Social Science Class Eight  



Land, Soil, Water, Forest and Wildlife Resources

LAND

Land covers about 30% of the total area of the earth’s surface. Due to variations in topography, all parts of the land is not habitable. 90% of the world population lives only on 30% of the land area. The remaining 70% of the land is either sparsely populated or uninhabited.

Plains and river vallys are densely populated because they are suitable for agriculture. On the other hand, steep slopes and water logged areas are sparsely populated.

Land Use

Land is used for various purposes; like agriculture, forestry, mining, building houses, roads, industries, etc. Factors which affect the use of land are topography, soil, climate, minerals and availability of water. Human factors also determine the land use pattern. Ownership of land also determines the land use pattern.

Increasing population means there is an ever growing demand for land. But the availability of land is limited. Land degradation, landslides, soil erosion, desertification are the major threats to the environment.

Human encroachment has lade to large scale destruction of forest cover and arable land. This is creating a danger for quality of land. Land degradation can be prevented by afforestation, land reclamation, regulated use of chemical pesticide and fertilisers and by checking overgrazing.

SOIL

The topmost layer of land which is composed of grainy substance is called soil. Soil is made up of organic matter, minerals and weathered rocks. Soil formation takes place because of weathering of rocks. The soil becomes fertile because of the right combination of minerals and organic matter.

Soil Profile: The arranment of different layers of soil at a place is called soil profile. The typical soil profile is composed of following layers:

  1. Topsoil: Topsoil is composed of humus and fine particles of clay and sand.
  2. Subsoil: This is the second layer of soil. It is composed of sand, silt and clay.
  3. Weathered Rock Material: The third layer is composed of large pieces of rocks.
  4. Bedrock: The last layer of soil profile is composed of huge rocks.

Factors Of Soil Formation

Following are the factors of soil formation:

  1. Parent Rock: The parent rock determines the colour, texture, permeability, chemical property and mineral content of the soil.
  2. Climate: Temperature and rainfall influence the rate of weathering.
  3. Relief: Altitude and slope determine the accumulation of soil at a place.
  4. Flora, fauna and microorganism: These are the biotic factors which affect the rate of humus formation.
  5. Time: Time determines the thickness of soil profile.

Soil Erosion

Removal of topsoil is called soil erosion. Deforestation, overgrazing, overuse of chemical fertilisers or pesticides, rainwash, landslides and floods are the factors which lead to soil erosion.

Methods of Soil Conservation:

Mulching: In this method, the bare ground is covered with organic matter like straw. Covering the soil helps in retaining the moisture in soil.

Contour Barriers: Contour barriers are made by placing stone, grass or soil along the contour. Trenches are made in front of the barriers to collect water. Contour barriers help in preventing soil degradation which may happen due to rainwash.

Rock Dam: Rocks are piled up to make a dam. Such dams slow donwn the flow of water. Thus, it prevnts gullies and soil loss.

Terrace Farming: Terrace farming is done in hilly areas. Plots are made in the shape of terraces to ensure flat surface for growing the crops. It helps in reducing soil erosion which may happen because of run-off.

Intercropping: In this method, different crops are grown in alternate rows. Crops are grown at different times. It helps in preventing soil erosion from rain wash.

Contour Ploughing: In this method, ploughing is done parallel to the contours of the hill slope. This helps in forming a natural barrier and prevents water from flowing down the slope.

Shelter Belts: This method is used in coastal areas and in dry regions. Rows of trees are planted along the boundary of the farmland. This helps in preventing soil erosion from wind.

WATER

About three-fourths of the earth’s surface is covered with water. But most of the water on earth is in the oceans. Ocean water is saline and hence is not fit for human consumption. Just 2.7% of the total water on the earth is available as freshwater. But 70% of the total freshwater on the earth is available as frozen ice in glaciers and icebergs. This leaves less than 1% of the total water on earth for human consumption. This is available as groundwater, as surface water and as water vapour.

