Class 8 Social Science Natural Resources Exam Notes

Class 8 Social Science Natural Resources Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Covers the following topics:

1. Introduction
2. Land Resources
3. Soil Resources
4. Water resources

Class 8 Social Science exam notes on Natural Resources, covering land resources and land use patterns, factors affecting land use, land degradation and its conservation, soil resources, soil formation and profile, soil erosion and its conservation, and water resources, including water distribution, water scarcity, water pollution, and rainwater harvesting and other methods of water conservation.

Topics Covered

1. Introduction
2. Land Resources
3. Soil Resources
4. Water Resources

INTRODUCTION

Earth is the only known heavenly body in the universe which has suitable environmental conditions for the survival of human beings, animals and plants. The surface of the earth is made up of land (about 29 per cent) and water (about 71 per cent). We satisfy most of our needs from our immediate natural environment. The different elements of the environment, such as land, water, soil, plants, animals, etc. acquire meaning and value with reference to the needs of people living in the region.

The needs of the people are not the same everywhere and depend mostly on the level of cultural and technological development of the people. The natural resources of the earth acquired value as a result of technological development. The gifts of nature become resources only when human beings locate them, find a use for them or propose to use them. For example, a river is a gift of nature and it becomes a resource when we utilise the water in the river for irrigation, power generation, navigation, etc.

The distribution and possible uses of the various types of natural resources, especially land, water and soil, are examined in this chapter. These natural resources are greatly influenced by the natural environmental conditions, such as different elements of weather and climate, the hydrological cycle, weathering of rocks, etc.

A. LAND RESOURCES

1. Land is the solid portion of the surface of the earth. It is a product of nature. It is that part of the earth which supports life and has usefulness in various ways. Land is a very important resource needed by human beings. It is ubiquitous and inexhaustible in nature. It is one of the most important gifts of nature for the growth of life and development of human civilisation. In fact, it is both a renewable and a non-renewable resource.
2. The concept of land resource was first defined and developed by a geographer named Barloe in 1950 A.D. He defined land resource as: "There is no difference between land and nature; it is basically identified with natural environment including man, water, soil and variety of other things."
3. Land includes all the earth's surface in addition to building sites, farms, soil, growing forests, mineral deposits and water resources. It takes many physical forms, climatic characteristics, vegetation belts and soil patterns. It provides a base for production and also a field where every human activity can take place.

Land is:
Ubiquitous (found everywhere)
Provides base for all natural and manmade phenomena
Fixed in nature and is immobile
Never ending and renewable
A property and capital

The land surface has a variety of landforms, such as mountains, hills, plateaus, plains, river valleys, deserts, marshlands, etc. Thus all parts of the land surface are not equally habitable. The uneven distribution of population on the surface of the earth is mainly due to the varied relief features and highly variable climatic conditions.

About 90 per cent of the total population of the world occupies about 30 per cent of the total land area. The rest of the land area does not have suitable conditions for the survival of human beings. The thickly populated areas in the world are the river valleys, coastal plains and plateaus, which are rich in mineral resources and have industrial centres. The sparsely populated areas are hot and cold deserts, grasslands, rainforests and mountainous regions.

The land is put to different uses, and the use varies from one region to another and also from time to time in the same region. Recently, in many parts of the world, forests have been cleared to provide land for cultivation, mining or other uses, resulting in the reduction of total land under forests.

LAND USE

Land use is characterised by the arrangements, activities and inputs by people to produce, change or maintain a certain land cover type. This land use is determined by various environmental factors such as soil, climate, topography and vegetation. Land use is governed mainly by two sets of factors:
1. Physical Factors: These include temperature, moisture, soil and terrain. They influence the capability and use of land.
2. Non-physical Factors: This includes physical conditions and technoeconomic status, demands, etc.

