The following is an excerpt from The Book of Vanishing Species: Illustrated Lives by Beatrice Forshall, published by Bloomsbury.
TAKE A DEEP BREATH.
Half of the oxygen that just entered your lungs was made by plankton.
Look in your fridge – if you find seafood, it comes from plankton.
Now get in your car. The petrol that fuels your engine was made by plankton.
If you were to take a teaspoon of water from the ocean and look at it under a microscope, you would see many shapes – possibly millions, mostly translucent – of varying sizes and colours. Little spheres, tubular bodies with drooping tendrils, circles within squares, squares within circles; triangles, rectangles; spiralling helixes, some bristly, some hooked, some frilled; oval wreaths, concertinas, braided zigzags; antennae emerging from cone-shaped bodies; umbrellas, crossbows, sickles, bells, fans; barrels trailing thin, wispy veils behind them; hexagonal prisms like jewels; darting arrows and little suns. You could be forgiven for thinking that instead of a microscope, you were looking through a telescope, and instead of water, you were gazing into the sky – at galaxies, spaceships and planets with alien creatures – yet plankton are very much a part of this world. We depend on them.
Their ancestors were here when life on Earth began 3.5 billion years ago. The early atmosphere was mostly methane, ammonia, nitrogen and carbon dioxide. Early plankton were able to survive this oxygen-deprived environment. They were the first photosynthesisers, and over billions of years they absorbed and converted carbon dioxide into oxygen, making it possible for other creatures to exist.
In the water, plankton flutter, whirl, hover ghost-like, glide, shimmer and pulse with glowing light along their glassy bodies – flashing pink, purple, blue and orange. They are water wanderers, carried by ocean currents – planktos, from the ancient Greek, ‘drifter’. Until they are able to swim, the larvae of fish, starfish, squid, shrimp, sea urchin, cockle, oyster, crab and barnacle are also plankton. Together they make up 98 per cent of the Earth’s living aquatic biomass.
There are two main groups of plankton. Phytoplankton are plants. Most are microscopic, but under certain conditions they multiply in such numbers that, collectively, they can be seen from space. Around a quarter of the carbon dioxide we produce is absorbed by the ocean, and most of it is photosynthesised by phytoplankton. The oceans produce 50 to 80 per cent of the oxygen on Earth, as much as all the land-based plants and forests combined, and Prochlorococcus, a picoplankton, is instrumental in this process.
Zooplankton are animals: sea butterflies, paddle worms, sea gooseberries, sea angels, mysid shrimps, arrow worms, water fleas, comb jellies, krill, ribbon
worms and giant lion’s mane jellyfish. They feed on phytoplankton and other zooplankton, which in turn are eaten by whales and fish. Every night, in the largest synchronised migration on the planet, zooplankton rise from the deep to feed at the surface of the ocean, returning to the depths at dawn. They vary greatly in size, from a fraction of a hair’s breadth to 50 m in length. Siphonophores, some longer than blue whales, are the longest animals in the world.
The calcium carbonate in the shells and skeletons of zooplankton form limestone. Millions of years ago, the Earth’s crust shifted and these rocks were brought to the surface. Without plankton there would be no pyramids, no Pantheon and no St Paul’s Cathedral. Their waste and decaying bodies fall to the seabed, with the carbon they contain, and over millions of years this forms gas, coal and oil, which we burn. Until recently, living plankton were able to absorb the carbon dioxide this produced, but now we are burning their ancestors so quickly that their ability to photosynthesise has been outpaced. The excess carbon dioxide causes global warming and makes the seas more acidic. The increased acidity is corroding the shells of plankton.
PLANKTON HELPED TO CREATE THE WORLD that brought us into existence, and even their remains help to maintain the biosphere in which we are able to survive. In North Africa, deposits of plankton, now dust, fertilise Amazonia. Once a lake, but now one of the driest parts of the world, the Bodélé Depression, on the southern edge of the Sahara, holds the remnants of plankton that once lived there. Every year the trade winds blow over the desert, lifting this dust high into the sky and carrying it for days until it settles on the Amazon basin. The phosphorus contained in the dust almost exactly replaces the amount of phosphorus washed away by the forest rains.
Krill eat phytoplankton. The cell walls of some of these plankton contain the molecule dimethyl sulphide (DMS), and when they break down, this chemical is released, giving the sea its unique smell. DMS rises into the atmosphere and reacts with light to form clouds. In this way, phytoplankton help to cool the planet. The odour of DMS also alerts seabirds to the presence of krill feeding on plankton. By eating the krill and defecating, the birds both protect and fertilise the plankton that drew them there.
