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Trees, wood and people

Brian Clifford


Although there are numerous new materials available today, such as the great variety of plastics, many people maintain an appreciation of wood. This is partly because of its tactile and visual qualities and partly, perhaps, because of a bias that is built into our genes. Many people also have great regard for the trees from which the wood comes and are concerned about the wanton destruction of large areas of forest and the implications of this for the future of the planet.

Despite these concerns it is possible that the full importance of trees, and the wood they provide, to the historic, current, and future needs of the human race is still not fully understood. Since they evolved trees have had a great influence on the shaping of the ecology of the planet and in determining the present arrangements of life on earth. Of particular importance for us has been the role of trees in the evolution of mankind and the development of human cultures and communities.

The way in which the relationship between mankind and trees has developed has led to a deep paradox. We love trees, we need trees, but with chain saws and boxes of matches we are eating into their surviving strongholds. And, when the few great forests that are left in the world have been felled, the human race may become an endangered species too.

How has this situation come about? In part it is because in developing into an organism that has had great evolutionary success the tree has created a material with many useful properties. At the same time, because trees have been so successful in colonizing large areas of the surface of the world, they now find themselves in competition for living space with a very recent newcomer. So we burn trees to make room for ourselves.

Thus mankind has had a relationship with trees which has developed over millions of years. In the future, too, if we permit it, trees will continue to provide great benefits to mankind. This relationship, which now embraces ethical as well as spiritual and material values, deserves detailed consideration.

The origins of man

As life on earth evolved trees became the dominant plants over much of the land surface of the earth. At on time tropical, sub-tropical and temperate forests covered much of the Americas, Africa, western Europe, China, Japan, Oceania, and southern Australia. These ancient forests had an important effect on the climate, both rainfall and temperature, and, as a consequence, on the evolution of other flora and fauna.

Among the creatures that evolved in this environment was the ancestor of man. This primitive animal was a prosimian, a small, rat-like animal, which lived on the ground. At some stage this creature took to the trees. Eventually, after a long period (about 50 million years), during which it evolved into an ape-like creatures, it returned to the ground.

The period spent in the trees was of great formative importance; this was the environment in which man's basic structures, brain, sense organs, limbs and reproductive system, evolved. In response to the exigencies of living in trees the animal's paws were modified into members able to grip: the claws atrophied, the digits lengthened, and an opposed thumb developed. The eyes became larger and moved towards the front of the head providing three-dimensional vision. In concert with these bodily changes, and their application in confronting the dangers in the tree tops, the creature's brain developed new features and increased in power.

In time more adaptations, coupled with subtle changes in the environment, took place. The shape of the face continued to change, the nose receded, the eyes moved right to the front, and colour vision developed. The hands and fingers became more flexible making them capable of delicate and precise movements. The limbs developed too, providing an increase in agility and reaction speeds. These transformations were again mapped by physical changes, and increased capacity, in the brain.

Thus, prosimian developed into simian. In response to environmental pressures some species in the simian line developed greatly increased body size that permitted still larger brains. The increase in stature resulted in changes in posture that enabled some of them to stand upright. Eventually, at least one of these species was able to walk. It was these changes that led to the descent from the trees and eventually to homo sapiens. So, it can be seen, without trees the evolution of prosimian into homo sapiens would never have taken place. We would not be here.

The wonder and the mystery

There is another aspect of the effect of trees to consider: on many people they exert a powerful emotional influence. Since our ancestors lived in, and depended on, trees for millions of years it is conceivable that they work their magic on us through ancestral memories derived from that formative period.

To many people a tree is a source of spiritual sustenance and renewal. A tree is a thing of beauty and wonderment, huge, but full of life and movement. A deciduous tree is the embodiment of the changing seasons: a stark framework in winter, bursting life in spring, a vast green canopy in summer and the bearer of seeds and fruit in the autumn. It is the embodiment of man's condition: birth, life, death, regeneration and rebirth. The rising sap is the spirit of life, seeds and fruit are the symbols of fertility.

