CHAPTER SEVEN: HUMAN ECOLOGY
Survival and Health
Despite mounting problems and difficulties, most official statements on environmental change tend to be reassuring and optimistic. We are told repeatedly, for example, that the amount of strontium-90 in a quart of milk or the quantity of DDT in a fruit is “trivial”; that in order to ingest harmful doses of a radioactive element or a pesticide residue, an individual would have to consume enormous quantities of a contaminated food at a single sitting. These piecemeal explanations are little more than subterfuges. Many toxicants appear in all the fruits and vegetables we consume; in fact, strontium-90 and DDT are in almost every food in the modern diet. We ingest these substances daily with nearly every glass and spoon we raise to our lips. They appear in the air we breathe and the water we drink. Since the 1940’s, strontium-90 and DDT have become an integral part of man’s environment; the toxicants are almost as widespread as bacteria and dust particles.
An over-all view of our synthetic environment, even if cursory and superficial, reveals a picture worse than that disclosed by the most exhaustive specialized investigations. Foods are sprayed not only with DDT but with a large assortment of inorganic and organic insecticides; they contain not only strontium-90 but additional radioisotopes created by man. A large part of the modern diet consists of highly processed foods to which questionable artificial materials have been added. Although the average man is engaging in less and less physical activity, his intake of carbohydrates and fats is very high. The growth of urban centers has been accompanied by increasing air and water pollution. The anxieties and tensions of modern life promote the consumption of cigarettes, drugs and analgesics. Modern man ingesta and appalling variety of toxic materials every day, many of which are additive or interact in the body to produce a synergistic effect. (Two widely used organophosphorus insecticides, EPN and malathion, for example, are known synergists; each is toxic when ingested singly, but when they are taken together, EPN inhibits the hydrolyzing enzyme that detoxifies malathion, thus producing a toxic effect that is more than additive. Ionizing radiation, to cite another example, is not only carcinogenogenic in its own right, but also reinforces the activity of chemical carcinogens in tobacco smoke. As John W. Berg, associate editor of Cancer, notes:” …what we gain with cigarette filters we probable lose to fallout from atomic explosions.”) The initial damage created by these toxicants is likely to be disregarded, partly because the more immediate symptoms of low-level, chronic poisoning, such as persistent fatigue and continual sense of ill-being, are so common that they are no longer taken seriously.
How does this conclusion compare with evidence that human longevity has been increasing? Actually, the claim that man is living longer today than he did a half century ago requires qualification. “It is important to realize that most of the gains in longevity have come about through prevention of mortality at young ages,” observes James M. Hundley, of the National Institute of Health. “Great progress has been made in this sector. Relatively little has been gained in older age groups.” Since 1900 about 19 years have been added to the life expectancy of newly born white male children. A white male born at the tun of the century had a life expectancy at birth of 48.2 years; by 1958, newly born white males had a life expectancy of 67.2 years. But the gain diminishes sharply after the second decate of life and virtually disappears after the sixth. A man who is 20 years of age can expect to live 7.8 years longer than his counterpart in 1900; a man of 45 years of age, only 2.9 years; a man 65 years of age, merely 1.2 years. A child today has a better chance of reaching the age of 40, but after that his life expectancy is not appreciably greater than what it would have been at the turn of the century.
Moreover, it should not be forgotten that in 1900 millions of Americans lived in an environment in which survival was almost miraculous by present-day standars. The majority of urban dwellers lived in slums with a minimum of sanitation and medical care. A large number of children worked in factories. Their parents were shackled to a grim industrial routine for ten or twelve hours a day in patently unhealthful surroundings. Almost any improvement in social conditions or medical techniques would have rescued large numbers of people from premature death and added substantially to their life span. Today, sanitation, housing, working conditions, and income have been improved greatly, while medicine and scaled undreamed-of heights. Nevertheless, most of the increase in longevity is due to the fact that more children survive the diseases of infancy and adolescence today than two generations ago. What this means, in effect, is that if it weren’t for the extraordinary medical advances and great improvements in the material conditions of life, today’s adult might well have a much shorter life span than his grandparents had. This is a remarkable indication of failure. It suggests that modern man would find it very difficult to survive outside a medical and pharmaceutical hothouse.
