Arctic tundra, prairie grasslands, and the desert are examples. The earth, its surrounding envelope of life-giving water and air, and all its living things comprise the biosphere. Finally, man's total environmental system includes not only the biosphere but also his interactions with his natural and manmade surroundings.

Changes in ecosystems occur continuously. Myriad interactions take place at every moment of the day as plants and animals respond to variations in their surroundings and to each other. Evolution has produced for each species, including man, a genetic composition that limits how far that species can go in adjusting to sudden changes in its surroundings. But within these limits the several thousand species in an ecosystem, or for that matter, the millions in the biosphere, continuously adjust to outside stimuli. Since interactions are so numerous, they form long chains of reactions. Thus small changes in one part of an ecosystem are likely to be felt and compensated for eventually throughout the system.

Dramatic examples of change can be seen where man has altered the course of nature. It is vividly evident in his well-intentioned but poorly thought out tampering with river and lake ecosystems. The Aswan Dam was primarily built to generate electric power. It produced power, but it also reduced the fish population in the Mediterranean, increased the numbers of disease-bearing aquatic snails, and markedly lowered the fertility of the Nile Valley.

In the United States, the St. Lawrence Seaway has contributed significantly to the economic growth of the Great Lakes region. Yet it has done so at a high and largely unforeseen cost to the environment. The completion of the Welland Canal let the predatory sea lamprey into the Great Lakes. Trout, which had been the backbone of the lakes' fishing industry, suffered greatly from the lamprey invasion. By the mid-1950's the trout and some other large, commercial predatory fish were nearly extinct. And with their near extinction, smaller fish, especially the alewife, normally kept under control by these predators, proliferated. The aggressive alewife dominated the food supply and greatly reduced the numbers of small remaining native fish, such as the lake herring. The alewife became so numerous, in fact, that on occasion great numbers died and the dead fish along the shore caused a major public nuisance.

Man attempted to restore the ecological balance by instituting sea lamprey control in the 1950's and 1960's and by stocking the lakes with coho salmon beginning in 1965-to replace the lost native predatory fish. Feeding on the abundant alewife, the salmon multiplied

rapidly and by 1969 had become important both as a commercial and sport resource. Some of the salmon, however, were contaminated by excessive concentrations of DDT and were taken off the commercial market.

The lesson is not that such activities as the St. Lawrence Seaway must be halted, but that the consequences of construction must be carefully studied in advance of construction. Planners and managers must begin to appreciate the enormous interrelated complexity of environmental systems, weigh the tradeoffs of potential environmental harm against the benefits of construction, look at alternatives, and incorporate environmental safeguards into the basic design of new developments.

The stability of a particular ecosystem depends on its diversity The more interdependencies in an ecosystem, the greater the chances that it will be able to compensate for changes imposed upon it. A complex tropical forest with a rich mosaic of interdependencies possesses much more stability than the limited plant and animal life found on the Arctic tundra, where instability triggers frequent, violent fluctuations in some animal populations, such as lemmings and foxes. The least stable systems are the single crops called monocultures-created by man. A cornfield or lawn has little natural stability. If they are not constantly and carefully cultivated, they will not remain cornfields or lawns but will soon be overgrown with a wide variety of hardier plants constituting a more stable ecosystem.

The chemical elements that make up living systems also depend on complex, diverse sources to prevent cyclic shortages or oversupply. The oxygen cycle, which is crucial to survival, depends upon a vast variety of green plants, notably plankton in the ocean. Similar diversity is essential for the continued functioning of the cycle by which atmospheric nitrogen is made available to allow life to exist. This cycle depends on a wide variety of organisms, including soil bacteria and fungi, which are often destroyed by persistent pesticides in the soil.

TYPES OF PROBLEMS

Pollution

Although pollution may be the most prominent and immediately pressing environmental concern, it is only one facet of the manysided environmental problem. It is a highly visible, sometimes danger

ous sign of environmental deterioration. Pollution occurs when materials accumulate where they are not wanted. Overburdened natural processes cannot quickly adjust to the heavy load of materials which man, or sometimes nature, adds to them. Pollution threatens natural systems, human health, and esthetic sensibilities; it often represents valuable resources out of place. DDT, for instance, is a valuable weapon in combating malaria. But DDT, when out of place-for example in lakes and streams concentrates in fish, other wildlife, and the smaller living things on which they depend.

Historically, man has assumed that the land, water, and air around him would absorb his waste products. The ocean, the atmosphere, and even the earth were viewed as receptacles of infinite capacity. It is clear now that man may be exceeding nature's capacity to assimilate his wastes.

Most pollutants eventually decompose and diffuse throughout the environment. When organic substances are discarded, they are attacked by bacteria and decompose through oxidation. They simply rot. However, some synthetic products of our advanced technology resist natural decomposition. Plastics, some cans and bottles, and various persistent pesticides fall into this category. Many of these materials are toxic, posing a serious health danger.