Factors Affecting Land Use

1. Physical Features: Physical features like mountains, plateaus, plains, rivers, hills and the slope of the land influence the land use pattern in numerous ways, which indirectly have a great bearing upon human beings.
2. Geology: Rocks such as igneous, sedimentary and metamorphic help in soil formation. These rocks disintegrate by various agents of gradation and form the soil of a particular region. So the geology or the rocks also determine the land use.
3. Climate: Climate includes rainfall, temperature, pressure and humidity. Climate also influences the land use pattern of a particular place. Extreme climatic conditions do not support human habitation.
4. Population Characteristics: The population of an area has a great impact upon the land use pattern. Densely populated areas of the world experience more intensive land use than thinly or sparsely populated areas.
5. Slope: The steeper the slope, the more difficult life will be; the gentler the slope, the more freedom there is for movement and the simpler the living conditions. People prefer to settle on gentler slopes rather than steeper slopes.
6. Human Wants and Needs: At different places, people's wants and needs are different. People living in urban areas require land for construction of buildings, stadiums, hotels, restaurants, roads and railways, etc., while people living in rural areas require land mainly for agriculture. So the land use pattern is affected according to human wants and needs.
7. Other factors:
    (a) Presence or absence of soil cover.
    (b) Availability of surface or underground water.
    (c) Level of technology available.
    (d) The improvement value of the available land.

Distribution of Land

1. Land covers only about 30 per cent of the total area of the earth's surface.
2. About 90 per cent of the world's population occupies roughly 30 per cent of its land area.
3. The remaining 70 per cent is either sparsely inhabited by 10 per cent of the population or is uninhabited.
4. Sparsely populated areas mostly include the deserts and grasslands of Asia and Africa, the tropical forests of South America, Africa and Southeast Asia, and the polar areas.
5. Antarctica is uninhabited, except for the temporary occupation by a few scientists conducting research.
6. The subtropical and mid-latitude zones are occupied by approximately 66 per cent of the world's population because of the availability of arable land.

Land Use Pattern

Physical factors such as topography, soil, climate, availability of water and mineral resources determine the probable use of land. For example, fertile plains are used as croplands, the occurrence of mineral deposits favours mining, and in densely populated areas land is used for other human requirements like buildings, houses, roads and rails.

Land use pattern of a few countries of the world (in per cent):

The above table shows:
1. India has a very high percentage of arable land, but its forest cover is quite low. 57 per cent of the total land falls under croplands and 22 per cent under forests.
2. Some countries like Australia and the U.K. have high percentages of pasture lands.
3. Japan has 67 per cent of its land under forests.

Land use pattern in India
Croplands: 57 per cent
Pasture: 4 per cent
Forest: 22 per cent
Other uses: 17 per cent

Land use can also be divided on the basis of private land and community land. Private land is owned by individuals, whereas community land is owned by the community for common uses such as the collection of fodder, fruits, nuts or medicinal herbs. These community lands are also called common property resources.

People and their demands are ever growing, but the availability of land is limited. The quality of land also differs from place to place. People have started encroaching on common lands to build commercial areas and housing complexes in urban areas, and to expand agricultural land in rural areas. Today, the changes in the land use pattern also reflect the cultural changes in our society. Land degradation, landslides, soil erosion and desertification are the major threats to the environment because of the expansion of agriculture and construction activities.

LAND DEGRADATION

Degradation is a Latin word meaning 'reduction' in the quality or quantity. Land degradation is any change in the land that reduces its condition or quality and hence its productivity or productive potential. It has become a universal problem. In developing countries, it is a symptom of underdevelopment. The following are the factors responsible for land degradation:

1. Soil Erosion: It is one of the serious factors for land degradation. It removes a huge amount of nutrients in suspension or in solution from one place to another, causing depletion of nutrients. Various agents of gradation like wind, water, ice (glaciers) and the ocean transport soil from one place to another. Besides these, there are several other factors responsible for soil erosion, such as tremendous population pressure on land, deforestation and faulty agricultural practices.

  

Estimated Soil Loss for the World

2. Desertification: Land degradation also takes place due to the expansion of deserts. This process is mainly related to arid and semi-arid areas. Land becomes degraded mainly when the pressure of population on land is high. Fringe areas are very sensitive, and any disturbance leads to desertification or the expansion of deserts. These deserts advance during drought and retreat during wet seasons.
3. Encroachment on Agricultural Land: Most of the population of the world is concentrated in and around fertile agricultural land (including river valleys and plains). Urban areas are continuously expanding with time. The outward expansion leads to the loss of fertile agricultural land at the outskirts of cities. Urban areas promote land degradation in various ways, such as:
    (i) Alteration in climate, vegetation and overall encroachment
    (ii) Pollution and garbage dumps
    (iii) Alteration in the hydrology of those specific areas
4. Degradation due to Mining Activities: The earth's surface is a storehouse of metals, non-metals and precious elements. These are extracted by mining activities. There are numerous places around the world that were sites of mining operations but have now become degraded and derelict (abandoned sites). For example:
    (i) Appalachian Mountains of USA
    (ii) Chotanagpur plateau in India
    (iii) Ruhr basin in Europe
5. Degraded Forest Lands: Forest soils contain most of the organic matter. These soils become degraded when forests are cleared and trees are burnt, so the organic matter is depleted.

