CBSE 12 - Environmental Issues. This is a document based on the NCERT Book. Will be helpful to students of biology
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CHAPTER 16: ENVIRONMENTAL ISSUES INTRODUCTION 1. What is pollution? (Memorise) Pollution is any undesirable change in physical, chemical or biological characteristic of air, land, water or soil. 2. Agents that bring about pollution are called pollutants. In order to control environmental pollution, the Government of India has passed the _____ Act, 1986, to protect and improve the quality of our environment. Environmental (Protection) AIR POLLUTION AND ITS CONTROL 3. Air pollutants adversely affect the ____ system of humans and animals. respiratory 1
Transcript
CHAPTER 16: ENVIRONMENTAL ISSUES
INTRODUCTION
1. What is pollution? (Memorise)
Pollution is any undesirable change in physical, chemical or biological
characteristic of air, land, water or soil.
2. Agents that bring about pollution are called pollutants. In order to
control environmental pollution, the Government of India has
passed the _____ Act, 1986, to protect and improve the quality of
our environment.Environmental (Protection)
AIR POLLUTION AND ITS CONTROL
3. Air pollutants adversely affect the ____ system of humans and
animals.
respiratory
4. The harmful effects of air pollution depend on the _____ of
pollutants, ____ of exposure and the organism.
concentration, duration
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5. Smokestacks of thermal power stations, smelters and other
industries release ____ and gaseous air pollutants together with
harmless gases such as nitrogen, oxygen, etc. These pollutants must
be separated/filtered out before releasing the harmless gases into
the atmosphere.
particulate
6. There are several ways of removing particulate matter the most
widely used of which is ____ _____, which can remove over ____%
particulate matter present in the exhaust from a thermal power
plant.
electrostatic precipitator, 99
7. Look below for the schematic diagram of the electrostatic
precipitator.
8. Describe an electrostatic precipitator.
(i) An electrostatic precipitator has electrode wires that are
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maintained at several thousand volts, which produce a corona
that releases electrons.
(ii) These electrons attach to the dust particles giving them a net
negative charge. The collecting plates are grounded and attract
the charged dust particles.
(iii) The velocity of the air between the plates must be low enough to
allow the dust to fall.
(iv) A scrubber can remove gases like sulphur dioxide. In a scrubber,
the exhaust is passed through a spray of water or lime.
9. Mention one limitation of the electrostatic precipitator.
The electrostatic precipitator is unable to remove particulate matter,
which is extremely small.
10. According to the Central Pollution Control Board (CPCB),
particulate size ____ or less in diameter, are responsible for causing
the greatest harm to human health.
2.5 µm (PM 2.5)
11. Particulate matters of size of about PM 2.5 are very harmful. Why?
These fine particulates can be inhaled deep into the lungs.
12. Particulate matters of size of about PM 2.5 can be inhaled deep into
the lungs and can cause breathing and respiratory symptoms,
irritation, inflammations and damage to the lungs and ____ death.
premature
13. ____ are a major cause of atmospheric pollution, at least, in the
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metro cities.
Automobiles
14. How can automobile pollution be reduced?
(i) By proper maintenance.
(ii) By use of lead-free petrol or diesel.
15. How is the emission of poisonous gases reduced in automobiles?
Catalytic converters, having expensive metals, namely platinum-
palladium and rhodium as catalysts, are fitted into automobiles for
reducing emission of poisonous gases.
16. How do catalytic converters operate?
(i) As the exhaust passes through the catalytic converters, unburnt
hydrocarbons are converted into carbon dioxide and water.
(ii) Carbon monoxide and nitric oxide are changed to carbon dioxide
and nitrogen gas, respectively
17. Motor vehicles equipped with catalytic converter should use
unleaded petrol. Why?
Because lead in the petrol inactivates the catalyst.
CONTROLLING AIR POLLUTION: A CASE STUDY OF DELHI
18. Delhi has more cars than the states of Gujarat and West Bengal put
together.
