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- 5 - MAN AND THE ECOSYSTEM Any undisturbed land mass is eventually occupied by an assemblage_of plants referred to as climax vegetation. This vegetation is stable and self-perpetuating and may consist of many species living together in a small area. When it is destroyed, the area is quickly occupied by plants that have the ability to grow and multiply rapidly. In due course other species invade the area and restoration of the climax begins. When the human population was small, it was possible for man to depend on climax vegetation and its associated organisms for food, fiber, and shelter. However, it was necessary for man to disturb and to modify some of the earth's climax systems in order to provide sufficient food, fiber, and shelter for the growing human population. Besides being an initial step in establishing present-day civilizati.ons, the development of agriculture was the first stage in destroying the relatively stable ecosystem in which man once lived. To maintain the resultant ecologically unstable situation, he was obliged to initiate many remedial actions, including pest control. Basic ecological principles dictate that an unstable state will change unless maintained by balancing forces. Monoculture, which is essential today to food production, is ecologically unstable. Continued effort is necessary to maintain it. The effort includes pest control and the use of fertilizers, machines, and selected plant varieties. At present, pests are controlled primarily by use of pesti- cides, but no matter what method is used, the basic problem remains: monoculture is inherently unstable. Society could allow farmers to maintain monocultures by any means that they chose, except for the fact that man is a part of the whole ecosystem. Whatever is done in one part of an ecosystem often produces an effect in other parts. Pesticides applied in one area may be transported to remote areas and produce unexpected results. Complete insect control in a cotton field may destroy the bees necessary for pollinating an adjacent alfalfa field. Therefore,
- 4 - it may be desirable to reexamine the basis of market quality in the interest of reducing pesticide residues in the environment. In home gardening and household uses, pesticides may be applied at excessive rates because the user does not know the proper type of pesticide for best results and because he applies them improperly. In doubt as to proper quantity, he may reason that "if some is good, more is better" and thus may apply too much. Under some conditions, persistent pesticides are the most effective means of controlling pests; under others, they are the only practical means. Many serious public health problems associated with insect vectors of human disease still require the use of persistent pesticides in some countries, either because a suitable short-lived alternative is not available or because the developing countries cannot bear the cost of nonpersistent pesticides, which are usually more expensive than persistent pesticides. Reasonably priced alternative chemicals or nonchemical means may be found in time. Meanwhile, any action to reduce the availability of persistent pesticides needed by developing countries might have serious health conse- quences in those countries. There is no satisfactory alternative to persistent pesticides for protecting wood against insects. Long-lived materials may be placed in the soil, or timber may be impreg- nated to achieve long-term protection, without danger of contaminating the environment. In the United States, persistent pesticides have some uses for which satisfactory alternatives do not exist. Economic entomologists state that at present, the only chemicals that effectively control certain insects are the persistent ones. The insects to which they refer include certain pests of cotton, corn, wheat, alfalfa, fruit, forest trees, lawns, and turf. Despite the present need for persistent pesticides, their availability must not inhibit the search for more desirable means of pest control.