What does life in a medical and pharmaceutical hot house entail? The answer, in cold statistics, is shocking.Nearly 41 percent of the American people have some form of chronic illness. ( “About 40.9 per cent of persons living in the United States were reported to have one or more chronic conditions,” reports the U. S. Public Health Service. “While some of these conditions were relatively minor, others were serious conditions such as heart disease, diabetes, or mental illness.” Ten per cent of the American population are forced to limit their activity because of chronic conditions.)Many of these individuals are confined to wheel chairs, nursing homes, and hospital beds, faced with lifelong pain and inactivity. The statistics include numerous victims of heart disease, whose existence is marred by continual apprehension and fear. They include hundreds of thousands of cancer victims, a large percentage all but departed from the pale of the living. Worse still, however, the likelihood exists that the hothouse will begin to fall apart as the pace of chemicalization, urbanization, and pollution is increased. We have yet to feel the full burden of disease slowly being created by nuclear weapons tests, motorcar exhausts, and the newer chemical additives in our food. We are exchanging health for mere survival. We have begun to measure man’s biological achievements, not in terms of his ability to live a vigorous, physically untroubled life, but in terms of his ability to preserve his mere existence in an increasingly distorted environment. Today, survival often entails ill health and rapid physical degeneration. We are prepared to accept the fact that a relatively young individual will suffer from frequent headaches and digestive disturbances, continual nervous tension, insomnia, a persistent “cigarette cough,” a mouthful of decaying teeth, and respiratory ailments every winter. We expect his physique to acquire the rotundity of a barrel shortly after the onset of middle age; we find nothing extraordinary in the fact that he is incapable of running more than a few yards without suffering loss of breath or walking a few miles without suffering exhaustion.
What, then, is health? At the very least, health must be regarded as the absence of all the persistent pains, aches, tensions, and physical disturbances now accepted as a “normal” part of life. A healthy body is not a burden; it does not provoke an irritating awareness of its presence without reason. When we are in good health, we sense that our bodies are completely at our command, that they are in the service of our purposes and desires. Normally the “sound body lives in silence,” observes Alexis Carrel. “We do not hear, we do not feel, its working. The rhythms of our existence are expressed by cenesthesic impressions which, like the soft whirring of a sixteen-cylinder motor, fill the depths of our consciousness when we are in silence and meditation. The harmony of organic functions gives us a feeling of peace.”
This is, of course, a minimum definition of health- a definition that might be taken for granted if it were not for the fact that, as Carrel adds, many people, “although they are not ill, are not in good health. Perhaps the quality of some of their tissues is defective. The secretions of such gland, or such mucosa, may be insufficient or too abundant. The excitability of their nervous system, exaggerated. Their organic functions, not exactly correlated in space or in time. Or their tissues, not as capable of resisting infections as they should be.” Carrel is obviously concerned with complex, interacting biochemical factors that are often difficult to pinpoint and measure in the laboratory. Nevertheless, many individuals whose response to conventional diagnostic tests indicates that they are “normal” and hence “healthy” undoubtedly lack the energy, recuperative powers, and “harmony of organic functions” required for the full enjoyment of life. Although these individuals are considered “healthy” by current medical standards, they are not getting what they should out of life. In many cases, they can be expected to succumb prematurely to chronic diseases.
It is difficult to formulate a complete definition of health in general terms. Today, “glowing health,” to use an old phrase, is very uncommon among adults. As a result, we are usually constrained to think of it not as the attribute of a population but rather as that of a few individuals. We have not yet determined the potentialities of physical development for the community as a whole Anthropologists and physicians have explored the relics of the past and traveled to remote primitive areas in an attempt to find evidence of robust, healthy communities. These explorations have yielded a great deal of useful information, but very few of the reports give us an adequate idea of what health could be if science and technology were placed completely in the service of human needs. Man is capable of being a great deal more than he is today-physically as well as intellectually-if his resources are employed in a rational manner.
