Timescales and Environmental Change

Graham Chapman, Thackwray Driver

• Publisher: Routledge
• Year: 2002
• eBook ISBN: 9781134787531
• Topic: Physical Sciences
• Subtopic: Geography
• Index: Geography

Time is an unstated but ever present element in all debates about environmental change - and the subtext of many disagreements. Geomorphologists think in the context of millions of years, politicians in election terms, the media in decades, and the public ceases to worry about global warming with one bad summer. This volume brings together experts from a diverse range of disciplines, to offer a range of both temporal and geographical perspectives. It does not seek to provide clear answers about right time-scales, but rather to encourage the reader, from whatever perspective, to think about change and environmental issues in a new light through different time-scales.

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TIME, MANKIND AND THE EARTH

Graham P.Chapman and Thackwray S.Driver

INTRODUCTION

This book is set firmly in the present. It is set in the present context of the debates about environmental change, and specifically the concerns over potentially damaging anthropogenic environmental change—be it at the larger scale of issues like global warming, or the smaller scales concerned with soil erosion in limited areas. But it is our conviction that many of these debates demonstrate that the protagonists have not been well informed about the differing time-scales of the phenomena examined, and that consequently both unnecessary alarm and unnecessary complacency may result. On occasion misunderstanding may even lead to pointless international political friction. The present intention of the book is therefore to explore many different aspects of time, and the manner and treatment of time by differing disciplines.

In the introduction to this chapter we start with an example of the significance of an understanding of time-scales with reference to environmental change and stability in the British Isles. There are conservationists who see the protection of particular plant communities on stable sand-dunes as a priority, as though there is or ought to be a natural permanence to what is at other scales transient and ephemeral. There are others who believe that there is a natural flora in the UK, that can admit of no new members. But the natural species diversity of the British Isles is lower than that of the nearest similar European environments, and in turn the natural species diversity of those is less than that of roughly similar environments at similar latitudes at the other side of the Eurasian landmass. A plausible explanation of this is to do with the cyclical impacts of ice advances and retreats during the Ice Age, the configuration of the basic physical geography of these areas, and the stage we have reached during the current interglacial period.

The period of the most recent Ice Age (there have been other, earlier ones in earth history) is known as the Pleistocene, which roughly speaking is synonymous with the Quaternary era of geology, and covers the last 1.5–2.0 million years of earth history. During this time the ice has advanced and retreated several times; globally there are indications of about seventeen major cold periods, many of which may have supported valley glaciers and ice-sheets in Britain. The actual number of times is uncertain because successive advances erase most of the evidence of previous ones. The duration of the cold periods has been about 100,000 years, with interglacial warm periods in between when conditions in Europe have been as mild as now or milder. These periods have lasted approximately 60,000 years.

Current theory suggests that as the ice advances, some species migrate towards the tropics, sometimes in new combinations—although the tropical rain forests survive in refugia. As the ice retreats, the belts readvance. In southern Scandinavia the birch and the pine reappear 10,000 years ago, the oak forest 7, 000 years ago, and the beech trees just 2,000 years ago. How does this process affect Western Europe and Britain? Western Europe is a peninsula cut off on its southern flank from Africa by the Mediterranean Sea. It is also a landmass marked by extensive east-west mountain chains, such as the Pyrenees and the Alps. As the ice advances from Scandinavia and highland Britain, so simultaneously it advances from the Alps and the Pyrenees. Thus, cut-off, most of the southwards-moving ecosystems have nowhere to retreat to, and even those that move south down the Rhone valley face the Mediterranean Sea. Successive ice advances and retreats might therefore eliminate many pre-Pleistocene species, and recolonization has to take place from more distant refugia such as the Balkans.

At the height of the last glaciation sea levels were 100–150 metres below current levels. As the ice retreated, for a time Britain was still connected to the continent of Europe, but as sea levels recovered, the land bridge was breached about 6,000 years ago, and Britain became an island.

To put the case simply, because of its peculiar configuration and its latitude, stable conditions have to prevail for a very long time in Europe for species diversity to be augmented. There simply has not been enough time for diversity to be re-established, and in Britain this situation has been aggravated by the presence of the sea barrier.