---
19. In the 1990s, Delhi ranked ____ amongst the 41 most polluted cities
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of the world.
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20. Following the filing of a Public Interest Litigation (PIL), the
Supreme Court issued certain directions to the government. What
were these directions?
(i) Government was directed to take appropriate measures within a
specified time period;
(ii) Switching over the buses from diesel to Compressed Natural Gas
(CNG) by the end of 2002.
21. Why is CNG a better fuel?
Because it burns most efficiently, unlike petrol or diesel.
22. What are the other advantages with CNG?
(i) It is cheaper than diesel or petrol.
(ii) It cannot be siphoned off or adulterated.
23. What are the problems with CNG?
Difficult of laying down pipelines for uninterrupted supply to
distribution points.
24. What other steps were taken by the Government to reduce
pollution in Delhi?
(i) Phasing out of old vehicles;
(ii) Use of unleaded petrol;
(iii) Use of low-sulphur petrol and diesel;
(iv) Use of catalytic converters in vehicles;
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(v) Application of stringent pollution level norms for vehicles.
25. The Government of India, through a new auto ____ policy has laid
down a roadmap to cut down vehicular pollution in Indian cities.
fuel
26. The Government of India, through a new auto fuel policy has laid
down a roadmap to cut down vehicular pollution in Indian cities.
What provisions have been made towards this?
(i) Stringent norms for fuels, which means steadily reducing the
sulphur and aromatics content in petrol and diesel.
(ii) The goal, according to the roadmap is to reduce sulphur to 50
ppm in petrol and diesel and bring down the level to 35%.
27. What are the stipulations of Euro II norms?
(i) Sulphur should be controlled at 350 ppm in diesel and 150 ppm
in petrol.
(ii) Aromatic hydrocarbons are to be contained at 42% of the
concerned fuel.
28. What requirements has the Government provided for emission
norms in some cities?
The Bharat Stage II (equivalent to Euro II norms), which are currently
in place in Delhi, Mumbai, Chennai, Kolkata, Bangalore, Hyderabad,
Ahmedabad, Pune, Surat, Kanpur and Agra has been made applicable
to all automobiles throughout the country from April 1, 2005.
29. What requirements has the Government provided for the
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implementation of the Euro III and Euro IV norms?
(i) Euro III norms have to be met for all automobiles and fuel (petrol
and diesel) in the above-mentioned 11 cities from April 1, 2005.
(ii) These cities have to meet Euro IV norms by April 1, 2010.
(iii) The rest of the country will have Euro III emission norms
compliant automobiles and fuels by 2010.
30. As a result of the efforts made, air quality in Delhi has improved
significantly. There has been a substantial fall in ____ and ____
levels in Delhi between 1997 and 2005.
CO2, SO2
31. In India, the _____ (an Act) came into force in 1981 but was
amended in 1987 to include ____ as an air pollution.
Air (Prevention and Control of Pollution) Act, noise
32. What is noise?
Noise is undesired high level of sound.
33. A brief exposure to extremely high sound level, ____ dB or more,
generated by take off of a jet plane or rocket, may damage the ear
drums thus impairing hearing ability permanently.
150
34. ____ exposure to a relatively lower noise level of cities may
permanently damage hearing abilities of humans.
Chronic
35. Mention some adverse effect of noise on human health.
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(i) Sleeplessness;
(ii) Increased heart beating;
(iii) Altered breathing pattern;
(iv) Increased stress due to the above.
36. Reduction of noise in our industries can be achieved by use of ____
materials or by ____ noise.
sound-absorbent, muffling
37. What needs to be done to control noise pollution?
(i) Stringent implementation of laws;
(ii) Delimitation of horn-free zones around hospitals and schools;
(iii) Permissible sound-levels of crackers and of loudspeakers;
(iv) Timings after which loudspeakers cannot be played, etc.
WATER POLLUTION AND ITS CONTROL
38. Name the law enacted in India to control water pollution.
The Water (Prevention and Control of Pollution) Act, 1974
DOMESTIC SEWAGE AND INDUSTRIAL EFFLUENTS
39. A mere ____% impurities make domestic sewage unfit for human
use.
