A n d r e a s  S u c h a n t k e
What Do Rainforests Mean To Us?

The idea that the rainforest is of purely local significance is mistaken, particularly when one looks at the connections and interdependencies among the Earth's living systems. For although the rainforest comprises only 3% of the Earth's land surface, it accounts for almost one-third (29%) of terrestrial plant biomass, which represents a vast amount of fixed carbon, and which is now in the process of being "released" into the atmosphere. Forests exert a large-scale influence upon climate. They store enormous quantities of water, and release it in small doses, through transpiration, to the environment at large. Thus they prevent extremes of temperature and keep the air moist, just like a large body of water (the lack of this regulatory activity is already being sharply felt in southern Brazil, where only about 1% of the original forest cover of the state of Sao Paulo is still standing).

The white South Americans perceive the wild environment around them as a chaotic and hostile world, which must be resisted, driven back, destroyed. In Brazil the rainforest is usually referred to as mato, which means something like "bush" or "scrub." To burn, to destroy this useless mato is regarded well-nigh as a duty. Any bits of forest still left beside major highways, for instance, are at the mercy of roadside picnickers, who are very likely to set it on fire-just for fun. On weekends this is a common sight in Brazil.

Nature, for her part, and this is the other side of the story, does almost nothing to accommodate humans. The rainforest, the climax and most resplendent manifestation of plant life on Earth, is rooted for the most part in completely infertile, agriculturally worthless soils. This is an apparent paradox: surely where plant life grows in such profuse abundance the soil should be exceptionally fertile. The explanation is that the tropical flora, having extracted, over eons, the life-essential minerals from the formerly fertile soil, now retains them in cycles which no longer include the soil, for no sooner do they reach the ground than they are taken up by surface-creeping roots.

The rainforests of the Congo and Amazon basins in fact, resemble gigantic saturated sponges. Their root systems retain a good part of the daily downpour, absorbing the floodwater that streams out of the mountains in the rainy season or when the snow melts. The Amazon catchment area contains 18% of all the freshwater that flows into the Earth's oceans, in other words, almost one-fifth. It is not difficult to imagine what will happen once the forests have finally disappeared: floods and erosion will make vast regions uninhabitable, turning them eventually into desert.

Of course, such events might not have to wait so long… In the South American rainforest, the indigenous peoples are facing extinction at the hand of outside pressures, and the people settling in their place are "Neo-Europeans" who bring with them exploitative forms of agriculture (namely plantations), totally foreign to the natural landscape. These newcomers have so far failed to establish any true connection to nature in their new homeland; its ecology remains a closed book to them.

This ignorance stands in stark contrast to the fact that the ecology of the rainforest is now very well known. So well known, indeed, as to provide a basis for its sound and sensitive management, which could even include cultivating it in ways that would be beneficial for both nature and humans. But before we turn to this point it is important to form some idea of what the rainforest is and of its intrinsic nature as a composite whole.

Monotony in Green

Upon first approaching the edge of the rainforest it appears completely impenetrable, all ways barred by bushes, trees, and giant ferns, matted together by lianas and a surfeit of epiphytes clinging to every branch and trunk. Behind this tangled facade the forest interior appears enveloped in profound darkness. Of course, what the eye here observes is not the actual forest, but the structure by which it seals itself off from the outside world. Temperate forests present a similar picture where their margins have been left undisturbed: a wall of green with never a chink from the ground to the treetops. A forest has its own identity as an organism, and while it interacts with its environment, like any other living thing, at the same time it separates itself off by means of a boundary layer or "skin."

