by Lancelot Femando PhD
Life cannot be separated from the environment. If there is any doubt about this statement, consider the following. From the first breath we take at birth to our last breath,we are directly connected to the environment by the air we inhale deep into our lungs. In fact, it is difficult to point out an exact boundary between ourselves and the air we breathe in - it is virtually a continuum between ourselves and the environment.
Unfortunately, human generated pollutants have now become a part of the global environment. Our great-grandparents' generation believed that our oceans, our forests, and even the atmosphere, were so vast that they could absorb any level of abuse we bestowed on them and could recover from any amount of damage. In fact, in the past the damage we could do to the environment was somewhat limited. Only localized areas were directly affected by human mis-adventures. Our ancestors did not even dream of a scenario in which the survival of Homo sapiens would be in question. The situation is entirely different now. The primary resources upon which we depend, clean air, safe drinking water, habitable land, and a supportive biota, are all under threat. The survival of the human species is no longer a given.
The destruction of the biosphere need not be sudden as in the case of nuclear war. It may occur slowly over a long period of time. Environmental damage usually starts with an innocuous pollutant being released to the environment for years before it is linked to health or environmental problems. After all, automobiles were thought to have got rid of pollution caused by horses drawing the carriages of the past. It was decades before auto emissions were found to be harmful to the environment. Thus it takes a long time for the negative effects of pollutants to be felt. The insidious nature of environmental pollution is that after a slow and apparently harmless accumulation of a pollutant, a critical threshold might be exceeded causing unforeseen catastrophic consequences.
To illustrate how this can happen, we can look at a simple ecosystem. Let us look at the example of yeast in the fermentation broth. In the brewing of beer, yeast is added to a nutrient cereal broth. The yeast uses the carbohydrates in the broth as their food source and produces alcohol as their waste product. For awhile the yeast happily consume the nutrients, grow and reproduce, and the yeast population keeps on increasing. For a short time it looks like the yeast population can go on increasing forever. There is an abundant supply of food surrounding them and they have no enemies. However, unknown to the yeast, the concentration of alcohol - their waste product - keeps on increasing. Unfortunately, alcohol is a poison to the yeast. Once the alcohol concentration in their environment reaches a critical level, guess what happens to the yeast? They die.
But can this happen on a global scale? Can a pollutant produced by an organism poison the whole Earth and lead to actual species extinction? According to one school of thought, it has already happened at least once. Early in the Precambrian - the time from 4.5 billion to 570 million years ago is known as the Precambrian - the atmosphere contained very little oxygen. There were only anaerobic organisms, thus they did not need oxygen to survive. These single-celled anaerobic organisms flourished wherever there was water, extracting nutrients from the surrounding water. A subset of these organisms were harnessing sunlight as the energy source to break apart hydrogen sulfide gas to obtain hydrogen which in turn was used as internal fuel.
About 3 billion years ago, there appeared organisms that used the abundant water molecules around them to obtain hydrogen instead. They broke the molecular bonds of water to form hydrogen and oxygen. They utilized the hydrogen, but the one atom of oxygen in every molecule of water became a waste product that was released to the environment. As long as the population of these bacteria was low, the waste oxygen posed no problem to the bacteria. But they were so successful that the population of these oxygen-producers exploded world wide. Their waste oxygen not only polluted the oceans, but began to change the atmosphere itself. By two billion years ago the atmosphere had changed dramatically to contain an appreciable concentration of oxygen. New aerobic species evolved and became dominant. Today, most life uses oxygen for respiration, including humans. The anaerobic organisms had unwittingly poisoned the atmosphere with their own waste products. The results were inevitable. In the new atmosphere not only were the anaerobic organisms no longer able to dominate, the new conditions turned out to be a complete catastrophe for them. This was a major environmental change on a global scale brought about by living organisms which turned out to be disastrous to the very organisms that brought about the change. A waste product that has a negligible effect at a low concentration, becomes a species threatening poison when the concentration exceeds a tipping point. This should be a valuable lesson for us, for we are also polluting the environment on a global scale. Hopefully we will be able to change our ways, for unlike the anaerobics, we possess that rare gift, high intelligence. But judging from how we have used this rare gift thus far, I have my doubts. If we make the mistake of continuing to pollute our environment, we will also be unceremoniously dumped onto the dust-heap of evolutionary history, for nature's solution to pollution seems to be .... extinction!
Taken from the Vortex (organ of the California Section of the American Chemical Society) Vol. LXVIII, No. 7, p. 14