LIVING PLANET EB

David Attenborough

• Publisher: William Collins
• Year: 2021
• Print ISBN: 9780008477868, 9780008518585
• eBook ISBN: 9780008477844
• Topic: Biological Sciences
• Subtopic: Ecology
• Index: Biological Sciences

The Sunday Times Bestseller

A new, fully updated narrative edition of David Attenborough's seminal biography of our world, The Living Planet.

Nowhere on our planet is devoid of life. Plants and animals thrive or survive within every extreme of climate and habitat that it offers. Single species, and often whole communities adapt to make the most of ice cap and tundra, forest and plain, desert, ocean and volcano. These adaptations can be truly extraordinary: fish that walk or lay eggs on leaves in mid-air; snakes that fly; flightless birds that graze like deer; and bears that grow hair on the soles of their feet.
In The Living Planet, David Attenborough's searching eye, unfailing curiosity and infectious enthusiasm explain and illuminate the intricate lives of the these colonies, from the lonely heights of the Himalayas to the wild creatures that have established themselves in the most recent of environments, the city. By the end of this book it is difficult to say which is the more astonishing – the ingenuity with which individual species contrive a living, or the complexity of their interdependence on each other and on the habitations provided by our planet.
In this new edition, the author, with the help of zoologist Matthew Cobb, has added all the most up-to-date discoveries of ecology and biology, as well as a full-colour 64-page photography section. He also addresses the urgent issues facing our living planet: climate change, pollution and mass extinction of species.

ONE

The Furnaces of the Earth

The titanic forces that built the Himalayas and all the other mountains on earth proceed so slowly that they are normally invisible to our eyes. But occasionally they burst into the most dramatic displays of force that the world can show. The earth begins to shake and the land explodes.

If the lava that erupts from the ground is basalt, black and heavy, then the area may have been continuously active for many centuries. Iceland is just such a place. Almost every year there is volcanic activity of some kind. Molten rock spills out from huge cracks that run right across the island. Often it is an ugly tide of hot basalt boulders that advances over the land in a creeping unstoppable flood. It creaks as the rocks cool and crack. It rattles as lumps tumble from its front edge. Sometimes the basalt is more liquid. Then a fountain of fire, orange red at the sides, piercing yellow at its centre, may spout 50 metres into the air with a sustained roar, like a gigantic jet engine. Molten basalt splashes around the vent. Lava froth is thrown high above the main plume where the howling wind catches it, cools it and blows it away to coat distant rocks with layers of grey prickly grit. If you approach upwind, much of the heat as well as the ash is blown away from you, so that you can stand within 50 metres of the vent without scorching your face, though when the wind veers, ash will begin to fall around you and large red-hot lumps land with a thud and a sizzle in the snow nearby. You must then either keep a sharp eye out for flying boulders or run for it.

Flows of cooling black lava stretch all round the vent. Walking over the corded, blistered surface, you can see in the cracks that, only a few inches beneath, it is still red hot. Here and there, gas within the lava has formed an immense bubble, the roof of which is so thin that it can easily collapse beneath your boot with a splintering crash. If, as well as such alarms, you also find yourself fighting for breath because of unseen, unsmelt poisonous gas, you will be wise to go no further. But you may now be close enough to see the most awesome sight of all – a lava river. The liquid rock surges up from the vent with such force that it forms a trembling dome. From there it gushes in a torrent, 20 metres across maybe, and streams down the slope at an astonishing speed, sometimes as much as 100 kilometres an hour. As night falls, this extraordinary scarlet river illuminates everything around it a baleful red. Its incandescent surface spurts bubbles of gas and the air above it trembles with the heat. Within a few hundred yards of its source, the edges of the flow have cooled sufficiently to solidify, so now the scarlet river runs between banks of black rock. Farther down still, the surface of the flow begins to skin over. But beneath this solid roof the lava surges on and will continue to do so for several miles more, for not only does basaltic lava remain liquid at comparatively low temperatures, but the walls and ceiling of solid rock that now surround it act as insulators, keeping in the heat. When, after days or weeks, the supply of lava from the vent stops, the river continues to flow downwards until the tunnel is drained, leaving behind it a great winding cavern. These lava tubes, as they are called, may be as high as 10 metres and run for several kilometres up the core of a lava flow. In a striking example of how similar processes produce similar effects, lava tubes are even found on the Moon and on Mars.