0.1
40. Look below for the composition of waste water.
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41. Look at the schematic diagram below for the effect of sewage
discharge on some important characteristics of a river.
42. Solid pollutants are easy to remove. What pollutants are difficult to
remove?
Dissolved salts and other nutrients and toxic metal ions and organic
compounds.
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43. Domestic sewage primarily contains ____ organic matter, which
readily decomposes due to bacteria and other micro-organisms.
These can multiply using these organic substances as substrates
and hence utilise some of the components of sewage.biodegradable
44. It is possible to estimate the amount of organic matter in sewage by
measuring _____.
BOD (Biochemical Oxygen Demand)
45. Discharge of sewage in water affects fish and other aquatic
creatures. Why?
Micro-organisms involved in biodegradation of organic matter consume
a lot of oxygen. Hence, there is a sharp decline in dissolved oxygen
downstream from the point of sewage discharge. This causes mortality
of fish and other aquatic creatures.
46. Presence of large amounts of nutrients in waters also causes
excessive growth of ____ (free-floating) algae, called an ____ ____,
which imparts a distinct ____ to water bodies.
planktonic, algal bloom, colour
47. What are the harmful effects of algal blooms?
(i) Deterioration of water quality;
(ii) Fish mortality;
(iii) Some bloom-forming algae are extremely toxic to human beings
and animals.
48. Look below for the pictorial view of an algal bloom.
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49. Which plants having mauve-coloured beautiful flowers are seen
floating on water bodies? Also give its scientific name.
Water hyacinth, Eichhornia crassipes
50. Explain the problem caused by water hyacinth.
Due to their excessive growth, they block our waterways. They grow
faster than our ability to remove them.
51. Water hyacinth is the world’s most problematic aquatic weed. It is
also called ____.
Terror of Bengal
52. Water hyacinth grows abundantly in ____ water bodies and leads
to an imbalance in the ecosystem dynamics of the water body.
eutrophic
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53. Sewage from our homes as well as from hospitals are likely to
contain many undesirable ____ micro-organisms and its disposal
into water without proper treatment may cause outbreak of serious
diseases such as dysentery, typhoid, jaundice, cholera, etc.
pathogenic
(Note that the diseases caused are usually those caused by consuming
infected food)
54. Waste from industries often contain toxic substances notably ____
metals and a variety of organic compounds.
heavy
55. Heavy metals are those metals which have a density > ____ g/cm3.
Examples are ____, ____, copper, lead, etc.mercury, cadmium
56. A few toxic substances, often present in industrial waste waters,
can undergo biological magnification (_____) in the aquatic food
chain.
biomagnification
57. What is biomagnification?
Biomagnification refers to increase in concentration of the toxicant at
successive trophic levels.
58. Biomagnification happens because a toxic substance accumulated
by an organism cannot be ____ or ____, and is thus passed on to
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the next higher trophic level.
metabolised, excreted
59. Biomagnification is well known for ____ and ____.
mercury, DDT
60. High concentrations of DDT disturb ____ metabolism in birds,
which causes thinning of ____ and their premature breaking. This
leads to a decline in the bird population.
calcium, egg-shells
61. Look at the figure below to understand biomagnification of DDT in
an aquatic food chain.
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62. What is eutrophication?
Eutrophication is the natural ageing of a lake by biological enrichment
of its water.
63. Read this to understand how a lake ages.
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64. What is cultural or accelerated eutrophication?
(i) The natural ageing of a lake may span thousands of years.
However, pollutants from human activity can radically accelerate
the ageing process.
(ii) This phenomenon is called Cultural or Accelerated
Eutrophication.
