James Lovelock 1979
• Earth is a “super
organism”
• It is alive
• Like one single
organism
• Name is from
Greek Earth Godess
- Gaia
The Gaia hypothesis
• One Step further than “Mother
Earth”
• Lovelock is a reputable scientist
with a hypothesis that it pretty
far out
• Proposed as a testable scientific
hypothesis
“Gaia is a complex entity involving the
Earth’s biosphere, atmosphere, oceans, and
soil; the totality constituting a feedback of
cybernetic system which seeks an optimal
physical and chemical environment for life on
this planet”
James Lovelock
How Does Gaia work?
• Similar to ideas of James Hutton
(1726-1797)
• Lewis Thomas
• Life regulates the
climate and
atmosphere at an
optimum for itself
• Homeostasis
– Like a thermostat
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• But, the earth is
mostly dead rock.
How can it be
alive???
• A Redwood tree
is mostly dead
but it is very
clearly alive
Is there Life on Mars?
Probably not
Why is this important?
Venus
Nitrogen <2%
95%
CO2
No oxygen
Atmosphere
In chemical
equilibrium
Earth
Nitrogen 77%
CO2 .03%
Oxygen 21%
Atmosphere
NOT in chemical
equilibrium
Mars
Nitrogen <3%
CO2 95%
No oxygen
Atmosphere in
Chemical
equilibrium
Homeostatic Mechanisms on
Earth
• Atmospheric chemistry is tightly controlled by Gaia
– At 25% oxygen fires would be very much more
frequent
– Less than 21% oxygen would prevent multicellular
animal life
• Temperature control
– Albedo – reflectivity of earth
– Clouds prevent heating of earth
• Heat produces clouds because of increased
evaporation
– Phytoplankton and DMS – cloud nucleation
• Life keeps atmosphere
out of equilibrium
• Photosynthesis
• There are no fires on
Mars
Current Status of Hypothesis
• Weak Gaia hypothesis
– Life has a substantial effect on Earth’s abiotic
processes
• Certainly true
• Strong Gaia hypothesis
– Original hypothesis
• Earth is a living thing
• Life creates conditions on Earth to suit itself
• Probably too strong a statement
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George C. Williams’ Critique
• The unfitness of the cosmic environment for
life
• Gaia is supposed to regulate earth to
optimize environment for life – it doesn’t
– Forest Fires
– Open ocean phytoplankton and nutrient loss
• Fallacy of planetary
homeostasis
– What sensors keep
earth’s environment
constant?
– Is “Old Faithful” an
example of
homeostasis - NO
What does this have to do with Environmental
Management
Lovelock’s Arguments
• Human activities will not affect earth
permanently
– Gaian homeostatic mechanisms will control
earth’s environments
• The problem is that earth’s reactions to
human activities may threaten humans
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