NCERT / CBSE NOTES | Class 8th (VIII) : Chapter Summary
Land, Soil, Water, Natural Vegetation and Wildlife Resources
The part of the earth’s surface that is not covered by water is called land. Land is an important natural resource and covers around 30% of the earth’s total area.
Plains and river valleys are densely populated because they offer suitable land for agriculture, apart from more moderate climatic conditions.
Land is used for agriculture, forestry, mining, building houses, roads and setting up various industries. Some pieces of land are good for agriculture, while others are suitable for erecting buildings.
Land use depends on factors like topography, soil, climatic conditions, presence of mineral reserves and the availability of drinking water.
A piece of land is either owned by an individual or by a community. Land owned by an individual person is called private land. Land that is owned collectively by a community is called community land.
Number of houses, malls and commercial complexes are encroaching on the common land. Agriculture is expanding into rural areas.
This is denuding common areas of forests and arable land, which are vital natural resources. Landslides, soil erosion, land degradation and desertification are becoming major threats to the environment because of this pressure on land.
Planting more trees is one way to help restore the forest cover. This process is known as afforestation. Land reclamation is another method of land conservation. For farmers, an important measure is to check and regulate the use of chemical pesticides and fertilizers and prevent overgrazing.
When rock, debris or loose earth move down a slope in a huge mass, it is termed as a landslide. A landslide caused by prolonged heavy rainfall can block the path of a river. These river blocks, when they burst, can lead to floods in the settlements downstream.
To curb landslides, it is important to protect the forest cover in hilly regions. Tree roots hold soil and rocks in place, and are thus effective in preventing soil from sliding down a slope.
Some measures to control damage from landslides:
- Identify landslide-prone areas through hazard mapping and avoid building houses in such regions.
- Build retention walls to stop land from slipping. The city of Anaheim in California, USA, located in a landslide-prone area, uses retention walls.
- Increase vegetation cover to curb landslides.
- Build surface water drainage control systems. This will help regulate the movement of landslides along with rain water and spring flows.
Soil is the thin layer of matter that covers the earth’s surface, made up of organic matter, minerals and weathered rocks.
Weathered rocks are a result of the breakdown and decay of rocks by changes in temperature, frost and actions of living organisms. This process is very slow, and is called weathering. During weathering, rock debris gets mixed with organic matter and minerals, increasing the fertility of the soil.
There are a number of factors that affect the physical and chemical properties of soil in a landform.
The primary factors are parent rock and climate in the area. The parent rock from which the soil is formed, influences its: Colour, Texture, Chemical properties, Mineral content and Permeability.
Climatic conditions, like temperature and rainfall, determine the rate of weathering and the formation of humus. The other factors that affect soil formation are: Relief, Flora, fauna and micro-organisms and Time.
Steep slopes are more prone to soil erosion, so the layer of soil on them may not be very thick. Low-lying, flat areas retain the layers of sediments for longer periods, and thus, have a thick layer of soil. Living or organic matter, like plants, animals and micro-organisms, influence the rate of humus formation.
Humus is the degraded organic material in soil and helps increase its fertility. The process of decomposition is helped by micro-organisms that break down the organic matter when they feed on it.
The thickness of the soil profile is affected by the time taken for the soil to form. Older soil has a thicker soil profile, as over time, several layers of soil have been deposited and formed. The types of soil found in India include: Alluvial, Black, Red, Laterite, Desertand and Montane soil.
Soil erosion occurs when soil and rock particles are carried away by wind, water or ice, and deposited in another location. Soil depletion takes place when the nutrients in soil are removed and are not replaced. It affects the quality and fertility of the soil.
Soil degradation is caused by: Deforestation, Overgrazing, Excessive use of chemical fertilisers and pesticides, Rain wash, Landslides and Floods.
Some methods to conserve soil quality are: Mulching, Contour barriers, Rock dams, Terrace farming, Intercropping, Contour ploughing and Shelter belts.
Mulching helps to trap moisture in the soil and moderate soil temperature and involves covering the bare ground between plants with a layer of organic material like straw.
Contour barriers refer to barriers of stone, grass and soil built along the contour lines of a slope. Trenches are built in front of the barriers to collect water and prevent it from flowing down the contours and washing away the soil.
Rock dams are dams created from piles of rocks that are stacked up to slow down the flow of water and prevent the formation of gullies. This curtails soil erosion.
To provide flat surfaces for farming on steep slopes, terraces are created. This is called terrace farming. Using terraces also prevents soil erosion and surface run-off.
Intercropping is a widely used practice in China to reduce soil erosion due to rain wash. In this method, different crops are grown in alternate rows and are sown at different times.