65. During the past century, lakes in many parts of the world have
been severely euthrophied by sewage and agricultural and
industrial wastes. The prime contaminants are ____ and ____,
which act as plant nutrients.
nitrates, phosphates
66. Nitrates and phosphates over-stimulate the growth of algae,
causing unsightly ____ and unpleasant odours and reducing the
BOD.
scum
67. Other pollutants flowing into a lake may poison whole populations
of fish, whose decomposing remains further deplete the water’s
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dissolved ____ content.
oxygen
68. Heated wastewaters flowing out of electricity generating units
constitute another important category of pollutants. Thermal
wastewater eliminates or reduces the number of organisms
sensitive to high ____ and may enhance the growth of plants and
fish in extremely ____ areas, but, only after causing damage to the
____ flora and fauna.
temperatures, cold, indigenous
69. Heated (thermal) water also reduces the solubility of ____ in water,
thereby, reducing the BOD of water.
oxygen
A CASE STUDY OF INTEGRATED WASTE WATER MANAGEMENT
70. Wastewater, including sewage, can be treated in an integrated
manner by utilising a mix of artificial and natural processes. An
example of such an initiative is the town of ____ located along the
northern coast of ____.
Arcata, California
71. How is water treated in Arcata?
(i) An integrated wastewater treatment process within a natural
system has been created in collaboration with biologists from the
Humboldt State University.
(ii) Cleaning occurs in two stages: (Described later)
(iii) Hence, as water flows through the marshes, it gets purified
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naturally.
72. Describe the first stage of water treatment in Arcata.
In the first stage, conventional sedimentation, filtering and chlorine
treatments are given. After this, lots of dangerous pollutants like
dissolved heavy metals still remain.
73. Describe the second stage of water treatment in Arcata.
In the second stage, biologists developed a series of six connected
marshes over 60 hectares of marshland. Appropriate plants, algae, fungi
and bacteria were seeded into this area. These neutralise absorb and
assimilate the pollutants.
74. What is noteworthy about the marshes of Arcata?
(i) The marshes also constitute a sanctuary, with a high level of
biodiversity in the form of fishes, animals and birds.
(ii) A citizens group called Friends of Arcata Marsh (FOAM) is
responsible for the upkeep and safeguarding of this project.
75. How can water consumption be minimised for the disposal of
human waste like excreta?
(i) Ecological sanitation is a sustainable system for handling human
excreta, using dry composting toilets.
(ii) This is a practical hygienic, efficient and cost-effective solution
to human waste disposal.
(iii) With this composting method, human excreta can be recycled
into a resource as natural fertiliser, which reduces the need for
chemical fertiliser.
(iv) There are working ‘EcoSan’ toilets in many areas of Kerala and
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Sri Lanka.
SOLID WASTES
76. Solid wastes refer to everything that goes out in trash. ____ solid
wastes are wastes from homes, office, etc. collected and disposed off
by the municipality.
Municipal
77. What are the advantages and disadvantages of burning of
municipal waste?
(i) It reduces the volume of the waste.
(ii) However, the waste is not completely burnt.
(iii) Open dumps serve as the breeding ground for rats and flies.
78. ____ landfills were adopted as a substitute for open-burning
dumps.
Sanitary
79. What is the process that takes place in sanitary landfills?
In a sanitary landfill, wastes are dumped in a depression or trench after
compaction and covered with dirt everyday.
80. Why are landfills not a sufficient and suitable solution for solid
wastes?
(i) The amount of garbage generation, especially in the metros, has
increased so much that these sites are getting filled too.
(ii) There is danger of seepage of chemicals, etc. from these landfills,
thereby, polluting underground water resources.
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81. All wastes can be categorised into three: ____, ____ and ____.
recyclable, biodegradable, non-biodegradable
82. Read this:
CASE STUDY OF REMEDY FOR PLASTIC WASTE
83. ____, a fine powder of recycled modified plastic, is mixed with
bitumen to lay roads.
