All this results from a simple fact about ecosystems—everything is connected to everything else: the system is stabilized by its dynamic self-compensating properties; these same properties, if overstressed, can lead to a dramatic collapse; the complexity of the ecological network and its intrinsic rate of turnover determine how much it can be stressed, and for how long, without collapsing; the ecological network is an amplifier, so that a small perturbation in one place may have large, distant, long-delayed effects.
The Second Law of Ecology: Everything Must Go Somewhere
This is, of course, simply a somewhat informal restatement of a basic law of physics— 25 that matter is indestructible. Applied to ecology, the law emphasizes that in nature there is no such thing as "waste." In every natural system, what is excreted by one organism as waste is taken up by another as food. Animals release carbon dioxide as a respiratory waste; this is an essential nutrient for green plants. Plants excrete oxygen, which is used by animals. Animal organic wastes nourish the bacteria of decay. Their wastes, inorganic materials such as nitrate, phosphate, and carbon dioxide, become algal nutrients.
A persistent effort to answer the question "Where does it go?" can yield a surprising amount of valuable information about an ecosystem. Consider, for example, the fate of a household item which contains mercury—a substance with environmental effects that have just recently surfaced. A dry-cell battery containing mercury is purchased, used to the point of exhaustion, and then "thrown out." But where does it really go? First it is placed in a container of rubbish; this is collected and taken to an incinerator. Here the mercury is heated; this produces mercury vapor which is
emitted by the incinerator stack, and mercury vapor is toxic. Mercury vapor is carried by the wind, eventually brought to earth in rain or snow. Entering a mountain lake, let us say, the mercury condenses and sinks to the bottom. Here it is acted on by bacteria which convert it to methyl mercury. This is soluble and taken up by fish; since it is not metabolized, the mercury accumulates in the organs and flesh of the fish. The fish is caught and eaten by a man and the mercury becomes deposited in his organs, where it might be harmful. And so on.
This is an effective way to trace out an ecological path. It is also an excellent way to counteract the prevalent notion that something which is regarded as useless simply "goes away" when it is discarded. Nothing "goes away"; it is simply transferred from place to place, converted from one molecular form to another, acting on the life processes of any organism in which it becomes, for a time, lodged. One of the chief reasons for the present environmental crisis is that great amounts of materials have been extracted from the earth, converted into new forms, and discharged into the environment without taking into account that "everything has to go somewhere." The result, too often, is the accumulation of harmful amounts of material in places where, in nature, they do not belong.
The Third Law of Ecology: Nature Knows Best
In my experience this principle is likely to encounter considerable resistance, for it appears to contradict a deeply held idea about the unique competence of human beings. One of the most pervasive features of modern technology is the notion that it is intended to "improve on nature"—to provide food, clothing, shelter, and means of communication and expression which are superior to those available to man in nature. Stated baldly, the third law of ecology holds that any major man-made change in a natural system is likely to be detrimental to that system. This is a rather extreme claim; nevertheless I believe it has a good deal of merit if understood in a properly defined context.
I have found it useful to explain this principle by means of an analogy. Suppose you were to open the back of your watch, close your eyes, and poke a pencil into the exposed works. The almost certain result would be damage to the watch. Nevertheless, this result is not absolutely certain. There is some finite possibility that the watch was out of adjustment and that the random thrust of the pencil happened to make the precise change needed to improve it. However, this outcome is exceedingly improbable. The question at issue is: why? The answer is self-evident: there is a very considerable amount of what technologists now call "research and development" (or, more familiarly, "R & D") behind the watch. This means that over the years numerous watchmakers, each taught by a predecessor, have tried out a huge variety of detailed arrangements of watch works, have discarded those that are not compatible with the over-all operation of the system and retained the better features. In effect,
the watch mechanism, as it now exists, represents a very restricted selection, from among an enormous variety of possible arrangements of component parts, of a singular organization of the watch works. Any random change made in the watch is likely to fall into the very large class of inconsistent, or harmful, arrangements which have been tried out in past watch-making experience and discarded. One might say, as a law of watches, that "the watchmaker knows best."
There is a close, and very meaningful, analogy in biological systems. It is possible 30 to induce a certain range of random, inherited changes in a living thing by treating it with an agent, such as x-irradiation, that increases the frequency of mutations. Generally, exposure to x-rays increases the frequency of all mutations which have been observed, albeit very infrequently, in nature and can therefore be regarded as possible changes. What is significant, for our purpose, is the universal observation that when mutation frequency is enhanced by x-rays or other means, nearly all the mutations are harmful to the organisms and the great majority so damaging as to kill the organism before it is fully formed.
In other words, like the watch, a living organism that is forced to sustain a random change in its organization is almost certain to be damaged rather than improved. And in both cases, the explanation is the same—a great deal of "R & D." In effect there are some two to three billion years of "R & D" behind every living thing. In that time, a staggering number of new individual living things have been produced, affording in each case the opportunity to try out the suitability of some random genetic change. If the change damages the viability of the organism, it is likely to kill it before the change can be passed on to future generations. In this way, living things accumulate a complex organization of compatible parts; those possible arrangements that are not compatible with the whole are screened out over the long course of evolution. Thus, the structure of a present living thing or the organization of a current natural ecosystem is likely to be "best" in the sense that it has been so heavily screened for disadvantageous components that any new one is very likely to be worse than the present ones.
This principle is particularly relevant to the field of organic chemistry. Living things are composed of many thousands of different organic compounds, and it is sometimes imagined that at least some of these might be improved upon if they were replaced by some man-made variant of the natural substance. The third law of ecology suggests that the artificial introduction of an organic compound that does not occur in nature, but is man-made and is nevertheless active in a living system, is very likely to be harmful.