Hence, freshwater is a precious resource for us. The total volume of water on the earth remains constant. Water keeps on getting cycled through oceans, the air, the land and back to ocean; through a process called water cycle.

Human beings use water for a variety of purposes; like drinking, bathing and washing. Water is also used in production of various things for our use. Moreover, water is used in agriculture, industries and in electricity generation.

Increasing population has resulted in exploitation of water on an even larger scale. This has resulted in shortage of water at many places. Shortage of drinking water is a major problem in many parts of the world. Almost all the continents are facing the problem of water scarcity.

Conservation Of Water Resources

Access to clean and adequate water is a major problem in the world. Overuse and pollution of water have made it unfit for use at many places. Sewage, agricultural chemicals and industrial effluents are often discharged into water bodies either in partially treated or untreated form. They pollute the water with various kinds of contaminants. Treatment of these effluents can help in controlling water pollution.

Forest and vegetation cover slow the surface runoff and thus help in recharging the grounwater. Surface runoff can also be reduced by applying the methods of water harvesting.

Canals should be properly lined to minimise the losses by seepage. Sprinklers and drip irrigation help in minimising the use of water for irrigation and thus help in conservation of water.

Natural Vegetation and Wildlife

Biosphere: Natural vegetation exists only in the biosphere. The narrow zone of contact between the lithosphere, hydrosphere and atmosphere; in which life exists; is calle biosphere.

Ecosystem: The living beings are inter-related and interdependent on each other for survival. This life supporting system is called ecosystem.

Importance of Natural Vegetation: Vegetation provoide shelter to animals and provide us with timber and many other forest produce. Plants also produce oxygen when they make food and oxygen is the gas we breathe. Plants protect soil from degradation. Plants help in recharging the grounwater.

Wildlife: Animals, birds, insects as well as the aquatic life forms comprise the wildlife. We get meat and leather from animals. Honey bees provide us with honey. Insects are the major pollinators and thus help not only the plants but also the human beings. Some animals play the role of scavengers and clean the dead remains of animals. All animals play important role in maintaining the balance in the ecosystem.

Distribution Of Natural Vegetation

Temperature and moisture determine the growth of vegetation in a particular region. Forests, grasslands, scrubs and tundra are the major vegetation types in the world.

Huge trees can thrive in areas of heavy rainfall. Thus, dense forests are present in areas which have abundant supply of water. The size and density of trees decreases with relative decrease in moisture.

Short stunted trees and grasses grow in the regions of moderate rainfall. Thorny shrubs and scrubs grow in dry areas which get low or negligible rainfall. The Tundra vegetation is found in cold Polar regions and comprises of mosses and lichens.

Evergreen Forests: Trees of evergreen forests do not shed their leaves at a particular time in a year. Evergreen forests are found in tropical regions which get plenty of sunshine and rainfall.

Deciduous Forests: Trees of deciduous forests shed their leaves at a particular time in a year. Deciduous forests are found in subtropical regions which get moderate sunshine and rainfall.

Conservation Of Natural Vegetation And Wildlife

  • Deforestation, soil erosion, construction activities, forest fires, tsunami and landslides are some of the factors which are causing extinction of forest and wildlife resources. Poaching is another concern which is leading to extinction of valuable wildlife.
  • The government has made national parks, wildlife sanctuaries, and biosphere reserves to protect the natural vegetation and wildlife.
  • Many awareness programmes; like social forestry and Vanamahotsava are also encouraged to conserve the wildlife and forests.
  • Many laws have been passed to make poaching an illegal and punishable offence. In India, killing of lions, tigers, deers, etc. have been banned.
  • An international convention CITES has been established that lists several species of animals and birds in which trade is prohibited. CITES stands for Convention on Internatioal Trade in Endangered Species of Wild Fauna and Flora. About 5,000 animal species and 28,000 plant species are being protected under the CITES.

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Land, Soli, Water, Natural Vegetation and Wildlife Resources - Class eight SST -NCERT Solution
   
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