Polyblend
84. Collaboration between R.V. College of Engineering and the
Bangalore City Corporation, showed that a mixture of polyblend
and bitumen, when used to lay roads, enhanced the bitumen’s ____
____ properties and helped to increase road life by a factor of ____.
water repellent, three
85. The raw material for creating Polyblend is any ____ ____ waste.
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plastic film
86. Hospitals generate hazardous wastes that contain disinfectants and
other harmful chemicals and also ____ micro-organisms. Such
wastes require careful treatment and disposal. The use of ____ is
crucial to disposal of hospital waste.
pathogenic, incinerators
87. Irreparable computers and other electronic goods are known as
____ wastes.
electronic (e-wastes)
88. How are e-wastes disposed off?
They are buried in landfills or incinerated.
89. Over half of the e-wastes generated in the developed world are
exported to developing countries, mainly to China, India and
Pakistan, where metals like ____, iron, ____, gold and also ____ are
recovered during the cycling process.
copper, nickel, silicon
90. Unlike developed countries, which have specially built facilities for
recycling of e-wastes, recycling in developed countries often
involves ____ participation. Thus, the workers are exposed to ____
substances present in e-wastes.
manual, toxic
91. _____ is the only solution for the treatment of e-wastes provided it
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is carried out in an environment-friendly manner.
Recycling
AGRO-CHEMICALS AND THEIR EFFECTS
91. Pesticides, herbicides and fungicides are also toxic to ____
organisms, which are important components of the soil ecosystem.
non-target
CASE STUDY OF ORGANIC FARMING
92. What do you understand by integrated organic farming? What are
its benefits?
(i) Integrated organic farming is a cyclical, zero-waste procedure
where waste products from one process are recycled in as
nutrients for other processes.
(ii) This allows the maximum utilisation of resource and increases
the efficiency of production in a sustainable manner.
93. ____, dairy management, ____ harvesting, ____ and agriculture
can be carried out so as to support each other and allow an
extremely economical and sustainable venture.
Bee-keeping, water, composting
94. How are manure and compost obtained in integrated organic
farming?
Cattle excreta is used as manure. Crop waste is used to create compost,
which can be used as natural fertiliser or can be used to generate natural
gas for satisfying the energy needs of the farm.
95. Integrated organic farming has been practised by Ramesh
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Chandra Dagar, a farmer of Sonipat, who has formed a 5000-
member strong Haryana ____ Welfare Club.
Kisan
RADIOACTIVE WASTES
96. The use of nuclear energy has two very serious inherent problems.
What are they?
(i) Accidental leakage;
(ii) Safe disposal of radioactive wastes.
97. Name two incidents of accidental leakage of radioactive wastes.
(i) Three Mile Island;
(ii) Chernobyl incident.
98. What are the dangers presented by radioactive radiation?
(i) It causes mutations to occur in biological organisms at a very
high rate.
(ii) At high doses, nuclear radiation is lethal. But, at lower doses, it
creates various disorders, the most frequent being cancer.
99. How is nuclear waste disposed off?
(i) It has been recommended that storage of nuclear waste, after
sufficient pre-treatment, should be done in suitably shielded
containers buried within the rocks, about 500 m deep below the
earth’s surface.
(ii) However, this method of disposal is meeting stiff opposition
from the public.
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GREENHOUSE EFFECT AND GLOBAL WARMING
100. The greenhouse effect is a naturally occurring phenomenon that is
responsible for heating of Earth’s surface and atmosphere.
---
101. Without the greenhouse effect, the average temperature at the
surface of the earth would have been ____ oC rather than the
present average of 15 oC.
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102. Look at the figure below to understand greenhouse effect.
103. Clouds and gases reflect about ____ of the incoming solar radiation
and absorb some of it. But, almost ____ of the incoming solar
radiation falls on the earth’s surface heating it while a small
proportion is reflected back.
¼, ½
104. The earth’s surface re-emits heat in the form of infrared radiation
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but part of it does not escape into space. Why?
Because a major fraction of it is absorbed by atmospheric gases like
CO2 and methane.
105. The molecules of the gases that have absorbed the infrared
radiation radiate heat energy, a major part of which comes back to
the earth’s surface. Thus, the earth is heated up once again. The
cycle is repeated many a times.---
106. The gases ____ and ____ are commonly known as greenhouse gases
because they are responsible for the greenhouse effect.
