How does Gaia resemble a redwood tree?
If you find it hard to believe that anything
as large and seemingly inanimate as the Earth is alive, then it
may help to compare the planet with a giant redwood tree. The tree
is undoubtedly alive, yet more than 97 per cent of it is composed
of dead wood. The thin circumferential skin of living cells (known
as the cambium) just beneath the bark is what keeps the tree alive
In a similar way the Earth also has a "cambium"
composed of the surface layer of living organisms spread thinly
over its circumference.
The bark and the atmosphere both protect
the living matter at the surface. All the gases of the air
nitrogen, oxygen, carbon dioxide, and methaneare the direct
products of living organisms, except for the 1 per cent contribution
made by the noble gases, such as argon.
(see variation 31)