Iceland is one of a chain of volcanic islands that runs right down the centre of the Atlantic Ocean. Northwards lies Jan Mayen; to the south, the Azores, Ascension, St Helena and Tristan da Cunha. The chain is more continuous than most maps show, for other volcanoes are erupting below the surface of the sea. All of them lie on one great ridge of volcanic rocks that runs roughly midway between Europe and Africa to the east, and the Americas to the west. Samples taken from the ocean floor on either side of the ridge show that, beneath the layers of ooze, the rock is basalt, like that erupting from the volcanoes. Basalt can be dated by chemical analysis and we now know that the farther away from the mid-ocean ridge a sample is taken, the older it is. The ridge volcanoes, in fact, are creating the ocean floor which is slowly growing away from them, on either side of the ridge.

The mechanism that produces this movement lies deep within the earth. Two hundred kilometres down, the rocks are so hot that they are plastic. Below them, the metallic core of the earth is hotter still and this causes slow, churning currents in the layers above, which rise up along the line of the ridge and then flow out on either side, dragging the basaltic ocean floor with them like solid skin on custard. Such moving segments of the earth’s crust are known as plates. And most of these plates carry on them, like lumps of scum, continents.

One hundred and twenty million years ago, Africa and South America were joined together, as you might guess from the jigsaw similarity of their coastlines and as is demonstrated by the likeness of the rocks on opposite sides of the ocean. Then, about 60 million years ago, a current welling up beneath this supercontinent created a line of volcanoes. A fracture developed across the supercontinent and the two halves slowly moved apart. The line of the split is today marked by the Mid-Atlantic Ridge. Africa and South America are still moving away from one another and the Atlantic is getting wider by several centimetres each year.

Another similar ridge, extending from California southwards, was responsible for creating the floor of the eastern Pacific. A third, running from Arabia southeast towards the South Pole, produced the Indian Ocean. It was the plate on the eastern side of this ridge that dragged India away from the flank of Africa and carried it towards Asia.

The convection currents that flow up at the ridges must clearly descend again. The lines along which they do so are where a plate meets that of a neighbouring system. It is here that continents collide. As India approached Asia, sediments on the sea floor between the two continents were crumpled and piled high to form the Himalayas, so the plate junction here is concealed beneath a mountain range. But farther along the same junction line, to the southeast, a continental mass exists on the Asian side only. The line of crustal weakness, therefore, is much more exposed and is marked by a chain of volcanoes that runs down from Sumatra through Java to New Guinea.

The descending convection current sucks down the ocean floor, creating a long deep trench. This runs along the southern coast of the Indonesian chain. As the edge of the basaltic plate descends, it takes with it water and much of the sediment that was eroded from the Indonesian land mass and had been lying on the ocean floor. This introduces a new ingredient into the melt deep in the crust, so that the lava that wells up into the Indonesian volcanoes is crucially different from the basalt issuing from a mid-ocean ridge. It is much more viscous. In consequence, it does not pour out of cracks or flow like a river, but congeals in the throat of the volcanoes. The effect is like screwing down the safety valve of a boiler.

