Gaia Hypothesis

The Gaia (jee'-uh) hypothesis presents the idea of a control system for earth. Gaia is an evolving system made up from the rocks, oceans, fields, forests and the atmosphere. It is a self regulating system. The authors of the hypothesis, James Lovelock and Lynn Margulis state that

the temperature and composition of the Earth's surface (including the atmosphere) are actively regulated by the sum of life on the planet. The Gaia hypothesis, when we first introduced it in the 1970's, supposed that the atmosphere, the oceans, the climate, and the crust of the Earth are regulated at a state comfortable for life because of the behavior of living organisms. Specifically, the Gaia hypothesis said that the temperature, oxidation state, acidity, and certain aspects of the rocks and waters are at any time kept constant, and that this homeostasis is maintained by active feedback processes operated automatically and unconsciously by the biota . . . life and its environment are so closely coupled that evolution concerns Gaia, not the organisms or the environment separately.

Using Energy: Chemotrophs and Phototrophs

Sunlight is the main source of energy near the earth's surface ( in the first 60m of the ocean serface and up to about the tree line-13,000 ft.- on the crustal surface. All organisms on earth either use sun-light or stored chemical bonds. Phototrophs or "light feeders" capture photons of light with chlorophyll pigment systems and store the energy as chemical bonds in organic molecules like starch and sugar. This includes green plants, algea and groups of bacteria that use photosynthetic processes.
Fermentation , a chemical process for breaking the chemical bonds found in sugars (polysaccharides) and starches is used by chemotrophs to release some of the stored energy. Glycolysis is the term for describing the breakdown of the glucose and respiration is the term that describes the process organisms use to link available oxygen to the available chemical bonds in the sugars, starches, fats and proteins i.e organic molecules.
When the sun sets, most phototrophs are capable of continuing the energy exchange process by alternative chemical methods that shows them to be a mixture of the photrophic and chemotrophic methods.

Thermodynamics

The first law of thermodynamics states: the conservation of energy: energy can be converted from one form to another but can never be created or destroyed. Any open system, such as the earth, must be left with an energy surplus after account for the influx of energy (sunlight) minus any reactions that consume energy as the net consumption of all living things on the planet. Obviously, as the methods of human life attest to, there is an abundant energy surplus on the surface of the planet. It is the purpose of biogeochemistry to explain the historical processes that caused that to be able to happen.

Sources of Energy on the Earth's surface
Energy Souce	Calories/cm²/year
Solar radiation	260,000
Electric discharge	4
Radioactivety	0.8
Heat (volcanic)	0.13
Chemical Energy (photosynthesis)	100
Chemical energy (stored in geological deposits)	10²⁶ calories

The total energy stored within a system is the internal energy of the system or E. The change in internal energy, D E is the difference between the energy that went into the system and the energy that is left.

The main feature of life is its orderly use of energy; the Universe, as a whole is not so convivial. The energy system we are suspended in is running down; someday, 60 billion years from now, so the cosmologists say, all motion in the Universe will cease, including electrons orbiting atomic systems of protons and neutrons. The reason behind this winding down is the directional nature of events-the temperature of things is always going down.
SECOND LAW OF THERMODYNAMICS: Heat cannot be changed completely into work, with no other change taking place; moving heat from a body of low temperature to another of higher temperature requires an expenditure of work. Engines and refrigerators are common devices for moving heat; none of these devices achieves 100% efficiency-some heat is always lost to the surrounding environment and dissipated into the earth's surface, atmosphere or oceans. From there it will eventually make its way into space.

Another statement of the Second Law was made by Lord Kelvin

No process is possible in which the exclusive result is the absorption of heat from a reservoir and its complete conversion into work.

   He was stating, again, that no engine can draw on a heat source and change that radiance completely into work. All real heat engines have both a hot source and a cold sink, and some heat is always discarded into the cold sink and not converted into work. The Kelvin statement is a generalization of another everyday observation, that a ball at rest on a surface has never been observed to leap spontaneously into the sky. An upward thrusting of the ball would be the same as converting heat from the surface into work.
   What determines the direction of spontaneous change? It is not the total energy of the isolated system. The First Law of thermodynamics states that energy is conserved in any process, and we cannot disregard that law now and say that everything tends towards a state of lower energy: the total energy of an isolated system is constant.
   When a change occurs, the total energy of an isolated system remains constant but it is parcelled out in different ways.

The earth's atmosphere is part of the living system that regulates the flow of energy in Gaia. How, for example, could the earth's average temperature be maintained within a suitable range for life when the average flow of heat and light from the sun has been on the increase by roughly 25% for the past 4 billion years? Thunder Storm

Carbon dioxide is a key gas of Gaia which is fed into the system from volcanoes. The cycle of carbon between producers and consumers in the planet's food webs keeps the balance in favor of an excess of Carbon dioxide that is optimal at 4%. Excess is buried in sea sediments. Basalt extruded from volcanoes contains calcium silicate and when struck by rainwater saturated with CO₂ it slowly dissolves. This leaves a water solution of calcium bicarbonate and silicic acid. This solution makes its way to the ocean floor as sediments where it becomes the source of limestone.

