Gaia = Planetary Homeostasis

{10.31.08}

Below is an annotated outline for an essay about Gaia that evolved from a lecture offered recently at Cozmic Pizza.

It will evolve. (Nothing is static on this blog.)
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Basic concept

• Gaia theory (aka geophysiology) is science (even mainstream science in Britain & parts of Europe, even if not in America), but is neither mysticism nor religion.

• "Gaia" is the name that James Lovelock & Lynn Margulis use to denote a planetary-scale, self-regulating system that automatically (without thought, because it is not sentient or conscious) maintains the temperature & chemical composition of Earth's air, water & rocks at far from (thermodynamic & chemical) equilibrium. Gaia is, to borrow a concept from systems sciences, an emergent, self-organizing, dissipative system.

• It has been in continuous existence for ~ 3.9 billion years.

• If one understands the physiology, homeostasis & metabolism of any life form - say, human - then to understand Gaia, one simply scales up to a planetary scale. (Which is why Gaia theory is called "geo-physiology": planetary physiology.)

• How does one “explain” self-regulation? Answer: One does NOT explain it in simple mechanistic terms. Self-regulation is an emergent phenomenon. "Explanation" of planetary self-regulation requires computer models. The most relevant one for Gaia is Daisy World, which is also used in other modeling situations (e.g., glucose regulation in humans).

• Gaia does not contradict natural selection. In fact, one gains a new, deeper understanding of natural selection via Gaia theory. Natural selection does not work by competition among species along: that battle plays out in the context of environmental constraints, I.e., feedbacks from abiotic factors; otherwise, models of species interaction do not stabilize.

• A key to understanding Gaia & it's relationship to natural selection: constraints, especially those based on temperature & it's effects on water, both ocean stratification & evaporation from land surfaces. Other constraints: salts, pH & redox potential (esp. oxygen levels).
  
  Multicellular organisms can somewhat ameliorate constraints via temperature regulation, adaptation to salt & gas levels, etc. But single-celled organisms – e.g., phytoplankton - cannot do so as easily & are constrained by environmental variables, notably the ones above, but also have the capacity to modify them ... to an extent.

• Gaia is Earth's climate regulation system.

More on “climate regulation system”

For the last 2 - 3 million years, because our Sun's luminosity has increased by ~ 30% since the origins of Earth, the planetary self-regulating system has pumped down most carbon gases out of the atmosphere in order for the temperature of the planet to remain habitable for life. (That's actually driven by natural selection.)

As a result of that gas pump down, a few million years ago, Gaia "popped" (underwent a phase transition) into a new colder attractor state called "ice ages". As Lovelock says, "Gaia likes it cold" (where "likes" is his intentionally anthropomorphic metaphor; he understands fully that Gaia is not sentient).

According to Lovelock, the global system - Gaia - is healthier during an ice age because:

1. Ocean temperatures are cooler, favoring the growth of marine phytoplankton (which can't exist stably when water temperatures exceed 10*C because the water stratifies, preventing nutrients from reaching the surface layers);

2. So much ocean water is trapped in ice caps during ice ages that the oceans are 120 m lower than now, exposing land mass the size of Africa, allowing more land plants to exist. Both of those are what help keep carbon gases (especially carbon dioxide) at low levels.

Yet, every few 10's of thousands of years, due to a set of complex variations in Earth's orbit called Milankovitch cycles, the system is unable to remain in that colder ice age attractor state. That's because small increases in solar luminosity cause average global temperature to cross a critical threshold (tipping point), after which our climate undergoes a phase transition into an interglacial like the one that has existed for the last 11,000 to 12,000 years during which human civilization was born (which humans incorrectly believe to be normal). Lovelock refers an interglacial as a "Gaian fever". (Remember: Gaia "prefers" it cold.)

But there in lies the root of our current climate crisis. Humans discovered fossil fuels in the last few hundred years, & used them to power industrial growth. The carbon emissions or heat-trapping "greenhouse gases" resulting from burning said fossil fuels are, as Lovelock says, "like piling blankets on a fevered patient". Simply put, we are making Gaia's "fever" worse, kicking the planetary system into a much hotter attractor state that hasn't existed since the PETM, 55 million years ago.

As Lovelock writes in his opening paragraph of Revenge of Gaia, this promises to have consequences for civilization that will make the current global financial crisis look like kindergarten games.

Wake up: your planet is burning.

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OK, that's a reasonable 2nd draft.
More to come.