Chapter 9

 Chapter 9

CHAPTER NO.9 GLOBAL ISSUES AND IMPROVEMENT OF ENVIRONMENT

 

The rapid degradation of the environment due to pollution has led to several global issues facing the modern world. These global issues include depletion of ozone layer, global warming, protection

of water sources, protection of land sources, conservation of biological diversity, management of hazardous chemicals and protection of human health. The first two important global issues are dis-cussed here in this chapter.

 

OZONE LAYER DEPLETION AND ITS EFFECTS

The atmosphere is a gaseous envelope surrounding the planet earth. It is divided into five zones,the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The troposphere is clos-

est to the earth's surface and extends upto a height of 10km. The next division of the atmosphere, the stratosphere, extending from 10km to 45km above the earth's surface, contains a layer of ozone.This ozone layer acts as a filter to prevent the entry of excessive amount of harmful ultraviolet radia-tion into the atmosphere. In this way, it serves as a life saving protective cover for all the life forms and helps in maintaining relatively stable climatic conditions. Chemically, ozone is a bluish gas and one molecule of ozone consists of three atoms of oxygen. The problem of ozone layer depletion was

first noticed over Antartica in 1985. This ozone hole was investigated with the help of highflying aircrafts and a high concentration of chlorine was recorded in the upper atmosphere. It was con-cluded that the chlorine had reacted with ozone and created this hole in the ozone layer. In 1992, a relatively smaller hole in the ozone layer over the Arctic was also detected.

 

The most important cause of depletion of ozone layer is a group of chemicals known as chloroflurorocarbons (CFCs). These are commercially important chemicals and are used as coolants in air conditoners and refrigerators, as prepellants in aerosol cans, as foam for insula-tion and packaging and as medical sterilizers. In addition to  chlorofluorocarbons, halons found

in many fire extinguishers; methy] bromide, used as a fumigant in agriculture; methyl chloroform,

used to degrease metals, and carbon tetrachloride used in manufacture of pesticides and dyes,also deplete the ozone layer. Under action of ultraviolet radiation, these chemicals breakdown

to release free chlorine atoms. This chlorine then attacks the ozone and converts it into oxygen.As the chlorine atom itself remains unchanged, a single chlorine atom is capable of breaking

thousands of ozone molecules. In this way, the ozone layer is being depleted by chlorine freed from these chemicals.

 

The depletion of ozone layer would allow more amount of ultraviolet radiation to reach earth's sutface. The excessive exposure to these harmful radiations may cause serious health problems in

lnman beings. These include eye cataracts, suppression of immume system, skin cancer and severe sun burns, The increased amount of ultraviolet radiation is harmful to other living organisms too. It may effect the growth and yield of food crops such as corn, rice and wheat. The phytoplankton

present in the aquatic ecosystems is very essential for survival of different aquatic food-chains. It has been scienitifically discovered that the increased exposure to ultraviolet radiation has reduced the amount of phytoplankton population in surface waters around Antarctica. If this trend continues, the food-chain of Antarctica which includes fishes, seals, penguins, whales and sea birds will be ad-

versely affected and may dissappear in future.

 

In view of the potential economic, health and environmental concerns, the problems of depletion of ozone layer has emerged as a global issue facing the modern world. Since 1978, the United States has completely banned the use of CFCs as propellants in products such as hair sprays and antiper-spitants. The Montreal Protocol, 1987 is an important international initiative to mitigate this climatic changes. More than 175 countries, including India have signed this agreement till-date. The agree-

ment aims at reducing the amount of CFCs being used by different nations. Unfortunately, the CFCs are extremely stable chemicals and will continue to deplete the ozone layer for years to come, At-tempts are also being made to find the suitable altematives for CFCs.

 

GREEN HOUSE EFFECT AND GLOBAL WARMING

The term green house refers to a framed or inflated structure covered with a transparent or translucent matezial. It is used for growing plants under controlled environment. The visible light from the sun penetrates the transparent material of the green house and warms the ground surface and

other objects placed inside. The heated surface and objects then emit heat in the form of invisible infra-red radiation. This heat or infra-red radiations cannot pass back through the glass of the green house and are trapped inside. As a result of the warming effect so produced, the temperature inside the green house increases and it is much higher than the air outside.

 

The atmosphere surrounding the earth is like a large green house. Carbon dioxide, water vapours,ozone, methane, nitrous oxide and CFCs present in the atmosphere absorb the infra-red radiations and act like the glass of a green house. This prevents the escape of infra-red radiations back into the

space. The resulting trend of gradual increase in the average temperature of the earth's atmosphere due to accumulation of green house gases is termed as global warming.

 

The long term emission of carbon dioxide since industrial revolution, alone has made 50-70 petcent contribution to the problem of global warming. Its global amount has increased by more than

26 percent in the past 200 years. This increase is primarily due to buming of fossil fuels, especially coal and oil in industries, thermal power plants, automobile; deforestation and increased human popu-lation. If the present rate of fossil fuel consumption and deforestation continues, it is estimated that the amount of carbon diaxide will become double by the end of 21st century. The levels of other green house gases such as ozone, methane, CFCs and nitrous oxide produced from different sources ate also rising at an alarming rate.

