toucan eats its eggs and young. Some more sensitive bird species have already vanished from the site altogether.
Then, during the winter dry season of 1987, in the mossy rainforests that clothe the mountain’s slopes one and a half kilometres above the sea, thirty of the fifty species of frogs known to inhabit the 30-square-ki-lometre study site vanished. Among them was a spectacular toad the colour of spun gold. The creature lived only on the upper slopes of the mountain, but there it was abundant, and at certain times of the year the brilliant males could be seen by the dozen, gathering around puddles on the forest floor to mate. Aptly named the golden toad (Bufo periglenes), its disappearance particularly worried researchers, for it is one of the most spectacular of the region’s amphibians and was found nowhere else.
The golden toad was discovered and named in 1966. 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 underground, in burrows amid the mossy root-masses of the elfin 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 (perhaps ‘toad’ was too off-putting for a title), amphibian expert Marty Crump tells us what it was like to see the creature in its mating frenzy.1
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, and Crump had the privilege to record it. Despite the fact that 43,500 eggs were deposited in the ten pools she studied, only twenty-nine tadpoles survived for longer than a week, for 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’ve come to associate with this [wet] weather. I don’t understand what’s happening. Why haven’t we found a few hopeful males, checking out the pools in anticipation…?’ Yet even after the season closed without another sighting there was no undue pessimism. 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 male who, for the second year running held a lonely vigil, waiting for the arrival of his fellows. He was, as far as we know, the last of his species, for the golden toad has not been seen since.
Toads and toucans, it transpired, were just two of the species affected by the changes. Lizards in particular suffered population crashes in the years following 1987, especially the anoles, small relatives of the iguanas; by 1996 two species—the cloud forest anole (Norops tropidolepis) and the montane anole (Norops altae)—had 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 and most beautiful gems.
Suspecting that some odd weather event might be the cause of the changes, researchers began to pore over the monthly records of regional temperature and rainfall, but they could find nothing unusual in this data. Fortunately, an alternative and more detailed source of information existed on the mountain top—a weather station is situated on the edge of the study site, and it provided the finer grained record of local changes required to solve the mystery. It would be twelve years before the researchers published their findings, but in 1999 they announced that they had identified the cause of Monteverde’s despoliation.
Examination of the meteorological record revealed that, ever since Earth had passed through its first climatic magic gate in 1976, the number of mistless days experienced each dry season had grown, until they had coalesced into runs of mistless days. By the dry season of 1987, the number of consecutive mistless days had passed some critical threshold. It was apparently so subtle as to be undetectable to the researchers working on the mountain, yet it had plunged the entire ecosystem of the mountaintop into crisis. Mist, you see, brought vital moisture, and without it the forest dried out sufficie
ntly to trigger a landslide of catastrophic changes that swept before it mountain birds, anoles, golden toads and other amphibians alike.
Why, the researchers wanted to know, had the mist forsaken Monteverde? The cloud-line is the level at which clouds sit against mountainsides, bringing misty conditions, and 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 that heralded the magic gate of 1976. A hot ocean had perhaps heated the air, elevating the condensation point for moisture in it. By 1987 the rising cloud-line had, on many days, forsaken the mossy forest altogether and hung about in the sky above, bringing shade but no mist. It was this shade, and the cool it brought, which had been recorded in the original regional weather records and that had first confused the researchers.
The golden toad’s permeable skin, and its propensity to wander in daylight hours, had left it exquisitely vulnerable to the desiccation brought on by the run of mistless days. By the time the study was published in 1999, this wondrous creature had been extinct for a decade.
It’s always devastating when you witness a species’ extinction, for what you are seeing is the dismantling of ecosystems and irreparable genetic loss. The golden toad’s extinction, however, was not in vain, for when the explanation of its demise was published in Nature, the scientists could make their point without equivocation. The golden toad was the first documented victim of global warming. We had killed it with our profligate use of coal-fired electricity and our oversize cars just as surely as if we had flattened its forest with bulldozers. It was as if, having experienced it, we did not recognise what happiness was.
As the reason for the extinction of the golden toad became thoroughly comprehensible, frog researchers worldwide began to re-evaluate their experiences, for since 1976 many had observed amphibian species vanish before their eyes without being able to determine the cause. Could climate change, they wondered, be responsible?
South Australian Museum researcher Steve Richards has documented a series of amphibian declines in the mossy mountain rainforests of eastern Australia. These began in the late 1970s, when a remarkable creature known as the gastric brooding frog (Rheobatrachus silus) disappeared from south-eastern Queensland. When first discovered in 1973 this brown, medium-sized frog astonished the world. The surprise came when a researcher looked into a female’s open mouth—to observe a miniature frog sitting on her tongue! Not just the frog—scientists were open-mouthed too. This might lead the casual observer to think the species was cannibalistic, but this was not the case; it just had 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.
When this novel method of reproduction was announced, some medical doctors understandably got very excited. How, they wondered, did the frog transform its stomach from an acid-filled digesting device into a nursery? They thought the answer might assist in treating a variety of stomach complaints. Alas, they were unable to carry out many experiments, for in 1979—six years after its existence was announced to the world—the gastric brooding frog vanished, and with it went another inhabitant of the same streams, the day frog (Taudactylus diurnus). Neither have been seen since.
Five years after the last gastric brooding frog hopped into oblivion the discovery of another species in the same genus was announced. This one, Rheobatrachus vitellinus, lived further north, on Queensland’s central coast. It was larger, but otherwise strikingly similar. You may have noticed that it lacked a common name, so it won’t be a surprise to learn that the herpetologists’ excitement was short-lived. Before it could be studied in detail this species too could no longer be found—its existence as a known species was measured in months rather than years.
