So wrote Robert Burn in 1854. For a long time people had been puzzling over what was the actual driving force behind the steam engine. It is interesting that Savery stated that his engine would work by the ‘impellent force of fire’ and that the early atmospheric engines were called ‘fire engines’. Watt also was acutely conscious of the importance of heat in a steam engine which was shown by his use of the steam jacket and hence, in effect, lagging the cylinder. We have seen how this awareness was, in some degree, due to his understanding of the science of heat through his connections with the men of science of his day like Black who had just founded the new science of heat. Engineers after Watt, like Smeaton, Brindley, Ewart, and Fairbairn, had no such link with this science and they derived their theories from hydraulic engineering which thought in terms of water pressure or weight. The result was that often their concept of the operation of steam engines was deficient.

An example of these confused ideas was shown by the thinking of Farey. He could see that the role of heat was essential when he wrote in Rees's Cyclopaedia,

All living organisms interact with their environments. They are influenced by a host of environmental factors and, to some extent, they modify their environment. The human species is no exception. We respond to patterns of temperature, rainfall, abundance of food and other resources and to the incidence of competitors, predators and disease. However, the relationship of mankind with the environment is unique. The extent and degree to which quite small populations can modify the environment is unparalleled, and this combines with the success of the species to make an overwhelming impact.

Although the environment has some intrinsic resilience to deleterious change, the rate of growth of the human population is such that its environmental effects are far outstripping the recovery potential of the earth. As the population continues to grow at an ever-increasing rate, so the capacity of the earth to support life is being eroded: reports of famine, deforestation, loss of plant and animal species, soil erosion and atmospheric pollution are becoming all too familiar.

However, for the first time in history we are in a position to begin to evaluate our many and complex relationships with our environment and to attempt to tackle the deleterious consequences of our activities. Major new initiatives among all disciplines concerned with the environment are beginning to get under way, with the aim of understanding the workings of the biosphere, and particularly man's effects upon it.

Many of the problems associated with overexploitation of the environment are multinational in origin and are consequently very difficult to resolve.

Introduction

Forests are arguably the most important vegetation zone on the face of the earth today. They play a far greater role in the well-being of the planetary ecosystem than they are often given credit for, and we may soon find that forests will effectively be called upon to make a still more critical contribution to planetary stability. Yet on every side, from the equator to the arctic, forests are being depleted or will shortly be depleted through human agency at a rate that could well reduce many of them to impoverished remnants by the end of the next century. Indeed, forests, which have been the predominant form of vegetation on our planet for hundreds of millions of years, may soon become a minority presence – whereupon we shall discover (by default) the full measure of their part in underpinning the ecological welfare of our biosphere.

What is the nature and scope of the role of forests in planetary workings? By ‘forests’ I mean tree-dominated communities with substantial canopies, Fig. 2.1 (by contrast with woodlands which feature much sparser tree cover) that are the repository of a greater abundance and diversity of terrestrial life forms than the rest of the earth put together. Tropical forests are specially rich in species and in the evolutionary capacity to generate new species. As tropical forests are cleared wholesale, there will be an impoverishing impact on the very course of evolution itself.

Moreover, forests help to regulate the hydrodynamics of great watersheds and river basins such as those of the Ganges and the Amazon.

The Darwin College Lecture Series was inaugurated in 1986 to provide a range of public lectures on topics of general interest. The first series was entitled Origins and it considered subjects such as the origin of the universe, the origin of man, and the origin of language. The present volume contains the second series which was delivered in Cambridge in 1987, under the original title ‘Man and the Environment’. We are grateful to Richard Grove, Christopher Viney and Jamie Whyte for their help in organising this second series.

The contributors to each series have been selected from a wide range of disciplines to allow a broad look at the topic. Although the contributors are acknowledged specialists in their fields, the lectures are aimed at nonspecialist readers.

It is all but impossible to make any statement about human attitudes to animals that is both a generalisation and true. There are few areas of our lives where our attitudes to anything are as confused and tangled as they are in the way we think about and treat animals.

This is perhaps not surprising. We are confused enough in our attitudes to just one kind of animal – members of our own species. Just think what humans do to other humans: love them, nurture them, defend them with our lives, kill them, torture them, let them die of neglect, use them as slave labour, admire, revere, despise and so on. Attitudes to other species of animal include all this variety as well as an even greater range of attitudes brought about by the even greater range of roles that animals can play in our lives: they can be food, companions, entertainment, sport, deities or dangerous nuisances. No wonder that our attitudes towards animals vary between extremes.