However, apart from the twists and coils of lianas here and there and the hanging aerial roots of epiphytes, there are no major obstacles, so going into the forest interior is much easier than its "skin" would lead one to expect. Undergrowth makes a rather feeble showing because of the dimness of the light: in some places only one one-thousandth of the light falling on the forest canopy reaches the ground. Even the densest temperate deciduous forest is not nearly so dark. Massive smooth trunks strive upward to the light, branching out only when they have reached a great height. Those that fail to make it remain thin and stunted, topple over, and die. Other plant forms attain the heights either by climbing up tree trunks, or by occupying the light-filled canopy from the very outset, like the innumerable epiphytes-especially ferns, orchids, and of course lichens and mosses. There are even trees, the strangler figs, that germinate in the airy upper regions and use other trees as props. After germination they send aerial roots down along the trunk of the host tree, which branch, intermesh, and gradually form a solid coat of armor around the unfortunate prop. The host tree is prevented from growing any thicker and eventually dies, leaving the strangler fig, which in the meantime has rooted in the soil and sprouted its full complement of branches, standing in the original tree's place.

The world of the forest is monotonous. Hours of walking produce scarcely any change of scene. This makes it all the easier to lose one's way, for in spite of the loose density of trees, the field of vision remains very restricted, especially as the forest canopy permits only fleeting glimpses of the sky. Blossoms abound only in the upper layer of the forest canopy: here there is enough light to create the right conditions for flowers and the birds and insects to pollinate them.

Morphological Convergence

To come into the forest expecting to find a wide range of different leaf forms would also lead to disappointment, for here again monotony is the order of the day. Most trees have almost identical leaves, which on first view gives little hint of the tremendous species diversity underlying it: every ten hectares contains up to 400 tree species. Even in wild forests of central Europe no more than ten species of tree can be expected, but most of these will differ markedly in terms of growth form and leaf shape. In the rainforest, however, what we have is the uniformity of the unrelated. Environmental pressures dictating uniformity of structure seem to be stronger than genetic differences peculiar to individual species.

The same picture emerges from a survey of the butterflies of the rainforest. Butterflies are abundant; they prefer the humid shade of the forest interior and margins to the baking heat of the open landscape. But in spite of the great variety of species considerable convergence in color and markings has taken place. Any differences correspond instead to different levels of the forest: all butterflies belonging to a particular level wear the same "uniform."

The tropical forest displays a characteristic vertical structure in being divided into a series of layers. There is one at ground level, and in the canopy there are lower, middle, and upper layers. In each layer the light and color conditions, and the associated vegetation, are different. The higher the layer the more light it will receive and the richer it will be in flowering, herbaceous epiphytes. The layers here arranged one above the other also occur in temperate forests, but there they are found side by side. Therefore, moving upward in the tropical forest is equivalent to moving out from under the trees into the flower meadow. And just as in temperate latitudes there is a color contrast between meadow and forest-loving butterflies, so here we find the same phenomenon, only one layer is above the other, instead of side by side.

The butterflies of a particular layer, however, not only resemble each other, but also match the colors and the intensity, as well as the relative distribution, of light and shade in their surroundings. The same goes for the birds, in which we find the dull ones closest to the ground, mainly light reddish-brown forms at the halfway level, and in the treetops the strikingly colored species, whose dappled plumage renders them invisible in the flickering light and shade of the sunlit canopy.

Intolerant of any kind of separateness, the rainforest subsumes everything into itself, and so it is not amenable, for instance, to warm-blooded animals with their natural tendency to emancipate themselves from the environment through the development of a complex "mental" life. Thus the animals that here come into their own are the insects. They are not noted for their rich mental life, but instead are perfectly geared to their environment through powerful instincts, which act in complicated, but rigidly determined, almost mechanical ways. Insect "camouflage," by which they, as it were, "become" their environment, is the living image of this. It appears in the way grasshoppers mimic leaves, not only with veins and ribs but even with chunks eaten out of them and fungal damage; in moths that look just like wilted leaves; in stick insects that imitate dry twigs; etc.

Organisms emancipated from their environment will have a hard time in the rainforest. This applies chiefly to mammals, but also includes human beings. It is no surprise, then, that highly evolved mentally endowed animals are the exception rather than the rule in the rainforest. And, moreover, many of those that do occur tend toward dwarfish proportions (the hare-sized pygmy antelope-the smallest in the world-does not run in the savanna, but keeps to the forest). In the few genera with species in both forest and savanna, the forest-dwelling species are always smaller: forest buffalo, forest elephant, pygmy hippopotamus. The same goes for many forest-dwelling peoples, the most extreme example among these being the Pygmies.

