Few topics are as significant to today's world as the inter-relationship of organisms and their environments -- the subject scientists call ecology. In recent times, as we become aware that humans are also organisms living on the environmental home we call the Earth, the study of ecology has leapt into the political realm as well. Now we know that the depletion of the ozone layer -- which was first documented in a yearly cycle above Antarctica -- threatens us all. Nearly all responsible scientists accept global warming as more than a theory, but a fact -- a catastrophe waiting to happen, which could flood millions people out of their coastal cities.

Ecology has become a global concern, and the effects of humanity on the planet itself endanger the delicate balance of the earth's environments -- even in Antarctica.

Krill Harvesting

A Crucial Species

The higher species of flesh-eaters or carnivores in the Antarctic (the penguins, seals, seabirds, fish and squid, as well as the giant baleen whales) all feed on krill. This makes the Antarctic marine food web relatively simple, with krill as the key or central species. In the entire food chain there are only three or four levels of species: from the basic photosynthetic organisms or primary producers - the phytoplankton - to the higher flesh-eating levels that include species such as whales, seals and birds. The top carnivores are the orca and leopard seals who feed on penguins, squid and other seals.

Ironically, it is the largest animals that are most endangered -- because of their dependence on this one food source, krill, baleen whales such as humpbacks, fins and blue whales would be most susceptible to changes in the krill population.

While a stock quantity of up to several hundred million tons of Antarctic krill is believed to exist, this figure is based on the estimated consumption of krill by its predators, numbers which are unreliable at best. Until the abundance and the biology of this little-known species is better understood, biologists remain concerned about the possibility of over-fishing and the enormous damage it could cause to the Antarctic marine food chain.

Over Fishing

These small crustacea so important to the marine ecology of Antarctica were first seriously fished in the late 1970s. By 1982 the catch was over 500,000 tons, ninety-three per cent of which was taken by the Soviet Union. Other krill-fishing nations have been Japan and, to a lesser extent, Chile, South Korea and Poland. Today the annual catch is around 400,000 tons annually.

Over half the krill harvest is for non-human consumption - usually ending up as fish-meal or animal feed. If it is for human consumption, krill must be processed within three hours of being caught. Otherwise, following the death of the animal, its enzymes begin to break down the exoskeleton, allowing large concentrations of fluoride -- which in high doses is harmful to humans -- to build up in the flesh. Processed krill for human consumption is usually either minced, turned into a paste, or presented as fresh or canned tail meats.

Other Threats to Krill

Human activity such as fishing is not the only potential threat to krill. As phytoplankton is the main diet of the krill, this crustacean, and all the higher animals that feed on it, may be at risk if the suggested rise in sea temperatures (as a result of the greenhouse effect) alters the pattern of the phytoplankton blooms. In addition, krill is also believed to be threatened by the higher levels of ultraviolet light that now reach the Antarctic as a result of the thinning of the ozone layer over the continent each spring.

Other Threatened Sea Life

Krill, and the animals dependent on them, are not the only creatures of the sea threatened by human activity. The impact of commercial whaling in the earlier decades of this century may be behind us, thanks to the creation of an international Whale Sanctuary in the Southern Ocean. But pelagic fish and the Antarctic Icefish Champsocephalus gunnari were among the first types to be harvested commercially after the decline of whales.

Some species of Antarctic fin fish have already been drastically over-exploited. As early as 1970-71 peak catches of over half a million tons were taken around South Georgia Island, but today this fishery is no longer commercially viable as the stock of this species has been reduced to less than 12.5 percent of its original amount. However, global politics may have saved the species from total extinction: the primary fin-fishing nation in the Southern Ocean was, until its collapse, the Soviet Union. Return

Global Warming

Ice Ages

Ice ages are those periods during the earth's history when large portions of the earth were covered by icecaps. There have been some ten ice ages during the last one million years, occuring at intervals of about 100,000 years. Geological records suggest that the ice ages developed slowly but disappeared relatively quickly. Their origins have long puzzled scientists.

It is now believed that a cycle of three main irregularities, in the Earth's orbit are the main factors initiating an ice age. These are as follows:

  • The first irregularity is the tilt of the earth's axis from 22 to 25 which occurs in a cycle that repeats itself every 41,000 years. (A change in the earth's tilt changes the amount of heat from the sun that reaches the polar regions.)