The wonder and the mystery of trees is such that they have an important place in religion, myth, folklore, superstition and story telling; as a consequence the tree has been a powerful cultural symbol in many societies from primitive times to the present day. Many trees have been worshipped as gods or seen as the dwelling place of spirits. Groves of trees have become sacred places. Such trees, or woods, have also become the places where tribal rituals or ceremonies are carried out. Objects made from wood - icons, images, masks, amulets and lucky charms - have also incorporated this magical status. The common saying 'touch-wood', to save the tempting of fate, probably has its origins in these associations.

The symbol of the tree may also provide a structure for a wider system of belief. The legendary ash tree of Scandinavia, Yggdrasil, forms the basis of Norse mythology; whilst its branches reach into the heavens, the home of the gods, its roots go down to the underworld. The trunk passes through middle Earth, linking the three realms, and forming the bridge along which the gods can pass. In this way the tree can be seen as the greatest symbol of all: a representation of the whole cosmos.

The spectacle of the tree as it passes through the seasons of the year can exert a strong emotional effect on people. Many of us feel this. But there is yet another way in which trees may have affected primitive peoples. Trees live a long time and, in relation to the lives of men and women, they may have seemed immortal. This would have added to their magical quality.

The elders of a village may have sat under the same tree for generations. And trees which had particular importance to the tribe, perhaps as markers, or signposts, to food or other significant locations, might have seemed to have had a permanent place in its traditions and oral history.

Numerous species of trees live 500 years or more, some live much longer still. There are bristlecone pines growing today on the mountains of California and Nevada that are confirmed to be 4,300 years old. Some yew trees in England may have been living even longer than that, possibly 5,000 years. This could well be the reason why yew trees have marked the location of religious sites in the British Isles over the millennia. Many Christian churches, which so often have yews in their grounds, were built on sites that had a tradition of pagan religious rituals. So the yew tree probably had magical significance to ancient Britons.

Thus, trees have been of continuing spiritual benefit to the human race; they are beautiful organisms carrying a great weight of symbolism. We have seen, too, that we owe our very existence to trees. But our debt to trees goes much farther than this. The development of human cultures and civilization has been dependent on wood based technologies.

The importance of wood

Let us think for a moment about some of the important discoveries or techniques that have been crucial to the development of modern society. Where would we be without fire, agriculture, the wheel, the use of metals, sources of power, spinning and weaving, building, printing and music?

Wood burns readily and produces heat. As a consequence it has long been used for cooking and protection from the cold. These factors assisted early man to change his diet and to migrate to colder regions where he was forced to use his ingenuity to survive. Wood can also be changed into charcoal; without that early man would have been unable to smelt metals. Before the use of coal developed with the industrial revolution, wood was also used to provide heat for making pottery, glass and bricks.

The first farmers probably just scraped a furrow with a stick. Later the wooden plough was invented. At first this may have been drawn by people but eventually the power of animals was harnessed with the aid of wooden yokes for both oxen and horses. As farming skills developed, and productivity increased, more artefacts of wood were required. These included devices for scattering seed, for harvesting the crop, and for threshing. Bowls, churns, butter moulds, cheese presses, and other items, were required in the dairy.

The wheel is one of the great inventions - many developments in transport, machinery and power stemmed from this one idea. The first crude wheels, made of solid planks butted together, were supplanted by the spoked wheel as skills in carpentry improved. Wind and water mills, the earliest sources of power (other than animals), were largely constructed of wood with a minimal proportion of metal parts. The transmission of power in these mills was achieved by trains of wooden gear wheels.

Similarly wood formed a large part in the development of transport. Wooden ships, bridges, locks, and staithes formed the basis of water transport. A multitude of wooden wagons and carriages were employed on land. For handling goods there were wooden barrels, tubs, wicker baskets and wooden cranes. Wooden pipes were used extensively to transport water. The first railways consisted of wooden trucks running on wooden track. Even the first aircraft were made of wood.

Wood was used extensively in mechanisms of all kinds from clocks to mill machinery; these included weaving looms, cotton spinning machines, and agricultural implements. Wood was used for furniture and all manner of things in the home. Even when metal performed an important function such as the head of a hammer or an axe, or the blade in a plane, wood would have been used for the handle, or the body, of the tool.