Some pollutants, which may be thinly spread throughout the environment, tend to reconcentrate in natural food chains. Pesticides tend to diffuse in ocean water. The physical effects of 1 pound of a wellmixed pesticide in 10 billion pounds of water may seem negligible. But many sea animals filter out particular kinds of chemical compounds, including pesticides, and collect them in certain parts of their bodies at concentrations far higher than in the water in which they live. Algae may concentrate some component of a pesticide which is then concentrated further in the fish that eat the algae. In turn, still further concentrations may occur in the birds that eat the fish. When the accumulation of the toxic substances reaches a high enough level, it may kill the organism directly or interfere with its reproduction. A wellknown example of such accumulation occurred in 1957 at Clear Lake, Calif. DDD (similar to DDT) was diffused through the water in a concentration of only 0.02 parts per million. The lake's plant and animal organisms, however, had stored residues of DDD at 5 parts per million-250 times greater than the concentration in the water itself. Fish, which consumed large quantities of these small organisms, accumulated DDD concentrations in their body tissues of over 2,000 parts

per million. And there was heavy mortality among grebes which fed on the fish.

Radioactive fallout from the air also concentrates through food chains. Arctic lichens do not take in food through their roots but instead absorb their mineral nutrition from dust in the air. Radioactive fallout tends therefore to collect in the lichens and is further concentrated by grazing caribou, which eat huge quantities of lichen. Caribou meat is a major part of the Eskimo's diet. Although reconcentration of radioactive fallout at low levels has not been proved damaging to health, the effects of long-term, low-level exposure to radioactive pollutants are still not well known.

Water pollution is a problem throughout the country, but is most acute in densely settled or industrial sections. Organic wastes from municipalities and industries enter rivers, where they are attacked and broken down by organisms in the water. But in the process, oxygen in the river is used up. Nutrients from cities, industries, and farms nourish algae, which also use up oxygen when they die and decompose. And when oxygen is taken from the water, the river "dies." The oxygen is gone, the game fish disappear, plant growth rots, and the stench of decay reaches for miles.

Air pollution is now a problem in all parts of the United States and in all industrialized nations. It has been well known for some time to Los Angeles residents and visitors who have long felt the effect of highly visible and irritating smog from automobile exhaust. Now Los Angeles's local problem is becoming a regional problem, because noxious air pollution generated in the Los Angeles Basin has spread beyond the metropolitan area. This same problem, which seemed unique to Los Angeles in the 1950's is today common to major cities in the United States and abroad. Smog is but one of the many types of air pollution that plague the United States, especially its cities.

Land Use

Urban land misuse is one of today's most severe environmental problems. The character of our urban areas changes rapidly. Old buildings and neighborhoods are razed and replaced by structures designed with little or no eye for their fitness to the community's needs. A jumble of suburban developments sprawls over the landscape. Furthermore, lives and property are endangered when real estate developments are built on flood plains or carved out along unstable slopes.

Unlimited access to wilderness areas may transform such areas into simply another extension of our urban, industrialized civilization. The unending summer flow of automobiles into Yosemite National Park has changed one of nature's great wilderness areas into a crowded gathering place of lessened value to its visitors. The worldwide boom in tourism, teamed with rapid and cheap transportation, threatens the very values upon which tourist attraction is based.

The proposed jetport west of Miami and north of the Everglades National Park raised a dramatic land use problem. The jetport, together with associated transportation corridors, imperiled a unique ecological preserve. Planners for the jetport had considered density of population, regional transportation needs, and a host of other related variables. But they gave slight consideration to the wildlife and recreational resources of the Everglades. The jetport could have spawned a booming residential, commercial, and industrial complex which would have diminished water quality and without question drastically altered the natural water cycle of Southern Florida. This in turn would have endangered all aquatic species and wildlife within the park and beyond.

Natural Resources

Natural resource depletion is a particular environmental concern to a highly technological society which depends upon resources for energy, building materials, and recreation. And the methods of exploiting resources often create problems that are greater than the value of the resources themselves.

A classic case was the Federal Government's decision to permit oil drilling in California's Santa Barbara Channel. There, primary value was placed on development of the oil resources. The commercial, recreational, esthetic, and ecological values, which also are important to the residents of Santa Barbara and to the Nation, were largely ignored. The President recently proposed to the Congress that the Federal Government cancel the 20 Federal leases seaward from the State sanctuary extending 16 miles along the Santa Barbara Channel. This is where the blowout erupted in January 1969, spreading a coat of oil across hundreds of square miles including the sanctuary. This action illustrates a commitment to use offshore lands in a balanced and responsible way.