Conservation of Degraded Land

1. Controlling salinisation and alkalinisation
2. Clearing the waterlogged lands
3. Practising crop rotation
4. Practising terrace farming
5. Afforestation
6. Checking overgrazing
7. Planned use of land
8. Control of land pollution
9. Checking urban expansion on good quality agricultural land

B. SOIL RESOURCES

Introduction

The word 'soil' is derived from the Latin word 'solum', which means floor or ground. The term 'pedology' is the study of soil, and the term 'pedogenesis' refers to the process involved in the formation of soils. "Soil is the loose and unconsolidated material derived through the wearing down or disintegration of rocks." Soil may contain minerals along with organic and inorganic matter, which are helpful for the growth and development of plant and animal life.

Soil is the upper-most layer of the earth's crust, consisting of loose products obtained by the disintegration of rocks, mixed with organic matter. Generally, soil includes four types of materials: weathered rock, organic material, water and air. The mineral matter is sand and clay, while the organic materials include decayed leaves, dead tissues of organisms, minute bacteria and earthworms.

The rocks on the surface of the earth are broken into smaller pieces by various agents of weathering. Eventually, a thin layer of broken rock fragments may cover the underlying rocks. The upper layer may remain undisturbed over a long period of time. Over a period of time, chemical and organic changes lead to the formation of soil. The underlying rock is called the bedrock, and the rocks from which soil is formed are called parent rocks.

Formation of Soil

Soil formation is an extremely slow process. It takes hundreds of years to form one centimetre of soil layer. Soil formation is controlled by five factors:
1. Nature of parent rock: The original rock from which the soil is formed determines its basic characteristics, such as colour, texture, chemical properties, mineral content and permeability. For example, shale contributes clay, while sandstones contribute sand grains.
2. Relief and topography: Altitude and slope determine the accumulation of soil. On a steep slope there is no accumulation of weathered rock, while in plains and areas with gentle slopes soil accumulates without any hindrance.
3. Climate: Temperature and rainfall influence the rate of weathering and the formation of humus. For example, frequent temperature changes and the presence of water quicken soil formation through increased weathering.
4. Flora, fauna and micro-organisms in the soil: They affect the rate of humus formation. Dead plants and animals provide humus to the soil. Organisms like earthworms and ants create space for air and water in the soil through their movements.
5. Time: Time determines the thickness of the soil profile. The longer the time for soil formation, the deeper the soil layer.

[Figure: Factors affecting soil formation, arranged as a diagram. Parent rock determines colour, texture, chemical properties, mineral content and permeability. Climate (temperature and rainfall) influences the rate of weathering and humus. Relief (altitude and slope) determines the accumulation of soil. Time determines the thickness of the soil profile. Flora, fauna and micro-organisms affect the rate of humus formation. All these act to form the soil.]

Soil Profile

Soil formation is a slow process, and it may take thousands of years to form even a thin layer of soil. As soil develops, it forms layers called horizons. These horizons make up the soil profile. In a mature soil, four distinct horizons can be seen. These are called horizon A, B, C and D from the top layer downwards.
1. Horizon A is the top layer, also called topsoil. It has most of the minerals and organic materials needed for the growth of plants.
2. Horizon B is below the topsoil and is also called subsoil. This layer has enough minerals but less organic material. The subsoil may have some living organisms. Horizons A and B form the true soil.
3. Horizon C is below the subsoil and has partly weathered rocks. These rocks are producing new soil, but this layer is not affected by biological processes.
4. Horizon D is at the base of the soil profile and consists of unbroken solid rock.

[Figure: Soil profile showing four horizons from top to bottom: Horizon A (topsoil), Horizon B (subsoil), Horizon C (partly weathered rock) and Horizon D (unbroken solid rock at the base).]

Soil Erosion

Soil is a very important natural resource, not only for human beings but for the whole of the biotic world. Soil erosion is the process of detachment and transportation of soil particles.

Soil erosion is the accelerated process of soil removal brought about by human interference with the normal balance between soil building and soil removal.