More than 8 million tonnes of plastic enter our oceans each year, breaking into microscopic particles. In some places there are now six times as many of these microplastics as there are plankton.
Plankton eat the plastic, fish eat the plankton and we eat the fish. Through our food and water, it is estimated that each of us consumes, on average, a credit card’s weight in plastic a week; if you include what we breathe in, the figure is likely to be half as much again. Many of these particles are made from toxic chemicals, like phthalates and bisphenol A (BPA). Both are used in food packaging and mimic reproductive hormones, thus lowering fertility. Phthalates increase the incidence of premature birth, failure to ovulate and miscarriage; they impair the development of children’s brains and have been linked to breast cancer. The chemicals in plastics are also affecting the growth of Prochlorococcus, hindering its ability to photosynthesise.
Plankton, the tiny creatures at the base of the chain of life, perform heroically – absorbing carbon, producing oxygen and providing food for our food. For this generous cascade of bounty to continue as it has done for millions of years, all we need to do is look after their home.
Never think that you are too small to make a difference.
DO THEY KNOW OF THE RIVERS that await them? Of the grey heron, standing hunched in anticipation, of the shadows of trees and the smell of wet earth?
Their story begins 5,000 km away, in the warm waters of the Sargasso Sea, under a golden canopy of Sargassum algae. It is a sea with no shores, the only body of water in the world shaped not by land but by four spiralling currents. A thousand miles east of Bermuda, it is the size of central Europe, a sea of legend and the only known spawning ground of the European eel.
Their eggs are as round and clear as bubbles, with a drop of dark oil in their centre: the rich yolk, which will sustain their first days in the deep. They are born travellers. Only days old and less than 1 cm long, gummy and as fragile as tadpoles, they rise from the depths to brave the ocean and find a land they have never seen. What lures them away from their native waters no one knows. They partly swim but mostly drift, river pilgrims riding the warm pull of the Gulf Stream. Carried by currents, it might take them two years to reach Europe.
They begin their journey as leptocephali, ‘slim heads’. Their eyes are dark and large, their bodies transparent and flat, the shape of willow leaves, bending like sails to the ocean’s current. Closer to land, they lengthen, becoming tubular, their snout softer and rounder. As the swallows swoop in, the glass eels gather in estuaries from Britain to Russia.
It is thought that it is the smell of land that draws them, in time for the spring tides to carry them upstream. In fresh water they turn silver, to bootlace eels – elvers. No one knows why or how, but only then is their sex determined. They weave their way into alien, shallower, busier waters.
With heroic determination, they swim against the river’s current, clinging to pebbles for rest. Few are able to overcome the weirs, salmon leaps and dams many times their size. Females travel furthest, males preferring waters closer to sea. They are solitary, and once happy with a stretch of river, will make it their home for up to twenty years, feeding on worms, insects, molluscs and frogs, hiding from otters, herons and bitterns. Now dressed in a river glaze of muddy browns and dusty olive, flanked by a sheen of yellow, they disappear against the reeds and riverbed. Their scales, barely visible gills and movement are serpentine, but their large eyes – jet black and rimmed in silver – are those of a fish, as is their hooked mouth.
The eel ripples like reeds in the current. Its shovel-shaped head enables it to burrow under silt and hide between pebbles. Eels are shy creatures, hunting by night. In winter they remain coiled in a half-slumber, preserving the fat that will one day carry them home. Fully grown, their bodies are as thick as a fist and longer than an arm. They strike prey or flee with speed.
No one knows what makes them return to the sea. It happens on the turn of a new moon, on a wet, starless night in October, not long after the salmon have arrived and the rivers run high. Under the cover of darkness, they make their way downstream. Some avoid dams by travelling partly across land and watery ditches, their scales allowing them to breathe through their skin. As they reach estuaries, they adapt to the sea once more. Their skin thickens and their fins broaden, their underside darkens, their eyes enlarge and adapt, developing pigments for ocean vision, and their gut dissolves, making it impossible to eat. Throughout their 5,000 km journey to the Sargasso they have to rely solely on the energy stored during their river years.
To avoid predators, they remain in the depths, only swimming nearer the surface at night. They have been found in the guts of lantern and viper fish over 1,000 m down, but no one has followed their full migration nor seen them spawn.
