THE LIVING ORGANISMS of the earth, including human beings, depend on all of the above constituents.

1. Plants use water, carbon dioxide, and sunlight to convert raw materials into carbohydrates through photosynthesis.
2. Animals (including human beings) are dependent on plants, in a sequence of interconnected relationships known as the food web.

However rapid industrialization over the past century has caused a threat to the environment. Smoke billowing from industrial smokestacks, including carbon dioxide, sulphur dioxide, and other types of contaminants contribute to the worldwide atmospheric pollution. Carbon dioxide contributes significantly to global warming, while sulphur dioxide is the principal cause of acid rain in eastern and northern Europe and northeastern North America. Other environmental problems stemming from smokestack emissions include respiratory diseases, poisoned lakes and streams, and damaged forests and crops.

ENVIRONMENTAL PROBLEMS

Human beings appeared late in the Earth’s history, but were eventually able to modify the Earth’s environment, by their activities. Due to their unique mental and physical capabilities human beings quickly spread throughout the world. They were also able to escape the environmental constraints that limited other species and to modify the environment to fulfill their wants.

With the first, prehistoric agricultural revolution and the discovery of fire and more importantly the ability to control and use it, the human beings began to modify or eliminate natural vegetation.

1. The domestication of grazing animals eventually resulted in overgrazing and soil erosion.
2. The natural vegetation in the forests and on the mountains was destroyed to:
   1. Make room for crops
   2. Cater to the demand for wood for fuel
3. Wild animals were slaughtered for food and destroyed as pests and predators.

Initially everything was fine as it was on a limited scale, however as populations increased and technology improved and expanded, more significant and widespread problems arose.

The Industrial Revolution, involving the discovery, use, and exploitation of fossil fuels, as well as the extensive exploitation of the Earth’s mineral resources was the major harbinger of the problems being faced by the world today. With it the humans began in earnest to change the face of the Earth, the nature of its atmosphere, and the quality of its water. The situation has reached such an alarming stage today that the unprecedented demands on the environment are causing an enduring and accelerating decline in the quality of the environment and its ability to sustain life.

The major areas of concern are being elucidated as under:

1. Carbon Dioxide

   Carbon dioxide and hydrocarbon emissions are produced as a by-product of the combustion of petroleum-based fuels and are the two major components of vehicle exhaust. They have made a significant contribution to the increasing global warming and adversely affect the health of animals and plants and the chemical nature of the atmosphere.

   The Greenhouse Effect: The high levels of carbon dioxide and hydrocarbon cause sunlight to be reflected and trapped within the atmosphere, which slowly raises the temperature of the atmosphere, as more heat is produced and less escapes. It would be noteworthy to mention here that the amount of atmospheric CO2 apparently remained stable for millennia, at about 260 ppm (parts per million), but over the past 100 years it has increased to 350 ppm. This is also referred to as the Greenhouse Effect.

   The Effects of the Global Warming: The significant effects of the global warming would be:

   1. To speed the melting of polar ice caps
   2. To raise sea levels
   3. To change the climate regionally and globally
   4. To alter natural vegetation
   5. To affect crop production.

   These changes would, in turn, have an enormous impact on human civilization. Since 1850 there has been a mean rise in global temperature of about 1° C (1.8° F). It has been predicted by most scientists that the rising levels of CO2 and other “greenhouse gases” will cause temperatures to continue to increase, with estimates ranging from 2° to 6° C (4° to 11° F) by the mid-21st century.

2. Acid Deposition

   Acid rain is caused by the combination of sulphur dioxide and nitrogen compounds interacting with sunlight, moisture, and oxidants to produce sulphuric and nitric acids, which are carried with the atmospheric circulation and come to Earth in rainfall and snowfall, commonly referred to as acid rain i.e. rain with a very low pH. The rainwater normally has a pH of 6.5, making it very slightly acidic. However the addition of sulphur and nitrogen compounds drops the pH of to as low as 2.0 or 3.0, similar to the acidity of vinegar.

   The Effects of Acid Rain: The significant effects of acid rain are:

   1. Acid rain burns the leaves of plants chemically and as such slows forest growth.
   2. It poisons lake ands stream water thus killing most if not all of the aquatic inhabitants.
   3. Acid rain corrodes metals, weathers stone buildings and monuments.
3. Ozone Layer Destruction

   The global ozone layer is a region of the atmosphere, found at about 40 km asl, that shields the Earth from the Sun’s harmful ultraviolet rays. No life could survive on the planet without this gaseous layer.

   Studies beginning 1980’s showed that the ozone layer was being damaged by the increasing use of industrial chemicals called chlorofluorocarbons (CFCs, compounds of fluorine) that are used in:

   1. Refrigeration
   2. Air-conditioning
   3. Cleaning solvents
   4. Packing materials, and
   5. Aerosol sprays.

   Chlorine, a chemical by-product of CFCs, attacks ozone, which consists of three molecules of oxygen, by taking one molecule away to form chlorine monoxide. Chlorine monoxide then reacts with oxygen atoms to form oxygen molecules, releasing chlorine molecules that break up other molecules of ozone, thereby depleting the ozone layer.

   A thinning of the ozone layer exposes life on Earth to excessive ultraviolet radiation, which can:

   1. Increase skin cancer and cataracts,
   2. Reduce immune-system responses,
   3. Interfere with the photosynthetic process of plants, and
   4. Affect the growth of oceanic phytoplankton.

