Seeing Further: The Story of Science, Discovery, and the Genius of the Royal Society - Bill Bryson (2010)

17. OLIVER MORTON

GLOBE AND SPHERE, CYCLES AND FLOWS: HOW TO SEE THE WORLD

Oliver Morton is a writer, currently working for The Economist. He is the author of Mapping Mars and Eating the Sun, and currently at work on a book about geo-engineering.

THE PICTURES OF THE EARTH FROM SPACE BROUGHT HOME BY THE APOLLO ASTRONAUTS TRIGGERED A NEW AWARENESS OF OUR PLANETARY HOME WHICH FED INTO NEW SCIENCE. BUT THE VIEW OF OUR PROBLEMS FROM ASTRONOMICAL DISTANCE IS AN ODD ONE, AS OLIVER MORTON EXPLAINS.

‘I know we’re not the first to discover this,’ Gene Cernan radioed back from about 29,000 kilometres, ‘but we’d like to confirm, from the crew of America, that the world is round.’ Apollo 17 had been thrown up into the night sky over Florida five hours before, but for most of that time the command module America and its lunar module Challenger had been in low orbit. Only now, having been kicked off to the Moon by the last stage of their Saturn V booster, were the astronauts far enough away to see the planet as a whole. Challenger was to land on the edge of the Moon’s face as seen from the Earth, rather than near the centre, as previous missions had done, and this meant that Apollo 17 was the first of its kind to head off more or less straight into the Sun, thus allowing Cernan and his crew an unprecedented look back at the shadowless face of the noon-time Earth.

Their photographic record of that view, it is often claimed, is the most reproduced photographic image in history; given that it is free to use, beautiful and moving, the claim seems not unlikely. Taken from the window of the America without the benefit of a viewfinder, the almost-perfectly circular image is dominated by blue oceans and white cloud, an obscuring and captivating pattern which makes the picture clearly and immediately something other than a map. This is a body in space, three-dimensional, a highlight glinting off the ocean, the features at the edge distant and foreshortened. But in this picture, unlike those taken from the Moon itself, there is no doubting what the bewitching body is. The mass of Africa, though centred in a way no traditional map maker would think of, is unmistakable. 

When, in late 1946, George Orwell wondered in an essay how he would convince a committed sceptic that the Earth was spherical,1he concluded with some reluctance that he would be unable to do better than appeal to the authority of astronomers and to the utility of charts that astronomical observations made possible. Twenty-five years on, the figure of the planet became a matter of direct observation for the select few, and of photographic fact for the rest. There was no longer any need to rely on the astronomer’s authority; by looking at the Apollo pictures one could in effect become an astronomer.

The ability to see the Earth as an astronomer would another planet marked a fundamental shift, the long-term effects of which we still cannot gauge. It has provided valuable new perspectives and treasure troves of data. But no image can reveal everything; and every revelation obscures something. For all that it is an image of the whole, the vision of the Earth from space is necessarily partial. By leaving things out, it makes the Earth too easy to objectify, too easy to hold at a distance, too easy to idealise. It needs to be offset by a deeper sense of the world as it is felt from the inside, and as it extends out of view into past and future. Because of the changes we are putting the planet through, we need as many ways of looking at and thinking about it as we can find. We need ways to see it as a history, a system, and a set of choices, not just a thing of beauty – one which, from our astronomical perspective, we seem already to have left. There are other ways to see the beauty of the world than in the rear-view mirror of progress.

This needs to be stressed in part because the astronomer’s gaze is a peculiarly powerful, seductive thing; it is not just thin air that brings dizziness to mountain-top observatories. Its charms are those of photography in general; a form of seeing more removed from direct experience, and frequently from obvious meaning, than any other, its subjects unavailable to any cross-examining form of scrutiny. Like photography, astronomy looks, takes joy in looking – but can do no more than keep looking. 

In their desire to see and see again, astronomers are particularly well served. Many of the objects of their gaze are eternal and predictable, travelling into our future according to knowable rules. The universe reveals itself in rhythm and return. This is one reason why the visions of astronomy have often stood as an emblem for all the other precise, disinterested but forward-looking observations of science.