 

EFFECTS OF GLOBAL WARMING

The probable impact of global warming is much diversified. The average global temperature would be increased due to global warming. This increase in temperature will result in melting of polar ice sheets and it will raise the sea level. There exists a possibility that the sea level may rise 18cm by

2030 and 58cm by 2090. This will result in flooding of low lying coastal areas. In this way, millions of people will be displaced. There will be more chances of damage by hurricanes and typhoons in

these areas. The countries such as Bangladesh, Egypt, Vietnam and Mozambique are most vulner-able to such risks arising due to rise in sea level. Global warming is also expected to change the rainfall distribution pattern of the world. There may be an increase or decrease in rainfall in different

areas. The arid and and semiarid areas may have to face severe shortage of water. The frequency and intensity of storms may also increase. The climatic changes due to global warming will pose

several problems for the agriculture. The flooding of coastal areas will destroy the vast stretches of

agricultural low lands and deltas in Bangladesh, India and China. The changes rainfall pattem would effect the crop yield and food production. it may increase in some areas while there will be a decline in crop yield and food production in some other areas. The warmer climatic conditions would en-

hance insect breeding and there could be more damage expected to crops form different insect pests. Several crops disease causing organisms will probably proliferate and damage the crops. The

increased frequency of droughts may generate water scarcity for cultivation of different crops.

 

Several possible effects of global warming on animals and plants have been predicted by scien-tists. Global warming will have a severe impact on plants because they cannot migrate directly to

new areas. Their migration takes places by dispersal of seeds. The animal life inhabiting wetlands,coral reefs, polar seas, temperate forests and mountain ecosystems is likely be affected by global warming. The change in global temperature will influence different animal species in different ways.

Some of the species having a narrow temperature tolerance range will become extinct and the others will be reduced in number. Some species may be able to get adapted to new climatic conditions in their native places or they will migrate to other areas for survival. It is expected that disease causing

organisms, insect pests of different crops and weeds will be benefited from the global warming.These harmful organisms will further enhance the health problems for man, animals and crops. All these probable effects of global warming indicate that the climatic changes will have serious implica-tions on human society, agriculture and living organisms.

 

STRATEGIES FOR REDUCING POLLUTION AND

IMPROVING ENVIRONMENT

During the past century, the population explosion, industrilization, urbanization, extensive agri-culture, transportation and deforestation have done a serious damage to the quality of our environ-ment. The pollution of air, water and soil, depletion of ozone layer, global warming, conservation of

biological diversity, management of hazardous wastes and protection of human health have emerged as major challenges to the modern world. These issues must be attended by devising appropriate

strategies and hence finding  constructive solutions to improve the quality of the environment. The

important strategies for reducing pollution and improving the environment are discussed here:

 

Disposal and treatment of wastes : The industrial, domestic and agricultural wastes are major sources of environmental pollution. Approrpriate waste disposal and treatment tech-

niques can reduce the pollution to a considerable extent. Many substances such as paper,plastic, glass, metal etc. present in the solid waste may be separated and recycled. In this

technique the used items are collected, remelted and reprocessed into new products. Recy-cling reduces the total amount of solid waste and also generates employment opportunities for the people. The solid and liquid wastes can be neutralized and detoxified by a number of toxicity of different wastes. Some commonly followed physical processes are sedimentation,filtration, evaporation, floatation, screening etc. Chemical treatment includes neutralization of

acids and alkalis, precipitation and absorption or activated charcoal, In biological treatment or bioremediation, the hazardous waste is exposed to the action of micro-organisms. These

friendly bacteria convert the harmful waste into harmless or less harmful substances. In addi-tion to proper treatment, the disposal of wastes at relatively safer and stable sites also re-duces environmental pollution.

 

Organic farming : Excessive use of chemical fertilizers, pesticides, herbicides, and fumigants causes severe pollution of air, water and soil. Continued use of inorganic fertilizers has dete-tiorated the natural conditions of the soil. In this regard, organic farming is an ecofriendly approach aimed at improving soil conditions and reducing pollution. Following this tecnhique,the crops are grown without the use of synthetic fertilizers and pesticides. Instead of using inorganic synthetic fertilizers, organic farming involves use of farm yard manure, compost,vermicompost and biofertlizers. Compost can be prepared from weeds, paper, food wastes,leaf litter, branches and cattle dung, This also solves the problem of management of solid waste. Now-a-days, different speices of earthworms are being utilized to prepare vermicompost litter, crop residues, food waste and cattle dung (Fig 9.1.)

Biofertlizers are, useful blue green

algae and bacteria which live in soil and provide nutrients to the ctops. They are environmentally safe, The worldwide demand for organically produced crops is in-creasing every year.

 

Insect pest control : Many species of insects cause damage to different crops and result in great economic losses. Different commercial crops such as wheat, rice, sugarcane, maize, cot-

ton, potatoes etc. are attacked by numerous insect pests. In order to minimize the yield logs, a wide range of synthetic chemicals are applied to control the pest populations. The excessive use of chemical methods leads to environmental pollution, besides the problem of resistance to pesticides. These harmful effects have forced man to think about alternative means of insect

pest control. Integrated Pest Management (IPM) is one such strategy. It makes the use of all different methods in an integrated fashion. The basic purpose of IPM is to reduce the use of chemicals, Biological control is a method of controlling insect pests by their natural enemies.Both these methods reduce the use of pesticides and hence are ecofriendly.

