Lesson #5: The Gaia Hypothesis

After a LONG hiatus, here is your next lesson:

The Gaia Hypothesis.

I actually took a class based around the Gaia Hypothesis back at Zoo-Mass. It was taught by none other than Lynn Margulis, a rather famous scientist in the biology/geology field.

Why both fields? And why fields that seemingly have nothing to do with each other?
Mainly because the Gaia Hypothesis melds these two fields together in quite the amazing way...

Loosely stated, the hypothesis goes like this:
[size=18]Living things on a planet wide scale work in conjunction to create the optimal environement.[/size]

The hypothesis was first coined in the late 60's by James Lovelock, a man working for NASA. His job was to propose a hypothesis that could demonstrate if life existed on a given planet or not.

The main hypothesis that arose was that the atmosphere of a lifeless planet would be in chemical equilibrium. This means that all chemical reactions that could occur have already occured to the point where the composition of the atmorshpere was pretty much fixed at a very specific point.

This made so much sense to Lovelock, when asked if he thought life existed on Mars, he said, absolutely not.

If we compare the atmospheres of mars and venus, we see what he meant.
Mars: 95% CO2, ~3% N2
Venus: 95% CO2, ~2% N2

Now add in earth and look at the difference...
Earth: 77% N2, 21% O2, ~.03% CO2

Now for those who don't know, O2 (i.e. Oxygen gas) is very reactive. I'm sure you've all heard or read about "Oxidation". Oxidation is very simply when oxygen reacts to a chemical to change it into something new. This happens all the time, such as oxygen (not water!) reacting to iron to make it rust. You can also see the effects of oxygen by simply taking a bite out of an apple and letting it sit for a while (it turns brown).

So in other words, if oxygen is so reactive, ALL of it on a planet should react relatively quickly and add itself to another element somewhere...i.e. no more pure oxygen on a planet.

Well, if both Venus and Mars are about the same age as Earth, why are the atmospheres so different? The oxygen SHOULD be used up within a couple centuries.

Life of course.

Lovelock's original idea was that life controls just the atmosphere. He has since added pretty much everything else about our planet. Temperature, air, oceans, land, even rocks...

So let me give an example...very simplified mind you...
Plant life and Animal life.

Plants take in carbon dioxide and give off oxygen.
Animals take in oxygen and give off carbon dioxide.

If we have an over abundance of animals, the amount of oxygen in the atmosphere will go down rather quickly and the carbon dioxide will go up. Basically, the plant life will not be able to "keep up" with the grabbing of CO2.
But at some point, animals will begin to die down. The atmosphere and land will have excellent condition for more plant life. So more and more plants begin to grow. More CO2 is taken out of the atmosphere and more O2 is put in.
Eventually, the amount of O2 gets too high. (As an iteresting side note, if the earth had 2 or 3% MORE oxygen in the atmosphere, we'd have MAJOR fire problems). We have less CO2, so the plants start to die down.
Animal populations rebound...

Basically the two populations will bounce back and forth until a perfect amount for each is reached (i.e. an equilibrium).

Obviously the planet is much more comlex than this. There are millions of small ecosystems and evironments that work together to make the optimal environment.
And obviously, the organisms are not regulating the world consciously. The world as we know it is the result of millions of years of life taking in gases, releasing them, eating, drinking, etc.

And most obviously, the Gaia Hypothesis does not take into account the destructive nature of man (such as our penchant for adding LOTS of CO2 into the atmosphere while simultaneously removing trees).