Wood was employed throughout the world as a building material for houses and other structures. Even where a great building, such as a cathedral, was principally made of stone, it could not have been built without wood. This was required for frameworks of various kinds to provide support during construction, scaffolding for work platforms, as well as providing the means to transport the stone.

Writing, the printed word, and books, have been key elements in the development of civilization. There are a number of materials that can carry writing, and paper can be made from any organic fibre; nevertheless, the spread of books, and reading, has been dependent on the manufacture of paper from wood pulp. Printing was originally carried out with wooden printing blocks, first on textiles and then on paper.

Wood has also been important in the development of art and culture in many different societies. Men learned to carve and decorate their wooden buildings and furniture in increasingly elaborate ways. The significance of trees in religion has already been referred to but, in addition, wood has also been carved to create statues, icons, talismans, charms, and other kinds of religious symbols.

The development of music also depended on the use of wood for making instruments. Because wood is relatively easy to work it has been used to make musical instruments from very early times. Most primitive societies have percussion instruments such as clappers and drums. Some 5000 years ago the Sumerians used rattles, tambourines, flutes, reed instruments, and horns. Except for the last mentioned all of these would have required the extensive use of wood for its constructional and resonant qualities.

The development of these instruments continued through the Greek and Roman civilizations. It achieved its full flowering (in the western European tradition) when public concert giving began in the late 17th century. At that time most of the instruments of the orchestra were still made almost entirely of wood. Even today, with modern metal working techniques, plastics and electronic devices, the use of wooden instruments in orchestras is likely to continue for the indefinite future.

Many important chemicals were, and still are, derived from trees. Gum arabic, Canada balsam, cedarwood oil, rubber and the so called 'naval stores', turpentine, rosin, pitch and tar, are exuded by, or tapped from, trees. Tannin, used to cure leather, is obtained from bark. Cork, used as a float for fishing nets (amongst other things), is the bark of a species of oak tree. The leaves and fruits of trees, besides being an important foodstuff and source of vitamins for both people and animals, have been used in many folk medicines.

Other chemicals used in industry today are derived from wood pulp. These are mainly cellulose based and include cellophane, celluloid, rayon and other plastics. Purified wood pulp, which is almost pure cellulose, is regenerated in the form of synthetic fibres or sheets. These have great tensile strength and protective qualities. Cellophane, for example, is ideal for use as wrapping and the strength of rayon is utilized in industrial belts and tyre cords.

In all the uses outlined above wood has had a benign influence as an ingredient in the development of the modern civilized state. But there is also a negative aspect: as well as providing a material for the fabrication of hunting implements wood has enabled men to make weapons to assault and kill each other. Without wood to make charcoal it is unlikely that gunpowder would have been invented. Nitrated cellulose, derived from extracts from wood, is used to make gun-cotton and cordite. This, of course, is not the fault of trees but of man. But war and conquest, politics and diplomacy, have played a significant role in the way in which civilization and culture have developed. Trees have contributed to this as well.

Until the industrial revolution had got well underway, at the end of the 18th century, the use of wood, in one way or another, was essential for practically every industry. In a short article such as this it is impossible to do more than sketch in the many uses of wood before modern times.

As industrialization progressed with the development of the steam engine, the increased use of coal and the spreading employment of metals (particularly iron and steel), the importance of wood diminished to some extent. Nevertheless, despite the introduction of new materials, such as plastics, enormous amounts of wood are still being consumed.

Carbon fibre has been called a 'miracle material' but really it is wood which deserves that accolade. When linked with the inventive genius of mankind wood is amazingly versatile. This versatility is enhanced by the fact that different species have different characteristics all of which can be exploited by man for particular purposes. In general, however, the main structural qualities of wood are that, in relation to its weight, it is strong (in both compression and tension), it is flexible, and it is easy to work. When well finished, wood has decorative and tactile qualities: it has attractive figure plus a warm and silky feel.

The nature of wood

Trees evolved to become such a successful group of species that at one time forests covered much of the fertile land surface of the earth. In becoming so dominant the trees grew above other vegetation and spread out a canopy of leaves to catch the sunlight. As a consequence of this process trees are among the largest and longest living organisms on Earth. A North American redwood, for instance, can grow to 100 metres in height and weigh more than 2000 tons. A specimen of eucalyptus is said to have reached 130 metres (435 feet).