Spectacular gains have been made by turning the astronomer’s gaze on the Earth. The wetness of clouds, the strength of winds, subtle shifts in the shape of the sea’s surface, the thickness of smogs, the colours of the savannah: all are now available on a worldwide scale. Not only can everything be seen: in some of these images, like that icon from Apollo 17, we seem to see everything at once, the Earth entire. It was this completeness which, in the 1970s, gave such images a key role in both the inception and reception of James Lovelock’s ideas about Gaia, the self-regulating Earth system – ideas presented, in the subtitle of his first book, as ‘A New Look at Life on Earth’.2

Such images made clear what Arthur C. Clarke had suggested years before: the archetype for space travel was the Odyssey, an adventure completed only in its moment of return. The view that little ship of Apollo brought back gave new reality to the notion, first voiced by Adlai Stevenson in 1965, of ‘Spaceship Earth’: like the smaller ships, the larger one was a prerequisite for its crew’s survival, isolated, fragile. The image of the living Earth as seen from space became a rallying point for environmental activism, an ever-present rebuke to those who would deny the environment’s fragility, the finitude of its resources, the limits that it must surely impose on us. It turned the primary concern of the ‘space age’ from the outward urge of a few to the common heritage of the many.

In ‘Globes and Spheres: The Topology of Environmentalism’,3 the anthropologist Tim Ingold voiced an elegant dissent to the way that heritage was represented by those pictures. The global environmental movement represented by that objectified, photographed Earth, he argued, was an oxymoron; the environment of a globe is what lies outside it, not what lies within. Thinking about the environment ‘from the outside’ was a contradictory pursuit that showed a rationalist, map-making mentality taken to its ultimate extreme. To give the planet as a whole precedence over everything it contains, he thought, hid the realities of life as it is lived, and was thus inimical to a deeper-rooted form of environmental awareness. ‘The notion of the global environment,’ he wrote, ‘far from marking humanity’s reintegration into the world, signals the culmination of a process of separation.’

The Earth does, as it happens, have an environment in the surrounding sense, a space environment that is both nurturing (a magnetosphere that keeps cosmic rays at bay), a little alarming (near-Earth asteroids, which have in the past caused spectacular calamities and even mass extinctions) and increasingly besmirched (600,000 pieces of space junk and counting). Recognising this cosmic connectedness may in time help to expand our notion of the world we live in, providing new perspectives of its own. But that is not Ingold’s point; his point is that to see the earthly environment as something out there and separate is to misunderstand what an environment is.

To agree with Ingold is no to say that everything must be local first and last, nor to deny that there are environmental problems on a planetary scale. It is to say that they are not the planet’s problems. They are ours. The drawback of space-age iconography is that it has made the Earth itself the focus of environmental action, the thing at risk, the mother to be celebrated on a consecrated Earth Day. This way of speaking about the planet in peril, of invoking a need to ‘save the Earth’, suggests either that the needs of people and the needs of the planet are directly opposed – or, at best, that human needs can be reduced to planetary needs.

This line of thinking runs the risk of leading us into futility and sin. Take the futility first. The Earth and its biosphere have, after all, been through far greater, if not faster, fluctuations in temperature than those currently underway. At the hands of those pesky asteroids it has undergone calamities far more sudden. Its seas have frozen; its continents have been licked with flame. Yet even when it has lost species by the bushel, the biosphere has endured, and in the aftermath flourished. Human agriculture, by contrast, is terrifyingly fragile, largely developed during ten millennia of climatic stability, already thin-stretched over too much of the Earth, with ever more people to feed. The late, great comedian George Carlin summed up the true stakes with foul-mouthed pith: ‘There is nothing wrong with the planet – the planet is fine. The people are fucked.’

This leads on to the question of morality. To focus on the planet, and not on its people, is wrong; to assume that their interests are identical is to ascribe to the planet attributes it does not possess. It is not an abstracted Earth floating in the velvet vault of space that needs protecting; it’s the people inhabiting that world who are at risk of harm, particularly poor people who lack the resources to adapt, to migrate or otherwise to opt out of what is happening to them.

And yet ‘planet in peril’ rhetoric and attendant catastrophic imagery is everywhere. A quick Google search reveals there to be seven, ten, five, four or eight ‘years to save the planet’, depending on your headline writer and expert of choice (‘Eleven years to save the planet’ seems at the moment a rallying cry still up for grabs). It may be that ‘planet’ here is being used simply to mean the environment on which humanity depends. But this way of talking still acts to raise some abstract notion of the environment above the problems that people actually face, many of which are not environmental. The debates needed to assign priorities to human development, to the reduction of consumerism, to the health of the world’s children – important topics all – cannot be reduced to a question about what is good for the planet. Using the planet as a polar bear writ large, a photogenic emblem of the imperilled, obscures more than it illustrates.