Since the ice sheets covering Britain retreated perhaps 15,000 years ago, we could perhaps imagine that we are in only the very first stages of a new interglacial thermal period, and that at some stage in the future the ice will return, again condemning 30 per cent of the earth’s land surface to the practically lifeless sterility of current Antarctica, and yet again gouging soils and exposing bare rock. Mankind has been on the planet throughout the Pleistocene, mostly deriving an existence from hunting and gathering. It is only in the current postglacial phase that mankind has developed settled agriculture, urban settlements, writing, and, in the last two hundred years, an industrial economy. This most recent and brief period of earth history therefore encompasses the ancient civilisations of Egypt, Mesopotamia, the Indus Valley, and China, the subjects of intensive archaeological study as we try to recover and understand our past. To someone focusing on this archaeological record, the founding of the First Dynasty of Egypt in about 3100 BC apparently happened a long time ago, almost unimaginably long ago, because a human being finds it difficult to imagine the experience of feeling the passing of 5,000 years.

By extension, the retreat of the ice from Europe 15,000 years ago seems so long ago that it is almost before time began. But, if the reference point is not man looking at the earth, but the earth itself, then 15,000 years takes on a very different feeling. If we recalibrate the earth’s actual age of 4.6 billion years to be represented by a whole year, then the last 15,000 years become less than the last two minutes of that year. Seeing a high-speed film of the earth’s history that started on 1 January at 00.00 hours, the ice retreats from Europe on the following 31 December at 23.58 hours. Suppose we have completed watching this film for a whole year and are now at midnight on 31 December and are preparing to drink the champagne poured in the last two minutes; these last two minutes seem like part of the present.

Students of geology and geography learn to develop intellectually a long time perspective. The majority of people are not exposed to such a perspective, and develop their understanding of time within very different frameworks. The most basic and the one which a child develops first, from its prenatal days, is the circadian rhythm, determined not only by its own biological clock, but by the parental rhythms surrounding the child. As we grow older, we learn other perspectives and understanding, as birthdays come and go, and as we query the chain of human being through knowledge of our parents, and their parents…. Many of us will extend our understanding from that to the collective memory of the culture to which we belong. As Cicero observed of the necessity of understanding history, ‘Not to know what took place before you were born is to remain for ever a child.’ To understand what happened before you were born requires an imaginative leap to extend an understanding of time beyond your own lifespan. But we must remember that this is still the time-scale of human history, to which Cicero refers, not the time-scale of the planet earth. That time-scale is so different it is almost unimaginable: the earth has existed for 4.6 billion years already, and may easily exist for another 4.6 billion and more. We can hope that the biosphere will continue to live on earth for that time too—and even if some intelligent human descendants of some form survive, the one thing we can be sure of is that they will be a distinct species that has evolved new abilities.

We hope enough has been said to persuade the reader that a closer examination of the concepts of time is worthwhile, for that is where we go next.

THE HUMAN IDEA OF TIME

We talk blithely of living in four dimensions: the three dimensions of space, and the one dimension of time. Space is something we can apprehend directly—we can see near objects, set against further horizons. We can reach out with our hands and feel the width of a tree trunk, or try to put our hands round its girth. We can also standardise our measurements internationally, against the wavelength of light. In this we are using the sense organ with which evolution has equipped us best to negotiate the spaces around us—the eye. But there is no sense organ associated with time. Apparently we experience the passing of time, and we can compare our experiences. Older people typically feel that ‘time is passing faster’, perhaps because each successive year is a smaller part of their accumulating length of life. But this has not said what it is we experience, and how we sense it. Time is colourless, odourless, invisible, and silent. So what is it?

Time and intuitive human experience

The identification of time with subjectivity is probably as old as philosophy: all that we can touch or handle…has shape or magnitude, whereas our thoughts and emotions have duration and quality, a thought recurs or is habitual, a lecture or a musical composition is measured upon the clock.

(Yeats 1937, p. 71)

For the moment it will suffice to distinguish between an absolute view of time and a relative view. The absolute view of time is of time as the fourth dimension, an axis marked out with intervals, and along which events can be located. The other view is that time is relative—relative to changes that mark its passing. For most of human history, it is relative time that has mattered. Relative time can be much more complicated than absolute time: since it is not constrained to a single dimensional axis, repetition is possible. Cyclical time—the repeating of a day, or a week, or a year—is part of such a time frame. In absolute time 16 December 1994 cannot be repeated. But in relative time, Fridays keep returning.

