June 2012 ISSN 2070-4593 - NGC

a “greenhouse gas” and is one of the factors
responsible for global warming. However,
carbon dioxide is needed in our atmosphere
to regulate our planet’s temperature. Without
it we would be very cold and devoid of many
of the organisms we know.
It is estimated that about 3.5 billion years
ago the sun’s energy has increased by 25% to
30%. However, computer-generated climatic
models suggest that such low solar radiation
would produce a global temperature between
-10 to -52 oC. Therefore if the temperature
had to be maintained at the average global
temperature of 15 oC as it is today, carbon
dioxide levels had to be much higher in the
past.
Therefore some mechanism must have
existed to remove this extra carbon dioxide
from the atmosphere when solar radiation
levels increased. This mechanism of removal
was the conversion of carbon dioxide into
fossil fuels such as oil, coal and natural gas.
This has led to the question of how
biodiversity on a whole influences the
Gaia hypothesis, which has resulted in two
schools of thought. The first is called the,
“species redundancy” hypothesis proposed
by Australian ecologist Brain Walker.
This hypothesis proposed that most of the
species in the ecosystem contributes very
little to the overall stability of the ecosystem,
so that only a few key species play a big role
in ecosystem stability.
The second hypothesis is the “rivet popper
theory” proposed by Paul and Anne Ehrlich in
the “rivet popper theory”, where although on
a plane many rivets are present when one
pops out other start to pop out. Therefore
many other species are needed for these key
species to be present. These other species
may for example act as food or they may
be predators that regulate populations of
competitor species.
So although this hypothesis was at first
not widely accepted, it is now a component
of many areas of Earth system and
geophysiological sciences. However, the
message it conveys is very important, which
is both the biotic and abiotic are necessary
for the equilibrium and maintenance of an
environment capable of sustaining life.
Jo-Anne Nina Sewlal (BSc., MPhil., FLS.,
AMSB.) works at the Department of Life
Sciences, University of the West Indies.
June 2012 Earth Conscious 37