To grow tall the tree has become a miracle of engineering. In proportion to its height the trunk of a tree is a slender column. From this column numerous branches are cantilevered outwards; these in turn support further branches and twigs. On these grow the multitude of leaves that are required to perform functions necessary to sustain the entire organism. The roots underpin the structure, keep it standing, and seek out the nutrients it needs to grow and survive.

The tree not only needs to be able to defy gravity it also has to be able to withstand the stresses caused by wind. The leaves, twigs, branches, and much of the trunk too, are flexible; as a consequence they are able to align themselves with the wind, so cutting down the resistance. To be a successful organism, therefore, a tree must be both strong and flexible.

It is also a complex natural factory. It is a machine that is able to lift water and mineral salts out of the earth and carry them up to the multitude of leaves high above. Each leaf is a tiny chemical processing plant where photosynthesis takes place. Using energy, provided by sunlight, and chlorophyll, the green substance produced by the tree itself, the leaves perform the biochemical process of carbon fixation.

The root sap, the mixture of water and salts drawn from the roots, is combined with carbon dioxide gas in the air to form carbohydrates which flow away from the leaf as leaf sap, a sugar solution, which feeds the tree's life processes and enables it to create the tissues which form its structure.

The secret of a tree's growth lies in the cambium, a thin sheath of cells just beneath the bark, which covers every stem, twig and root. During the growing season the cambium creates new cells. The cells on its inner surface form rings of sapwood, first as early wood (or springwood) and then latewood (or summer wood) which is usually denser and darker. Together, the early wood and latewood form one annual ring. On its outer side the cambium forms a layer of bast. Outside the bast is the bark.

The living cells in the sapwood and the bast are hollow and, together with other specialist cells, form a network of tubes through which sap circulates around the tree, feeding it with nutrients. The walls of the cells are made up from ribbons of 'microfibrils' which, in turn, are formed from chains of cellulose molecules. The microfibrils are laid down in a series of layers which cross at different angles forming a kind of mat. As the cell ages this mat becomes impregnated with lignin (another hydro-carbon) which acts as a cement, thus creating a structure somewhat similar to glass reinforced plastic. This is one of the ways in which wood obtains its strength.

Thus, the characteristics of trees which enabled them to be such successful organisms also made their wood of great utility to man. The carboniferous nature of wood also made trees easy to destroy by burning.

The destruction of trees

As wood is so useful to man it may seem surprising that man has been so profligate with this natural legacy. There are a number of distinct reasons for this. One is that man has used up timber in manufacturing objects with complete disregard for the consequences. Another is the use of wood for heating and cooking. In some parts of Africa, and in Nepal, for instance, there are few trees left because the local people have cut them down to provide heat for cooking.

But the most significant reason of all is that in many cases trees are regarded as weeds which are preventing the use of land for other purposes: as somewhere to live and build, for agricultural use, for mining, and sometimes, as in the case of the Amazonian rain forest, to create a title to real estate. In such cases trees may be regarded as having a nil, or even a negative value, and will be regarded as rubbish to be disposed of in the most convenient way, usually by burning.

Another aspect of the problem is that short term gains have been preferred to much greater long term benefits. When harvested by clear felling, or other improper methods, hardwood trees represent a diminishing resource similar to fossil fuels and metal ores. However, when hardwood forests are correctly managed and the trees are extracted with care they can provide a sustainable yield of timber. At the same time, the tropical forests in particular, provide an environment which supports a wide range of sustainable products such as nuts, oils, juices, grains and pulses, rubber, and coca. They are also a source of important pharmaceutical products.

The problem, however, goes much deeper than this. The destruction of the tropical forests is not only short sighted in measurable economic terms but is leading to a potentially devastating erosion of the general environment.

The erosion of the environment

The reduction in the number of trees has two major effects as far as man is concerned: one is that it leads to a diminished environment, the other is that there is a loss of biological diversity.