The term “rational” should not be taken to mean natural or primitive. Man could not have advanced beyond a level of precarious subsistence if he had not consciously altered his natural environment and hammered it into a form that favored human life. The change was made at the expense of other species and, to some extent, by violating time-honored ecological relationships. Civilization was achieved by clearing forests, draining swamps, restricting animal predators, replacing many wild botanical species with food plants, fertilizing the soil, cultivating crops, probing the earth for fuels and metals-in short, by rearranging the natural world to satisfy human needs for food, shelter, and leisure. Modern man now has the power, knowledge, and resources to do substantially better than both his ancestors and his primitive contemporaries. His technology and science have given him an enormous influence over many natural forces. Chemistry has illuminated part of the darkness that once surrounded important aspects of soil development, nutrition, and physiology. In conjunction with research in microbiology and physiology, it has given society powerful therapeutic agents, such as antibiotics and hormones. Technology can remove much of the drudgery that burdens human life and leave men free to use their bodies and minds for highly satisfying activities. Work can be pleasant as well as useful. Neither science nor technology, however, is a substitute for a balanced relationship between man and nature. Medicine and machinery may modify this relationship, but they cannot replace it. Few drugs are as effective as biological resistance to disease; no system of technology is likely to free man from his dependence on soil, plants, and animals. The two spheres, natural and synthetic, must be brought into a complementary relationship based on a clear understanding of man’s needs as an animal organism and the effects of his behavior on the natural world.
A study of the interaction between man and nature may be called human ecology. Our synthetic environment is the product of man’s interaction with the natural world, just as a dam is the product of a beaver’s interaction with a stream and forest. The improverishment and destruction of the soil, repeated insect infestations, and the rising incidence of certain diseases represent the reaction of the natural world to man’s adverse environmental changes. To become what biologists term a “dominant organism,” man is compelled to make sweeping demands upon nature, but nature, in turn, makes demands that man must fulfill if he is to enjoy health and well-being. Whether he likes it or not, there are “rules of the game,” which must be obeyed if an environmental change is to advance human vigor, resistance to disease, and longevity. When these rules, simple as they may be, are transgressed, nature takes its revenge in the form of ill health and disease. When they are obeyed, man’s life can be full, creative, and remarkably free of physical impairment.
Ecology and Health
In a witty review of popular attitudes toward food, David Cort remarks that he has encountered absurdly conflicting dietary recommendations in books and articles on nutrition. One authority advises his readers to avoid fat; another advises that it should be eaten, on the theory that fat is the least fattening of all foods. Potatoes have been alternately damned and praised; mixed meals have been both frowned upon and approved; the consumption of alcohol, criticized and recommended. “The cruelty and irresponsibility of offering one single, standard dietary solution for everybody is obvious,” Cort adds. “What a person eats is, in many important respects, his life. But every individual is different from every other individual. No doctrinaire solution will work for them all. Each individual has conditioned habits of eating, of taste, of appetite, of expenditure of energy, of nervous rhythms and, most important of all, of metabolism. Few modern doctors have the interest, time or genius to find out all about any one individual; and many are themselves overweight. But the individual has the time and interest and, at least about himself, perhaps the genius. After all, it’s his life.”
Although Cort’s remarks are confined to nutrition, they are quite relevant to a number of problems in human ecology. It would be an error to form rigid concepts of a normal man, a normal diet, or a normal way of life. Any such image would be woefully lacking in biochemical and physiological support. The biologist and physician must still admit, as Carrel did nearly a quarter of a century ago, that “most of the questions put to themselves by those who study human beings remain without answer. Immense regions of our inner world are still unknown.” Impressive advances, to be sure, have been made during the past two decades in solving major problems of cellular biochemistry, endocrinology, and physiology. Knowledge of the transformation of energy in the cell is very far advanced, for example, and great strides have been made in understanding the chemistry of the genetic material in the cell’s nucleus. Despite this newly acquired knowledge, however, nutritionists have an extremely limited understanding of the function of many trace elements in the body and of the way in which vitamins prevent deficiency diseases. The nutritional requirements of the various tissues, essential details of the blood-forming system, the mechanisms of resistance to disease, and many key relationships within the body await clearer understanding.
