F. FRASER DARLINGThis is a working document for the Unesco Intergovernmental Conference of Experts on the Scientific Basis for Rational Use and Conservation of the Resources of the Biosphere-held at Paris, from 4 to 13 September 1968. It has been prepared on the basis of a draft by Dr. F. Fraser Darling (United Kingdom) with comments and additions by Professor Vladimir Sokolov (U.S.S.R.) Professor Frederick Smith (United states), Professor François Bourlière (France) and the secretariats of Unesco and FAO. R. G. Fontaine is the FAO representative on the conference secretariat.
The manifold effects which the physical presence and activity of man have had on the face of the planet Earth through the relatively short period of man's history tend to be dynamic and interlocking, yet it is worth while attempting to classify them for a clearer understanding of temporal and spatial factors. The world as it existed before man used tools and fire was one of immense richness in natural resources, organic and inorganic. But to say that is to put the cart before the horse natural resources were not resources at all until man was both present and able to make use of them. The ability to identify, reach and use natural resources has been a continuous process for man, and there is now a fair archaeological and historical understanding of the differing rates of exploitation in different parts of the world, the sudden changes of rate and style caused by changes in human condition and the enormously accelerated rate of change within the last century. It seems certain that man's ingenuity is running ahead of his wisdom. But the mistake must not be made of thinking men are wise if they express their notions with the constantly wagging finger and negatively-shaking head of Jeremiah. If civilization a flower of evolution, it could not have grown had not man gained leisure to think and flexibility to act by actively managing to turn some of his environmental wealth to his own advantage beyond that of mere sustenance.
From the beginnings of civilization, man has altered environmental processes as he dug into the organic store of the planet's ecosystems. Even to light a fire of dead wood for keeping warm is to deflect a natural process of decay, which would be humus-building, into the production of inorganic ash. For a long time man may not have been much else than the equivalent of an indigenous animal of limited change-producing activity, but even at the advent of the neolithic revolution, hunting and food-gathering man had changed parts of his world more or less unintentionally by the use of fire. This is a point to remember in considering the influence of man on the biosphere as a species his impact goes far beyond the immediate contact. Fire would run and change vegetational complexes, fires would be used to help drive herds of game animals, a prodigious expenditure of organic matter for momentary expedience, and burning in season would be done to draw grazing animals to new grass, a path of inevitable impoverishment of habitat. Man was controlling the behavior of wild animals to some extent by these expedients which were slowly altering his habitat and theirs.
Men were so few and the world apparently so large that it would have been strange had man dwelt philosophically on his own numbers and the fate of naturally riches. Even in the present century men speak proudly of their duty and their success in pushing back the wilderness. The student of the human condition, however, although he may hold to the philosophy of conservation, will accept the price of civilization which has been the loss of much natural wealth. When was the critical moment when man should have become conscious that a halt must be called to bald exploitation and exploitation must be matched with rehabilitation? It is possible that this moment has been reached now. The fear today is whether rehabilitation is possible or whether causes and consequences are setting up their own percussive oscillations to an extent beyond control.
It is worth while attempting some classification of man's impact on the biosphere, possibly in developmental and qualitative order which could be flexible and capable of being redistributed as an ecological diagram of interconnecting factors. It can be much expanded and given change of emphasis. Man's impact is not to be thought of as being wholly to the detriment of his ultimate welfare though it may be preponderantly so. Certain man-modified habitats may represent ecosystems of equal or greater production and wealth-building power than the natural condition. Wealth-building in this connotation means the storing of organic capital as in a tropical forest or in a prairie soil or Chernozem.
An attempt has also been made to identify the now problems created by accelerated development and also to list the various measures taken until now by man to maintain the quality of the environment.
FOOD GETTING
Animal hunting with the use of fire
Fire has been used for animal hunting, destroying forest incidentally and preventing much regeneration. But production of savannas as in parts of Africa with a rich spectrum of ungulate species may lead to a rich habitat for organic production. The savannas of Brazil and Guyana seem definitely to lose out as to their qualitative potential. Is this because of a limited array of ungulates as compared with Africa? Again, in North America, the Indians extended the prairie range of bison by burning forest and the resulting humid prairies maintained a very high rate of production, accumulating an immense store of rich soil.
Sometimes the terrain is also being burned intentionally to produce fresh young grass this leads to impoverishment of the array of plants present originally, which upsets flexibility of the grazing complex in face of seasonal climatic variation. Examples are production of Molinia and Scirpus swards in the Scottish Highlands and the gradual elimination of grass, giving way to gall acacia and lantana bush in parts of Africa and mesquite in the southwest of North America. Many important variants originate according to the frequency of burning and, in tropical countries particularly, the time of burning in relation to the dry and wet seasons.