In relative time, duration is measured in relation to something. For most of human history these measures have been quite crude. A society that lives by daylight knows enough about the passage of the day to indicate when to go to or come from the fields. If for other purposes a measure is needed, some common activity will often suffice. In India a common rural unit of time was the time taken to boil a pot of rice. In ancient Egypt time was measured by shadow clocks—a kind of early sundial—or by water dripping from a tank, or by sand flowing in the hour glass. The length of time measured of course depended upon an arbitrary gradation or calibration of the contrived event. All these times stress the human dimension and human utility. Perhaps the most significant duration of all is the very idea of a human lifetime or of human life span. The duration of a human being’s life is in a direct sense the maximum length of time which he or she can directly experience: for the sake of the argument, let us say the biblical three score years and ten.

If this is the human scale of time, then quite clearly the larger questions about time and change will be understood from this perspective. The passing of history is recorded in the Old Testament in terms of the generations that are begotten of each other since Adam. And to know where we are in time at present, the Christian West uses a calendar which counts in years the age (at the time of publication of this book this is 1,996 years old) of the one human being who has reputedly escaped death and a normal seventy-year lifespan. This quite clearly establishes the very idea of 2,000 years as in some sense being ‘a lot’, or ‘a long time’, since obviously it is now 1,996 years since ‘proper’ time began.

If in human terms 2,000 years may be long, what is short at the other end of the human scale? It seems that there is a short duration below which a human being cannot distinguish. Psychologists testing people’s ability to estimate the length of short intervals conclude that this is about 0.1 seconds. This, it would seem, is tied up with limits in our ability to process information.

The question then arises, how do we even recognise that there are shorter and longer time spans than these scales suggest? A separate question follows which is just as important: how do we experience or imagine these shorter and longer time intervals? Quite clearly we have to use methods of indirect observation in the first instance, and in the second instance we have to be able to imagine things beyond common-sense experience. For many phenomena we use indirect methods and then recalibrate them to our own time-scales. Some we can apprehend through devices such as high-speed photography and slow play-back. Conversely, we also need very slow-lapse camera work and subsequent speeding up to appreciate relatively slow phenomena, such as the growth of a plant. In other words, we calibrate these other processes to the human dimensions of time experience. Unfortunately we do not have a time lapse sequence of photographs of the last Ice Age advancing and retreating over Europe. By contrast, the experience of large spaces does not present us with quite the same difficulties. Not only can we see large distances from suitable vantage points, we can also traverse by foot, by car, or by aeroplane vast distances which allow us to sense the significance of large spaces.

Tolstoy observed that to accept the Copernican theory that the earth revolves round the sun, we have to suspend our obvious sensation that the sun is going round the earth. Our obvious temporal sensations of the earth are that continents do not move, that mountains do not change, that ‘ol’ Man River, he just keeps rolling along’. These are the assumptions that underlie most traditional accounts of the earth—thereby, in a tautological way, reinforcing in folk memory the human scale of earth history. Next we consider two of these cosmologies, the Judaic-Christian and the Hindu, which still underpin common understandings of the earth by many people in the West and in the East. The scientific refutation of these accounts has occurred considerably more recently than the refutation of either flat-earth theory or the pre-Copernican solar system.

The cosmologies of mankind

As far as we know, mankind is the only species on earth to have achieved consciousness—defined as self-consciousness. Moreover, the human species is the only one which has evolved a language sophisticated enough for the development of abstract concepts, and for their verbal communication to other members of the same species. It seems probable these two properties—of self-awareness and communication—are evolutionary interlinked, and that they contain within themselves the need and the means to explain the origins of the world in which we find ourselves, the origins of man, and the relationship between the two. The most ancient stories of the most ancient societies are stories of the creation. By definition they have to be stories about space—the creation of the world as matter—and about time, since they are narratives about events ordered in time. Most of these stories are in a modern scientific sense objectively wrong—though nearly all contain some surprising aspects of ‘the truth’, which hint at a deeper understanding of the world than is apparent at first sight. The impact of deep and old folk histories itself runs deep and long. The extent to which our values and attitudes may be guided by an unacknowledged, older, and wrong ‘truth’ rather than a modern scientific new ‘truth’ is clearly apparent only when we start looking at the larger patterns of human behaviour. There is considerable evidence in this book that outdated cosmologies can still sway the professional as well as the popular mind.