The Global cycles of the elements and the fingerprints of life

A traveler from the outer realms of galactic space would notice a distinct signature to the earths's atmosphere as it came up on his long range scanners. 99% of the earth's atmosphere is made up of oxygen and nitrogen, elements that would normally have combined with other elements through chemical processes lasting no more than several dozen millions of years. This chemical disequilibrium is the result of billions of years of work done by living organisms

Picture a planet about the same size as the Earth, spinning on its axis and orbiting, at the same distance as the Earth, a star of the same mass and luminosity as the Sun. This planet differs from the Earth in having more land area and less ocean, but it is well watered, and plants will grow almost anywhere on the land surfaces when the climate is right. This is the planet Daisyworld, so called because the principal plant species are daisies of different shades of color: some dark, some light, and some neutral colors in between. The star that warms and illuminates Daisyworld shares with our Sun the property of increasing its output of heat as it ages. When life started on Earth some 3.8 billion years ago, the Sun was about 30 percent less luminous than now. In a few more billion years, it will become so fiercely hot that all life that we know will die or be obliged to find another home planet. The increase of the Sun's brightness as it ages is a general and undoubted property of stares. As the star burns hydrogen (its nuclear fuel) helium accumulates. The helium, in the form of a gaseous ash, is more opaque to radiant energy than is hydrogen and so impedes the flow of heat from the nuclear furnace at the center of the star. The central temperature then rises and this in turn increases the rate of hydrogen burning until there is a new balance between heat produced at the center and the heat lost from the solar surface. Unlike ordinary fires, star-sized nuclear fires burn fiercer as the ash accumulates and sometimes even explode.
     Daisy world is simplified, reduced if you like, in the following ways. The environment is reduced to a single variable, temperature, and the biota to a single species, daisies. If too cold, below 5�C, Daisies will not grow; they do best at a temperature near 20�C. If the temperature exceeds 40�C, it will be too hot for the daisies, and they will wilt and die. The mean temperature of the planet is a simple balance between the heat received from the star and the heat lost to the cold depths of space in the form of long-wave infrared radiation. ON the Earth, this heat balance is complicated by the effects of clouds and of gases such as carbon dioxide. The sunlight may be reflected back to space by the clouds before it can reach and warm the surface. On the other hand, the heat loss from the warm surface may be lessened because clouds and molecules of carbon dioxide reflect it back to the surface. Daisyworld is assumed to have a constant amount of carbon dioxide, enough for daisies to grow but not so much as to complicate the climate. Similarly, there are no clouds in the daytime to mar the simplicity of the model, and all rain falls during the night
    The mean temperature of Daisyworld, is therefore, simply determined by the average shade of color of the planet, or as astronomers call it, the albedo. If the planet is a dark shade, low albedo, it absorbs more heat from the sunlight and the surface is warmed. If light in color, like fallen snow, then 70 to 80 percent of the sunlight may be reflected back to space. Such a surface is cold when compared with a dark surface under comparable solar illumination. Albedos range from 0 (wholly black) to 1 (wholly white). The bare ground of Daisyworld is usually taken to have an albedo of 0.4 so that it absorbs 40 percent of the sunlight that falls upon it. Daisies range in shade of color from dark (with an albedo of 0.2) to light (with an albedo of 0.7)
    Imagine a time in the distant past of Daisyworld. The star that warms it was less luminous, so that only in the equatorial region was the mean temperature of bare ground warm enough, 5�C, for growth. Here daisy seeds would slowly germinate and flower. Let us assume that in the first crop multicolored, light, and dark species were equally represented. Even before the first season's growth was over, the dark daisies would have been favored. Their greater absorption of sunlight in the localities where they grew would have warmed them above 5�C. The light-colored daises would be at a disadvantage. Their white flowers would have faded and died because, reflecting the sunlight as they do, they would have cooled below the critical temperature of 5�C.

The next season would see the dark daisies off to a head start, for their seeds would be the most abundant. Soon their presence would warm not just the plants themselves, but, as they grew and spread across the bare ground, would increase the temperature of the soil and air, at first locally and then regionally. With this rise of temperature, the rate of growth, the length of the warm season, and the spread of dark daisies would all exert a positive feedback and lead to the colonization of most of the planet by dark daisies. The spread of dark daisies would eventually be limited by a rise of global temperature to levels above the optimum for growth. Any further spread of dark daisies would lead to a decline in seed production. In addition, when the global temperature is high, white daisies will grow and spread in competition with the dark ones. The growth and spread of white daisies is favored then because of their natural ability to keep cool.

As the star that shines on Daisyworld grows older and hotter, the proportion of dark to light daisies changes until, finally, the heat flux is so great that even the whitest daisy crop cannot keep enough of the planet below the critical 40oC upper limit for growth. At this time flower power is not enough. The planet becomes barren again, and so hot that there is no way for daisy life to start again.

The evolution of the word Gaia

Gaia is the name the ancient Greeks used for the Earth Goddess. This goddess in common with female deities of other early religions was at once gentle, feminine and nurturing. The other side of the goddess is a ruthless cruelty to any who fail to live in harmony with the planet.

References

1. Current Greenhouse gas concentrations
2. The Ages of Gaia, A Biography of Our Living Earth, ; James Lovelock, � 1988 W. W. Norton & Company Inc. New York NY ISBN 0-393-02583-7
Library of Congress Shelf # QH331.L688 1988

A simulation of DaisyWorld More about Gaia theory Table of Contents	Saturday, March 26, 2005 8:11:50 AM
United Nations Framework Convention on Climate Change	Scientists discuss Gaia Read what the scientists have to say.
	Information on forests exploration of ecological concepts

A popular web magazine covering ecological issues.
European Space Agency has new mission planned for exploring earth from space.


Webmaster: Ray Phenicie	� 2005 - Ray Phenicie