Settled cultivation
Settled cultivation, in opposition to shifting cultivation, leads to soil exhaustion if replenishment is not understood or impossible, or to possible aridity if active steps are not taken. The English "brecks" or broken lands are thought to have developed from neolithic cultivation. The dust bowl of the United States in the 1930s showed what continuous extractive cultivation without adequate replenishment could do when a cycle of drought years was encountered. Broadly, cultivation must manage to sustain the level of organic matter, or the soil either bakes or blows away. But many examples can be given where settled agriculture, under various ecological conditions, had been successfully carried out for centuries in the Far East, the Near East, the Mediterranean area and Central America. The ancient Negev demonstrated the efficacy of counterworks for the conservation of water abandonment of these resulted in almost complete degradation of the habitat.
Shifting cultivation
There tends to rise in the collective mind of conservation-minded people an antipathy toward shifting cultivation as being wholly deleterious to habitat. Examples could be given of this practice, however, that produce variety and valuable "edge effects" (that is, creation of ecotones) so long as the human population is low. The chitemene system in Central Africa is a good example the gardens are not larger than half a hectare or so and, being surrounded by bush on fairly level terrain, soon return to bush after three to five years of use, and are not used for a further 40 years. Immediately after being relinquished these gardens are taken over by colonies of Tatera rats while the soil is loose and friable. The rats form a secondary protein crop for a year or two, when caught by small boys. Following this, the bush slowly recovers and replenishes the soil. Another good example of sophisticated and conservative shifting cultivation is given by Hanunóo agriculture in the Philippines.
Increasing human population causes the bush to be broken again too soon and deterioration of habitat follows. Shifting cultivation on steep slopes is almost wholly bad and, on some geological formations such as limestone, milpa cultivation may be quickly disastrous. Shifting cultivation is the bane of central and northern South America and land hunger with rapidly increasing human population creates a vicious circle from which it is difficult to break. Erosion is having long-term effects on far greater areas of country through interference with water relations.
Irrigation
Irrigation has a long history and is still a popular line of development, but in large-scale irrigation projects, improvement or maintenance of soil fertility over a long period raises many problems. As they are so often sited in arid areas where a high evaporation rate has kept salts in the soil, irrigation tends to redissolve the salts and deposit them again as a crystal crust lie-use of irrigation water (as from the Colorado river) can mean good ground being made saline and useless at lower levels of operation. This also happens on Bear river, Utah, and on the great Sind scheme. Wise irrigation, or possibly fortunate irrigation, uses rainwater and, if this is adequate in supply, it can wash the more saline ground of the arid parts where the water is used. The Gesira scheme in the Sudan is an excellent example, where the country's economy has been much strengthened by nonsaline water from the Blue Nile (which runs at a higher level than the White Nile) which is taken off and spread over the triangle of the Gesira. The used water drains into the White Nile on the lower side of the triangle, the volume of which renders insignificant any salinization suffered by the Blue Nile water passing across the Gezira.
Overgrazing and overbrowsing by domesticaded livestock
Once domestication has occurred, sedentarization limits movements of stock and overgrazing is often the case. Different species of domestic stock adopted for different climatic conditions make for maintenance of habitat, but this can easily be upset by natural fluctuations of conditions. Technique of successful grazing has to be learned, and even when learned may not be generally followed. A modern research station can fall short, as for example during the reindeer era in Alaska when deterioration outpaced the research and both the grazing and the reindeer population dangerously affected Modern examples of extractive grazing such as in parts of Africa, Australia, and New Zealand, and the short-grass prairies of North America have rapidly caused deterioration of the soil.
Nomadism of pastoral origin
This deserves special mention because it can be so easily upset or broken, to the detriment of the habitat. Nomadism is at best a pursuit of the steppe regions of the world and produces least deterioration. It is utterly bound up with movement if habitat is to be conserved. Any undue lingering punishes the vegetational complex, reduces its numbers of species and therefore impoverishes it. The finest nomadic areas of the world were the Chernozem plains, dike those of the Kuban where the Scythians roamed in the time of Herodotus. Their capacity for and dependence on movement exasperated Darius. Nomads depended on animal products for sustenance and warmth, and as protein consumers were an ecological elite, at the top of the food pyramid if they increased in numbers, families, clans or tribes had to split off and move on. We know of these frightening nomadic emigrations in history. Less good steppe was used, forest edges on mountain ranges were used, and there was an inevitable slow change, usually for the worse.