The human organism is extremely sensitive to very small quantities of hormones and nutrients. A variation by only a few drops in the daily output of insulin, a pancreatic hormone, will determine whether an individual will handle sugar properly or succumb to diabetes. A difference of a few thousandths of a gram (milligrams) in the intake of certain vitamins and trace elements makes for either well-being or nutritional disorders. According to the National Research Council, a man twenty-five years of age requires a daily intake of 1.6 milligrams of thiamine and riboflavin, 7.5 milligrams of vitamin C, and 12 milligrams of iron to preserve good health. His minimum daily requirements of iodine and copper are believed to be as little as 0.1 and 0.2 milligrams, respectively. If the daily intake of these nutrients is reduced by a few thousandths of a gram or less for a long period of time, the result will be a marked impairment of health. Despite the minute quantities involved, deficiencies of vitamins and minerals occur on a fairly large scale in the United States. If A. F. Morgan and L. M. Odland are correct in their claim that a dry, roughened skin and lesions of the eyes and mouth “may be considered a useful pointer to possible dietary faults,” about so per cent of the adolescents examined in the affluent northeastern states and 20 per cent in the western states may have nutritional disorders.
We tend to look upon diseases as though they were localized disturbances, confined to definite parts of the body. Although it is customary to acknowledge the body’s unity in sickness and in health, the whole is often overlooked in favor of the parts, and vital interrelationships are ignored in favor of isolated events. Actually, every major deficiency and physical impairment has far-reaching effects. “Disease consists of a functional and structural disorder,” Carrel notes. “Its aspects are as numerous as our organic activities. There are diseases of the stomach, of the heart, of the nervous system, etc. But in illness the body preserves the same unity as in health. It is sick as a whole. No disturbance remains strictly confined to a single organ. Physicians have been led to consider each disease as a specialty by the old anatomical conception of the human being. Only those who know man both in his parts and in his entirety, simultaneously under his anatomical, physiological, and mental aspects, are capable of understanding him when he is sick.”
A clear understanding of illness and health requires a greater appreciation not only of man but of men. Physical needs and responses vary enormously from one individual to another. Roger J. Williams, one of America’s most eminent biochemists, emphasizes that within the same racial groups, even in the same families, men differ from one another in the shape and weight of their vital organs, the composition of body fluids, the output of endocrine glands, the rate of metabolism, temperature control, and many other respects. Individual differences in the amount of nutrients required for health and in the amount of nutrients absorbed by the body are of major practical importance. Individual requirements of calcium, trace elements, amino acids, and vitamins are highly variable. For example, two normal five-year-old children who ate the same food and were exposed to the same environmental conditions showed a great variation in the amount of calcium they retained from their diets. One child retained 264 milligrams of calcium per day for 45 days, whereas the other retained 469 milligrams, a difference of nearly 80 per cent. A high degree of variability is also found in individual responses to common environmental toxicants. Williams cites an account of 78 men who were exposed to vapors of carbon tetrachloride, of whom I 5 suffered acute poisoning. Six became sufficiently ill to require hospitalization. “All were white men within 5 to 8 years of the same age and in general good health . . . ,” observes Fredrich H. Harris, the source for Williams’s account. “All 15 of the men poisoned were exposed from 3 to 8 hours; however, many of those who developed no symptoms were exposed for a similar length of time or longer.”