At the same time, rather reprehensibly, planet in peril rhetoric trades on a terrible new form of the feeling of the sublime. We are so powerful and so bad, it says, that we threaten the tough old planet itself; we flatter our human power even while condemning it, seeing ourselves as a problem too big to solve. Thus the old vision of humans as vulnerable to an overpowering nature is reversed. The unstoppable threat is us – and we stand aside, wringing our hands but secretly in awe, as that threat sweeps on. 

How better, though, can people see the world than as a fragile blue marble separated from their own experience, cut off from any cosmic continuity by a sharp 360° horizon? And why, given the objective truth of the world as revealed by Apollo, should we even try? To the second question, the answer is that there is more than one way of seeing, just as there is more than one way of speaking. There are times when seeing the Earth as a discrete object, a thing in a picture, is peculiarly helpful; there are times when something else is called for.

Contemporary artists have been confronting this issue for decades. History offers any number of fine traditions of landscape art, in both paint and photography, and invoking a variety of responses in their intended viewers. But more recently something new has arisen: art that seeks not merely to reproduce, or evoke, what it looks like, but to involve it in the artistic process directly, to provide art in which viewers meet the world, rather than just contemplate it – an art that interacts. The British artists Ackroyd and Harvey use the growing of grass as a medium with which to reimagine architecture and photography; Richard Long is fascinated by the traces, material and immaterial, left by walking, and how they can be shared; David Nash grows trees into sculpture while Tim Knowles lets them trace out their own drawings, guided only by the wind; and Andy Goldsworthy imprints and erases ideas on the landscape. As David Nash puts it: ‘I think Andy Goldsworthy and I, and Richard Long, and most of the British artists’ collectives associated with Land art, would have been landscape painters a hundred years ago. But we don’t want to make portraits of the landscape. A landscape picture is a portrait. We don’t want that. We want to be in the land.’ 4

Ingold’s response to the inadequacy and contradiction he perceived in the Earth seen as a blue marble was very similar: to look for ways of thinking that put you in the land, rather than just looking at a portrait. He contrasted the outside-in view with cosmologies that look on the world, or cosmos, as a set of spheres experienced from the inside out. Cultures from Ancient Greece to the Inuits have found ways to layer and interpret their worlds in such nests, privileging the local while connecting it to the cosmos. I would not want to suggest that cosmologies should be chosen on aesthetic or practical grounds, assembled piecemeal from those of other cultures, or generated on the basis of what they have to offer. But it seems to me that there is an appealing way of casting the nested-sphere view in the concepts of modern science that does no disservice to that science: transform the spheres into cycles.

Throughout the twentieth century, the Earth sciences have increasingly treated their subject in terms of cycles, whether the oscillations of the atmosphere or the circulation of the core. The past fifty years have seen acceptance of the Milankovitch cycles – subtle variations in the Earth’s orbit and attitude – as the causal framework for the ice ages, with ice sheets waxing and waning to their heavenly rhythms. They have seen Earth’s magnetic field revealed as a creature that rocks back and forth from North to South, the plaything of dynamic currents circulating in the planet’s core. Most fundamental of all, they have seen the uncovering of the great three-dimensional cycles of plate tectonics, in which the slow and mighty overturning convection of the mantle is coupled to the opening and closing of oceans, the merging and scattering of continents.

In the 1950s Victor Goldschmidt, frequently described as the father of modern geochemistry, put cycles at the centre of that discipline’s study of the Earth, defining it in terms of ‘the circulation of elements in nature’. Both geochemistry and biogeochemistry remain studies of cycles – in the latter case, quite intimate ones: the carbon dioxide given back to the plants with each animal breath, the nitrogen returned to the world in each drop of urine. The ‘Earth Systems Science’ that emerged in the 1980s and 1990s, often informed by Lovelock’s Gaia, assembled ideas from all these disciplines and subdisciplines into further cycles, cycles made not of matter, but of cause and effect: feedback loops that could stabilise the Earth system or force it into flip-flop oscillations.