CO2, methane
107. Look at the chart below to appreciate the relative contribution of
various greenhouse gases to total global warming.
108. During the past century, the temperature of the earth has increased
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by ____ oC. Most of this increase has happened during the last
three decades.0.6
109. What are the effects of increasing global temperatures?
(i) Deleterious changes in the environment resulting in odd climatic
changes, e.g. El Nino effect.
(ii) Melting of polar ice caps and glaciers.
(iii) Rise in sea level that can submerge many coastal areas.
110. How can global warming be checked?
(i) Reduce fossil fuel consumption;
(ii) Efficient energy usage;
(iii) Reduce deforestation and increase afforestation;
(iv) Slowing down human population growth.
(v) International initiatives are also been taken to reduce the
emission of greenhouse gases into the atmosphere.
OZONE DEPLETION IN THE STRATOSPHERE
111. The ozone layer occurs in ____ and acts as a shield absorbing uv
radiation from the sun.
stratosphere
112. Why are uv rays harmful?
DNA and proteins of living organisms preferentially absorb uv rays and
its high energy breaks the chemical bonds within these molecules.
113. The thickness of the ozone in a column of air from the ground to
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the top of the atmosphere is measured in terms of ____ ____.
Dobson units (DU)
114. How is ozone gas continuously formed in the stratosphere?
By the action of UV rays on molecular oxygen.
115. Why is ozone depletion taking place?
(i) Ozone is being continuously formed by the action of UV rays on
molecular oxygen and is also being degraded in the stratosphere.
(ii) There should be a balance between the production and
degradation of ozone in the stratosphere.
(iii) Of late, the balance has been disrupted due to enhancement of
ozone degradation by chlorofluorocarbons (CFCs).
116. CFCs are widely used as ____.
refrigerants
117. How do CFCs degrade the ozone layer?
(i) CFCs discharged in the lower part of the atmosphere move
upward and reach the stratosphere, where UV rays act on them
releasing chlorine atoms.
(ii) Chlorine catalyses the degradation of ozone into molecular
oxygen and are themselves not consumed in the reaction.
(iii) Hence, the CFCs reaching the stratosphere have a permanent and
continuing effect on the Ozone Layer.
118. What do you understand by ‘Ozone hole’?
(i) The ozone layer of the stratosphere is gradually getting depleted
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due to the use of CFCs.
(ii) This depletion is particularly marked over the Antarctica region.
(iii) This has resulted in the formation of a large area of thinned
ozone region, commonly called the ozone hole.
119. Look below at the figure of the ozone hole.
120. The ozone over the Antarctica develops each year between late
____ and early ____.
August, October
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121. UV radiation of wavelengths shorter than ____ are almost
completely absorbed by the earth’s atmosphere if ozone layer is
intact.
UV-B
122. How can UV-B be harmful to humans? OR What are the harmful
effects of ozone depletion?
(i) UV-B damages DNA and mutation may occur.
(ii) It causes ageing of the skin, damage to the skin cells and various
types of skin cancers.
(iii) The cornea of the human eye absorbs UV-B radiation and a high
dose of UV-B causes inflammation of cornea, called snow-
blindness, cataract, etc. Such exposure may permanently damage
the cornea.
123. What international efforts have been made to control ozone
depletion?
(i) Recognising the deleterious effects of ozone depletion, an
international treaty, known as Montreal Protocol was signed at
Montreal (Canada) in 1987 (effective in 1989) to control
emission of ozone depleting substances.
(ii) Subsequently, many more efforts have been made and protocols
have laid down definite roadmaps, separately for the developed
and developing countries for reducing emission of CFCs and
other ozone depleting chemicals.
