The Biosphere

The face of the Earth⁷ viewed from celestial space presents a unique appearance, different from all other heavenly bodies. The surface that separates the planet from the cosmic medium is the biosphere, visible principally because of light from the sun, although it also receives an infinite number of other radiations from space, of which only a small fraction are visible to us. We hardly realize the variety and importance of these rays, which cover a huge range of wavelengths.

The biosphere may be regarded as a region of transformers that convert cosmic radiations into active energy in electrical, chemical, mechanical, thermal, and other forms. Radiations from all stars enter the biosphere, but we catch and perceive only an insignificant part of the total; this comes almost exclusively from the sun²⁶ The existence of radiation originating in the most distant regions of the cosmos cannot be doubted. Stars and nebulae are constantly emitting specific radiations, and everything suggests that the penetrating radiation discovered in the upper regions of the atmosphere by Hess²⁷ originates beyond the limits of the solar system, perhaps in the Milky Way, in nebulae, or in stars of the Mira Ceti type²⁸ The importance of this will not be clear for some time,²⁹ but this penetrating cosmic radiation determines the character and mechanism of the biosphere.

Life exists only in the biosphere; organisms are found only in the thin outer layer of the Earth’s crust, and are always separated from the surrounding inert matter by a clear and firm boundary. Living organisms have never been produced by inert matter. In its life, its death, and its decomposition an organism circulates its atoms through the biosphere over and over again, but living matter is always generated from life itself.

The diffusion of living matter by multiplication, a characteristic of all living matter, is the most important manifestation of life in the biosphere and is the essential feature by which we distinguish life from death. It is a means by which the energy of life unifies the biosphere. It becomes apparent through the ubiquity of life, which occupies all free space if no insurmountable obstacles are met. The whole surface of the planet is the domain of life, and if any part should become barren, it would soon be reoccupied by living things. In each geological period (representing only a brief interval in the planet’s history), organisms have developed and adapted to conditions which were initially fatal to them. Thus, the limits of life seem to expand with geological time (§119,122). In any event, during the entirety of geological history life has tended to take possession of, and utilize, all possible space.

The amount of living matter in the biosphere (10²⁰ to 10²¹ grams) does not seem excessively large, when its power of multiplication and geochemical energy are considered.

Photosynthetic living matter does not include all the essential manifestations of life in the biosphere, because the chemistry of the biosphere is only partially controlled by the vegetable world. Certain regularities that can be regarded as empirical (if not fully understood) generalizations are frequently encountered in nature, and in spite of their uncertainties must be taken into account. The most essential of them are described below.

In 1875, one of the most eminent geologists of the past century, Prof. E. Suess of Vienna University, introduced the idea of the biosphere as a specific, life-saturated envelope of the Earth’s crust.¹⁷² Despite the importance of life in the structure of the Earth’s crust, this idea has only slowly penetrated scientific thinking, and even today is not much appreciated. This idea, focusing on the ubiquity of life and the continuity of its manifestations, represented a new empirical generalization of which Suess could not have seen the full implications. Only as the result of recent scientific discoveries is this beginning clear.

While the boundaries of the biosphere are primarily determined by the field of vital existence, there is no doubt that a field of vital stability extends beyond its boundaries. ²⁰¹ We do not know how far beyond the confines of the biosphere it can go because of uncertainties about adaptation, which is obviously a function of time, and manifests itself in the biosphere in strict relation to how many millions of years an organism has existed. Since we do not have such lengths of time at our disposal and are currently unable to compensate for them in our experiments, we cannot accurately assess the adaptive power of organisms. ²⁰²

The field of stability of life extends beyond the limits of the biosphere, and the independent variables which determine the stability (temperature, chemical composition, etc.) attain values well beyond the characteristic biospheric extremes of these quantities.

Thus far, we have seen that the biosphere, by structure, composition, and physical makeup, is completely enclosed by the domain of life, which has so adapted itself to biospheric conditions that there is no place in which it is unable to manifest itself in one way or another.

The vital phenomena of the hydrosphere have remained unchanged in many respects since the Archean. Moreover, these phenomena have occurred only in certain regions of the hydrosphere during this entire period, despite the variability of life and changes in the oceans, and must be regarded as stable characteristics both of the biosphere and of the entire crust.

The geochemical effects of multiplication appear in the rhythm of terrestrial chemical processes, which create specific chemical compounds in each living film and concentration. Once chemical elements have entered into the cycles of living matter they remain there forever and never again emerge, except for a small portion that become detached in the form of vadose minerals. It is precisely this fraction that creates the chemistry of the ocean. The intensity of multiplication of organisms is thus reflected in the rate of formation of vadose deposits.

The land presents a totally different picture from that of the hydrosphere³³⁹ It contains only one living film,³⁴⁰ consisting of the soil and its population of fauna and flora. The aqueous basins are living concentrations ³⁴¹ and must be considered separately, because they are quite distinct biochemically and biologically, and completely different in their geological effect.

It follows from the preceding that life presents an indivisible and indissoluble whole, in which all parts are interconnected both among themselves and with the inert medium of the biosphere. In the future, this picture will no doubt rest upon a precise and quantitative basis. At the moment, we are only able to follow certain general outlines, but the foundations of this approach seem solid.