Like the components of an astrolabe, the cycles of the Earth system seem to nestle within each other, arranged not by size – they are all, in the end, the size of the planet – but by intimacy and speed, reaching out from the food in our bellies and the wind on our faces to the vastest of vegetable empires and the yet slower, greater mineral realm. Our sweat, once evaporated, spends only days in the sky before falling back as rain. The carbon dioxide we breathe out may be in the air for decades before being eaten up by plants, or take refuge in the oceans for millennia before resurfacing. Other cycles are slower still. While nitrogen compounds can be pumped from sea to sky by microbes, once phosphorus makes its way from soil to the sea it has no easy way back to the atmosphere, and must wait millions of years before, incorporated into sediments, it is lifted up into new mountains to fertilise the soils again. The cycles interpenetrate in such ways all the time, passing through each other in a daunting clockwork of teeth and differentials, their nesting anything but neat, their gearing prone to glitches.

Such a vast machinery seems more daunting to the imagination than a blue marble in space. But while what is circulating, and how it circulates, can be hard and complex questions to fathom, the idea that the world is endlessly recycling itself is an easy perception to train oneself into. The growth of a plant, or the erosion of a gully, are easily seen. And to see a plant grow armed with the knowledge that it does so out of thin air – that is, after all, where the carbon that makes up most of its mass comes from – is to realise that something else must be restoring that nutritive goodness to the atmosphere. To see water cutting into highland rock and washing soil downstream is to realise that, if this is going to go on indefinitely, there must be some way of making new highlands to replace those endlessly whittled away. When Joseph Priestley and James Hutton first had these insights in the eighteenth century they were hard-won breakthroughs. But once known, they become compellingly obvious; it is hard to see how things could be otherwise in a world that endures.

This dynamic image of the Earth is a corollary of one of the most striking aspects of that timeless, static image of the Earth in space: its limits. The Earth is, in material terms, isolated. Very little arrives (those asteroid impacts are few and far between), and only a whisper of gas escapes. Everything else must be endlessly recycled: and so it is. The rain becomes the ocean and the ocean becomes the rain, the mountains are ground down to cover the sea-floors with silt, ancient silts rise up to make new mountains. Nothing stays the same, and yet the system, mostly, persists. Everything is in flux, but nothing is at risk.

And this flux illustrates perhaps the most useful sense of that unhappy phrase, the ‘balance of nature’. Nature was not designed to balance, any more than it was designed for anything else. It does not have preferred states with which people meddle at their peril, or that carry some sort of moral weight, or to which it wishes necessarily to be restored. It is precisely to the extent that the Earth is off balance that it works; its rolling cycles are like wheels on slopes. But if there is no static equilibrium, there is balance of another sort – a balance like that of a bank account, its debits and credits constrained always to match over time. For every output there must be an input. Any earthly process not looped back on itself in some way, anything that does not carry the seeds of its own recreation, will either be remarkably slow, or will have run its course long ago, or only just have started. Otherwise it will simply run out of credit.

The existence of the Earth’s great recycling can thus be explained by the fact that, in terms of material, it is a closed system. But to explain it this way is immediately to need something more; a source of energy that comes from beyond the system that it powers, and provides the slopes down which the wheels roll. There is work going on in those cycles – pumping, breathing, lifting, grinding – and work can only be done where there are flows of energy. The second law of thermodynamics, the bane of the perpetual-motion-machine designer, means that such flows of energy cannot, themselves, be recycled; the same energy cannot do the same work twice. If work is to be done continuously, fresh energy needs to be provided continuously, and old energy – waste heat – needs to be disposed of. A world closed in one way must be open in another. The Earth depends on there being a beyond.

The Earth’s circulating carbon atoms and continents and other constituents depend on three streams of energy from the beyond – and, in the case of the heat of the Earth’s interior, from the before as well. Almost all the energy that now comes from within the Earth was put there, in one form or another, at the time of its creation (a tiny amount is now added by the flexing of the planet under the tides of Moon and Sun, but it is the merest smidgen). One stream of energy stems simply from the immense store of heat generated when a planet’s worth of gas and dust fell in upon itself, the ingredients smashing into each other in ever larger pieces and at ever greater speeds as the process went on. The Earth thus started off with vast supplies of heat inside it, and a rocky planet, like any other rock, takes a long time to cool down. Stones in a campfire may still be hot the morning after; a stone the size of the Earth can hold heat for billions of years.