Conversion of Chernozem steppe from protein production, whether of livestock in the Ukraine and Kuban or bison in the American prairies, in order to increase production of wheat and maize, was a relinquishment by the human being of his ecologically aristocratic position. He now converted a complex community of grasses into a monoculture of one annual grass, wheat or maize, the seeds of which he could eat. This permitted a much larger number of mouths to be fed from the rich steppe by substituting human mouths for the grass-eating mouths of horses, cattle and sheep, but also meant a loss in reciprocation of the system as it had existed. Organic matter was stripped out as grain, for that commodity was not consumed on the steppe as had been the animal products, so there was profound loss of organic matter. The same thing happened in North America, when the Indian-bison continuum was replaced. The Chernozem soils of America and Europe have stood up well to the extractive agriculture imposed upon them and there is the likelihood that good agricultural methods will maintain them in the future, but a revolution of the plow of this kind always extend) beyond those soils which are best able to bear it. Higher, poorer, and more arid steppe has been subjected to the dry farming of wheat with disastrous results.
Wherever sedentary populations have impinged on nomadic grazing there has been degradation of habitat for which the nomads are invariably blamed. Yet nomadism as a careful pastoral continuum is the least traumatic of human influences and as a form of husbandry utilizes areas which could not be utilized by man in any other way. It is essentiality ecological in structure, relying on movement and use, a wide spectrum of grazing animals adapted to well understood differences in habitat and producing much energy without loss organic matter.
Nomadism is always unstable apparently small political changes reduce it to habitat spoliation. The Masai in east Africa are a Nilotic tribe moved from a humid homeland into high, dry, steppe country. Yet their knowledge was good and accurate and their habitat did not deteriorate until the white man's veterinary skill broke the full incidence of mortality which formerly kept the herds to a proper level for the stock-carrying capacity of the ground, The Masai and their country are a good example of integration of nomadism with the indigenous animal population. Wild game existed alongside domestic herds, tolerated and-respected. This harmony may well have originated in the Nilotic home-land, as in the Bahr-el-Ghazal, where the Dinka accept giraffe as part of the cattle herd. The Nilotics practice a restricted nomadism seasonally between the toich (grass flood plain) and the slightly elevated bush to which the herds return in the wet season. The Dinka's practical, empirical knowledge and acceptance of the ecosystem approach to living in his rich world is further exemplified by his tolerance of a small poisonous snake which inhabits his thatch and keeps insects within bounds. Even in this paradise of symbiotic cattle culture, the march of modernity and the hungry mouths elsewhere are demanding rice culture, the exclusion of game animals, and the distended but unsatisfied belly of the carbohydrate eater.
This section may be concluded with an example of nomadism having become allied with political power and made so powerful by law that a whole country was devastated. This is what happened with the transhumant society of the Meseta in Spain in the sixteenth century, to which Ferdinand and Isabella agreed for the profit of the Crown. Flocks of Merino sheep were driven through cultivated areas, and it even became illegal to fence against them. It took Spain nearly 200 years to beat the Meseta but the bare hills of Spain remain to this day.
ACTIVE DEPLETION OF RENEWABLE NATURAL RESOURCES
Deforestation
This has taken place from earliest times and is probably -better documented than most other types of change of habitat. The earliest effect of restricted deforestation is one of enrichment of the habitat by providing change in a situation of little or no change. Parkland in forest is appreciated by many grazing animals. Primitive and later man, utterly surrounded by forest, arrives at a psychological state eventually when he must push back the forest and not be enfolded. The mediaeval horror sylvanum was very real, and should be remembered for a better understanding of history.
The Anglo-Saxon colonizing a fifth century Britain which had islands of plowland and pasture connected by roads in a sea of forest was not only knowledgeable in tools and woodwork, but clever ecologically. To create new arable ground in the long term he used the snouts of herds of swine, descendants of the European wild boar, as a biological plow or grubber in the oak and beech forest. They garnered the pannage and by concentration of effort prevented regeneration. As actual felling took place, grass followed on the cultivation by the pigs and grass parklands or lawns were created, to be plowed as needed. In temperate, humid Britain, the changed biological system of forest to grassland with occasional trees made for little loss of organic matter and the output of free energy was probably not far behind that of the forest. Certainly it allowed more to be made available for human consumption.
The tendency to export natural resources leads to devastation, as has been documented many times. The oak forests of England did not all fall by the axes of the early Anglo-Saxons. The rise of England as a naval power involved heavy felling, and the use of iron demanded more felling for smelting fuel. In the early seventeenth century the unrestricted felling of English timber was prohibited. This drove the iron smelters to the woods of western Scotland where the long sea lochs allowed ships laden with iron ore to penetrate deep into the forests of Scots pine and oak in the glens. Here devastation came quickly because of the high rainfall, acid soils and steep slopes. The Forestry Commission of the present day is still concerned with the repair of this damage, but at great cost because active humus has long disappeared from the once-timbered slopes.