The fact that man’s knowledge of important bodily processes is incomplete and that many individuals exhibit marked deviations from “normal” responses and needs does not imply that the role of medicine is inconsequential in promoting health or that scientific generalizations are useless. The healthiest of men will undoubtedly require medical attention at some time in their lives, and every physician must use physiological and anatomical generalizations as points of departure for the diagnosis of a disorder. Basic research in biochemistry and physiology promises to increase vastly our understanding of the preconditions for human health and well-being. But a phenomenon does not cease to exist because it cannot be readily explained by current methods and theories. On the contrary, we are often profoundly affected by phenomena that are too complex to lend themselves to precise analysis at the present stage of scientific development. The way in which stress produces illness and the role that nutrition plays in the occurrence and prevention of chronic diseases constitute fields of research that have scarcely been penetrated. It would be a major setback if the roles of these factors were minimized simply because they present formidable problems to research. Man must try to conserve many practices that, on the basis of long experience, are known to promote good health, even if the reasons why they are beneficial cannot be stated in precise biochemical terms.
What are some of these practices? As it is clear that our bodily functions are interdependent, we should not permit any part of our biological equipment to atrophy. This means that we must use all the parts of our bodies. Our musculature must be as fully employed as our minds. Many activities and experiences that have been restricted by our sheltered civilization seem to play important roles in preserving health. There is a suspicion that modern man indirectly harms his body by failing to use certain physiological resources that once supported his ancestors during periods of hunger and cold. “There exists in the body of man, as of all animals, biological mechanisms for the storage of food developed for meeting the irregularities and cyclical changes in nature,” Rene Dubos writes. “It may still turn out that a nutritional way of living permitting continuous growth at a maximum rate may have unfortunate distant results. Fasting fads may have some justification after all by providing an opportunity for the operation of certain emergency mechanisms built by nature into the human body.”
Although it remains to be seen whether this conclusion will be accepted by nutritionists and physicians, it is reasonably clear that a one-sided manner of life is biologically undesirable. An existence anchored in either muscular exertion or inactivity, surfeit or poverty, stress or an overly sheltered manner of life, tends to produce physiological disequilibrium. A prolonged period of muscular exertion causes marked damage, whereas protracted physical inactivity appears to increase both the effect and the incidence of heart and circulatory disorders. When the coronary arteries of dogs are surgically narrowed to simulate atherosclerosis, a lack of exercise makes it difficult for new blood vessels to form and provide more blood to nourish the diseased area of the heart muscle. There also seems to be more coronary illness among men whose occupations are sedentary than among those who engage in physical work. In contrast to the well-exercised individual, the “physically inactive individual shows signs of aging earlier in life,” emphasizes Hans Kraus, of New York University. “He exists physiologically at a lower potential and is less well-equipped to maintain homeostasis [stable bodily conditions] and to meet daily stresses. This low level of function, combined with enforced suppression of the ‘fight and flight’ response, enhances the incidence of disease.”
Not only does health require all the elements of a full life; it also requires that they exist in balance. A moderate amount of exertion, a balanced intake of nutriment, and a reasonable amount of exposure to stress are necessary for the maintenance of well-being. Almost any kind of excess is harmful. This has become apparent in respect to nutrition. “In laboratory experiments rats fed an unlimited diet were found to die sooner than animals prevented from gaining weight by a diet severely restricted in quantity but well balanced in composition,” Dubos observes. “Likewise insurance statisticians have repeatedly emphasized that in man the obese have a short expectancy of life. Indeed, obesity is now publicized as the most common nutritional disease of Western society. This was apparently true also in Imperial Rome, as during all periods of great material prosperity. (And in periods of social decline and demoralization as well. The pursuit of “pleasure,” which affluent Romans of the Imperial Age carried to the point of license, would have been frowned upon during the Periclean Age, when ancient Athens, too, enjoyed “great material prosperity.”) ‘In the old days,’ wrote Lucretius in the fifth book of De Rerum Natura, lack of food gave languishing limbs to Lethe; contrariwise today surfeit of things stifles us.’ Thus, history repeats itself. Like the prosperous Romans of two thousand years ago, countless men of the Western world today are digging their own graves through over-eating.”
