1. The GAIA hypothesis: a New Look at Life on Earth CSCI 1210 Fall 2003

2. James Lovelock British atmospheric scientist Invented electron capture detector Discovered presence of CFC’s in atmosphere of remote regions

3. Lovelock’s “Discovery” of Gaia In 1960 Lovelock was asked to design an instrument to be landed on Mars and detect Martian life by sampling the Martian atmosphere. Lovelock asked, “What is life? And how does it affect the atmosphere?”

4. Lovelock’s “Discovery” of Gaia Using telescopic data, Lovelock and a colleague analyzed the atmospheres of Earth, Venus, and Mars The results showed that the atmospheres of Venus and Mars are in chemical equilibrium, but the atmosphere of Earth is far from equilibrium

5. Atmospheric compositions http://www.prototista.org/E-Zine/evidenceatmosphericdiseq.htm GasEarthVenusMars CO 2 0.03%96.5%95% O2O2 21%Trace0.13% N2N2 79%3.5%2.7%

6. Interpretation? Mars and Venus, which are similar planets, have very similar atmospheres Earth is similar to Mars and Venus, except for one major difference: LIFE. LIFE is responsible for maintaining Earth’s atmosphere in a non-equilibrium state

7. Temperature regulation Astrophysical theory suggests that the Sun’s luminosity should have increased 25% - 70% over past 4.5 billlion years However, Earth’s temperature has remained roughly stable for that time Lovelock postulated a negative feedback loop: plants sucked CO 2 from the atmosphere, reducing greenhouse effect.

8. Why this is radical Traditional evolutionary theory: life exists in a predefined chemical environment Lovelock’s theory: life is controlling the physical environment Life maintains the physical environment in a condition favorable to life Novelist William Golding suggested the term GAIA for this process.

9. Lynn Margulis Youngest woman ever admitted to the National Academy of Science Her work on bacterial sediments earned her the nickname “Queen of the Ooze” Author, Endosymbiosis theory of cell evolution

10. Bacteria: heavy lifters of Gaia Margulis showed that bacteria and algae are the prime movers of the biological processes that keep Earth’s atmosphere far from equilibrium and favorable to life. Bacteria are also involved in the possible negative feedback loops for temperature regulation

11. What is Gaia? GAIA (if it exists!) is a collection of negative feedback loops These loops stabilize the Earth’s physical environment The physical environment is maintained in a condition favorable to life.

12. Problem with the Gaia theory Gaia theory seems to require cooperation among organisms to stabilize Earth physical conditions Conscious cooperation would involve mysticism Unconscious cooperation could not have evolved

13. Lovelock’s response: Daisyworld Daisyworld is a computer simulation of a hypothetical world inhabited by patches of black and white daisies Its purpose is to show that organisms can unconsciously cooperate to regulate temperature No mystical cooperation is needed!

14. Daisyworld Both black and white daisies grow best at 22.5° C Air is slightly warmer over black daisy patches Air is slightly cooler over white daisy patches

15. Inside the Daisyworld Model 1.Incoming solar and albedo determine absorbed solar 2.Use zero-D energy balance model to determine planetary temperature 3.Calculate daisy growth rates 4.Recalculate planetary albedo (feedback loop)

16. Daisyworld simulation First, run the model long enough for Daisyworld temperature to reach equilibrium Then, apply a sudden change in solar input Observe how Daisyworld reacts to restore its temperature

17. When Daisyworld is cool… Air temperature over the black patches is higher Black patches grow more Overall planet color becomes darker Planet albedo decreases

18. When Daisyworld is cool… Planet absorbs more sunlight and gets warmer Daisies have altered the climate! Daisyworld temperature is closer to optimal temperature for daisies!

19. When Daisyworld is warm… Air temperature over the black patches is higher White patches grow more Overall planet color becomes lighter Planet albedo increases

20. When Daisyworld is warm… Planet absorbs less sunlight and gets cooler Daisies have altered the climate! Daisyworld temperature is closer to optimal temperature for daisies Daisies have created a negative feedback loop! This process is what might have created GAIA.

21. A religious movement adopts a computer model… Neo-pagan religious movement grew out of dissatisfaction with existing ideas of God Feminist critique: male God encouraged patriarchal society Environmentalist critique: human domination is destructive to Earth Is GAIA another name for Mother Earth? Biocentric philosophical viewpoint