It was one of the Indonesian volcanoes that produced one of the most catastrophic explosions yet recorded. In 1883, a small island named Krakatau, 7 kilometres long by 5 kilometres wide, lying in the straits between Sumatra and Java, began to emit clouds of smoke. The eruptions continued with increasing severity day after day. Ships sailing nearby had to make their way through immense rafts of pumice that floated on the surface of the sea. Ash rained down on their decks and electric flames played along their rigging. Day after day, enormous quantities of ash, pumice and lava blocks were thrown out from the crater, accompanied by deafening explosions. But the subterranean chamber from which all this material was coming was slowly emptying. At 10 a.m. on 28 August, the rock roof of the chamber, insufficiently supported by lava beneath, could bear the weight of the ocean and its floor no longer. It collapsed. Millions of tons of water fell on to the molten lava in the chamber and two-thirds of the island tumbled on top of it. The result was an explosion of such magnitude that it produced perhaps the loudest noise ever to echo round the world in recorded history. It was heard quite distinctly over 3,000 kilometres away in Australia. Five thousand kilometres away, on the small island of Rodriguez, the commander of the British garrison thought it was the sound of distant gunfire and put out to sea. A tempest of wind swept away from the site and circled the earth seven times before it finally died away. Most catastrophic of all, the explosion produced an immense wave in the sea. As it travelled towards the coast of Java, it became a wall of water as high as a four-storey house. It picked up a naval gunboat, carried it bodily nearly 2 kilometres inland and dumped it on top of a hill. It overwhelmed village after village along the thickly populated coast. Over 36,000 people died.

The biggest explosion of the 20th century occurred on the other side of the Pacific, where the eastern edge of the Pacific plate grinds along the western coast of North America. Once again, there is continental cover on only one side of the junction, so the line of contact is not deeply buried. But because continents are made of rocks that are lighter than basalt, they override the downwards-plunging oceanic plate and the line of volcanoes breaks through some 200 kilometres inland from the coast. And once again, the lava that rises up in them carries the sedimentary ingredient that makes them catastrophically explosive.

Until 1980, Mount St Helens was famous for the beautiful symmetrical shape of its cone. It rose nearly 3,000 metres high and was crowned with snow the year round. In March that year, warning rumbles began to come from it. A plume of steam and smoke rose from its peak, dusting its snow cap with streaks of grey. All through April, the column of smoke grew. Most ominous of all, the northern flank of the mountain, about 1,000 metres below the summit, began to bulge outwards. The swelling grew at a rate of about 2 metres a day. Thousands of tons of rock were being pushed upwards and outwards. Every day there were fresh spouts of ash and smoke from the crater above. Then, at half past eight on the morning of 18 May, the mountain exploded.

The northwest face, about a cubic kilometre of it, simply blew out. The pine, fir and hemlock trees that had clothed the lower slopes of the mountain, over an area of 200 square kilometres, were laid flat, as though they were matches. An immense burgeoning black cloud rose above the mountain, towering 20 kilometres into the sky. Few people lived close to the volcano and there had been a lot of warning, but even so sixty people were killed. Geologists estimated that the force of the explosion was 2,500 times as powerful as the nuclear blast that destroyed the city of Hiroshima.

Nothing can live on a volcano immediately after its eruption. If there has been an explosion, steam, smoke and poisonous gas will continue to billow up from the wreckage of rocks in the crater for weeks. Nor can any organism survive the heat of the basalt flows that issue from the volcanoes of the mid-ocean ridge. If any parts of the earth are sterile and lifeless, it must be sites such as these. But if the convection currents deep beneath the surface shift slightly, the ferocity of the volcanic furnaces begins to wane. In these later stages, a dying volcano often produces eruptions not of lava but of scalding water and steam. Part of this water existed in the magma, and part is from the natural water table of the earth’s crust. It carries, dissolved in it, a great variety of chemical substances. Some will have come from the same deep source as the lava, others have been dissolved from the rocks through which the hot water passed on its way to the surface. Among them are compounds of nitrogen and of sulphur, often in such concentrations that the water can serve as food for very simple living organisms. Indeed, it is possible that the very first forms of life to appear on earth originated in just such circumstances, some 3.6 billion years ago.

At that unimaginably distant time, the earth had not yet acquired its oxygen-rich atmosphere and the position and shape of the continents bore no relation to their present distribution. Volcanoes were not only very much larger than those of today, but were very much more numerous. The seas, whether they had been brought by cometary bombardment or had condensed from clouds of steam that surrounded this new planet, were still hot and water was still gushing into them from volcanic sources deep in the crust. In these chemically rich waters, complex molecules were forming. Eventually, after an immense span of time, tiny microscopic specks of living matter appeared. They had little internal structure, but they were able to convert the chemical substances in the water into their own tissues, and to reproduce themselves. These populations of single-celled organisms can best be thought of as akin to bacteria.