Here we will for a moment reflect on two rather different ancient cosmologies: the Judaic-Christian understanding provided by Genesis and the subsequent events of the Old and New Testaments, and the understanding provided by Hinduism. Judaism is a dogmatic religion, in the sense that it has a revealed source of truth—the Old Testament—and that it postulates a God who exists outside of and before the Universe. This God created the world in six days, and on the seventh he rested. The oceans are created first, the heavens (the firmament) next. On the third day the land is separated from the waters and vegetation is created on the land. On the fourth day the sun, moon, and stars are created to mark the passing of day and night. These are followed on the fifth day by the creatures in the waters and the fowl of the air. On the sixth day he created the beasts of the field and finally, as the last act, he placed man in the garden of Eden: ‘And God said, let us make man in our image, after our likeness: and let them have dominion over the fish of the seas, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.’ This Old Testament order of the creation is not entirely wrong. The seas predate life, the fish and the fowl predate the cattle, and in the last act comes man. But it seems odd to place the vegetation of the land before the creation of the sun; and whales are made synonymous and contemporary with fish.

The story has many pointers in it.

1. Although a contrary reading is possible, it seems that the concept of a day, or more correctly what constitutes a day’s length, pre-exists the creation of the world—hence God managed to create it in seven days. This idea of time as a pre-existing axis, a Newtonian coordinate into which things are mapped, is a view of absolute time that is probably the easiest to comprehend and the one most instinctively articulated in modern society—dominated by clocks—though it may not be the most intuitive way of experiencing time.
2. A beginning is located in this absolute time. Beginnings and ends are something which concern all human beings. Stories have beginnings and ends—and to some extent this book does. The concept of a beginning and an end is obviously human—as any abstract concept is—but presumably explicable because of our own apprehension of our own birth and death. Accordingly, in the Christian West we have birthdays—days located in the axis of absolute time. The earth’s birthday implied by Genesis should have a date too. Archbishop James Ussher calculated in 1654, and his calculations were confirmed by the vice-chancellor of Cambridge University, that ‘Heaven and Earth centre and circumstance were made in the same instance of time, and clouds full of water and man were created by the Trinity on the 26th of October, 4004 BC at 9 a.m. in the morning’ (quoted in Chorley et al. 1964, p. 13).
3. The manner of the end of the earth is conjectured in both the Old Testament and the New, and both in a sense speak of a judgement day, when God will bring This wrath upon the earth, and the value of people’s lives will be judged. The end will be caused by an external event—God. It is not inherent in the earth itself, since the earth itself is inherently unchanging. The date of the ending is not fixed precisely, but is in some imaginable human future. Down through th...

Table of contents

• COVER PAGE
• TIME-SCALES AND ENVIRONMENTAL CHANGE
• TITLE PAGE
• COPYRIGHT PAGE
• FIGURES
• TABLES
• CONTRIBUTORS
• PREFACE
• 1: TIME, MANKIND AND THE EARTH
• 2: LONG-TERM ENVIRONMENTAL STABILITY AND INSTABILITY IN THE TROPICS AND SUBTROPICS
• 3: THE CENTURY TIME-SCALE
• 4: IDENTIFYING THE TIME-SCALES OF ENVIRONMENTAL CHANGE: THE INSTRUMENTAL RECORD
• 5: FUTURE GLOBAL WARMING: RESOLVING THE CLIMATOLOGIST AND ECONOMIST CONFLICT
• 6: GREENHOUSE POLICY DEVELOPMENT AND THE INFLUENCE OF THE CLIMATE CHANGE PREDICTION TIMETABLE: AN AUSTRALIAN PERSPECTIVE
• 7: CONFLICTING TIME-SCALES: POLITICS, THE MEDIA, AND THE ENVIRONMENT
• 8: ENVIRONMENTAL DESTRUCTION IN SOUTHERN AFRICA: SOIL EROSION, ANIMALS, AND PASTURES OVER THE LONGER TERM
• 9: REFRAMING FOREST HISTORY: A RADICAL REAPPRAISAL OF THE ROLES OF PEOPLE AND CLIMATE IN WEST AFRICAN VEGETATION CHANGE
• 10: ECONOMIC ACTION AND THE ENVIRONMENT: PROBLEMS OF TIME AND PREDICTABILITY
• 11: INDIA, DEVELOPMENT AND ENVIRONMENTAL CHANGE
• 12: CONCLUSION