Note: Attempt any five questions.


1. Why ecological significance of forest is more important in present day context? Explain.

Ans – Ecological Significance:

a) Moderation of global climate: Forests stabilise global climate in a significant manner by influencing natural cycles such as hydrological and carbon cycles. You might have read about these cycles when you were in school. As you know, spatial as well as temporal patterns of rainfall are greatly influenced by forest. How much of water is retained in the soil, and how much flows away, sometime causing floods, also depends on tree cover. Similarly forest can also influence the atmospheric carbon dioxide level. Tree biomass holds carbon dioxide in a fixed state. Therefore, forest acts as a major source of carbon sink i.e. ability to absorb carbon dioxide from the atmosphere.In other words, a carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period. When wood is burnt CO2 is released in the atmosphere. This has a direct impact on the extent of greenhouse effect and global warming. In other words, more forests lead to greater removal of atmospheric carbon dioxide during photosynthesis resulting reduction of the greenhouse gases in the atmosphere. Therefore, large-scale afforestation has been adopted as a measure to reduce greenhouse effect.

b) Protection of biodiversity: Forests are the greatest repository of biodiversity on the land as they provide ideal conditions for the survival and growth of living organisms. The number of species per unit area is much greater in a forest than in any other terrestrial ecosystem. For example, the tropical rainforest covers less than 7% of the earth’s land surface but accounts for more than 50% of all known species. About 62% of all known plants are found in these rainforests. That is why there has been a growing campaign for saving the rain forest in Amazon and Nile basin. The growing awareness about the importance and necessity to conserve biodiversity is helping human being to realise the significance of forest. Do you think this awareness or campaign is sufficient to protect rain forest? Think about it? We will discuss some of the conservation measures in the last section of this unit.

c) Supporting natural ecological systems and processes: As mentioned earlier forests perform certain activities which are crucial for supporting ecological systems and processes directly. Some of these functions and processes are as follows:

  • Forests check the soil erosion by preventing the action of winds and water thereby preserves the fertile top soil.
  • It prevents landslides and reduces the intensity of cyclones and floods.
  • By preventing soil erosion, forests reduce silting of water bodies including reservoirs.
  • Forest improves air quality by absorbing toxic gases and particulate matter.
  • It protect watersheds and ensure perennial supplies of fresh water.

2. Answer the following questions in about 125 words each.

a) Explain the characteristics of Western Ghats for inclusion as Biodiversity hotspots.

Ans – The Western Ghats represent one of the major tropical evergreen forest regions in India. The total area of Western Ghats is about 160,000 sq. km. In the west, the zone is bound by the coast and in the east, it shares boundary with the Deccan peninsular zone. The tropical evergreen forests occupy about one third of the total area of this zone. In recent years, a large chunk of the forest cover has been lost and this zone is now of great conservation concern, more so because of its exceptional biological richness. About two-thirds of India’s endemic plants are confined to this region. However, the potential of many of these species is yet to be tapped. Besides harbouring diverse biological communities, the forests in this zone also play an important role in maintaining the hydrological cycle.

The well known species found exclusively in Western Ghats include the following:

  • Among Primates – Nilgiri Langur and Lion-tailed Macaque
  • Rodents – Plataconthomys, the Spiny Dormouse
  • Squirrels – Several subspecies of Ratufa indica with separate forms in Maharashtra, Mysore, Malabar and
  • Tamil Nadu Ghats. The Grizzled Squirrel is restricted to two localities in the drier Tamil Nadu forest
  • Carnivores – Malabar Civet in southern evergreen forests, Rusty spotted Cat in northern deciduous forests.
  • Ungulates – Nilgiri Tahr in Nilgiris to Agastyamalai montane grassland.
  • Hornbills – Malabar Grey Hornbill

b) Why hydropower is regarded as the best source of energy? Explain it in detail.