Bacteria today are of many different kinds, and practise a great variety of chemical processes to maintain themselves. And they are found throughout the land, the sea and the sky. Some even still flourish in volcanic environments which may well parallel the circumstances in which they first arose.

In 2010, researchers dredged up mud from a volcanic hydrothermal vent deep in the arctic sea, known dramatically as Loki’s Castle. After five years of extensive study, they were able to identify in the mud the presence of DNA from a unique form of bacteria, the Lokiarchaeota. These organisms seem to stand at the crossroads of various forms of single-celled life, and in some respects resemble the ancestor of all multi-cellular life. In other cases, complex ecologies have been discovered at such sites. In 1977, an American deep-sea research ship was investigating underwater volcanoes erupting from a ridge south of the Galapagos Islands. Three kilometres below the surface of the ocean they found vents on the sea floor that were spouting hot, chemically rich water into the sea. In these jets, and in the crevices of the rocks around the vents, the scientists discovered great concentrations of bacteria consuming the chemicals. The bacteria, in turn, were being fed upon by immense worms, up to 3.5 metres long and 10 centimetres in circumference. They were unlike any other worms so far encountered by science, for they had neither mouth nor gut and they fed by absorbing the bacteria through the thin skin of feathery tentacles, rich in blood vessels, that sprouted from their tip. Since these organisms live in the black depths of the ocean, they are unable to tap directly the energy of sunlight. Nor can the worms obtain it second-hand from the falling fragments of dead animals drifting down from above, since they have no mouths. Their food comes entirely from the bacteria which in turn derive their sustenance from the volcanic waters. Indeed, the worms may well be the only large animals anywhere that draw their energy entirely from volcanoes.

Alongside the worms lie huge clams 30 centimetres long which also feed on the bacteria. The rising jets of hot water create other currents which flow towards the vents across the sea floor, bringing with them organic fragments which are eaten by other organisms – strange, hitherto unknown fish and blind white crabs – clustering around the clams and the worms. So in these submarine volcanic springs, a dense and varied colony of creatures flourishes in the darkness.

Hot springs also bubble up on land. The water they produce, which originates partly from sources far below and partly from rainwater that has permeated deep into the ground, has been heated by the lava chamber and so forced up again through cracks in the rocks, like water up the spout of a boiling kettle. Sometimes, because of the particular geometry of these conduits, the upward progress is spasmodic. Water accumulates in small subterranean chambers and becomes superheated under pressure until finally it flashes into steam and a column of water spouts to the surface as a geyser. In other cases the upward flow is more regular and then the water forms a deep, perpetually brimming pool. It may be so scaldingly hot that the surface steams, but even at these temperatures bacteria flourish. Growing with them here are slightly more advanced organisms – blue-green algae. These appear scarcely more complex in their internal structure than the bacteria but they contain chlorophyll, a remarkable substance that, by employing some astonishing physics, are able to to use the energy of the sun to convert chemical substances into living tissue, releasing oxygen as they do so.

Such organisms are found in the hot springs of Yellowstone in North America. There the algae and bacteria grow together to form slimy green or brown mats that cover the bottom of the pools. Algae have also thrived in upper layers of the sea for billions of years, turning sunlight into carbon and ultimately creating the vast underground seas of oil that have been burned by humans over the last century.

Nothing else can survive in the hottest parts of the springs occupied by these mats, but where the pool spills over to form a stream, the water cools slightly and so allows occupation by other creatures. The algal mats here are so thick that they break the surface. This living dam diverts the main flow to another freer part. As the water slowly trickles through, it cools further and above it assemble clouds of brine flies. If parts of the algae are cooler than 40°C, the flies settle. Some of them mate and lay their eggs on the algae and soon there are grubs grazing voraciously, pupating when they are large enough. But they are working towards their own destruction or that of their descendants, for as they chew away at the mat, so they weaken it. Eventually, it breaks up, the channel clears and much hotter water from the pool gushes down it, sweeping away the remains of the algae and killing all the grubs that were feeding on it. But enough will have hatched for the flies to survive this setback and to start the process all over again in another part of the spring.