Then there is the heat generated since the Earth’s creation from energy stored up long before. The chemical elements on Earth that are heavier than helium were created in stars that burned out before the Sun and Earth were born, the vast pressures in their hearts squeezing hydrogen into carbon, silicon, oxygen, nitrogen and iron. When such stellar furnaces explode into supernovae, the energies unleashed become great enough to forge elements even heavier. In the case of elements such as uranium and thorium, those great energies will, in time, leak out. The radioactive elements gathered into the Earth at the time of its creation have steadily meted out the supernova energies stored within them. Thus energy from dying stars helps drive the great internal convection currents which move tectonic plates.

Both these streams of energy, though, are small compared to that which rains down from above. The most easily overlooked and perhaps most fundamental feature of the Apollo 17 picture of the Earth is its brilliant over-the-shoulder illumination. Yes, the Earth floats in pitch-black space – but it floats in sunlight, too. It floats in a torrent of the stuff. The upward flow of ancient heat to the Earth’s surface is measured in tens of milliwatts per square metre; the flow from the Sun above is measured in hundreds of watts per square metre. This is the energy that warms the surface and the sky above it, that drives the circulation of atmosphere and ocean. This is the energy of cloud and rain, of sand dune and hurricane. This is the energy which powers the cycles of the biosphere. When plants fix carbon, when bacteria fix nitrogen, when plankton release sulphur from sea-water back into the sky, they do so, directly or indirectly, with solar energy. It is the energy of forest fire and Sunday lunch.

These solar-powered cycles of the biosphere are the ones in which humans are most intimately involved, both as beneficiaries and as rearrangers. Since the development of artificial fertilisers, the nitrogen cycle has come under human control to a remarkable extent, though not in a centralised way. The plough, the field, the roadworks and the building site have increased the rate of erosion far beyond its geological average; the rate at which water flows out of rivers depends on farmers and dam-makers.

And then there is the rate at which ancient sunlight stored in fossil form is used to drive the engines of industry and civilisation. The amount of energy actually liberated in the burning of these fossil fuels is tiny by planetary scales – ten terawatts or so a year, not that much more than the nugatory contribution made by the tides. But the side effects are huge. The carbon dioxide liberated in the burning renders the atmosphere less transparent to the flow of outgoing heat; with the flow thwarted in this way, the temperature at the surface goes up. The resultant warming is, in terms of energy flows, about one hundred times larger than the amount of energy released by the fossil fuels. 

This great short-circuiting of the geological carbon cycle, though, reveals one of the strengths of seeing the Earth in terms of its turning dynamics. In the purely human realm, cyclic theories of history tend to engender a feeling of hopelessness – the cycle will roll on, regardless. But, perhaps surprisingly, a view of the Earth that focuses on its relentless cycles and the flows of energy that drive them can be empowering. It is a view of the planet in which we are already involved, for good or ill, and to which we can make changes for better or for worse. These are cycles we can use. The Earth seen as a bauble in space is what it is – just a sight, not an experience. The only injunction that is possible faced with that gorgeous globe is ‘sustain’. Sustain the gaze; sustain the object. The Earth as an encompassing nest of cycles is a world which we are always already involved with, a Land-art world in which intervention is of the essence. This way of seeing makes things at once more frightening – this is the lived environment of wind in the face and water in the tap at risk, not some idealised representation – and more tractable.

Recognising the openness of the Earth system and the flows of energy that power it offers the clearest way of seeing the solution to the current global environmental crisis. If the manner in which humans currently reap their energy from fossil fuels ties the flow of energy to the material flow of the carbon cycle in a deeply damaging way, we must simply find other flows to tap. Energy is flowing through the winds, in the currents of the oceans, in the rivers, in the growing of the grass. It flows out of the ground and down from the sky. Geothermal plants can speed the flow of heat from the depths; kites in the stratosphere can harvest the endlessly circulating jet streams; mirrors in the deserts can drive turbines with sunshine. There is energy of all sorts flowing through our world; it is not hard to imagine new ways in which that energy can do the work of humanity, new ways to align our needs and the planet’s behaviours. And if that capacity for work is harnessed, many other problems can be solved. The carbon cycle could be expanded, the biosphere’s capacity for drawing carbon dioxide from the air increased and the greenhouse effect thus diminished. Other waste can be recycled, too, and material resources thus renewed; with a great enough flow of energy from beyond, any closed system can sustain itself with recycling.