   As a result of the growing threat of these dangerous environmental effects, many nations are working towards eliminating the manufacture and use of CFCs. However, CFCs can remain in the atmosphere for more than 100 years, so ozone destruction will continue to pose a threat for decades to come.

4. Chlorinated Hydrocarbons

   Extensive use of synthetic pesticides derived from chlorinated hydrocarbons (e.g. DDT) in pest control is another human activity that has had disastrous environmental side effects.

   Nature of the chlorinated hydrocarbons:

   1. These pesticides are highly persistent.
   2. They resist biological degradation
   3. They are relatively insoluble in water
   4. They cling to plant tissues
   5. They accumulate in soils, the bottom mud of streams and ponds, and the atmosphere.

   Once in being these pesticides are distributed worldwide, contaminating wilderness areas far removed from agricultural regions, and even the Antarctic and Arctic zones.

   These synthetic chemicals enter the food chain by the plant eaters or absorbed directly through the skin by such aquatic organisms as fish. It further passes from herbivores (plant eaters) to carnivores (meat eaters).

   Chlorinated hydrocarbons cause thinning of egg shells as it interferes in the calcium metabolism of birds which results in reproductive failure, bringing some large predatory and fish-eating birds close to extinction.

5. Other Toxic Substances

   Toxic substances are synthetic chemicals that enter the environment and persist there for long periods of time. They are chemicals and mixtures of chemicals the manufacturing, processing, distribution, use, and disposal of which present an unreasonable risk to human health and the environment.

   Major concentrations of toxic substances occur in chemical dump sites. By seeping into soil and water, these chemicals can contaminate:

   1. Water supplies
   2. Air
   3. Crops
   4. Domestic animals

   They have been associated with human birth defects, miscarriages, and organic diseases. Despite known dangers, new synthetic chemicals are being created at the rate of 500 to 1,000 each year.

6. Radiation

   Realising the menace of the nuclear radiation, atmospheric testing of nuclear weapons has been banned by most countries, eliminating a large source of radioactive fallout. However the possibility of nuclear accidents, in which massive amounts of radiation are released into the environment—as happened at Chernobyl, Ukraine, in 1986, is still a very large danger.

   The storage of nuclear wastes is a great problem being faced by the nuclear industry. These wastes remain toxic for 700 to 1 million years, depending on the type. Safe storage for geological periods of time is problematic; meanwhile nuclear wastes accumulate, threatening the environment.

7. Loss of Wild Lands

   Human beings are continuously encroaching on remaining wild lands—even in those areas, like the Arctic regions and the tropical forests, once considered relatively safe from exploitation, degradation, and pollution:

   1. The development of Arctic regions for oil and gas is threatening the delicate ecological balance of tundra ecosystems and their wildlife.
   2. Tropical forests, especially in south-eastern Asia and the Amazon River Basin, are being destroyed at an alarming rate for timber, conversion to crop and grazing lands, pine plantations, and settlements.

   It has been estimated that such forest lands were being cleared or converted at the rate of 20 hectares (nearly 50 acres) a minute. Over 750,000 species have become extinct due to this tropical deforestation, which is likely to eliminate millions if allowed to continue unchecked. This would also mean the loss of a multiplicity of products: food, fibres, medical drugs, dyes, gums, and resins. In addition the illegal trade in endangered species and wildlife products, could mean the end of Africa’s large mammals.

8. Soil Erosion

   Soil erosion is degrading 1/5th to 1/3rd of the world’s cropland thereby posing a significant threat to the food supply. In the developing world, increasing needs for food and firewood have resulted in the deforestation and cultivation of steep slopes, causing severe erosion.

   The loss of prime cropland to industry, dams, urban sprawl, and highways is another major problem. The amount of topsoil lost each year is at least 25 million tonnes, which is enough, in principle, to grow 9 million tonnes of wheat.

   About half of all erosion is in the United States, the former Soviet Union, India, and China. Soil erosion and the loss of cropland and forests also reduce the moisture-holding capacity of soils and add sediments to streams, lakes, and reservoirs.

9. Demands on Water and Air

   The erosion problems as described above are aggravating an increasing world water problem. Human beings need irrigation systems and water for industry. Dependence on the ground water is depleting underground aquifers so much so that salt water is intruding into them along coastal areas of a number of countries like the United States, Israel, Syria, and the Arabian Gulf states.

   In inland areas, on being drained of water, the porous rocks and sediments are compacting which causes surface subsidence problems. This subsidence is already a serious problem in Texas, Florida, and California.

   The world is also experiencing a steady decline in the quality and the quantity of water. As of now, the ever-increasing human population is already using 55 per cent of available freshwater run-off. About 75 per cent of the world’s rural population and 20 per cent of its urban population have no ready access to uncontaminated water. In many regions, water supplies are contaminated with toxic chemicals and nitrates leading to waterborne diseases and killing 10 million people a year.

CONCLUSION

For the humanity to save its habitat and to reduce environmental degradation, the societies must recognize that the environment is finite.

Environmentalists believe that, as populations increase their demands too would increase; however the idea of continuous growth must give way to a more sustainable exploitation and rational use of the environment.

To accomplish this a dramatic change in the attitude of the human species has to be brought about. The human attack on the environment is comparable to the dramatic upheavals of the Earth in the geological past. The humanity should recognize that this attack threatens human survival.