For millions of years eels have travelled to the Sargasso Sea to breed. So far from land, this sea’s abundant life is also a mystery. It is one of the deepest parts of the Atlantic, home to corals, sponges, the endemic frogfish and creatures barely known to science. Humpback whales migrate through it, porbeagle sharks give birth in it, and it is a nursery for turtle hatchlings, which travel thousands of kilometres from the Americas. Flying fish make nests of bubbles among the Sargassum. Wahoo, rainbow runner and trigger fish feed below the seaweed canopy, and seabirds rest upon it.
In Britain, there were once so many eels that people caught them with pillowcases and held competitions to see who could eat the most. They were turned into fertiliser and fodder for chickens and pigs, but by 2015 their population had been so reduced that in the Elver Eating Championships at the Frampton Country Fair in Gloucestershire, eels had to be replaced by Spanish surimi, a paste in the shape of eels.
European eels refuse to breed in captivity. They can only be farmed once they are elvers, and for unknown reasons most of these become males. Although the export of European eels outside the EU is not permitted, each year around 350 million elvers are trafficked to Japan and China. If the measure of a wildlife crime were the number of animals traded, this would be the largest in the world.
In the last thirty years, stocks of baby eels have plummeted by 90 per cent. Rising temperatures are weakening the currents that carry them across the Atlantic. Man-made chemicals like polychlorinated biphenyls (PCBs), used until 1986 in flame retardants, adhesives, pesticides, lubricants, plastics, paint and paper – and still leaking into the environment – kill eel embryos and render the adults infertile. PCBs do not easily break down and are carcinogenic in humans. The turbines of hydropower stations break the eels’ spines and injure their internal organs; the loss of one female means the loss of the millions of eggs she is carrying. The turbines could be stopped during the twenty or so October nights of the eel run, and eel passes built.
It is estimated that of the 1 million eels that leave the Sargasso Sea each year, only one will return. We are adding terrible obstacles to their journey, putting their very existence at risk before we have even solved its mystery.
BEFORE CITIES WERE SO LARGE and so bright at night, anyone could look up and see it: Ngân Hà, the Silver River; Linnutee, the Way of the Birds; the backbone of the night; the road on which your ancestors are hunting ostriches. It is over 100,000 light years wide and 1,000 light years deep, 13.6 billion years old. It is our home galaxy, the Milky Way – a giant spiral of gas, stars and planets.
On a moonless night, on a small planet many thousands of light years from its centre, a beetle, shining black, is rolling a ball of dung across the African savannah. He is travelling backwards and upside down, and he is in a hurry to get home. He is 2.5 cm long. His head is pointed towards Earth, his back feet towards the stars, whose lights guide him. The beetle uses his head and powerful forelegs to balance himself in a forty-five-degree handstand as he reverses a ball many times his own weight, while his other legs steer it in a straight line. Every few minutes, he stops, climbs on top of the ball, does a 360-degree turn and looks up. He is Scarabaeus satyrus. Like harbour seals, indigo buntings, large yellow underwing moths and sailors, he navigates by the stars. The small pupils of his eyes are unable to distinguish between individual stars and constellations, and they see the light of the Milky Way as a single beam. He gets his bearing by taking a mental snapshot of the galaxy’s differing light gradients, which he refers to every time he climbs on top of the dung ball. How a brain the size of a sesame seed is able to remember such complexity and judge such infinitesimal changes, we don’t know. His species is the only one in the animal kingdom, besides our own, that is known to navigate by the Milky Way. He descends headfirst, back into position, and continues rolling through the undergrowth and out of sight.
There are over 6,000 species of dung beetle, each belonging to one of three families: the dwellers, which live in the dung pile; the tunnellers, which dig burrows directly beneath it and carry their share to nests underground; and the rollers. To prevent their dung being stolen, the rollers need to move it away from the pat the fastest way possible, so travel in straight lines. Some dung beetles are guided by the wind, keeping it on one side of their body when the sun is at its zenith.
Male and female dung beetles meet near pats of dung. The male will attract a female by doing a handstand while hitting his bristly back legs against his abdomen to release pheromones. He offers her a dung ball. Once paired, some species construct a brood ball together. The female climbs on top of the ball and he rolls her away.
With Circellium bacchus, one of Africa’s rarest dung beetles, the roles are reversed, and the female pushes the ball while the male trundles behind her. Once underground, with their brood ball safely buried, the female lays a single egg inside it, which will emerge the following spring. The mother coats the ball with saliva and more dung, until her egg is safely cocooned and surrounded by enough food. Unlike most other insects, which might produce thousands of eggs at a time and never meet their offspring, female Circellium bacchus will rear just one a year and may stay to watch over her grub, protecting and cleaning it, and, if need be, repairing the brood ball. Dung beetle pupae often fall prey to aardvarks and honey badgers. Once the egg has hatched, the pupae eat their way through the dung that surrounds them. Like butterflies and moths, beetles go through a complete metamorphosis, slowly growing from pupae to larvae to beetle. Now, hard- shelled, the beetle digs itself out of the ground.