Finally, if man is to maintain good health, he requires diversity. It is hardly necessary to emphasize that a healthy psyche and a rounded response to stress are nourished- by a variety of experiences and by diversified surroundings. However, it does need to be emphasized that variety is also necessary for the satisfaction of man’s nutritional needs. By limiting his selection of foods, he may fail to acquire nutrients known to exist in natural foods but not yet identified by chemists or nutritionists. “Because we know that unidentified factors exist in foods of plant and animal origin,” observes George M. Briggs, of the National Institutes of Health, “it is wisest to eat a wide variety of foods from the many excellent food groups . . .” If this is done regularly, Briggs emphasizes, it is unnecessary to supplement the diet with vitamins and so-called health foods. It might be added that if food such as grain were not overly processed, it would be unnecessary to “enrich” bread with synthetic vitamins, which replace only part of the valuable nutrients lost in the milling process. In general, the more a food is processed, the greater the likelihood that identified nutrients as well as unidentified ones will be removed.
Completeness, balance, and diversity should be regarded as practical ecological concepts-as important in producing healthy human communities as they are in producing stable plant-animal communities. Indeed, it is not farfetched to say that when these concepts are correctly applied, they promote human health because they produce a stable ecosystem of men, animals, and plants. In the last analysis, the ecology of health is grounded in natural ecology. A complete way of life for man presupposes unrestricted access to the countryside as well as the town, to soil as well as to pavement, to flora and fauna as well as to libraries and theaters. A balanced way of life presupposes a lasting equilibrium between land and city; animals, men, and plants; air, water, and industry. Diversity presupposes an awareness that nearly every species perpetuates the stability of the biosphere, either directly or indirectly. As the city encroaches on the land, however, human life becomes increasingly restricted to a polluted, nerve-racking urban environment. As the city begins to dominate the land, physical activity yields to sedentary forms of work. Finally, as the aggregations of population swell to massive proportions, foods become laden with chemicals and human activities are standardized. By oversimplifying the natural environment, we have created an incomplete man who lives an unbalanced life in a standardized world. Such a man is ill-not only morally and psychologically, but physically.
Ecology in Use
Our environment difficulties would be understandable if we knew nothing about the requirements for a balanced relationship between man and nature. We could then answer every reproach with a confession of ignorance. Today, however, we know too much about ecology to have any excuse whatsoever for many of the abuses that are perpetrated in agriculture, food production, and urban life. The time is approaching when the ad hoc measures with which we have tried to stave off the problems of environmental change will have to be supplanted by lasting ecological solutions.
Ecology, as has been noted in an earlier chapter, deals with the interrelationships of living things (including man) and their environment. The more these interrelationships are explored, the more evident become the interdependence of most organisms in a given locality and the needs that each species fulfills for the others. Most ecological studies are limited and highly concrete, but the material at hand suggests a number of practical generalizations that are relevant to the problems discussed thus far, particularly those of agriculture and land use.
A rational agricultural program must begin by taking into account the natural characteristics of the soil. “Soil productivity is not simply a matter of available chemicals,” observes Edward Higbee, of Clark University. “It is also heavily dependent upon good structure, aggregation, texture, mellowness, and microorganic life.” Many of these characteristics are predetermined by the natural history of a given area, including its ecology under virgin conditions, its underlying rock formation, and its prevailing climate. In addition, there are likely to be important differences in the soils of individual farms owing to variations in the slope of the land, in drainage conditions, and in the depth of the solum, or true soil, in relation to underlying layers of clay and rock. The configuration of the land determines, to a large extent, the optimal conditions of growth for different kinds of vegetation, especially in rolling or hilly country. Some areas will be best suited for pasture, others for field crops. On many farms in eastern sections of the United States, a sizable acreage of land should almost certainly be returned to timber. Attempts to exploit these soils for the cultivation of food and grazing often result in extensive erosion and unsatisfactory crops.
