Some societies worshipped what they called Mother Earth, or Gaia, as a living being who should be thanked for generating and sustaining human beings. Although current science can’t confirm that the earth is like a god with a mind of her own, it does suggest that it/she is alive.
One of the most important characteristics of many living things, including all mammals, is the control of their temperature. When we’re hot we tend to maintain our body temperature by moving from the sun to the shade, perspiring so that evaporation cools us, and reducing our exercise to curtail heat production in our muscles. When we’re cold we exercise, shiver, and put on warm clothing. Other mammals adapt to the cold by grow hair or increasing layers of fat.
Rocks don’t do these things. When the ambient temperature is hot, they’re hot; when it’s cold, they’re cold. The earth is more like a mammal than a rock. Its temperature has stayed relatively constant since life began 3.5 billion years ago, yet it now receives 30% more heat from the sun than it did billions of years ago. If it were just a rock, it would be 30% hotter.
It seems that life on earth is the key. Plants use carbon in photosynthesis, thereby removing CO2 from the atmosphere and replacing it with O2. About 0.1% of the carbon that has been taken out of the air and added to the biomass of plants is buried where it can’t combine again with oxygen to form carbon dioxide. The resulting reduction in atmospheric CO2, a heat-trapping gas, helps to keep the earth’s temperature nearly constant. Other life-related processes may also help to keep the earth at a nearly constant temperature amidst changing external conditions.
Plants and other life forms seem to be responsible also for the oxygen content of the atmosphere, which was meager before plant growth absorbed carbon from CO2 and released free oxygen. The oxygen content of the atmosphere increased to its present 21%, where it has been for eons. Had the increase continued, life as we know it on land would be impossible. At 25% oxygen concentration, lightning strikes would burn even wet plants, destroying all forests from the tropics to the arctic. Few land animal species would have survived or evolved in a world of highly combustible plants.
Anaerobic bacteria are the primary agents that inhibit the continued increase of oxygen levels. These are bacteria that live without oxygen in such oxygen-free areas as mud flats, marshes, river estuaries, and sea beds. They produce methane (CH4) which, when it bubbles up into the atmosphere, combines with oxygen to form carbon dioxide and water. The result is less free oxygen in the atmosphere. Without this process, our atmosphere would contain 25% oxygen in a mere 50,000 years. We don’t (yet) know how the buildup of oxygen in the atmosphere causes additional methane production by anaerobic bacteria, but it seems again that life on earth keeps the earth suitable for life.
Similarly, salt concentration in the oceans has a tendency to increase as rain dissolves the salt on land and washes into the sea. Yet, the salt content of the seas has been steady for a long time, constituting 3.4% of the sea, which is good because few life forms in the ocean can live with a salt concentration above 6%. In this case, the life processes that protect the viability of sea life are largely unknown, but we must assume life processes are involved because all known inorganic processes tend to increase the sea’s salinity.
Several other example could be given that indicate that life on earth seems to maintain the conditions necessary for the perpetuation of life on earth. This suggests that the earth is a living individual. It contains inorganic as well as organic parts – rocks, minerals, sand, etc., but so do other living individuals. The carbon in the shells of many sea animals, and in our bones, is inorganic. All of these parts, living and non-living, contribute to the continuity of earth’s life.
Each of us is like a microcosm of the earth. We have many cells that function together with inorganic matter to constitute a single life. Each of our cells is also alive, but couldn’t live on its own. Similarly, each of us is to the earth like one of the cells in a single body. We contribute along with myriad other living beings to constitute the organic aspect of Mother Earth. Just as the cells in our bodies couldn’t live on their own outside of us, we couldn’t live on our own without being part of earth’s life (except in science fiction). Cancer cells tend to kill the life on which they depend. Long-term human survival depends on our being functional, not cancerous.
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