Perhaps the onslaught on North American forests was the main reason for the rise of the principle of conservation. Fairfield Osborn said in 1948 of the United States "The story of our nation in the last century as regards the use of forests, grasslands, wildlife and water sources is the most violent and destructive of any written in the long history of civilization. The velocity of events is unparalleled." This fact of weight and speed of destruction may find its absolution in the rise of the ideal and practice of conservation in the United States. Similarly, in Africa, an awareness of the need to conserve has often emerged as a result of destruction and denudation.
On a happier note, it may well be that the African Special Project carried out jointly by FAO and the International Union for Conservation of Nature and Natural Resources was the turning point in attitudes toward conservation in the rest of Africa that and the Arusha Conference of 1961.
The felling of tropical forests has been a story of unrestricted extraction. The massive and impressive accumulation of organic matter presented by this oldest life form on the planet tends to mask its fragility. Like most forest forms, the tropical is primarily a photosynthetic factory of cellulose, with any protein as very secondary production. The tropical forest floor has been protected from the sun for thousands of years with the niches for decay and conversion so well filled that nutrition of the trees and the life of the canopy are bountiful. When the forest is felled the tender soil exposed to the sun oxidizes rapidly and disappears as Omar Khayyam wrote:
"Like snow upon the desert's dusty face
Lighting a little hour or two - is gone."
The mahogany forests of Hispaniola have gone, those of Honduras are going and the results are only too well known.
Many countries, particularly within the tropics, have had their forest resources exploited without any provision for sustained yield management. It can be argued that because of local economics and political structures they had no alternative, and a good proportion is likely, to resort to such expedience in the future. In order to survive they need ready cash to operate politically. Politics are peculiarly bound up with such expedience. It must be realized that political decisions are, and have been, a major factor affecting the natural environment.
Drainage of wetlands
In general, wetlands are highly productive of protein in the shape of mammals, birds, fish, and invertebrates, but not always in a form acceptable to the human being as food. Drainage has throughout history created navigable channels in various parts of the world and provided more agricultural land. The Netherlands and the fen country of England are good examples, and there are many such areas in the United States. Where the soil is alkaline peat it becomes highly fertile when dry enough to manage, but so contracts in volume that diking and pumping become necessary, for the land won is then below the level of the adjoining sea. The situation is vulnerable and the soil itself is so friable that it tends to blow. The question must always be whether the considerable capital works necessary can be maintained and whether the potential fertility of wetland soils can pay for them. Once more the ecosystem is being changed from protein to largely carbohydrate grain production. Certainly more mouths can be fed on the "devaluated" product. The aesthetic loss of beautiful species, especially birds, as a result of drainage in wetlands is considerable. The United States has changed its former policy to some extent by allowing wetlands to refill and resume their former land form, for example the Klamath marshes in northern California. It might be said here that allowing marshes to refill is only possible as a policy in a country affluent enough to be producing grain surpluses and where wildlife is beginning to have extrinsic values for recreation.
The Everglades national park in Florida provides a beautiful example of the complexity of wetland habitats and what can happen when water is deflected from these areas. This is essentially a wilderness, and wildlife area on a flat oolite base slightly above sea level and tilting slightly southward. The Everglades depend on the seasonal passage southward of large quantities of water moving very slowly. During the wet season all wildlife disperses over the area and in the dry season it contracts to alligator holes. Alligator holes serve as survival reservoirs during the dry season. Drainage north of the park has deflected much of the water which should flow over the Everglades and the water table has thus been lowered. Further, a hole has been punched in the bottom of the system in the shape of a canal running up from the sea into the Everglades for the passage of pleasure boats. This both allows quicker loss of water and the occasional invasion of salt water. Finally, there has been a long period when alligators have been illegally hunted. Failing greater care of alligators, artificial alligator holes will have to be made to maintain many other species of plants and animals. The Everglades is a large national park, but is a vivid example of several thousand square miles being in sufficient as an ecologically independent area.
Africa has many interior wetlands and one of the most promising lines of development in recent years has the improved management and extended use of the fish resources of these wetlands. Zambia is an excellent example of the achievement of an improved standard of nutrition for a new industrial population from the freshwater fisheries of the numerous swamps. Yet the projected increase in human population has -caused serious consideration as to whether such areas as the Kafue and Chambeshi flats should be drained to serve as wheat-growing lands. Not only would fishing be constricted as a result, but the herds of game animals would also disappear, despite the fact that the red lechwe is an antelope moving in large herds, adapted to grazing inundated lands and potentially capable of management as a meat-producing animal.
