Text d The Biosphere: Natural, Man-Disturbed and Man-Initiated Cycles

1. When considered dynamically, the biosphere appears an arena of complex interactions among the essential natural cycles of its major constituents, with continuous fluxes of these constituents entering the biosphere, or being released by it. Once brought into being by evolution from an inorganic environment, the living matter has profoundly altered the primitive lifeless earth, gradually changing the composition of the atmosphere, the sea, and the top layers of the solid crust both on land and under the ocean. Since then, was one to ascribe a single objective to evolution it would be the perpetuation of life. This is the single end the entire strategy of evolution is focused on, with evolution dividing the resources of any location, including its input of energy among an ever increasing number of different kinds of users, which we recognize as plant and animal species.

2. What are the chemical elements that prove to be the essential constituents of the biosphere? The periodic table lists more than 100 chemical elements. Yet as defined by ecologists the biosphere is the locus of interaction of only four of them: hydrogen, carbon, nitrogen and oxygen, these four being numbered 1, 6, 7 and 8 in the periodic table. Although dealing handsomely with much of the chemistry of life, this definition turns out to be a little too restrictive, ignoring as it does, the biochemical role of sulfur and phosphorus. But when enlarged to include these two, it does not go any farther up the table than element No. 16. Thus, it is a fact that most problems, the environmental ones anyway, arise from the exceptional reactivity of six of the 16 lightest elements, with the first four actually forming protein molecules, sulfur being the "stiffening" in protein and phosphorus supplying the "high-energy bond", the universal fuel for all biochemical work within the cell.

3. If the biosphere is to continue in running order, the biologically important materials must undergo cyclic changes so that after utilization they are put back, at the expense of some solar energy, into a form in which they can be reused. So far it has been nature that saw to it that the whole arrangement went on smoothly, all cycles being governed by complex mechanisms that were fitted together and held the whole in balance. Yet during the few last decades the intervention of man in the natural cycling of that unique compound we call living matter, has been going on an unprecedented scale and at an unprecedented rate. Never before has nature been tempered with in such a drastic and not infrequently, irreversible way, with both immediate consequences an ultimate implications not even vaguely foreseeable. For too little do we know for certain about the way nature has been self-regulating for millions of years since life began, and too many variables are involved, to be able to foresee the final impact of our rapid technological development on the biosphere as an abode of life.

4. Thus, what is now recognized as a threat to our environment is caused primarily by disturbances either in the natural cycles of the six essentials, or in the energy cycle of the biosphere, energy being the driving engine of all life processes.

5. To cite but a few examples of such man-disturbed cycles of the biosphere let us consider very briefly the energy cycle. The energy that sustains all living systems is solar energy as fixed in photosynthesis and held briefly in the biosphere before being reradiated into space as heat. It is solar energy that moves every living thing on the earth. The total amount of solar energy fixed on the earth sets one limit on the total amount of life, with the patterns of flow of this energy through earth's ecosystems setting additional limits on the kinds of life on the earth. Increasing at an unprecedented rate now is the fraction of the total energy required by expanding human activities, which, paradoxical as it may seem, make large segments of it less useful in support of man. Not only is man replacing the earth's major ecosystems with cities and land devoted to agriculture, but leakage of toxic substances from man - dominated provinces of the earth is reducing the structure and self regulation of the remaining natural ecosystems. The trend is progressive. Easily available to man is a smaller and smaller fraction of the earth's fixed energy, and an unavoidable question arises as to how much of the energy that runs the biosphere can be diverted to the support of a single species: man.

6. Or take another example — the disturbance of the nitrogen cycle. Although man and other land animals live in an ocean of air that is 79 per cent nitrogen, their supply of food is limited more by the availability of fixed nitrogen than by that of any other plant nutrient. By fixed is meant nitrogen incorporated in a chemical compound that can be utilized by plants and animals. Naturally this is done by the comparatively few organisms that have the ability to convert the element to a combined form. Of all man's recent interventions in the cycles of nature it is the industrial fixation of nitrogen that far exceeds all the others in magnitude. Before the large-scale manufacture of synthetic fertilizers and the wide cultivation of the nitrogen-fixing legumes one could say with some confidence that the amount of nitrogen removed from the atmosphere by natural fixation processes was closely balanced by the amount returned to the atmosphere by organisms that convert organic nitrates to gaseous nitrogen. Now one cannot be sure that the denitrifying processes are keeping pace with the fixation processes. Nor can one predict all the consequences, were nitrogen fixation to exceed denitrification over an extended period. We do know that excessive run-off of nitrogen compounds in streams and rivers can result in "blooms" of algae and intensified biological activity that deplete the available oxygen and destroy fish and other oxygen-dependent organisms, the process known nowadays as eutrophication.

7. Added to the natural cycles of the biosphere are man-initiated processes which may also be regarded as cycles of the biosphere, namely the production of energy, food and materials on a commercial scale. For as soon as these commodities began to be produced in quantity their production, utilization and disposal have become comparable with the cycling of natural essentials, and a challenge to mankind. To take but one example of the problems involved, think of the urgent need to get rid of all steel in use after its utilization. If properly cycled, all metal, glass, paper, fabrics and the like could provide raw materials for different industries. From a purely technological point of view man could in principle live comfortably on a combination of his own trash and the leanest of earth substances by processing tons of rock to obtain a gram of a useful mineral. Such a way of life would create new problems, because under those circumstances man would become a geological force transcending by orders of magnitude his present effect on the earth. Different as the world might become from the present one, there is no reason a priori why it would be necessarily unpleasant.

8. Man has it in his power technologically to maintain a high level of industrial civilization, to eliminate deprivation and hunger and to control his environment for many millenniums. His main danger is that he will not learn quickly enough and that he will not take adequate measures in time to forestall situations that will be very unpleasant indeed.