In the early 1990s, frogs began to disappear en masse from the rainforests of northern Queensland and, as with the golden toad, these vanishings occurred in otherwise undisturbed rainforest. Today some sixteen frog species (13 per cent of Australia’s total amphibian fauna), have experienced dramatic declines. The cause is still debated, but the climate change experienced in eastern Australia over the past few decades cannot have been good for frogs, for a persistence of El Niño-like conditions has brought about a dramatic decline in Australia’s east coast rainfall. The latest analyses suggest that at least in the case of the gastric brooder and day frog, climate change was the most likely cause for their disappearance.2
When the first global survey of amphibians was completed in 2004 it revealed that almost a third of the world’s 6000-odd species was threatened with extinction.3 Many of these endangered species began their decline after 1976, and according to Simon Stuart of the International Union for the Conservation of Nature, ‘There’s almost no evidence of recovery.’4
After a decade of research, North American scientists produced their own elegant hypothesis that draws together the causes of these declines into a single, unifying concept.5 Their study focuses on the fate of the amphibians of the north-western United States, and typical of the patterns they found are those of the western Bufo boreas.
Amphibians in the genus Bufo are commonly known as toads. One fundamental discovery of the American study was that ultraviolet light retards the development of the toad’s embyros, and this in turn makes them more vulnerable to a chytrid-type fungal disease known as Saprolgenia ferax, a killer of amphibians worldwide. The toad embryos, it transpires, were receiving more ultraviolet light because their nursery ponds were shallower; this was because persistent El Niño-like conditions since 1976 have brought less winter rain to the Pacific north-west. Even a small change in pond depth can be critical. In ponds fifty centimetres deep just 12 per cent of tadpoles die from the fungus, but when it is only twenty centimetres deep, 80 per cent die.6 At worst some ponds dried up completely, killing all the tadpoles in them.
To compensate, some frogs tried to breed in larger water bodies, but these contained fish that ate the hatching tadpoles, and between the fungus, the drying ponds and the fish, the region’s amphibians had nowhere to go, and so joined the long list of species in freefall towards extinction.
The elegance of this hypothesis lies in drawing together a constellation of impacts under a single dominant factor. In various parts of the world researchers have documented one or more of these changes at work. In the case of the golden toad it was the loss of mist. Australia’s frogs have been reported to be infected with chytrid fungus, while elsewhere failing rains or tadpole deaths mean that reproduction is in decline. Yet, whatever the immediate cause, underlying it all is the change in the patterns of our weather brought about by the magic gate year of 1976, and perhaps that of 1998.
Playing at Canute
2005
The evening came, the rider of the storm sent down the rain. I looked out at the weather and it was terrible…With the first light of dawn a black cloud came from the horizon; it thundered within where Adad, lord of the storm, was riding…Then the Gods of the Abyss rose up; Nergal pulled out the dams of the nether waters, Ninurta the warlord threw down the dykes, and…the God of the storm turned daylight into darkness.
THE EPIC OF GILGAMESH
NESTLED DEEP WITHIN the human psyche lies a primal fear of the awful power of water. The epic of Gilgamesh tells of it, as does Noah’s flood and hundreds of lesser-known myths from around the world. As we have seen, our species’ cradle was most likely the lake region of the African rift valley, where our ancestors foraged on the bounty of fish, shellfish, birds and mammals. We have sought to live close to water ever since, for water draws living things from near and far. Camp near a waterhole and sooner or later animals will come to drink. For deeply embedded reasons, our species has always preferred to live with a water view, especially if it includes a beach, a lake or a lawn cropped short as if by great grazing beasts. Real estate agents well know our housing preferences and the amount we are
willing to pay for them. Today, two out of every three people on Earth live within eighty kilometres of the coast, and yet in our subconscious we understand that the waters can rise over the land, making all of our hard-won real estate count for nought.1
Fifteen thousand years ago the oceans stood at least 100 metres lower than they do today. Then, the North American continent was a veritable empire of ice, exceeding even the Antarctic in the volume of frozen water it supported. As the great American ice caps melted they alone released enough water to raise global sea levels by 74 metres. The sea rose rapidly until around 8000 years ago, when it reached its present level and conditions stabilised. All around the world people watched the waters rise, at times so fast as to change the coastline from year to year. Today, even a modest sea level rise would be disastrous, for the human population along coastlines is dense, and many of us lead vulnerable lives.
Although it is not related to climate change, the catastrophic Asian tsunami of 2004 gives some indication of how devastating rising seas and turbulent weather might be. The Netherlands is already planning for the construction of a super-dyke to save it from the encroaching ocean, and the Thames Barrier is to be strengthened. But countless millions of others live beside the sea—some in expensive real estate, others in humble villages—who have no protection. In Bangladesh alone, more than 10 million people live within one metre of sea level.2
All that remains of the great Northern Hemisphere ice caps today is the Greenland ice sheet, the sea ice of the Arctic Ocean and a few continental glaciers, and there are signs that after 8000 years these remnants are beginning to melt away. Alaska’s spectacular Columbia Glacier has retreated twelve kilometres over the last twenty years; while in a few decades’ time there will be no glaciers left in America’s Glacier National Park. Glaciers such as these only contain enough water to alter the sea level by a matter of centimetres. The Greenland ice cap, however, is a true remnant of the continental ice domes of the type mammoths would recognise, and it contains enough water to raise sea levels globally by around seven metres. In the summer of 2002, it, along with the Arctic ice cap, shrank by a record one million square kilometres—the largest decrease ever recorded.3 Two years later, in 2004, it was discovered that Greenland’s glaciers were melting ten times faster than previously thought.