The environment is eroded in a number of ways. The build up of carbon dioxide and other green house gases in the atmosphere, together with the damage to the ozone layer, presents a danger to all life on Earth. By taking up carbon dioxide the lost trees would have helped to mitigate the effects of global warming. Instead, slash and burn methods of forest clearance have added considerable amounts of carbon dioxide to the atmosphere.

Large scale deforestation can lead to significant and widespread changes in climate. A tree transpires a considerable amount of water through its leaves into the air around it. An area of shade is also created under the leaf canopy. A small wood can create a micro-climate of its own. In summer the air inside the wood can be damper and cooler than it is outside. As a consequence the humidity will also be relatively high. In winter the wind shelter provided by the trees means that the wood is warmer inside than it is outside.

In the case of vast areas of rain forest these features are magnified to such an extent that they modify the environment; particularly the temperature and humidity of the air above the forest. This not only affects the amount of rainfall over the forest itself. It can also lead to changes in the climate over a much wider area.

The roots of the trees create a mat which holds the soil of the forest floor in place. When the trees are on the side of a hill the mat not only stops the soil from being washed away but also retards the rate at which water runs off. When the trees are removed over a wide area the rainfall may be diminished but the rain which does fall immediately flows into the valleys carrying with it much of the top soil. The streams and rivers in the valleys become clogged with silt and the hydrology of the region is severely modified. On flat ground, without the shade of the trees, the soil may quickly dry out and, with no roots to hold it in place, it can be blown away. This leads to the formation of deserts.

The ecosystem of a rain forest is complex. Above ground the vegetation may be lush and the system may support an abundance of wild life; but often the soil itself is very poor in nutrients. Many of the nutrients are effectively stored in the tissues of the living organisms both above ground and in the soil. Once the trees are removed the soil quickly becomes impoverished and infertile. It is then able to support only poor vegetation. As the climatic conditions will also have been have been changed it becomes very difficult to re-establish the forest.

The diversity of species

A tropical rain forest such as that in the Amazon contains an extraordinary variety of living organisms both in the trees themselves and in the flora and insect fauna which they support. A single tree can support a number of species unique to itself. Neighbouring plots may share only 10 per cent of their species and over a distance of 50 miles plots may share only 1 per cent of their species. The total number of species of insects on the Earth has been estimated as at least five million (some scientists put the figure very much higher); about half of these are thought to be in the Amazon region. Other tropical rain forests are similarly rich in biological diversity. Thus the loss of only some of the rain forests has brought about a significant loss of species.

Chemists are continually deriving new medicines from species which hitherto have been unexploited. Who knows what life threatening diseases might have their cure in species which are being destroyed day by day? No-one will ever know how important this will be for future generations but it is necessary to preserve as many as possible of those species which remain.

Plants cultivated by man represent a very small number of species usually grown in monocultures. As such they are prone to attack by disease and from time to time, in order to produce new resistant strains, they need to be crossed with related species. Many of the latter are found only in tropical forests; if the variety of these species is severely reduced then important food crops may eventually be destroyed by disease.

The nature of the paradox

Until the development of man as a cultural animal, wielding the wood technologies outlined above, trees dominated much of the land surface of the earth. It was the characteristics of wood, which trees evolved in becoming such a successful group of species: its strength, its flexibility, and its combustibility, which made it so useful to man. The development of that technological culture led, eventually, to an exponential growth in the world population and that, in turn, to the continuing destruction of the forests. People are competing with trees for physical space and consuming them at an unsustainable rate.

This is not something new. The destruction of the temperate forest in western Europe (and elsewhere) began in the stone ages. Neolithic people managed to destroy an extraordinary amount of forest cover. Much of the rest was ravaged before the beginning of the industrial revolution in the 18th century. Since that time the remaining areas of forest have been eroded by further pressure from the activities of man. However, looking at the situation with concern for the preservation of species, and the global ecosystem, the rain forests have been, and continue to be, of prime importance.

The tropical rain forests have been steadily eroded since prehistoric times and have declined to less than half of their original size. Nevertheless, although they now occupy less than 6 per cent of the land surface of the earth, it is estimated that they contain more than half of the species on the planet. After a survey made in 1990 it was estimated that they were then being destroyed at a rate of about 2 per cent per annum.