Food scarcity is also part of the picture here, for both animal and human being. Large ground-dwelling animals are at a disadvantage because the richest source of food is in the treetops (which is where most forest animals live). In contrast to the grasslands with their abundance of cereals, the rainforest is especially poor in protein-rich food, and since the animal body is built up largely out of protein this places immediate constraints upon body size (and population size-there is nothing remotely comparable to the herds of the open landscape).

Understandably enough, the rainforest also sets limits to the unfolding of human culture. The extremely harsh living conditions, the shortage of food, and the impossibility of developing any kind of viable agriculture prevent populations from becoming large. Small groups, whose numbers must remain constant live in scattered pockets throughout vast territories. Instead, we find that all the great civilizations were the fruit of open landscapes, of the savannas and the great river valleys, not of the forests.

A Giant Organism in Decline?

The forest in its primeval form has traditionally been regarded by humans as hostile, no matter what part of the world we are talking about. The rise of European and American "culture," based upon well-ordered agriculture, really only got underway with the clearing of the forests. Although among many modern city-dwellers' there is a strong desire to go "back to nature"-and the forest is the idealized focus of this longing-the fact remains that, in its natural state, the forest has always been alive with dangers of one kind or another. Even in our myths and fairy tales the forest is shown as a hostile place, foreboding and full of demons and wild animals; in the forest you are likely to lose your way. The clearing of the forest was the outward expression of an inner need human beings had to make the landscape their own, to tame the power of wild nature and set their cultural stamp on the land. This desire lives undiminished to this day, and is expressed, for instance, in the Neo-European urge to push back the mato, as the rainforest is disparagingly known in Brazil.

That which in former times brought great benefits-the transformation of wild forest into a cultivated landscape-is a form of cultural behavior that has already overstepped the limit beyond which lies the threat of ecological catastrophes. Today the danger is increased by additional motivating factors that have already been in play for quite some time. We now have forest destruction pursued solely for profit, which is able to carve its irresponsible path through whole areas where laws and conservation regulations exist only on paper. For instance, in the fast-disappearing rainforests of Southeast Asia the destruction is carried out by corporations that control the tropical hardwood market. They simply flatten the forest, one large area at a time, damaging the host country on two counts-it not only loses the trees, but the profits are sent to foreign banks. In Amazonia, where there is little in the way of valuable timber, vast areas of forest are transformed into intensively managed ranches, which bring a large return to the multinational concerns engaged in this activity.

Is the rainforest inevitably doomed? No, there is hope for it yet, and considerably more than just a glimmer. But in order to appreciate the full significance of what hopeful signs there are, we first need to look at a further aspect of the rainforest.

In the rainforest, life processes tend to strain away from the ground, almost to detach themselves from the earth and form their own "realm of light" above ground; this is a typical feature of the tropics. The opposite picture is presented by the arctic regions, where the vegetation clings to the earth. Both these habits are clearly correlated to the angle of the Sun. By the same token, then, in temperate regions we have "arctic" conditions in winter-the trees become dormant and only the ground vegetation remains green-while in summer we have "tropical" conditions: the herbaceous layer expands upward and the sap rises in the trees.

In the tropics, then, the tree is the dominant form of vegetation. The purely American Bromeliaceae family (to which pineapple belongs) takes this tendency the furthest: many of its species dispense with roots altogether and instead take up minerals in the form of dust through special organs at the base of the leaves. In this way they are able to live even on telephone wires. Most epiphytes do not go quite so far, however-they live off the humus in the "hanging gardens" that form on the large branches of trees. Many microorganisms that live in the ground in temperate forests are here found between 40 and 60 meters up in this "elevated forest floor." Up there also are the large herbivores-the "grazers" of the treetops, among them one with what approaches a ruminant digestion, the sloth. But in all tropical forests this role is filled chiefly by monkeys: the langurs in South Asia, the colobus species in Africa, the howlers in South America. The forest canopy is also the home of an abundant bird life. The birds share the scene with many species of frogs, which breed their tadpoles in the miniature ponds that form in the rosettes of bromeliads. The pattern is similar for numerous species of ants and termites-they build their nests not on the ground, but up in the very tips of the trees. Some ant species even take the step of carrying certain seeds into their nests, where they germinate, so that before long the ants end up with their own "gardens."