To quote Albert Schweitzer:

Introduction

Charles Darwin provided the essential elements of the explanation for how species originated and thus how life has evolved on earth. This work has changed forever the way educated people see themselves in relation to the rest of the natural world.

Although correct in essentials, Darwin's ideas had some major technical problems in their own time. For one thing, in the absence of the then-undiscovered nuclear forces, it can be shown that neither the sun nor (by a separate argument) the earth can be more than a few tens of millions of years old. For another thing, heritable variation is roughly halved in each generation if inheritance blends the characteristics of mother and father (as was thought to be the case in Darwin's day), making it hard to understand how such variability – the raw stuff on which selection can act – is maintained. A widespread recognition that genetic inheritance operates in a discrete, particulate way, tending to conserve variability, had to await the rediscovery of Mendel's work some 50 years later. Many other questions, including the mode and tempo of evolutionary change, the role of ‘neutral selection’ as gene frequencies drift under random statistical fluctuations, the selective advantage of sex, and other topics, remain active areas of research today. But all this work takes place within the sturdy framework erected by Darwin.

Given a basic understanding of how species originate, the next question would seem to be how we use this understanding to estimate – from first principles – how many species are likely to be found in a given region.

Climatic changes in the past

The climate on earth has changed throughout the evolution of our planetary system over about 4500 million years. Sometimes these changes have been rapid. During other periods they have been slow, hardly noticeable over millions of years, as far as we can judge from the evidence that is found to-day in rocks and sediments. To be able to discuss possible future climates we must understand the mechanisms behind past changes. The climatic system is too complex for us to rely merely on simple extrapolation of observed trends and variations or theoretical models that have not been tested against past data.

We know the gross features of climatic change on earth during the last major geological epochs, i.e. during the last few hundred million years. These have been determined by analyses of the abundance of the oxygen-18 isotope in remains of planktonic micro-organisms (foraminifera). The ratio of oxygen-18 to the normal isotope, oxygen-16, reflects water temperature and global ice volume. High proportions of oxygen-18 correspond to glacial periods when more of the lighter isotope oxygen-16 was locked up in ice. These analyses reveal that water temperatures in the deep layers of the oceans have been close to zero degrees only during the last few million years, i.e. the Quaternary period, and also that ocean surface temperatures were probably higher during these earlier periods than they are today (Fig. 7.1). Presumably the climate on land was also significantly different from to-day.

A much more detailed record of the proportion of oxygen present as oxygen-18 for the Quaternary period shows marked variations on much shorter timescales.

Introduction

Much of our knowledge of the history of human relationships with the environment has resulted from close, long-standing links between the disciplines of geography and archaeology. Traditionally, such studies have centred on a desire to explain in terms of environmental influences either the distribution of human activities in space or the changing fortunes of human groups through time. For example, Huntington and his co-workers interpreted migration and the decline of cities in Central Asia in terms of environmental changes and saw dry phases as the driving force of the Pulse of Asia (1907). The archaeologist Gordon Childe saw the adoption of domestication and cultivation as a revolutionary response to desiccation in post-glacial times. More recently, many of the great collaborative ventures in environmental archaeology have sought to place archaeological sites in their environmental context. A new discipline – Geoarchaeology – has emerged.

In this chapter, however, I wish to approach the subject from a different perspective, seeking to outline some of the ways in which prehistoric groups have caused environmental changes. I shall concentrate on the use of fire, hunting, agriculture and settlement, with particular reference to the post-glacial peoples of Britain, and also on the exploitation of minerals. My hypothesis is that the changes brought about by these activities were rather substantial, though I recognise that the impacts will have varied from area to area, according to length of human occupation, technological level and population numbers.

Human life probably first made its appearance on our planet some three or so million years ago, before the start of the Ice Age (see the timescale in the Appendix to this chapter).

Stories told by distant travellers have long provoked the imaginations of placebound listeners. One such account telling about the adventures of a young former Cambridge student during his five-year circumnavigation of the earth was published in 1839. In The Voyage of the Beagle, Charles Darwin gives us his first narrative exploration of experiences and reflections that eventually created a lasting revolution in the sciences.