  • The second irregularity is the orbital procession which completes its cycle every 21,000 years. This determines the season at which the earth is closest to the sun during its orbit. Currently the earth is further from the sun during the northern hemisphere's summer than in the winter.

  • The third cycle, with a period of 100,00 years, alters the shape of the earth's orbit, and its eccentricity amplifies or minimises the effect of the procession. This was first put forward in the 1870's by a Scottish amateur scientist, James Croll, and verified in the 1920's by a Serbian mathematician, Milutin Milankovitch. He showed that these variations were the basis for the significantly cooler summers every 21,000 and 41,000 years. These could help cause an ice age by beginning the build up of ice at the poles. The additional time it took for the icesheets to grow to their maximum sustainable size has been suggested as reason for the ice ages occurring every 100,000 years.

Humanity's Role

Some scientists think the world is about due for another ice age. But for the first time in human history, there is the possibility that the world's climatic cycle is being changed through the effects of humanity itself -- due to a build up of carbon dioxide. The result would be global warming, a scenario which is rapidly gaining credibility and acceptance. The effects of global warming will first be visible in the ice-covered parts of the planet, for any incremental rise in temperatures would reduce the amount of water held in ice. Since Antarctica is a global repository of frozen water, we need to have a much greater understanding of Antarctic geography, glaciology and ecology in order to effectively monitor and predict such changes.

Effects of Global Warming

If all the ice in Antarctica melted, it would raise the level of the world's oceans by over 200 feet (60 meters). The possibility of this happening in the near term is not seriously considered by scientists, for the Antarctic icecap is currently believed to be in equilibrium. However, meteorologists studying the ramifications of global warming and the greenhouse effect expect there to be a decrease in sea levels in the short term -- a matter of decades -- of about 2 millimeters per year. This will be due to an increase in the amount of water vapor in the air as a result of higher air temperatures and will lead to greater snow fall on the continent.

Over the longer term higher global air temperatures are expected to generate higher icecap flow rates and more ice-bergs which are expected to raise sea-level by of 3 feet, or about a meter, in the next century. While such a rise does not seem a significant one, its effects could be devastating -- displacing more than 100 million people in low-lying coastal areas around the world. Accompanying this rise in sea level would be increased winter temperatures and warmer hot spells, increased rainfall and flooding, and overall unpredictable shifting of temperature and rainfall patterns that could wreak havoc with agriculture, natural ecosystems and other daunting effects. Return

Ozone Depletion

Without the protective covering of our atmosphere, the Earth would be an inhospitable place. But looked at from a distance, the thickness of the atmosphere relative to the planet's size has been compared to the skin of an apple. It is more fragile than we usually believe, and until the discovery of the thinning of the ozone layer, we took our air for granted.

In 1985, scientists discovered that more than half the ozone was being lost from the stratosphere over Antarctica each spring, following the return of the sun to the polar ice cap. After three years of intense study, the culprit was found to be the human-created compounds used in industry, especially chlorofluorocarbons (CFCs). Solvents, refrigerants, and spray-can propellants all contain CFCs, and their combined use releases more than half a million tons of chlorine into the atmosphere yearly. Chlorine is a very stable compound, and once it rises into the stratosphere, each chlorine molecule can destroy thousands of ozone molecules. The result is a dramatic reduction in the ability of the atmosphere to repel ultraviolet radiation.

The Dangers of Ultraviolet Radiation

UV radiation can have troubling if not devastating effects on surface life, including human. An increase in skin cancers, a suppression of human immune systems, disruption of plant life including increased susceptibility to pests or disease, reduction in phytoplankton growth, and the eventual decrease in the numbers of aquatic species -- all these effects and more are anticipated due to ozone depletion. (The causes and effects of ozone depletion are well documented elsewhere on the Web.)

Unfortunately, despite legislation in some countries to reduce the production and use of CFCs, the outlook is not optimistic. The annual thinning of the ozone layer over Antarctica got off to a jump start this year, and looks more severe than ever before. By the end of September, 1995, the ozone hole covered over 4 million square miles -- an area roughly the size of Europe. With ozone levels 10% lower in August 1995 than the previous record low (August 1994), pessimism is difficult to avoid.

Though Antarctica seems at the end of the world, its frozen wastes a distant aside in the lives of most of us, it is not unlike the canary in the coal mine -- a gauge of warning, an alarm sounding to wake the world to the danger we are all in, together. Return

1995 Terraquest. All Rights Reserved.