Whereas in temperate forests the greatest diversity of living processes and of species is found in or just above the ground, in the rainforest this diverse realm is transposed into the canopy. The fact that root systems are sparse and shallow is a telling indication of this. Most roots are above ground, in the form of angled buttresses or stilts, or actually hanging free in the air. The massive runners that coil all over the ground like thick snakes do not continue underground. They come to an abrupt end just under the surface, branching out into short, pencil-like rootlets, which grow down and branch out in turn into still smaller ones, eventually forming a fine mesh.

Moreover, there is nothing in the ground for the roots to take up; it is barren and contains no minerals of any use to plant life: soluble substances have long since been washed out of the ground by the torrents of rain that lash the forest, day in and day out. This is an astonishing paradox: the Earth's most luxuriant vegetation grows on the most infertile of soils. Minerals are, of course, present, but they never get into the soil, being totally bound up in the forest's biomass. The nutrient cycles are completely above ground. Leaf litter and deadwood immediately fall prey to fungi, which live in such close symbiotic association with the shallow root systems of the trees that they prevent the nutrient cycles from dipping any lower and feed all decomposition products straight back into the upward nutrient stream of their host plants.

This recycling, however, is not absolutely efficienct. Losses through leaching, which over time amount to considerable quantities, are unavoidable. The Amazonian rainforest would have been facing a natural doom if the deficit had not always been made up, and from a very unexpected quarter. The Passat, the wind that blows off the Atlantic from the northeast, brings with it mineral dust from the Sahara. The Earth's "death pole" is quite literally a key element in keeping the "vegetative pole" alive. This is a truly astonishing example of ecological interdependence. Here two of the Earth's large-scale ecosystems (Sahara Desert and Amazonian Rainforest), geographically separate and widely differing in function, are seen to be so attuned to each other that their behavior can only be compared to that of organs within an organism.

On a number of counts observation leads to the inescapable conclusion that in its present form the unique living system we call the rainforest represents the final state of a long process of development. It cannot have originated on soils poor in nutrients, otherwise it could not have come about at all. This is borne out by the fact that today the forest has almost no chance of regenerating once it has been destroyed. Its ability to fix the mineral nutrients in the living realm above ground can only have developed very gradually as a necessary response to the increasing depletion of the soil. That the rainforest is a very finely diversified ecosystem is seen both in the sheer number of species found there and in the astounding variety of highly complex symbioses between plants and insects.
If the climax of plant life on land is found in the rainforests of the equatorial belt, the most productive regions in the oceans lie close to the poles. These "algal meadows" have only a fifth of the amount of chlorophyll found in a comparable area of rainforest, but in spite of this their assimilation rate-the amount of oxygen given off into the atmosphere per unit of chlorophyll-is five times that of the rainforest (making the algal flora of the oceans the most important, almost the sole source of atmospheric oxygen).

Here lies one of the keys to understanding the rainforest. While the tiny, short-lived algae never build up any kind of appreciable mass and live in a constant dynamic flux of growth and decay, the life processes of the rainforest are more than correspondingly slow and have a tendency to bring the substances they take up to a standstill, to fix and store them. The result is the great accumulation of biomass found on land. To reiterate the figures quoted earlier: although the rainforest covers only 3% of the Earth's land surface, it accounts for almost a third of the total biomass-just as much as that in all the oceans, which together take up 65% of the Earth's surface!