Types of Soil Erosion

1. Sheet Erosion: Gradual and fairly even removal of the surface soil. It may occur so slowly that one is not aware that it is taking place.
2. Rill Erosion: A more rapid and visible type of erosion. Rills are small streamlets cut into the soil's surface by running water.
3. Gully Erosion: When rills become too large, they become gullies. Gully erosion is an advanced state of rill erosion in which water accumulates in channels and washes away soil to a depth ranging from two feet to as much as seventy-five or a hundred feet. For example, the Yamuna and Chambal area.

Causes of Soil Erosion

1. Deforestation: Trees and forests hold the soil firmly, but when they are cut down, the soil is easily carried away by wind or water.
2. Faulty Agricultural Practices: Ploughing the land along the slope leads to the easy removal of soil particles by wind or water. Ploughing against the slope reduces soil erosion.
3. Faulty Cropping Pattern: Growing a single crop in a field over the years leads to the depletion of nutrients and essential nitrogenous components from the soil. The time for regeneration of these components is too short, so the soil becomes devoid of nutrients within a few years.
4. Shifting Cultivation: Under this type of cultivation, forests are cleared by burning to make land available for cultivation. It is practised in many parts of the world by many tribal groups. In India it is practised in the North-East region and is popularly known as jhum cultivation.

Conservation of Soil

1. Afforestation: The roots of trees and plants hold the soil very tightly and do not let it loose. So the problem of soil erosion can be better dealt with by planting more and more trees.
2. Strip Cropping: On sloping regions, crops can be planted in contour strips, which are effective in checking soil erosion.
3. Crop Rotation: It means growing of crop one after another every year alternately. It helps in reducing erosion and also increases the fertility of soils.
4. Terracing: Terraced fields prevent erosion and conserve moisture. This has been practised in many parts of the world. Terraces control water runoff because they are spaced in a series like steps down the slopes. A terrace acts like an embankment constructed across a slope so that it controls water runoff and minimises erosion.
5. Bunding: Bunding refers to the construction of small bunds across the steps of the land as a contour. These bunds act as a barrier to check water runoff.
6. Shelter Belts: These are green belts of trees which help to check strong winds from picking up loose soil from the ground.
7. Gully Reclamation: Due to carelessness, small gullies are sometimes formed. These gullies prove dangerous and aggravate soil erosion. The best method of controlling them is to grow some vegetation.
8. Checking Overgrazing: Plants once eaten away by animals do not grow again. This mostly happens in hilly regions, so it is essential to check overgrazing.
9. Mulching: The bare part of the field is covered with a layer of straw. It does not allow quick evaporation, and the wind is not able to blow away the soil.
10. Contour Barriers: Barriers made of stones or grass are developed along the contour lines in the field. Trenches are also dug in front of the barriers to collect water.
11. Rock Dams: Dams built of stones across gullies check the flow of water. They can check the flow of flood water and help in filling the gullies with silt.
12. Inter-cropping: Different crops are grown in alternate rows and sown at different times. The soil can be protected from rain-wash, as the field remains under some crop throughout the year.
13. Contour Ploughing: The fields are ploughed and sown along the natural contours of the hills, instead of up and down the slope. The ridges formed act as a natural barrier for water flowing down the slope.

C. WATER RESOURCES

Introduction

Water is an essential resource for life on earth. We use it for drinking, bathing, relaxing, fishing, keeping cool, cooking food and irrigating fields. Most ancient civilisations flourished and developed along river valleys, for example the Nile, Indus, Tigris and Euphrates. Water provides the base for life to sustain.

Characteristics of Water

1. It is the most widely distributed substance on earth.
2. Seventy-one per cent of the earth's surface is covered with it.
3. It is present in all three states: solid, liquid and gas.
4. It is a renewable resource.
5. It is abundantly found on earth.
6. It is home to marine life.

Utilisation of Water

1. Water is essential for all forms of life. It is a major constituent of the body of several plant and animal species. About 70 per cent of the human body consists of water. Human beings use water for domestic purposes, agriculture, industries and the generation of electricity.
2. Increasing population, rising demand for food and cash crops, increasing urbanisation and rising standards of living are the major factors leading to shortages in the supply of fresh water, either due to drying up of water sources or water pollution.
3. In 1975, the consumption of water for human use was 3,850 cubic km per year. It soared to more than 6,000 cubic km per year in the year 2000.