 

Afforestation : Forest are very essential for maintaining ecological balance and stable cli-matic conditions. It is quite unfortunate that the world's forests are disappearing at an alarm-

ing rate of 16.9 million hectare every year. Afforestation is the best solution to combat this loss (Fig. 9.2.). It refers to the growing of more forest with an aim to protect and improve the

environment. In addition to protection of the environment, the afforestation also meets the needs of the public. In India, only about 19.27 percent of the total geographical area is under

forest cover and there exists an urgent need for afforestation.

 

Technological upgradation : Attempts are also being made to develop better techniques and equipments for reducing environmental particulate. The electrostatic precipitators, cy-

clone filters and wet scrubbers can be used to remove the particulate matter from the gas-eous waste produced by industries, before releasing it into the atmosphere. Similarly, the use

of catalytic converters in automobiles can minimize the emission of carbon monoxide. Every year, thousands of incompletely burnt dead bodies are dumped into the Ganges and other

rivers in India. The use of electric crematoria can prove very helpful in reducing the pollution of river waters caused by decomposition of these bodies. A number of transgenic crop vari-

eties have been developed through the tecnhiques of genetic engineering. These varieties are resistant to attack by different pests. After making a proper assessment of benefits and risks,

these transgenic crop varieties can be grown for use as food, fooder and pharmaceuticals.The use of alternatives is also helpful in ensuring safe environment. The ydrochlorofluorocarbons (HCFCs) are less dangerous than chlorofluorocarbons (CFCs).The use of compressed natural gas (CNG) in motor vehicles causes less air pollution than diesel fuel. Efforts are being mace to develop efficient technology for harnessing solar and wind energy. The advanced techniques and instruments can reduce the environmental risks associated with the hazardous wastes.

 

International efforts and legislation ; Different international conference recommendations and agreements are of great importance in raising a global concern about betterment of the

environmet by different nations. In this regard, the United Nations Conference on Human Environment, covened at Stockholm in June 1972 was the first serious international effort. It invited attention of people and governments towards the global recommendation for well being of the human environment. A long term international programme known as United Na-tions Environment Programme (UNEP) was started for protection of the environment. Montreal Protocol, 1987 is an important international agreement to minimize the amount of chlorofluorcarbons (CFCs) being used by different countries. More than 175 countries, in-cluding India have signed this agreement till date. In the first Earth Summit, 1992 held at Rio

de Janeiro, Brazil, the global issues of pollution, deforestation and declining biological diver-sity were addressed and a need for sustainable development was emphasized. Several laws have been enacted by different nations for reducing pollution and protecting environment. As legal measures in India, different acts relating to environment have been enacted from time to

time. Some important Acts are, the Forest Act, 1927; the Insecticides Act, 1968; The Forest Conservation Act, 1980; the Wildlife (Protection) Act, 1972; the Water (Prevention and Control of Pollution) Act, 1974; the Air (Prevention and Control of Pollution) Act, 1981, the Environment (Protection) Act, 1986 and the Biological Diversity Act, 2003.

 

Environmental awareness : In addition to the above discussed efforts, the public aware-ness and community participation is a must for improvement and protection of the environ-ment. In this concem, a number of international and national Non-Government Organizations (NGOs), clubs and societies are playing a significant role. More and more people are being made aware of the environmental issues. The ecological awareness is helpful in reviving the

traditional approach towards ecology, nature, water resources and wildlife in the minds of people.

 

(A) Very short answer type questions (1 mark each) :

1. What are atmosphere?

2. How many zones are there in the atmosphere?

3. In which zone of the atmosphere, the ozone layer is present?

4. When was the depletion of ozone layer first discovered 7

5. What is a green house?

6. What is the technique of recycling?

7. Which animal is used for preparing vermicompost?

8. What is a crop pest?

9, Whatis afforestation?

 

(B) Short answer type questions (2 marks each) :

1. What are different global issues facing the modem world?

2. How does the ozone layer protect the life on earth?

3. What are chlorofluorocatbons?

4. What are green house gases?

5. How will the global warming change the sea level?

6. Whatis bioremediation?

7. What are biofextilizers?

8. Whatis green house effect?

 

(C) Short answer type questions (4 marks each):

1. How do the CFCs damage the ozone layer?

2. How is the green house effect produced?

3. What do you understand by global warming?

4. Write about the role of carbon dioxide as a green house gas.

5. Howcan we minimize the use of pesticides and synthetic fertilizers?

 

 

Long answer type questions: (5 marks each):

1. White about the adverse effects of ozone layer depletion. What steps have been taken to Initigate this climatic change?

2. What is the probable impact of green house effect on agriculture, animals and plants?

3. Discuss organic farming and IPM as strategies for reducing pollution.

4. Comment upon the role of technological upgradation and public awareness for improv-ing environment.