The crucial point here is that only a small proportion of the rainforest's biomass is truly living substance. Of the 1,000 tons per hectare, only 20 to 30 tons are living leaf-matter. By far the most part is dead wood, in other words, carbon in fixed form. If we consider the rainforest from the point of view of the tremendous density and ironlike hardness of its timber-timber that sinks in water like a heavy stone-it appears in a rather strange light: it displays an extremely strong tendency toward mineralization, stronger at any rate than in any other living system, and on a scale that is outstripped only by coal formation. This affinity with coal appears nowhere so strikingly as in ebony, the black color being a clear indication of its high carbon content. That this mineralization process stops short of coal formation is due entirely to the combined efforts of the teeming hosts of decomposers and compost-making organisms in the forest: the fungi, ants (the actual lords of the forest) and termites.
Viewed in the context of marine vegetation, the earliest, one might say "youthful," phase of the plant world, the rainforest appears as the most highly differentiated and most aged stage in the development of the Earth's vegetation. This impression of old age is strengthened when the transferal of the forest's living processes from the ground into the canopy is added to the picture. Something that originally was closely bound up with the earth and permeated its upper layers has successively withdrawn. In the large-scale organism of the rainforest, something is occurring that is the same as the process all organisms go through when they die: the life processes withdraw, they "excarnate."

It is no wonder, then, that all it takes is a little nudge, and the rainforest is destroyed forever-a state of affairs quite unlike that in temperate latitudes, where living processes are (still!) so connected to the earth that if the landscape were left to itself the forest would quickly return.

Is Rejuvenation Possible?

What has been said up to now should in no way be misunderstood as a plea for a laissez faire attitude for the continuing destruction of the rainforest, based on the motto, What does it matter, we're only following nature by helping a dying ecosystem on its inevitable path to oblivion! Nothing could be further from the truth: the rainforest is not about to die tomorrow-we can expect it to last for many millennia yet.

The point is, the conventional attitude sees conservation as the only alternative to destruction, but what is required here is something more radical and far-reaching. Between the two extremes of wanton destruction and absolute protection there is another possibility: rejuvenation. This would involve intervening in the senescent stasis of the rainforest ecosystem in a way that would return it to a more "youthful" stage. This could mean introducing something new into the system or releasing the forest's own powers of rejuvenation, but either way it gives humans a creative role, which demands a great deal of effort and commitment. Utopian as this may sound, it is entirely practicable; and it is extremely urgent, for we are in a race against time, against the ever-encroaching destruction that is proceeding by giant steps and will soon attain a momentum that will prove unstoppable.

History provides us with ample evidence that humankind is capable of bringing about the rejuvenation of mature ecosystems that have reached a certain end-state (a state in which no further change will take place, assuming the climate stays constant). In many locations over the whole Earth the original natural landscape has been transformed into one shaped by agriculture and the patterns of human settlement. In Europe, before humans began to exert this cultural influence, a deciduous (mostly beech) forest, exceedingly poor in plant and animal species, had spread over large areas. Clearing it, of course, meant destruction-but that was by no means the end of the story. Human culture eventually replaced the forest with a newly created and richly structured landscape of meadows, fields, orchards, hedges, copses, and woods, which provided habitats for a wide variety of wild plants and animals that had not been present before. To these were added the many new breeds produced by animal husbandry. Such a reshaping of the landscape certainly involved radical intervention in nature-but in this nature was not diminished. Quite the reverse, in fact-nature underwent further development. Left to itself, nature would have maintained its achieved climax state indefinitely, with at most tiny variations from time to time.

If this sounds too optimistic or too much like wishful thinking, we should bear in mind that nature itself does not behave any differently. Two opposing tendencies are constantly at work within it. One moves toward invariance, stability, and balance, ensuring that organisms are perfectly adapted to their environment-in short, toward a steady state. The other moves toward drastic changes, usually occurring in the form of external attacks-climatic changes, floods, continental drift, mountain formation, etc.-which mean catastrophe for the steady state and lead to mass extinctions. At the same time, however, the changes provoke new developments-new landscapes with new ecosystems emerge, new animal and plant species spread over the land.