Contour ploughing is the method of soil conservation in which the land is ploughed parallel to the contours of a slope. This creates a barrier that prevents water from flowing down the slope.
In coastal and dry areas, rows of trees are planted to control the movement of wind, thus protecting the soil from being blown away. These rows of trees act as shelter belts.
Water is a vital renewable natural resource. Water keeps getting recycled from one form into another, so the total volume of water on the earth remains constant. Water evaporates from the oceans to transform into water vapour and falls back on the land through precipitation.
3/4th of the earth’s surface is covered by water and of this water, 2/3rd is in the oceans. However, the ocean water is salty and not suitable for drinking. Only fresh water is used for drinking.
Fresh water makes up only 2.7% of the total water available on the earth from which a maojiry oart is covered in ice in Greenland and Antarctica. Hence only 1% of the freshwater can actually be used as drinking water.
Freshwater can be found in: groundwater, surface water in rivers and lakes and water vapour in the atmosphere.
The factors responsible for the ever growing need of water are: Rising population, which leads to a greater demand for food and cash crops, Increasing urbanization and Rise in the standard of living.
Contamination of water can be due to the following reasons: release of untreated or semi-treated sewage, Agricultural chemicals and Industrial effluents.
There are various steps that can be taken to conserve water and prevent it from getting pollute: to ensure that effluents are treated properly before being discharged into water bodies, increasing forest cover and vegetation, rainwater harvesting, Canals should be properly lined, Sprinklers should be used for irrigation, methods like drip or trickle irrigation should be employed.
Natural Vegetation and Wildlife
Natural vegetation and wildlife are the plants and animals that survive naturally in a specific region and are part of the biosphere. The biosphere is the narrow zone where the lithosphere, the hydrosphere and the atmosphere interact with each other.
An ecosystem refers to the natural surroundings in which living beings and non-living beings support each other. Wild life includes animals, birds and insects and aquatic animals. All birds and animals, regardless of their size, contribute in different ways to maintain the balance in an ecosystem.
The natural vegetation in an area depends on the temperature and the moisture available. The main types of natural vegetation found the world over are: Forests, Grasslands, Scrubs and Tundra. The growth of vegetation in forests varies from region to region. Forests can be classified into evergreen or deciduous, depending on when the trees shed their leaves.
In evergreen forests, the trees do not shed their leaves all at the same time, hence they always remain green. The trees in deciduous forests, shed their leaves in the dry season to conserve moisture and prevent loss of water through transpiration.
Evergreen and deciduous forests can be further classified into tropical and temperate forests. This classification depends upon the latitude at which the forests are located.
The forests that lie within the Tropic of Cancer and the Tropic of Capricorn are called tropical forests like in Brazil. The trees in tropical forests form a dense canopy and are mostly evergreen.
Temperate forests are found in regions that lie within the Arctic Circle and the Tropic of Cancer, and between the Antarctic Circle and the Tropic of Capricorn. The trees in temperate forests form a moderately thick canopy and shed their leaves annually. Each forest type is associated with a certain type of animal life.
Conservation of Natural Vegetation and Wildlife
Forests provide a natural habitat for many species of animals. Change in climate and human activities has led to the loss of forest cover which is affecting the inhabiting animals. Several species of animals have become endangered or extinct due to the loss of their natural habitat and indiscriminate killing.
Deforestation, soil erosion, construction activities, forest fires, tsunami and landslides are the major factors that impact forest cover natural or man-made.
A forest fire is a threat to both plants and animals in a region and can be caused by: Lightning, Human carelessness or Arson. Ground patrolling, an efficient network of observation points, and a good communication network can monitor the occurrence of forest fires.
Poaching refers to the killing of animals for collecting and trading their hides, skins, nails, teeth, horns and feathers. Animals like the tiger, lion, elephant, deer, black buck, crocodile, rhinoceros, snow leopard, ostrich and peacock are the most vulnerable to poaching.
The best way to conserve the different species of animals and prevent poaching is by educating people about how important animals are to our ecosystem. Creation of national parks and biosphere reserves is another measure to protect our natural vegetation and wildlife.
A national park is a natural area protected against human development and pollution having the aim of protecting and conserving specific ecosystems for the present and future generations.
Biosphere reserves are protected areas created to maintain a balance relationship between conservation and development of flora and fauna.
Natural habitats like creeks, wetlands and lakes also need to be conserved to protect the natural resources and ecosystems in those areas for which adequate measures need to be implemented by the governments of various countries.
At the international level, there is an agreement called CITES which stands for the Convention on International Trade in Endangered Species of Wild Flora and Fauna.
This convention has been set up to make sure that wildlife and plant species do not become endangered or extinct because of their trade.