If no attempts were made to modify a natural ecological pattern, agriculture would be impossible, and, in many cases, superbly improved crop lands would be reclaimed by the forest and irrigated soils would again become unproductive. But we cannot ignore the ecological factors that clearly limit the cultivation of many foods. Large areas of land are now supporting crops for which they are definitely not suited, and society would profit more by giving a freer rein to nature than by forcing the soil to produce a low quality of vegetation. The dry plains from the Dakotas to western Texas, for example, were meant to be range lands, not crop lands. Weather conditions are too uncertain for the cultivation of grain, and the area suffers from repeated sieges of drought, whose effects are only aggravated by the systematic cultivation of food. The productivity of the arid plains is notoriously low, and attempts to grow commercial crops have resulted in widespread deterioration of the soil.
In most cases, the best soils of the world were developed under highly varied forms of vegetation. Although certain plant groups seemed to dominate the landscape of particular regions, a closer view usually disclosed a great diversity of species. The uniformity of the American prairies, long regarded as a “desert of grass,” was an illusion. “Many virgin forests cannot display so great a variety of plant and animal life as the now nearly vanished native grasslands . . . ,” Higbee writes. “For the patient individual who walks slowly and watches closely it is a world of infinite variety in small forms and subtle colors.” Although agriculture can never completely restore this variety, it can try to approximate it, not only to please the eye but to create a more complex ecological pattern for purposes of controlling pests and conserving the soil. Indeed, it would be wise to diversify as well as to rotate crops. Certainly no moderate-sized farm on forest soils should be without timber, and even on the prairies it is no longer necessary to prove to the farmer that he has much to gain by planting trees as shelter belts against the wind and as oases for bird life.
To achieve a lasting, stable agriculture, we must reserve a place for livestock on the modern farm. Not only are meat and dairy cattle sources of manure, but their mere presence tends to restrain the exploitation of crop lands. Most farmers who own herds of cattle are obliged, in order to feed the animals, to cultivate soil-protecting legumes; willingly or not, they thus follow practices that conserve the land. On the whole, however, the trend has been away from mixed forms of agriculture, in which both food plants and livestock are raised on the same agricultural unit. The small farmer, faced with heavy competition from larger enterprises, has begun to specialize; he either raises livestock or cultivates a limited number of commercial crops. Dairying, one of the most important forms of mixed agriculture, is more or less on the decline throughout the United States, except in parts of the South. The number of cows and heifers kept for milk has dropped more than 20 per cent since 1945.
It need not be emphasized that the oversimplification of agriculture creates ideal conditions for the invasion and proliferation of pests. But even variety in plant life and the presence of livestock are not likely to be effective in helping to control pests if the land is being exploited. Ecologists have found that an overgrazed range, for example, tends to attract a large number of rodents and insects. “It is generally observed . . . that jack rabbits are usually most numerous where the range is poorest and the grass most sparse,” notes Edward H. Graham, of the U. S. Soil Conservation Service. In a discussion on insect pests, Graham adds: “Even the abundance of grasshoppers, so destructive of crops and range vegetation, can be related in some degree to intensity of land use. Weese . . . has been credited with the statement that a barbed wire fence is the best device for controlling range insects, meaning that controlled grazing which permits good grass will automatically reduce the number of injurious insect forms.”
The effective control of pests requires an appreciation of many complex factors, some of which may seem; far removed from the outbreak of an infestation but play,; an important role in its occurrence. Albrecht has placed! a great deal of emphasis on the role of soil fertility in building up the resistance of plants to insect predators. Research at the University of Missouri suggests that certain species of insects are attracted to crops grown on deficient soils. As soil fertility is improved, the infestation declines. Each host plant and each insect species, of course, constitutes a separate problem that can be solved only on its own terms. Unwise methods of fertilizing the soil may actually make it easier for an infestation to occur. For example, if nitrogen fertilizer is used excessively, it produces heavy vegetative growth, but the maturity of the plant is delayed and its cell walls are thin and are easily penetrated by disease-causing organisms. These lush, immature plants, low in resistance to pathogens, tend to attract insect predators and often pave the way for a serious infestation.
