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The Biosphere

Introducing an issue on how the earth's thin film of living matter is sustained by grand-scale cycles of energy and chemical elements. All of these cycles are presently affected by the activities of man...

By G. Evelyn Hutchinson

The Energy Cycle of the Earth

The solar energy absorbed by the earth is eventually reradiated into space as heat. Meanwhile it is distributed over the surface of the earth by the circulation of the atmosphere and the oceans...

By Abraham H. Oort

The Energy Cycle of the Biosphere

Life is maintained by the finite amount of solar energy that is fixed by green plants. An increasing fraction of that energy is being diverted to the direct support of one living species: man...

By George M. Woodwell

The Water Cycle

Water is the medium of life processes and the source of their hydrogen. It flows through living matter mainly in the stream of transpiration: from the roots of a plant through its leaves...

By H. L. Penman

The Oxygen Cycle

The oxygen in the atmosphere was originally put there by plants. Hence the early plants made possible the evolution of the higher plants and animals that require free oxygen for their metabolism...

By Aharon Gibor and Preston Cloud

The Carbon Cycle

The main cycle is from carbon dioxide to living matter and back to carbon dioxide. Some of the carbon, however, is removed by a slow epicycle that stores huge inventories in sedimentary rocks...

By Bert Bolin

The Nitrogen Cycle

Nitrogen is 79 percent of the atmosphere, but it cannot be used directly by the large majority of living things. It must first be fixed by specialized organisms or by industrial processes...

By C. C. Delwiche

Mineral Cycles

Although the biosphere is mainly composed of hydrogen, carbon, nitrogen and oxygen, other elements are essential constituents of living matter. Notable among them are phosphorus and sulfur...

By Edward S. Deevey

Human Food Production as a Process in the Biosphere

Human population growth is mainly the result of increases in food production. This relation raises the question: How many people can the biosphere support without impairment of its overall operation?...

By Lester R. Brown

Human Energy Production as a Process in the Biosphere

In releasing the energy stored in fossil and nuclear fuels man accelerates slow cycles of nature. The waste products of power generation then interact with the fast cycles of the biosphere...

By S. Fred Singer

Human Materials Production as a Process in the Biosphere

Materials such as metals and concrete are not renewable. Man's problem is to devise cycles that will conserve resources of this kind and at the same time prevent their accumulation as solid waste...

By Harrison Brown

Departments

  • 50 and 100 Years Ago: September 1970

  • Science and the Citizen: September 1970

  • Letters

    Letters to the Editors, September 1970

  • Recommended

    Books

  • Mathematical Recreation

    Mathematical Games

  • Amateur Scientist

    The Amateur Scientist

  • Departments

    The Authors

  • Bibliography

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Scientific American Health & Medicine

Scientific American Health & Medicine