Jillian, being so busy lately, has asked me to contribute an entry to her blog. So for my first ever blog entry, here's what I came up with:
Have you heard about the Gaia Theory? I think Al Gore mentions it in An Inconvenient Truth. (Gaia, the Greek goddess of the earth, was the mother of all the gods.) The theory has been circulating since the 1960s. A British scientist and inventor, Dr. James Lovelock, developed the theory after working with NASA to determine that there was probably no life on Mars. As environmental concerns become more mainstream, the theory is getting more attention. The theory is not without dissenters, Richard Dawkins and Stephen J Gould among them, but it does sound a little self evident. It's all about homeostasis.
file://www.gaiatheory.org/synopsis.htm describes the theory this way:
The Gaia Theory posits that the organic and inorganic components of Planet Earth have evolved together as a single living, self-regulating system. It suggests that this living system has automatically controlled global temperature, atmospheric content, ocean salinity, and other factors, that maintains its own habitability. In a phrase, “life maintains conditions suitable for its own survival.”
In this respect, the living system of Earth can be thought of analogous to the workings of any individual organism that regulates body temperature, blood salinity, etc. So, for instance, even though the luminosity of the sun – the Earth’s heat source – has increased by about 30 percent since life began almost four billion years ago, the living system has reacted as a whole to maintain temperatures at levels suitable for life.
In addition to global temperatures, the "Gaian system" could also explain how the planet self-regulates ocean salinity and atmospheric content. Consistent ocean salinity is important for the survival of many organisms - most do not tolerate values over 5%. Over the years river salts should have raised the oceans' salinity levels much higher and scientists have had a hard time explaining why the levels haven't risen - they've been consistent at about 3.4% for a long time. But according the Gaia Theory, it's possible there are organic processes at work that influence the equilibrium. Lovelock believes that the Gaia Theory could also account for the consistent atmospheric composition. The Earth's atmosphere currently consists of 79% nitrogen, 20.7% oxygen and .03% carbon dioxide. Oxygen is one of the most reactive elements and should combine with gases and minerals of the Earth's atmosphere and crust. Traces of methane should not exist, since it's combustible in an oxygen atmosphere. This composition should be unstable and it's stability can only have been maintained with removal or production by living organisms.
To demonstrate the Gaia Theory, Lovelock developed a mathematical model called Dasiyworld.
Wikipedia explains it this way:
Lovelock has a book out called The Revenge of Gaia, in which he argues that the lack of respect humans have had for the planet is testing its ability to continue it's current homeostatic balance. Lovelock says our current efforts to off set our environmental impact, such as sustainable development and renewable energy, is 200 years too late. He believes more effort should go into adaptation - it's too late to repair the damage. Ever the pessimist, Lovelock believes the world population of more than 6 billion will be culled by floods, drought and famine by 2040.
Daisyworld examines the energy budget of a planet populated by two different types of plants, black daisies and white daisies. The colour of the daisies influences the albedo of the planet such that black daisies absorb light and warm the planet, while white daisies reflect light and cool the planet. Competition between the daisies (based on temperature-effects on growth rates) leads to a balance of populations that tends to favour a planetary temperature close to that which is optimum for the daisy growth. Lovelock … demonstrated the stability of Daisyworld by forcing the sun that it orbits to evolve along the main sequence, taking it from low to high solar constant. This perturbation of Daisyworld's receipt of solar radiation caused the balance of daisies to gradually shift from black to white but the planetary temperature was always regulated back to this optimum (except at the extreme ends of solar evolution). This situation is very different from the corresponding abiotic world, where temperature is unregulated and rises linearly with solar output. Later versions of Daisyworld introduced a range of grey daisies and populations of grazers and predators, and found that these further increased the stability of the homeostasis.
I can see some connections between the Gaia Theory and Emergence Theory (see Steven Johnson's book Emergence: The Connected lives of Ants, Brains, Cities, and Software) but we'll explore that another day.
NOTE: The theory's name was a suggestion of William Golding (him of Lord of the Flies fame) who lived in the same village as Lovelock at the time. : )