Overhunting of desirable species
The disappearance or decrease in numbers of species has altered the ecosystem and the habitat. Knowledge of niche function is growing but there is much to learn about habitats in which a niche occupant has been removed. The elephant would provide a good comparative study because there are plenty of habitats from which it has recently been removed by overhunting and others in which it is more numerous than ever because of protection. In the latter situation production of grassland and removal of bush with the tsetse fly is being pushed back. The elephant is the agent of change but man's distortion of the elephant's way of life is the instigator of change. Not enough thinking has been done about the influence of reduction of game on the African savanna. Bison on the North American prairies were followed by the plow, so little is known of the change which actual reduction would have caused except that, on the fringes of prairie, as in Wisconsin, there is a coincident rise of even-age forest.
Intended extinction or eradication of species
The wolf is perhaps the best example because of its direct challenge to extended pastoralism. The supposed behavior of the wolf has become a psychological fiction which can still influence habitat. In the recent past, bounties were still given for wolves killed in the Arctic where human predation of the caribou was quite insufficient to crop the caribou population and to safeguard the range which, if overgrazed, might take a century to recover - longer than caribou could wait. There were excellent object lessons in the extinct reindeer populations on the west coast after 30 years of overgrazing of the ranges, but the psychological obsession about wolves had blinded people to the real cause. These overgrazed ranges can still be seen as different from the surrounding terrain when viewed from an airplane at 6,000 meters.
The necessity for frequent or continuous movement was described in relation to nomadic pastoralism. Wild animals have their natural behaviour patterns but not entirely of their own volition. There is the curious habit of "yarding" with several species of deer, treading around as a large herd in one small area in dead of winter. Food may be found further afield but they do not go to it, unless wolves or other predators stimulate them to move. How far lack of this function of the predator was responsible for the sudden decline in numbers of mule deer on the Kaibab plateau, Arizona, in 1916 will probably never be known. Mountain lions were still being killed in the Grand Canyon national park in 1950, so deep rooted is aversion to them. The influence on habitat of violent fluctuations due to lack of predator populations, which not only cut down numbers but keep the herds of their prey moving, is a matter for concern. Recent work on the moose/wolf ratio and equilibrium on Isle Royale in Lake Superior shows how a woodland habitat carrying these large deer can be maintained when man allows the wolf to do all the necessary culling.
CONSEQUENCES OF MINING AND INDUSTRIAL PROCESSING
Toxic fumes and detritus
Smelting liberates toxic fumes which kill plants and sometimes animals. The sterilization of areas by copper smelting in Tennessee is well known. Aluminum smelting at the foot of the Great Glen in Scotland produced fluoride fumes which were blown northeastward up the glen by the prevailing winds. Grazing was affected and young cattle suffered. It took a court case and very dilatory action thereafter before scrubbers were installed to remove the hazard.
The lead mines and feldspar workings of Derbyshire, England, left areas of spoil with which the herbage was so impregnated that young stock could not be grazed on it. Lead poisoning affects the earth centuries after mining has ceased.
Interference with natural drainage
Coal and shale mining not only create conditions where subsidence occurs, but large quantities of detritus are dumped on the surface near the mine shaft. These vast dumps not only ruin the landscape aesthetically but also cause serious interference with surface drainage. At worst, these dumps are a menace to human communities as was experienced so tragically at Aberfan in Wales. The recent marriage of ecology and landscape architecture shows immense promise. The English counties of Durham and Northumberland have successfully initiated schemes for covering pit heaps with vegetation The United Kingdom National Coal Board has done much opencast mining in the north of England and immense care is being taken to rehabilitate the landscape afterward, to the extent of 11 percent of the Board's income. Similar spectacular results can be found in several regions of the Federal Republic of Germany.
The strip mining and auger mining of the hills of Kentucky, U.S.A., are leaving eyesores of dereliction along the faces of the hills, and the watershed erosion which follows is causing serious repercussions below these hills on the good soils of the Ohio river country. It is all the more distressing to hear that the coal is being mined for sale at the lowest possible price to that model of rehabilitation policy, the Tennessee Valley Authority. One of the difficulties in much conservation endeavor is to stop different agencies within one nation working to each other's disadvantage. Once more there is a lack of adequate legislation the process of law being largely by precedent, it can scarcely keep abreast of changes unimagined in the past.
Dumping of wastes into rivers
This is an obvious and well-documented way of changing the biosphere. The trouble arises from the primitive notion that a river is a natural sewer. Papermaking is a modern industry - in terms of centuries - which has been responsible for fouling many rivers. The State of Maine, U.S.A., has a relatively low human population, but its rivers are polluted to an extent that precludes most of them receiving a run of salmon. Where human population is dense, sewage is the main problem. Knowledge is being gained all the time of how to deal with industrial wastes, but regulation lags. The recent increase in the use of pesticides has had a few tragic sequels in the poisoning of rivers and ditches. In comparison, the carelessness of shepherds when draining out baths of sheep dip is a small thing, but indicative of the thoughtlessness that spreads man's deleterious influences over habitat beyond the immediate vicinity. There has not been sufficient realization that much marine productivity on the continental shelf has an estuarine basis.
