"There are two axioms in ecology. The first says
that everything is interconnected. If you change
one factor, all others are affected. The second
says that organisms in the environment have evolved
complex interactions over millennia. If you alter
just one, the whole thing could collapse.
- Dr. Alan
Teramura, University of Hawaii (Manoa)
The Earth is bathed constantly in a spectrum of radiant energy from the sun,
energy which is essential to support all life. A small proportion of
this spectrum is composed of short- wavelength, high-energy radiation
including ultraviolet light. Much of this is filtered out, through
absorption in the atmosphere or reflection from clouds, and life on the
planet had evolved to avoid or tolerate the small quantities which
naturally reach the Earth's surface.
The ozone layer, located in the stratosphere, is comprised of a blanket of
ozone molecules. It is the primary protective shield that life on Earth has
against the deadly ultraviolet rays of the sun. During the past sixty years
the ozone layer has been severely damaged by millions of tonnes of ozone
depleting substances (ODSs), most notably chlorofluorocarbons (CFCs),
released to the atmosphere by humans. Other ODSs include
hydrochlorofluorocarbons (HCFCs), methyl bromide (MeBr, halons and other
industrial compounds which contain chlorine and bromine. This chemical
warfare against the ozone layer continues to this day.
ODSs are very stable and can survive in the atmosphere for many years or
decades. They are carried up to the stratosphere by air currents where
eventually they disintegrate under UV light. Their disintegration releases
their chlorine or bromine molecules, which creates a chemical chain
reaction leading to the large scale destruction of ozone molecules. It is
estimated that one chlorine molecule can destroy up to 100,000 ozone
molecules before it is neutralized.
The ozone layer is a key element for a healthy, productive planet rather than a
scorched, barren one. A decrease in the number of ozone molecules in the
stratosphere reduces the atmosphere's ability to absorb UV-B radiation before
it reaches the surface of the Earth. Changes of only a few percent in the
thickness of the atmospheric ozone layer allow significant increases in the
amount of UV-B radiation that filters through, and can have a profound impact
upon all life.
This added UV-B radiation impacts on the stability of the global ecosystem;
on the genetic health of all life; on the quality of the air and nature of
the weather and climate; and on human health and welfare.
Depletion of ozone through man's activities has already raised the amount of
UV-B reaching large areas of the Earth's surface to levels capable of
widespread damage to life. There is now such a reservoir of ozone depleting
chemicals in the atmosphere that, even if further emissions ceased today,
current trends of ozone destruction are set to continue for several
decades. Unless emissions are stopped immediately, ozone depletion and damage
to the global biosphere could become very severe and even irreversible.
We could already be on the edge of a spiral towards the breakdown of the
biosphere as we know it.
We live on a radiantly beautiful planet. It is our responsibility, for the sake
of all future generations of life, to ensure that we don't leave behind us a
radiantly scorched Earth that can no longer sustain life.