DEGRADATION BY IMPROPER RESOURCE UTILISATION
AND MAINTENANCE
124. Degradation of natural resources can occur, not just by the action
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of pollutants but also by improper ____ utilisation practices.
resource
SOIL EROSION AND DESERTIFICATION
125. The development of the fertile top-soil takes ____. But, it can be
removed easily due to certain human activities resulting in ____
patches of land.
centuries, arid
126. Which human activities may cause degradation of soil?
(i) Over-cultivation;
(ii) Unrestricted grazing;
(iii) Deforestation; and
(iv) Poor irrigation practices.
127. When large barren patches extend and meet over time, a ____ is
created.
desert
128. Internationally, it has been recognised that desertification is a
major problem nowadays, particularly due to increased _____.
urbanisation
WATERLOGGING AND SALINITY
129. What causes water logging?
Irrigation without proper drainage of water leads to water logging in the
soil.
130. How is water logging harmful?
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(i) Besides affecting the crops, water logging draws salt to the
surface of the soil.
(ii) The salt is then deposited as a thin crust of the land surface or
starts collecting at the roots of the plants.
(iii) This increased salt content is inimical to the growth of crops and
is extremely harmful to agriculture.
131. What are the problems associated with the Green Revolution?
Water logging and soil salinity
DEFORESTATION
132. What is deforestation?
Deforestation is the conversion of forested areas to non-forested ones.
133. What is the status of deforestation in India?
(i) According to an estimate, almost 40% forests have been lost in
the tropics compared to only 1% in the temperate region.
(ii) The situation is particularly grim in India.
(iii) At the beginning of the 20th century, forests covered about 30%
of the land of India. By the end of the century, it shrunk to
19.4%.
(iv) The National Forest Policy (1988) of India has recommended
33% forest cover for the plains and 67% for the hills.
134. How does deforestation occur?
(i) One of the major reasons for the conversion of forests to
agricultural land to feed the growing human population.
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(ii) Trees are also cut down for their timber.
(iii) ‘Slash and burn’ agriculture.
135. What is ‘slash and burn’ agriculture?
(i) Slash and burn agriculture, commonly called Jhum cultivation in
the north-eastern states of India, has also contributed to
deforestation.
(ii) In slash and burn agriculture, farmers cut down the trees of the
forest and burn the plant remains.
(iii) The ash is used as fertiliser and the land is then used for farming
or cattle grazing.
(iv) After cultivation, the area is left for several years so as to allow
its recovery. The farmers move on to other areas and repeat the
process.
(v) In earlier days, enough time was given for the land to recover.
With increasing population and repeated cultivation, this
recovery phase is done away with, resulting in deforestation.
136. What are the consequences of deforestation?
(i) Enhanced carbon dioxide concentration in the atmosphere.
(ii) Loss of biodiversity.
(iii) Disturbs hydrologic cycle.
(iv) Soil erosion leading to desertification in extreme cases.
137. Deforestation causes increased carbon dioxide concentration in the
atmosphere. Why?
Because trees that could hold a lot of carbon in their biomass are lost
with deforestation.
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138. Deforestation causes loss of biodiversity. Why?
Because of habitat destruction.
139. What is reforestation?
Reforestation is the process of restoring a forest that once existed but
was removed at some point of time in the past.
140. Reforestation may occur naturally in a deforested area. However,
we can speed it up by planting trees with due consideration to the
____ that earlier existed in that area.
biodiversity
CASE STUDY OF PEOPLE’S PARTICIPATION IN
CONSERVATION OF FORESTS
141. In 1731, the King of Jodhpur in Rajasthan asked one of its
ministers to arrange wood for constructing a new palace. The
minister and workers went to a forest near a village, inhabited by
____ to cut down trees.
Bishnois
142. The Bishnoi community is known for its peaceful co-existence with
nature. The effort to cut down trees by the kings was thwarted by
the Bishnois. A Bishnoi woman, ____ ____ showed exemplary
courage by hugging a tree and daring the King’s men to cut her
first before cutting the tree. Unfortunately, the King’s men did not
heed her pleas and cut down the tree along with her. Her ____
daughters and hundreds of other Bishnois followed her and lost
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their lives saving trees.
Amrita Devi, three
143. Name the award that the Government of India has instituted in
