living per se, but something made by living things to
protect against an otherwise hostile world. Air,
Lovelock states, is “our protection against the cold
depths and harsh radiations of space.”

The most important change in the earth’s environ-
ment, the one that allowed current life to exist, was the
rise of free oxygen in the atmosphere. Before life on
earth, the atmosphere contained almost no free oxy-
gen, while today the atmosphere contains 21 per cent.
This level has been stable for about 570 million years.

The increase in atmospheric oxygen seems to be
due to the presence of bacteria that rely on sunlight
and carbon dioxide to produce energy. These bacteria
lived in the earth’s early oceans and thrived near the
surface where volcanic activity and high carbon atmos-
phere provided an ideal living environment. These
early bacteria released oxygen as a metabolic waste
product. As oxygen levels began to rise, other bacteria,
which depended on oxygen, evolved. As atmospheric

the

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xygen levels continued to increase
bacteria and non-oxygen using bacteria |
nip, eventually
ive in an

marshes become land, and water travelling through the
soil carries some salt back into the ocean. This ongo-
ing process works to maintain a balance in ocean
salinity.

Another example of a Gaian process is the removal
of carbon from the atmosphere. Organisms that use
carbon compounds to create shells, take carbon from
the atmosphere. As the organisms expire, the remain-
ing shells sink to the ocean floor and gather, eventual-
ly forming sedimentary rock. Carbon is entered back
into the atmosphere from sources such as volcanoes,
forest fires, and plants, which use carbon and nitrogen
found in soil.

Criticisms of Gaia

Most of the criticism of the Gaia theory comes from
scientists who challenge Lovelock to show how organ-
isms could unify in seemingly global acts of altruism,
when natural selection relies on survival of the fittest.

   

 

a feedback loop. Ultimately Lovelock states, “life
and the material environment evolved tightly cou-
pled together as a single entity. Self regulation is
an emergent property of the system.” Lovelock hes-
itates to say that Gaia regulates anything.

Gaia Will Die

Life on earth has been around for 2.5 billion
years. Lovelock doubts life will last an equal
amount of time. Since life on earth began, energy
output of the sun has increased about 25 per cent.
Throughout this time the average temperature of
the earth has remained relatively stable. The aver-
age temperature is a balance between periods of
warmth and periods of cold. Eventually the sun’s
output will become too great for the current envi-
ronment to exist, and life will begin to extinguish.
As Lovelock says, “It’s part of the cosmic cycle.
Gaia is simply a single cell in the universe.”