Ans – Hydro power is the cheapest, and cleanest and, hence, regarded the best source of energy. However, obtaining electricity from mega dams has given rise to many controversies in recent times and small hydro power plants are emerging as viable alternatives. These plants serve the energy needs of remote and rural areas where the grid supply is not available. Hydropower, or hydroelectric power, is one of the oldest and largest sources of renewable energy, which uses the natural flow of moving water to generate electricity. Hydropower currently accounts for 31.5% of total U.S.

renewable electricity generation and about 6.3% of total U.S. electricity generation. While most people might associate the energy source with the Hoover Dam—a huge facility harnessing the power of an entire river behind its wall—hydropower facilities come in all sizes. Some may be very large, but they can be tiny, too, taking advantage of water flows in municipal water facilities or irrigation ditches. They can even be “damless,” with diversions or run-of-river facilities that channel part of a stream through a powerhouse before the water rejoins the main river. Whatever the method, hydropower is much easier to obtain and more widely used than most people realize. In fact, all but two states (Delaware and Mississippi) use hydropower for electricity, some more than others. For example, in 2020 about 66% of the state of Washington’s electricity came from hydropower.

c) The importance of Biomass has been increasing day by day in our surroundings among renewable resources. Explain it with suitable examples.

Ans – Biomass energy is a renewable energy source derived from plant resources, animal waste and the waste of various human activities. It is also derived from the by-products of the timber industry, agricultural crops, raw material from the forest, major parts of household wastes and wood. Biomass is an important source of energy and the most important fuel worldwide after coal, oil and natural gas. Biomass does not add net carbon dioxide to the atmosphere as it absorbs the same amount of carbon in growing as it releases when consumed as fuel. Its advantage is that it can be used to generate electricity with the same equipment or power plants that are now burning fossil fuel Biomass fuels used in India account for about one third of the total fuel used in the country. Over 90% of the rural households and about 15% of the urban households use biomass fuels (e.g. wood, cowdung cakes, crop residues and sawdust). The inefficient burning of such fuels in traditional chulhas is causing a serious problem of indoor air pollution and consequent health hazards. Moreover, the unsustainable level of consumption of fuel wood leads to deforestation and desertification, which degrades the environment. Thus proper management of biomass as a resource is very essential. Biomass fuels used in India account for about one third of the total fuel used in the country. Over 90% of the rural households and about 15% of the urban households use biomass fuels (e.g. wood, cowdung cakes, crop residues and sawdust). The inefficient burning of such fuels in traditional chulhas is causing a serious problem of indoor air pollution and consequent health hazards. Moreover, the unsustainable level of consumption of fuel wood leads to deforestation and desertification, which degrades the environment. Thus proper management of biomass as a resource is very essential.

d) How does air pollution affect the atmospheric processes?

Ans – Apart from causing damage to materials, plant and animal communities and health problems in humans, air pollution affects the atmospheric processes. Acid rain, smog, global warming and ozone depletion are some of the effects of pollution in our atmosphere.

1. Suspended Particulate Matter (SPM) : SPM in the ambient air is complex and variable mixture of different sized particles with many chemical components. Larger particles are trapped by nose hair (vibrissae) and breathing tubes. Particles smaller than 10 mm in size, known as PM 10, are respirable suspended particulate matter (RSPM). Finer particles of size less than 2.5 mm are known as PM 2.5. They can be inhaled deep in the lungs and cause a lot of trouble. Study of ambient air quality of some Indian cities conducted by Central Pollution Control Board (CPCB) in recent years indicate that many Indian cities such as Raipur, Kanpur, Delhi, Gwalior and Ludhiana have RSPM more than 200 microgram per cubic metre. Standard level of RSPM is 60 microgram per cubic metre.

There was a decreasing trend in the levels of SO2 and NO2 in the past decade. This could be due to low sulphur diesel introduced in Delhi and prohibition from plying of commercial vehicles more than 15 years old in Delhi. The use of unleaded petrol has drastically lowered the level of lead in the air in India.

2. Acid Precipitation : Acid rain or acid precipitation (Fig.9.3) includes wet acidic depositions like rain, snow, fog, mist or dew and deposition of dry acidic particulates from the air. Acid precipitation occurs in and around the areas where major emissions of sulphur dioxide (SO2 ) and nitrogen oxides (NOx ) occur as a result of anthropogenic activities. Hydrochloric acid emitted from coal fired power plants also adds to acid rain problems. Acid depositions have disastrous effects on the life forms as well as the materials. Soil fertility is adversely affected because acidic water in soil releases immobile heavy metal ions which are highly injurious to plants and other soil biota. Apart from damaging forests and lakes, acid rain corrodes and harms building materials such as steel, paints, plastics, cement, limestone, sandstone and marble.