In colder parts of the world, the dwindling heat of a volcano may represent not a hazard but a haven. The line of volcanoes that built the Andes along the junction of the South American and eastern Pacific plates continues south and east into the southern ocean to form several small arcs of volcanic islands. Bellingshausen is one of a group called the South Sandwich Islands. The ferocious Antarctic seas have cut into its base, creating, on one side, a cliff which displays, with textbook clarity, alternating layers of ash and lava, cut through with zig-zag lines of lava-filled pipes. Ice floes rim it like a tattered white skirt and sheets of snow drape its slopes. Battalions of Adelie penguins march all over this white parade ground. If you climb up through their ranks to the top of the volcano, you find a vast gaping pit, half a kilometre across. Its floor is filled with snow, icicles hang from the jutting rocks in its throat and snow petrels, elegant pure-white birds, nest in the crags just beneath the crater’s lip. But its volcanic fires have not been totally extinguished. In one or two places around the rim, steam and gas still spurt from cracks, filling the air with the stench of hydrogen sulphide and coating the boulders with brilliant yellow encrustations of sulphur. The ground around the vent is warm to the touch so, as the polar gales bite into you, it is a pleasant place to crouch, in spite of the smell. And on the rocks at your feet, surrounded by snow, there are lush cushions of mosses and liverworts.

These few small patches are the only places in the entire island where it is warm enough for plants to grow. The islands are as isolated as any in the world. The Antarctic continent and the tip of South America are both some 2,000 kilometres away. Yet the spores of these simple plants are so widely dispersed by winds throughout the atmosphere of the world that even these tiny isolated sites in this hostile island are colonised just as soon as they become habitable.

It is not only in the bitterly cold parts of the world that organisms take advantage of volcanic heat. Even tropical creatures have learned how to exploit it. The megapodes are a group of birds living from Indonesia to the western Pacific which have developed extremely ingenious methods of incubating their eggs. Typical of them is the mallee fowl of Australia. When this remarkable bird nests, it first digs an enormous pit that may be 4 metres across, fills it with decaying leaves and then piles sand on top of it. Into this great heap, the female excavates a tunnel and there she lays her eggs. The male fills the tunnel with sand and relies on the heat produced by the rotting vegetation to keep the eggs warm. But he does not abandon them. On the contrary. Several times a day, he returns to the mound and pokes his beak into the sand. His tongue is so sensitive that he can detect a change in heat of one-tenth of a degree. If he considers that the sand is too cool for the eggs, he will pile on more; if too hot, he will scrape it away. Eventually, after an unusually long incubation, the young mallee fowl chicks dig their way up to the surface of the mound, emerge fully-feathered and scamper away.

The mallee fowl, however, has a relative in the Indonesian island of Sulawesi called the maleo. This creature buries its eggs in black volcanic sand at the head of beaches. Being black, this sand absorbs the heat and gets quite hot enough in the sunshine to incubate the eggs. Other maleo have left the coast and colonised the slopes of a volcano inland. There they have discovered large areas of ground that are permanently heated by volcanic steam; and there a whole colony regularly lays its eggs. A dying volcano has become an incubator.

Eventually, as the plates of the earth’s crust move and the currents beneath shift, volcanoes do become completely extinct. The ground cools and animals and plants from the surrounding countryside move in to colonise the new, sterile rocks and the devastated land. Basalt flows present considerable problems to the colonists. Their shiny b...

Table of contents

• Title Page
• Copyright
• Contents
• Preface
• Prologue
• 1 The Furnaces of the Earth
• 2 The Frozen World
• 3 The Northern Forests
• 4 Jungle
• 5 Seas of Grass
• 6 The Baking Deserts
• 7 The Sky Above
• 8 Sweet Fresh Water
• 9 The Margins of the Land
• 10 Worlds Apart
• 11 The Open Ocean
• 12 New Worlds
• Picture Section
• Index
• Acknowledgements
• About the Author
• Other titles by David Attenborough
• About the Publisher