CONSEQUENCES OF HUMAN POPULATION DENSITY
Losses and gains in plant and animal life
Obviously there must be losses when man becomes gregarious beyond the hunting and food-gathering stage. It was changing ecosystems so that more produce was available to man that created gregariousness and the development of civilization. Certain timid animals keep their distance from human aggregations, others adapt to them, even though they remain timid. The fox in the suburbs of London is an example. Plants, being less mobile, have less choice and many species are stamped out. The large human foot with our upright form above it is much heavier on herbage than many people imagine. This has become obvious, and even crucial, in large national parks such as those of North America where blacktop paving is having to be laid in growing quantities to safeguard fragile plant associations in alpine, desert, and forest areas. A spongy woodland floor will show footmarks for years the tundras of Alaska are crisscrossed by the tracks of cater pillar vehicles and jeeps, and it is doubtful whether some of these tracks will ever disappear. It may be thought that forest trees are immune to the tread of human feet, but not so. The French find it necessary to fence individually the largest oaks in the forest of Fontainebleau because impaction of the ground by picnic parties beneath them eventually kills the trees.
The rapid rise of the human population in India in a climatic situation of wet and dry seasons illustrates the power of human feet to remove vegetation. Village sites are now bare, dried mud where three years ago there was secondary jungle. In these situations, where physical building is quite flimsy and sometimes no more than poles, burlap and corrugated iron, it is not definite planned urbanization paving the surface of the earth, but the passage of human feet and of domestic animals. The latter contribute to the general denudation by their own browsing habits and the necessity to cut down branches of trees for their sustenance.
Certain tribes in propitious habitats realize the immediate advantage to be gained by cultivation within the forest edge. The Kikuyu of Kenya are an excellent example these people have pushed back forest to a dangerous extent, especially in recent years since the tenfold increase in the tribe under the Pax Britannica.
Man altering ecosystems purposely or unconsciously usually simplifies them and makes possible the invasion of plants and animals of earlier stages of succession. Annual and biennial seeds are good examples. The animal world has ready invaders such as the brown rat and the common sparrow, which follow man wherever the wheat plant is grown. This is not the place to explore the subject of exotics, but their influence on habitat is worthy of special study in relation to the changes man has brought about in the biosphere. There exists a limited field for congratulation in pleasant residential suburbs where gardens express beauty and birds come in greater variety than might be found in the countryside. In fact, unconsciously or no, a diversity has been created to which nature has been quick to respond by adding its own contribution.
Pollution of air, water, and soil
Pollution, the greatest problem of modern times, has been left till last. No longer is it just a matter of England's industrial north, Germany's Ruhr, the U.S.S.R's Yaroslavl and Gorky, as being instances of the polluted areas where money is to be made but where it is better not to live if possible. In the last quarter of a century the whole planet has been polluted by man so that the fat storing creatures of the remote Antarctic continent, penguins and seals, carry in their fat appreciable quantities of organo-chlorine compounds, commonly alluded to as pesticides and not used within many hundreds of miles of any part of the Antarctic continent. There is virtually a cessation of reproduction in some Species of birds which have not been the objects of dislike but only of pleasure Man himself carries these impurities in the fat-of his own body and is as yet unaware of any effects on him, for good or ill, but most thinking people are concerned about the possible effect of accumulations of these compounds over the years. Some developed countries have regulated the use of pesticides and cut down dosages, but this has meant the economic dumping of large quantities in tropical countries where there are sufficient pests and little control over the use of pesticides. The informed know that to regulate use in some countries but not on a world-wide basis does not prevent pollution of the biosphere. Man is today a world citizen.
Much also be said on radioactivity. In the recent past the radioactive level has been increased in air, soil, water, and living organisms over large areas of the world. Experimental A and H bomb explosions and some other works with radionuclides represent one of the greatest dangers for all living organisms on earth.
What might be the planetary profit and loss account in relation to the expenditure and production of oxygen? It is thought that the atmospheric figure of 20 percent oxygen has been evolved by the photosynthetic power of plant life and the slow deposition of organic matter in the deep ocean sediments. When a jet plane crossing the Atlantic burns 35 tons of oxygen, is industrial process and combustion dipping seriously into the margin of production over consumption, especially in terms of the rate of destruction of forest growth and other plant life? Oxygen consumption and carbon dioxide production are to some extent linked the carbon dioxide content of the atmosphere is rising and this could lead eventually to such an increase in the temperature of atmosphere and oceans as to cause a substantial ice melt which would appreciably raise the level of the oceans. Pollution, combustion and destruction are combined here in their ultimate power to change the biosphere.