3. Atmospheric Inversion : Atmospheric or temperature inversion occurs when a stable layer of warmer air lays above the cooler air. The normal phenomenon of temperature decline along the increasing height reverses and thereby, convection air currents that normally disperse the pollutants are prevented. An inverted temperature gradient occurs, air circulations are restricted and pollutants are trapped in the lower atmosphere within the stagnant air mass. Such atmospheric inversion is responsible for dangerous levels of air pollution over polluted cities in India

e) What is Disposal of waste? Why segregation of waste is needed?

Ans – As cities grow in size with a rise in population, the amount of waste generated will increase. The local corporations in cities adopt disposal of waste. In this process tremendous scope exists for reducing, reusing and recycling the waste. Amongst the various categories of waste, hospital waste like soiled bandages, disposables, cultures, anatomical wastes, chemical wastes, discarded medicines pose grave environmental risk. This waste is highly infectious and needs to be managed in a scientific manner. The final disposal of the hazardous wastes also needs to be carefully planned. There are four different ways in which hazardous wastes can be finally disposed. These four different ways are as follows:

  • Landfilldisposal.
  • Incineration
  • Dumping at sea
  • Undergrounddisposal

With respect to the increasing population and their consumption patterns, the problem of landfills is rising day by day. Waste segregation is important not only to reduce the impact it has on the environment, but also health issues that can arise from waste and toxins that have been improperly disposed of. Waste segregation is also an economically beneficial prospect because it makes recycling much easier. It also promotes the optimized use of our resources and helps in conserving it for future generations.

3. Explain the human-environment relationship by taking examples of biotic and abiotic components?

Ans – There are two distinct situations observed if we trace the history of human civilization. The first situation is that human being adjusted or adapted to the prevailing environmental conditions. Those who could not adapt or adjust perished. Similar situations can be observed amongst plants and animals also. As human civilization progress, people developed knowledge, skill and technology to subjugate nature. This happened faster after renaissance and Industrial revolution. It has improved standard of living as well as made human life comfortable. However, this has leads to irreparable damage of  environment and threat to the human society well as survival of the planet earth. Therefore, it has been realized that there should be a balance between development and protection of environment.

Determinism: This concept was developed by German Geographer Friedrich Ratzel, which was further expanded by Ellsworth Huntington. This approach is based on the concept of ‘nature controls human’ or ‘earth made human’. This is also known as environmental determinism. According to this approach, human being is largely influenced by nature. In fact, the determinism states that human being is subordinate to natural environment because all aspects of human life such as physical (health and well-being), social, economic, political, ethical and aesthetic not only depend on but are dominantly controlled by the physical environment.

Possibilism: This term was coined by the French historian, Lucien Febvre. Possibilism approach in the study of human-environment relationship is an offshoot of the criticism of environmental determinism. The evolution of such human-environment relationship was influenced by the advancement of science and technology. Possibilism indicates that the physical environment is passive and human being is the active agent at liberty to choose between wide ranges of environmental possibilities. According to this apporach, the pattern of human activity is the result of the initiative and mobility of human being operating within the natural framework. However, it was agreed upon by the possibilists that humans lack the abilities to fully tame the nature and is not always victorious over it. As a result of the above, some scientists and academics vouched for ‘cooperation with nature’ or ‘mutual interaction’ between human being and environment.

Environmentalism or Ecological Approach: This approach is based upon the basic principle of ecology, which is the study of mutual interaction between organisms and physical environment on the one hand, and the interaction among the organisms on the other in a given ecosystem. This approach describes human being as an integral part of nature or environment. Human being as the most skilled and intelligent has a unique role to play in maintaining a natural environment as healthy and productive as it should be. This approach emphasizes on wise and restrained use of natural resources and application of appropriate environmental management programmes, policies and strategies keeping in view certain basic principles of ecology so that already depleted natural resources are replenished, and health and productivity of the nature is restored. 

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