One of the most harmful misconceptions in agriculture is that all predators of crops are exclusively injurious and should be completely destroyed. Mention has been made of the valuable role played by forest rodents in limiting insect infestations (see pages 56-7); similar evidence can be adduced from areas such as the plains, where rodents have been singled out for vigorous extermination campaigns. In a study of the high plains grasshopper, Claude Wakeland observes that in some areas, rats, mice, and gophers “have devoured a great many grasshopper eggs, nymphs, and adults. Doubtless they have destroyed various forms of the species far more extensively than the meagre data available indicates.” On the plains, rodents have become pests as a result of overgrazed ranges and the extermination campaigns conducted against the coyote, which feeds primarily on carrion and small mammals. Ecological studies show that 20 per cent or more of the coyote’s diet consists of insects; during periods of heavy infestations, it feeds almost exclusively on grasshoppers. To be sure, biological control of pests, as distinguished from chemical control, is not a cut and dried affair. Many different approaches will have to be combined before the problems of pest control can be effectively resolved. But unless these methods are adopted and, above all, creatively integrated to suit the needs of each region, the use of pesticides will increase steadily in the years to come.
Another prevalent misconception about agriculture is that bigness per se makes for efficient and rational use of the land. The small farm has a potential advantage that the land factory and its close cousin, the plantation, seldom enjoy. A moderate-sized farm is dimensioned on a human scale. It lends itself to close scrutiny and careful management, to an intimacy between the farmer and the land that could engender a greater sensitivity to different soil needs and promote the employment of sound ecological practices. Small-scale farming could be successfully pursued as a form of applied ecology if blind economic interests were replaced with a sense of social responsibility. Unfortunately, many small farms in America are miniature replicas of the land factory. Agricultural units, large and small, tend to share the same ends-the “mass manufacture” of crops at the least cost.
A balanced system of food cultivation based on highly diversified, small-scale farms is not a utopian vision. The small farm still constitutes the backbone of agriculture in many areas of western Europe. Over many centuries heavy forest soils were slowly reconstructed to support livestock, orchards, and a large variety of field crops. Today, a diversified system of small-scale agriculture prevails in England, France, Scandinavia, and parts of West Germany. Most European farms, to be sure, are hardly models of good food cultivation; they often fail to make use of the ecological possibilities that exist in the moderate-sized agricultural unit. In contrast with most American farms, however, many European farms have created a workable relationship between man and the soil. These farms enjoy relatively high soil fertility despite centuries of use. Organic matter is often carefully returned to the land, and an entrenched tradition still resists the complete chemicalization of agriculture in many parts of England, France, and Germany.
So much for the dictates of ecology. If these dictates seem “unrealistic,” it should be noted that in England today about 75 per cent of the farms have less than 300 acres and the average is about IOO acres. Agriculture in England and Wales has largely been stabilized around a small, highly diversified farming unit, almost equally divided between pasture and crop lands. Although many of these farms have been cultivated for 500 years or more, they have a far greater yield of wheat per acre than the average American agricultural unit and compare favorably with the latter in the output of other crops. American agriculture, driven by competition and an appetite for high earnings, is so much in flux that it is difficult to speak of sanity, still less of stability, in many rural areas of the United States. What is the trend? Robert S. McGlothin, of the Stanford Research Institute, suggests that by the end of the century, the number of American farms will have declined from 1.7 million to between 300,000 and 400,000. These large agricultural units will produce about go per cent of the food cultivated in the United States. “Commercial farmsteads will be laid out and run like highly mechanized industrial plants. Crop and livestock production will be integrated into a comprehensive materials handling and marketing system. The independent family farmer will hire management counseling, which, with the aid of electronic computers, will help him program the operation of the entire farm system so as to achieve lowest unit costs of production. The computer will indicate-for each production season-which crops should be grown, where, in what quantities, when they should be fed to what livestock, and when and where marketed for greatest return.”
To many, this may seem to be progress. To the ecologist, however, it represents an attempt to bring the laws of the biosphere into accordance with those of the market place to reduce the natural world to merchandise. Nutritious crops can no more be expected to grow according to commercial schedules than man can be expected to adjust his pulse to the rhythm of machines.