The GAIA hypothesis:
a New Look at Life on
Earth
CSCI 1210
Fall 2003
James Lovelock
British atmospheric
scientist
Invented electron
capture detector
Discovered presence
of CFC’s in
atmosphere of remote
regions
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?”
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
Atmospheric compositions
http://www.prototista.org/E-Zine/evidenceatmosphericdiseq.htm
Gas
Earth
Venus
Mars
CO2
0.03%
96.5%
95%
O2
21%
Trace
0.13%
N2
79%
3.5%
2.7%
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
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 CO2 from the
atmosphere, reducing greenhouse effect.
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.
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
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
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.
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
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!
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
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)
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
When Daisyworld is cool…
Air temperature over
the black patches is
higher
Black patches grow
more
Overall planet color
becomes darker
Planet albedo decreases
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!
When Daisyworld is warm…
Air temperature over
the black patches is
higher
White patches grow
more
Overall planet color
becomes lighter
Planet albedo increases
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.
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