The deposition of sewage into rivers is of course age-old. Lakes receive this effluent, and eutrophic conditions are being reported from areas as far apart as Lake Erie on the border of Canada and the United States and Lake Baykal in the U.S.S.R. Life in some lakes is being asphyxiated through lack of oxygen and too great a deposit of organic matter. Riverbanks and lakesides are becoming overpopulated. In order to be able to live at high densities of population, all sewage and waste matter must be processed. Man is definitely trying to mend his ways but not fast enough. London's River Thames is improving thanks to civic action, and the sport of trout fishing has saved from pollution many streams that feed the Thames and other rivers in England.
The wreck of the Torrey Canyon focused the attention of everyone on the growing hazard of heavy oil- pollution of the sea and the secondary evil of detergents used to combat the oil - which killed more marine life than the oil itself. Responsible oil firms are taking the dangers of oil transportation by sea as a major task of research. Half the world's ocean cargo weight is oil - 700 million tons of it last year in 3,218 tankers. Separators of improved design at ports, plastic booms round oil harbors, flocculants for spillage at sea, jelling agents to solidify oil in threatened tankers and new methods of loading and ballasting giant tankers, show a willingness on the part of the oil firms that could well be imitated by those shore-based industries which are potential polluters of the environment.
Much of what has been said applies to the long, slow changes in past civilizations which have produced the developed nations of today and the undeveloped nations of a generation ago. The rapid advances that characterize developing nations have produced dramatic new kinds of interactions with the environment that were not so evident earlier. Nowhere is the problem of accelerated development and its devastating consequences more evident than in many regions of the tropics and subtropics, where two thirds of humanity now live. Here the relation between man and his environment are changing so rapidly that well-balanced development is seriously endangered and in extreme cases entire populations may be threatened with extinction.
Side ejects of large-scale modifications of tropical ecosystems
Owing to the rapid development of ever greater land areas and the widespread use of powerful technological methods, the various tropical biotic communities are today undergoing radical and extensive changes. Deforestation, irrigation, the introduction of exotic plants and animals' the large-scale use of weedkillers, the eradication of certain pathogenic agencies, etc., have transformed the tropical landscape more profoundly in ten years than the traditional agricultural and stock-raising methods in ten centuries. In addition to economic advantages, which are immediate and undeniable, this "reordering" of the tropical ecosystem has sometimes entailed a sudden collapse of the balance, generally going back thousands of years, between man and his environment and given rise to unexpected difficulties.
For example, the introduction of livestock into the savannas of tropical America has promoted the increase of rabies-transmitting haematophagous vampires. Irrigation of the savannas of the Sahel in Africa has caused the spread of bilharzia. Systematic deforestation has frequently brought about transmission to men and domestic animals of certain arboreal viruses normally confined to the pathogenic cycle of the forest canopy. Some are capable of causing sickness of little gravity to monkeys and tree-dwelling rodents, but they can be much more dangerous to humans yellow fever, dengue fever, Kyasanur forest disease, etc. The abandonment of certain traditional foods, both animal and vegetable, Or their replacement by other kinds of food more easily produced has often served to aggravate already existing nutritional deficiencies. Even eradication of a number of tropical diseases may give rise to long-term difficulties. Some of the peoples of west Africa appear to be protected against the effects of malaria by certain abnormal haemoglobins which they possess in a heterozygotic state. Once the parasite has been eliminated, however, only the adverse effects of this genetic adaptation to the environment will remain.
Biological, psychological and social consequences of hasty and chaotic urbanization in the tropics
In Africa, as in Asia and tropical America, the last 20 years have seen the rampant spread of bidonvilles, shantytowns, barrios and favelhas of every description, whose crowded inhabitants are all too often undernourished and illiterate, and have been frequently ruthlessly cut off from their traditional values. The pathology of this situation, which is still little known, is a combination of the effects of malnutrition and poverty, and the physical and psychical effects of manifold stress. It has resulted in the creation of a sub-proletariat in poor physical condition, which deprives agriculture of a source of manpower but at the same time is unable to offer skilled labor to industry. As regards public health, sanitary conditions in these shantytowns represent a constant menace to the great urban centers of which they are a part.
Biological, psychological and social consequences of migrations
This lure of new cities and industrial centers involves unprecedented population movements which are the cause of a demographic imbalance that is in every way detrimental to the development of many tropical countries. Such migrations are, moreover, frequently selective they tend to leave the less enterprising groups or individuals behind in the rural areas and to condemn the majority of the better elements to chronic unemployment. Populations biologically well adapted to a special environment (the high plateaus of the Andes, for instance), sometimes find themselves moved by these mutations into areas climatically unsuited to them.