The Earth of cycles can hardly be the icon that Apollo’s Earth has become; it is more a hum than a sight. But it is a valuable way of thinking of the Earth from inside, of seeing the human and the inhuman as close, interdependent, even indistinguishable. It is an experience that can be taught and shared, and even felt. Stretching from iron core to encompassing cosmos, it has the depth and scale to provide a sublime thrill of its own. True, it offers no gestalt vision to the objective eye. But it can be animated, if you have a mind to. When next you see a picture of the blue marble in space, imagine its clouds coming to life, their whorls beginning to turn like turbine blades. And as you see the scope of the planet’s circulation in your mind’s eye, let your other mental senses in on the act, too; feel the raw heat of the Sun on the back of your neck as it powers the vision in front of you. Embed the portrait in a vision of process. Turn it into part of something – of a solar system, of an act of the imagination, of a future.

With the right imagination, the world of cycles and the world of the astronomer’s gaze can be made to mesh. As mentioned before, the seemingly isolated Earth does in fact have an environment, discovered by astronomy in the abstract, realised as relevant only long after the fact. This environment is the source of the flows of energy that drive the workings of the Earth; it can also be coupled to those workings more directly. The revolutions of the Earth and sky are loosely linked. Orbital cycles carefully calculated by astronomers with no earthly agenda turn out to drive the ice ages. Objects in space affect, and even collide with, the planet from which we watch them. For a long time the possibility of such impacts was deemed of no practical importance, but now it is accepted that they have had great geological significance, and that they merit a certain continued vigilance. As a result of this, 2008 saw the first case of an object on a collision course with the Earth being discovered at an observatory, monitored at the appointed time as a fiery meteor in the sky, and later gathered up in fragments from the ground to which it fell. Asteroid 2008 TC3 was in most ways a small and inconsequential object, but it cut through an important disciplinary distinction. The world of cycles in which we live is not limited to the ball of rock on which we sit; objects elsewhere matter too, and to some extent this must change the way we think about the sky. 

And then there is the question of looking further off. Pull back from the Earth just as far as the Moon, and the blue marble loses its features, continents become hard to see, clouds swamping all other detail. From Mars you would need binoculars to even see it had a disc, from Jupiter you would be hard put to make it out with the naked eye. From six billion kilometres away, the greatest range at which the Earth has yet been photographed, Voyager 1’s powerful camera saw it as only the palest of blue dots. Yet space scientists now speak of seeing, and learning about, Earth-like planets around other stars.

No telescope currently conceivable could actually produce pictures of such planets as discs in space. But it is possible to look for their cycles, their rhythms. Already such planets are inferred from the way their orbits produce sympathetic wobbles in the movement of their parent’s stars, or the regular ways that they pass between those stars and earthly observers. When they become discernible in their own right, less astronomical signs of cycling will be looked for – hints of weather from changes in brightness caused by daily movements of cloud, traces of seasonality as colours shift over the year. Most vital of all, signs of the cycling biosphere will be sought out. As Lovelock pointed out in the late 1960s, biogeochemical cycling has pushed the Earth’s atmosphere far from chemical equilibrium. Such disequilibrium may yet, possibly even soon, be seen in the light of planets round other stars. Understanding the Earth’s endless recycling sets the stage for measuring the Earthliness of distant specks, and for reading life into a point of light that has no features that could ever be gazed upon.

The Earth is still a beautiful ball floating in space. The Apollo 17 camera did not lie. But by seeming to show everything, that portrait made it too easy to ignore the dynamism its stillness could not show. The Earth is not something put before us, or left behind us. It is around us and within us, turning on itself in every way it can as energy flows through it from the depths of the past and the fires of the Sun. It is not just a spaceship carrying a crew. It is a world, and now aware.

1 George Orwell, ‘As I please’, Tribune, 27 December 1946. In Sonia Orwell and Ian Angus (eds), Collected Essays, Journalism and Letters of George Orwell, vol. 4: In Front of Your Nose 1945–1950 (London, Secker and Warburg, 1968).

2James Lovelock, Gaia: A New Look at Life on Earth (Oxford, Oxford University Press, 1979).

3 Tim Ingold, ‘Globes and Spheres: The Topology of Environmentalism’ in Kay Milton (ed.), Environmentalism: The View from Anthropology (London, Routledge, 1993).

4 John Grande, ‘Real Living Art: A Conversation with David Nash’, Sculpture, 20:10 (December 2001).