Today we live in an age when travellers can circle the earth in approximately 90 minutes. Their stories and photographs, when coupled with the data returned by unmanned satellite sensor systems, can be the guide to new discoveries about our environment. In this chapter I propose to take the reader on an orbital photographic journey around the earth and to demonstrate that many of the issues discussed by the other contributors to this series can be examined through evidence seen by unaided vision from the altitude of the Space Shuttle orbiters, averaging about 280 km. Since in no way can one attempt to do justice to all NASA programmes of terrestrial observation and the many investigations currently pursued by other agencies and university research groups, I shall choose to focus on several topics of personal interest. These include the fate of tropical forests, the nature of the African drought environment, the factors changing global climate, the geological hazards posed by particular volcanoes and the dynamics and biology of the world's oceans.

Exploring the earth from orbit

Before beginning to consider environmental topics, it is useful to recall the historical development of earth surveillance from space.

In recent years the subject of famine has been greatly sensationalised by the media. This chapter nevertheless attempts to approach the subject in an objective, academic manner. It stresses the importance of never under-estimating the nutritional complexities of the Third World and the long-term political, social, economic and technical developments that will be needed to avert the threat of famine which is always just over the horizon in the great majority of Third World countries.

The acute crisis

I shall not attempt to discuss modern famines within a historical perspective. It would have been intellectually attractive to ponder upon, say, the Biblical Famine, now ascribed the date of 1708 BC, in Genesis, Chapter 41, or perhaps on the West Bengal famine of AD 1770, or the more recent one of 1943. The potato famine of 1845 in Ireland would have provided equally good academic mileage, though the Africa famines in Nigeria of 1968 associated with the Biafran Civil War, or those of Ethiopia and the Sahelian region as a whole in 1972, 1978 and 1984–5 might have been of more immediate interest, but I am not going to discuss any of these famines.

My primary reason for not concentrating on such crisis situations is that it might reinforce the belief that the single catastrophic events which occurred on these dates, for example seven years of crop failure starting in 1708 BC in the Middle East or the peak of the drought in AD 1984 in Ethiopia, were the primary causes of these famines.

Introduction

All human activity is ultimately based on resources found in nature. Whether it is consumption, production, or exchange, the commodities which are involved can always be traced to constituents provided by nature.

A tractor requires for its manufacture iron and steel, rubber, plastics, nonferrous metals, labour of various skills, factory-machinery, water, and so on. Of these, to take an example, the steel requires for its production iron-ore, coal, furnaces, water, labour, and so forth. The furnaces in turn require for their manufacture, among other things, iron ore, brickworks, and labour. One can thus break down any produced good into the inputs involved in its manufacture and one can, if one has sufficient patience, trace them ultimately to a combination of labour and natural resources. Of course, labour too is produced and sustained by natural resources. So ultimately all commodities and services can be traced to natural resources.

My purpose in reminding you of the morphology of produced goods and services is not to prepare a chapter on the resource-theory of value. Like Marx's labour theory, such a construct quickly runs into analytical difficulties. My purpose, rather, is to set a materialistic tone so that one may in an unhampered way view natural resources in the light of their use to us in running our lives. I am not suggesting that this is the only defendable perspective; I am merely indicating that this is the attitude I shall strike in this chapter. I need to declare my position at the outset, because if you scratch a resource economist you are likely to find a nature-worshipper trying to get out.

The military imagery which coloured medical discussions in New Guinea between the wars reflected Australia's traumatic tradition as supplier of shock-troops for the British Empire. Yet the Pacific War caught the Australian government unprepared. Military planners certainly expected a world war – but a re-run of the Great War. The troops were equipped to fight on the Western Front, but were actually sent to North Africa and to the Middle East, which had been a sideshow in the Great War. The soldiers were equipped badly for the North African desert, and not at all for New Guinea. Some had been despatched to Malaya, lest the Japanese join in the war. When Singapore fell, and Japanese forces swept through the western Pacific to occupy the Bismarck Archipelago in January 1942, most Australian troops were either committed in the Middle East or captured in South East Asia. Only the tiny garrisons in Rabaul and Port Moresby had direct experience of jungle conditions. Between 1942 and 1945, the brutal fighting in the Solomons and New Guinea would be won by those armies best able to maintain their fighting strength in enervating temperatures and humidity, beset by endemic malaria and epidemic dysentery.

Japan entered the Pacific War with every advantage of experience. As early as 1904, during their war against Russia, they had demonstrated that military discipline could restrict non-battle casualties. Since the early 1930s, their armies had been deployed abroad in Manchuria and China: their medical officers had experienced every environmental and logistical problem.