It must be admitted, of course, that the conditions that render European beech forests susceptible to transformation into fertile agricultural land are not those of the rainforest. This means that methods appropriate to the one region cannot be applied to the other. To do so would simply be propagating ecological imperialism (or colonialism) in a modern guise. Each specific situation demands specific methods, developed locally to establish the conditions that in more temperate climes such as Europe are given from the outset-in other words, to create a fertile soil. The cycles of life, which hold the key to fertility and which have been so rigorously withdrawn from the earth in the rainforest, must be anchored in it anew, must be, as it were, "reincarnated."

The Kayapó Indians of the Amazonian rainforest offer one of the most impressive examples of rejuvenation practices. In contrast to the other tribes ranging through the region, most of whom are hunter-gatherers, they pursue a highly developed form of forest cultivation, which goes hand in hand with careful conservation. For instance, the Kayapó plant tree seedlings all year round, especially Brazil-nut seedlings. Another of their practices is the occasional felling of single trees, which creates enclosed sunlit clearings where hundreds of medicinal herbs either are planted or seed themselves. In addition a luxuriant ground cover emerges, which is absent elsewhere and attracts game. In island-like clearings, the Kayapó manage, through highly refined composting techniques and the selective addition of certain plant ashes, to create fertile loam-an astonishing achievement considering that the untreated soil is as good as sterile. Crop plants are sown in mixed cultures made up of a large variety of selected species. The Kayapó call these ombiqua o-toro, which roughly means "friends in growth"-an accurate description, for the plants do grow better in these combinations than they would alone.

There are also other agroforestry approaches. They are all unconventional, pioneering enterprises, but they are standing the test of time. One of the keys to their success is treating the soil with the right kind of manure. Organic compost, when used correctly, is resistant to leaching, unlike chemical fertilizer.

Organic agriculture is proving its worth to a more striking degree in the tropics than in temperate regions. With its ability to come to terms with the fragile ecosystems and worn-out soils found there, it may indeed be the only way of giving agriculture a viable future in the tropics. Nature also stands to benefit from it. Through its rejection of monoculture and its creation of a diverse pattern of small cultivated plots of different kinds-fields, meadows, groves-it creates a rich mosaic of biotopes and habitats in which numerous wild plants and animals can find a home.

If such ecologically based agriculture were to spread, it would bring with it other advantages. In contrast to the giant monocultures of the plantations, which are tended by machines or migrant workers and have caused the depopulation of large areas in the South American interior, organic agriculture is very labor intensive. Many people forced to join the never-ending stream of migrants to the big cities could be resettled and could make their living on organic farms. Such resettlement will in any case have to take place sooner or later if a country like Brazil is not to collapse in hunger and social catastrophe.

For the Western world there are, of course, lessons to be learned here. We could begin, for instance, by correcting the false assumption that preservation and cultivation of the rainforest are totally incompatible. Unfortunately the media continue to promote this assumption, as well as many biologists who would prefer to exclude all humans from the rainforest (apart from a few highly qualified specialists) in order, at all costs, to avoid any disturbance of its biodiversity. They would like to turn the rainforest into a museum. This extreme, purist version of conservation holds no promise for the future and is only concerned with preserving the legacy of the past. While it keeps out people's destructive tendencies, so does it deny their creative potential.

The rainforest is very popular in the Western media. People react to its plight with a mixture of shock, nostalgia, and resignation: it is tacitly assumed that all attempts to save it are bound to come to nothing. Nevertheless, I have experienced time and again when speaking about the rainforest to students that as soon as the subject of the Kayapó or new agroforestry methods are broached, there is a spontaneous surge of enthusiasm, with not a few of the young expressing the wish to be there doing their bit. If these things could become general knowledge, international pressure upon the countries concerned would no longer need to consist merely of measures to force them to halt the destruction, but could be increasingly aimed at encouraging existing and genuinely workable alternatives. And that would be developmental aid worthy of the name.