These problems - and there are many - require urgent study by teams of specialists, including ecologists, medical experts, psychosociologists and economists, with a view to finding satisfactory solutions as quickly as possible. Tropical ecosystems are at once so numerous, complex and delicate that nothing could be more detrimental to the interests of the human beings who inhabit them than a pure and simple "transplantation" to the tropics of techniques (and sometimes even of ideas) which have proved their effectiveness in the temperate latitudes. It is not because the airplane has practically done away with distances, or because it is now possible to prevent or cure most tropical diseases, that the fundamental ecological differences between the great biomes have disappeared. To attempt to spread the way of life of the industrialized nations of the temperate zones over the whole planet is dangerously unrealistic. Western norms should be adapted to other environments and cultures and not imported into them just they are. And this applies not only in the of economics and technology but also as regards food, housing, and clothing.
Irrespective of past and present mistakes and of new problems created by accelerated development due to demographic, economic, and social growth, in the past man has already tried to solve these problems of habitat deterioration. Today new ways of thinking and changing technologies give him the desire and the opportunity to build or rebuild an environment which provides esthetic pleasure as well as goods and services.
Delight in organic forms and environmental diversity
There is ample reason to believe in the importance of this. There are the great villas of the past, their gardens and the arrangement of fountains and lakes for esthetic pleasure. One calls to mind Imperial China Ancient Rome, Persia, Renaissance Italy, the architectural gardens of France, and the English private parks. The parks designed by Capability Brown could not be enjoyed by his patrons as they are now enjoyed with the trees at their maturity, Gardening is becoming enormously popular and municipal authorities are gaining confidence in spending money on their public parks. Increased affluence creates a demand for environmental amenity.
Establishment of national parks
The is a major contribution to civilization from conservation-minded people who have a vision of future human aspiration. The best result of conservancy and the establishment of reserves and national parks with a staff of scientists working permanently in them.
Establishment of wilderness and natural areas
Action here is prompted by both spiritual and esthetic concern, and biological need. There is a widely diffused element of human feeling that wishes there to be wildernesses in existence even if unattainable. In addition, natural areas fulfill a biological need as reservoirs their study provides datum lines from which other environments can in turn be studied more intelligently.
Conservation agriculture
Some tribes of people in limited or constricted habitats have arrived at conservation practices empirically, but the science of conservation in farming and water relations, together with forestry, has come from change of heart after extravagant exploitation. It could be said guardedly that conservation agriculture was fairly firmly established in developed countries, but these same developed countries have made some shocking mistakes in advising the developing countries. This could be stopped if the necessary preliminary studies concerning site potential and limitation and the necessary investments for conservation were made.
Interest in sport
Many forms of outdoor sport in developed countries lead to care of the environment. Care of rivers has been mentioned already in the interests of fishing a diversified agriculture and the maintenance of strategic woodlands and covers has been followed in western countries in the interests of sport. Sometimes sport has removed animals from large areas, but understanding of the ecological place of predators is bringing about much greater tolerance. All in all, farms run by those who like to keep the sporting interest are richer in a variety of plant and animal life than others. Sometimes the sporting farmer progresses to the state of being a naturalist, even enjoying natural life with no sporting interest.
Changes in industry
In the United States, agriculture moved from the eastern seaboard to the Middle West. The forests that had never relinquished their hold took over again. Even 60 years ago much wood was being cut for fuel in these eastern forests. Now, oil-fired central heating is fairly general and the woods have grown more beautiful. What is more, the eastern woods have reached a new high destiny, and have become the suburban forest, the pleasure of the urban communities of the seaboard. Public opinion is now solidly behind the maintenance of these forests.
Likewise, in Europe, the concentration of agriculture on the best soils and the consequent abandonment of marginal lands, have opened the way for rural development based on afforestation for soil conservation, forest management for timber production and recreation, the establishment of national parks and, generally speaking, conservation, recreation, and the extensive management of natural resources.
To conclude does this imply optimism? Ecologists can scarcely afford to be optimists. But a pessimist is a defeatist, and that is no good either. There need not be complete disaster and if man's eyes were open wide enough, world wide, he could do much toward rehabilitation. The biggest danger of all is man's inability to control the explosive rate of growth of human population. Population control would lessen the all too frequent policy of expediency, bolstered by a technology divorced from the philosophy of science. The scientist as a social entity must eventually establish the necessity for the ecosystem approach to world problems as a safeguard against unbalanced technological action. It is yet to be realized that political guidance and restraint is nothing like so operative in regard to technology as in other major fields of human action.