Dung beetles are found on every continent except Antarctica. By clearing away dung, they clean the surface and fertilise the ground for fresh growth when young animals arrive in the spring. Dung beetles are thought to bury 70 per cent of the Serengeti’s dung. They aerate the soil and disperse seeds. In South Africa, those of the Ceratocaryum argenteum grass look and smell like the droppings of the bontebok antelope. This deceives the dung beetle, which buries the seeds underground and in doing so, plants them.
They are one of the few successful examples of species introduction: on Australian farms they have removed 90 per cent of flies. In parts of Texas, they have been known to bury more than 80 per cent of cowpats, reducing the need for synthetic fertiliser.
Their tunnels make the soil better able to absorb water and filtrate chemicals. By burrowing through pats, the beetles oxygenate the manure, killing the archaea microorganisms, which produce methane, one of the most powerful greenhouse gases. They are food for hundreds of other species, including the banded mongoose of Africa, the ornate box turtle of North America’s Great Plains and Europe’s greater horseshoe bat.
In Britain alone, their services to farmers are estimated to be worth hundreds of millions of pounds a year, but antiparasitic and antibiotic drugs given to livestock end up in their manure and damage the beetles. A quarter of British dung beetle species are now rare, four are extinct, and over sixteen are threatened by intensive farming. All over the world the populations of dung beetles are being reduced by habitat loss, agricultural chemicals and the absence of darkness. Researchers have found that where bush has been cleared for cattle, Scarabaeus satyrus has disappeared, and while it was once widespread across much of South Africa’s bushveld, Circellium bacchus is now restricted to national parks, where rhinos and elephants still roam.
Light pollution prevents 99 per cent of Europeans and North Americans from seeing the Milky Way. We are losing an important human experience. The loss of dark nights is bad for our health, but how much worse it is for the dung beetle, who lives and dies by stellar navigation. Humans might not need darkness as much as we need clean air and water, but we depend on species that do.
The ancient Egyptians recognised the importance of the dung beetle and believed him sacred, the embodiment of Khepri, who moved the sun across the sky and took it into the underworld at night, to emerge anew the next day. His constellation was the scarab, which we call Cancer. Today we are depriving ourselves not only of the beauty and wonder of the galaxy, but also of the services of this heroic and industrious little creature.
ATTENBOROUGH’S LONG-BEAKED ECHIDNA
IT IS DARK, BUT THE FOREST IS not quiet. Even in the night there are the cries of birds and the rustle of leaves being pushed aside. Into the clearing comes something that looks like a large hedgehog. At least that is what it would resemble, were it not for its long, cylindrical, downward-curving beak like that of a wader. Every now and then it stops to look for food in the damp leaves of the forest floor. This is an Attenborough’s long-beaked echidna, Zaglossus attenboroughi, one of the rarest creatures on the planet. So little is known about it that we have had to assume that its life parallels that of its cousin the short-beaked echidna.
There are four species of echidna, and they are thought to have existed longer than any other mammal; this is the smallest of them. Though a mammal, it lays an egg. At first, this grows inside the female, then it is laid into a pouch like that of a marsupial. After about ten days, a baby called a puggle hatches, feeding on its mother’s milk inside the pouch before emerging a few weeks later.
The powerful claws on its hind feet face backwards. To hide, it rapidly digs itself underground – cooling itself, hibernating and surviving forest fires. Its nose is sensitive to the electromagnetic radiation of its prey: earthworms, termites and ants.
The echidna’s survival kit – its defensive quills, its ability to bury itself, being nocturnal, preying on abundant food, its electromagnetic sensitivity – served it well for millions of years. It had no enemies on Papua New Guinea until the arrival of humans, who found this slow, gentle creature good to eat. Even then, echidnas were difficult to find, but hiding and quills are no defence against trained dogs.
Now the smallest of the echidnas is critically endangered. We are not even sure that Attenborough’s long-beaked echidna isn’t already extinct. The last time one was identified was in 1961, and it is conserved in the natural history museum in Leiden, laid out on grey paper and with a red label tied to one of its rear ankles, lest anyone forget its name. This species is a wonderful example of the possibilities of evolution, and a living link to a very distant past.