Distribution of Water

1. Water is a vital renewable natural resource.
2. Three-fourths of the earth's surface is covered with water. It is therefore appropriately called the 'water planet'.
3. The oceans cover two-thirds of the earth's surface and support a rich variety of plant and animal life. Ocean water is, however, saline and not fit for human consumption.
4. Fresh water accounts for only about 2.7 per cent. Nearly 70 per cent of this occurs as ice sheets and glaciers in Antarctica, Greenland and mountain regions. Due to their location, they are inaccessible.
5. Only 1 per cent of fresh water is available and fit for human use. It is found as ground water, as surface water in rivers and lakes, and as water vapour in the atmosphere. Fresh water is therefore the most precious substance on earth.
6. The total volume of water remains constant. Its abundance only seems to vary because it is in constant motion, cycling through the oceans, the air and the land and back again, through the processes of evaporation, precipitation and run-off. This is known as the 'water cycle'.

Problem of Fresh Water

1. There is scarcity of water in many regions of the world. Most of Africa, West Asia, South Asia, parts of western USA, north-west Mexico, parts of South America and the entire Australia are facing shortages of fresh water supply.
2. The region between the equator and 20° north and south, and the regions north and south of 40° latitude, are areas of surplus precipitation.
3. In both hemispheres, between 20° and 40° latitudes, evaporation exceeds precipitation. This has created deserts, for example the Sahara, the Arabian and the Gobi deserts in the Northern Hemisphere, and the Atacama, the Namib, the Kalahari and the Western Australian deserts in the Southern Hemisphere.
4. The surface water run-off from a large area gets collected in the form of small streams, which unite to make big rivers.
5. In 1999, 26 countries were experiencing water scarcity. By 2025, it is likely that 65 countries, including India, Korea, Nigeria, Peru and Poland, will face acute water scarcity.
6. Poor countries are located in the climatic zones most prone to drought, and they cannot afford to import water.
7. The drier areas are Australia, Africa, parts of South America, West and South Asia, the western U.S. and north-west Mexico.
8. More than 3 billion people are affected by water shortages.

Problem of Water Quality

1. Untreated or partially treated sewage, agricultural chemicals and industrial effluents contaminate water with nitrates, metals and pesticides.
2. Human and animal wastes introduce pathogens that cause serious diseases.
3. Diseases spread by contaminated water include typhoid, cholera, amoebic infections, dysentery and diarrhoea.
4. The child mortality rate has also increased due to water pollution.

Water Pollution

Water pollution means contamination of water by any external material, which makes it unsuitable for human consumption.

Sources of Water Pollution

1. Industrial Wastes: Industries generate wastes in various ways and in a variety of forms (solid, liquid and gas). This waste is often discharged into rivers and streams without treatment.
2. Radioactive Wastes: Elements such as radium, uranium and thorium are very harmful. They can cause various ailments if exposed to humans, and they also cause water pollution.
3. Organic Wastes: Organic wastes are discharged by both the agricultural and industrial sectors. Organic wastes increase the growth of bacteria, which consume more oxygen, leading to the death of fish.
4. Inorganic Wastes: Inorganic wastes are very harmful and are common in the manufacture of soaps, detergents, drugs, paints and fertilisers.
5. Domestic Effluents and Sewage: In daily life we use water for bathing, cooking, washing and many other things. This waste water is discharged into rivers and streams, which causes pollution.

Conservation of Water

The important methods of conserving water are:
(i) Surface run-off can be slowed down by forest and other vegetation cover, which improves underground storage.
(ii) Rainwater harvesting: Rainwater can be collected in storage tanks. It is the process of collecting rainwater from rooftops, directing it to a suitable location and storing it for future use. On average, one spell of rain for two hours is enough to save 8,000 litres of water.
(iii) Efficient irrigation: Over-irrigation should be avoided. Seepage losses from canals can be minimised by lining them.
(iv) Use of sprinklers: Sprinklers are very effective and efficient tools of irrigation. In dry regions, drip or trickle irrigation is very useful.
(v) Use of recycled water: Industrial water and domestic water can be recycled and used again. Waste water from the kitchen may be used for gardens.
(vi) Using water economically and preventing wastage.
(vii) Rational use of underground water.
(viii) Purification or treatment of waste water.
(ix) Treatment of waste before discharging it into rivers and streams.

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