It can easily be seen that if this rate of destruction continues for, say, 30 years then their size will be reduced by another 50 per cent or so. What will this mean in terms of loss of species?

The attempt to estimate this requires some complex analysis for which scientists use a variety of mathematical models. However, taking a reasonable compromise in the middle of the range of estimates, it seems likely that by the year 2020 the number of species found in the rain forests will be reduced by around 20 per cent. If half of the number of species found world wide are in the rain forests then it follows that some 10 per cent of global numbers of species will be lost due to the destruction of rain forest alone.

If the loss of species from all other habitats on a global scale is considered other estimates suggest that it might be of a similar order to that in the rain forests. That means that there may well be a global loss of 20 per cent of species over the next 30 years.

Such estimates are necessarily subject to a range of possible errors, higher or lower. But it should be borne in mind that high rates of extinction have been in progress for several decades and many species have already been lost forever.

On top of this there is the question of global warming and the effect of that on the habitat. Global warming is currently taking place. No-one knows for sure if this the result of man's activities or whether it is due to natural climatic variations. Be that as it may, one thing is certain: the concentration of carbon dioxide (together with other greenhouse gases) in the atmosphere is rising steadily. The greenhouse effect is real, global temperatures will rise, and will put further pressure on the ability of many species to survive.

Another important problem is that no-one knows how much damage the ecosystem can stand before the life support systems, that maintain a habitable planet, are knocked out.

For all these reasons there is a real danger that in the not very distant future man will destroy a large proportion of the present population of species on the Earth, create an uninhabitable environment and then die out himself. If this happens it will not be the first time that a large proportion of the species on the Earth have been extinguished.

Mass extinctions

Mass extinctions have happened a number of times, probably as the result of events which have altered the climate. On five of these occasions at least 80 per cent of the extant species have disappeared. The last time there was mass extinction was at the time of the dinosaurs. This made possible the development of mammals and thus the birth of the human race.

On these past occasions the reason for the mass extinction was probably a shock to the ecosystem caused by external events in its physical environment. But now the sixth extinction is in progress and it is not the result of an external force but of internal changes in the ecosystem. These have been brought about by the process of evolution itself, namely the emergence of man. It is also happening with great speed, probably much quicker than at any time in the past.

Up to now, however, the pattern of evolution has been one of collapse and regeneration. Unfortunately for mankind regeneration takes millions of years. If we and many other current species do disappear life itself will probably go on but it will take forms which are unimaginable today.

Fortunately, the current cycle of extinction has yet to run its course. It is human culture which has brought about the present situation, perhaps human culture can bring it under control. As well creating traits like war and greed our cultures also incorporate moral values and ethics.

We have seen that there are pragmatic reasons of self-interest for preserving as many species as we can. We have also come to understand that the ecosystem is so complex and inter-related that we do not know how many bricks we can remove without precipitating the collapse of the complete structure. But as well as the need to preserve as much biological diversity as we can for our physical needs we also need it for our spiritual well being.

As a result of the array of facts which are coming to light even urban man is beginning to realize that he has a close relationship with the natural world and that he is not a separate entity with a different destiny. Because of this knowledge many people are in the process forming new ethical standards which accept that human beings have no right to destroy other species.

There are, then, three sets of reasons for the growth of concern for conservation, self interest, spiritual values and ethics. Unfortunately, it has yet to be shown that this concern is being translated sufficiently quickly into the necessary action. How many of us are prepared to change our life styles, and our patterns of consumption, to the degree necessary to preserve the natural world in the form it has today?

It may be that, as individuals, we cannot do these things until a general framework for action has been mapped out which will embrace politics, economics, ethics and philosophies of life. This must take time but time is short. Our best chance of doing something quickly lies in saving as much as possible of the remaining rain forests.

So we come back to the tree; its symbolic importance now takes on a new dimension. The tree can be seen as a metaphor for the whole planet. It can be seen either as a finite physical resource (like oil) or as a sustainable source of cash crops. As the latter it can provide an environment which supports many other forms of life and act as a gene bank. For many people it is also a source of spiritual sustenance. If we can find the political will and energy to save the rain forest then, touch-wood, maybe we will have found the formula which will help us to preserve an Earth which is fit for people to live in.

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