Land and Water Resources | NCERT Standard 8 | Social Science

Land : Land is among the most important natural resources. It covers only about thirty per cent of the total area of the earth’s surface and all parts of this small percentage are not habitable. The uneven distribution of population in different parts of the world is mainly due to varied characteristics of land and climate. Ninety per cent of the world population occupies only thirty per cent of land area. The remaining seventy per cent of the land is either sparsely populated or uninhabited.

Land Use : Land is used for different purposes such as agriculture, forestry, mining, building houses, roads and setting up of industries. This is commonly termed as Land use. The use of land is determined by physical factors such as topography, soil, climate, minerals and availability of water. Human factors such as population and technology are also important determinants of land use pattern.

Land Use of India : Cropland - 57%, Pasture - 4%, Forest - 22%, Other Use - 17%
Land Use of World : Cropland - 11%, Pasture - 26%, Forest - 31%, Other Use - 32%

Major threats to Land : Land degradation, landslides, soil erosion, desertification are the major threats to the environment because of the expansion of agriculture and constructional activities.

Methods for Land Conservation : Afforestation, land reclamation, regulated use of chemical pesticide and fertilisers and checks on overgrazing are some of the common methods used to conserve land.
Landslides : Landslides are simply defined as the mass movement of rock, debris or earth down a slope. They often take place in conjunction with earthquakes, floods and volcanoes. A prolonged spell of rainfall can cause heavy landslide that can block the flow of river for quite some time. The formation of river blocks can cause havoc to the settlements downstream on its bursting. In the hilly terrain landslides have been a major and widely spread natural disaster that often strike life and property and occupy a position of major concern.

Mitigation Mechanism : Advancement in scientific techniques has empowered us to understand what factors cause landslides and how to manage them. Some broad mitigation techniques of landslide are as follows:
• Hazard mapping locate areas prone to landslides. Hence, such areas can be avoided for building settlements.
• Construction of retention wall to stop land from slipping.
• Increase in the vegetation cover is an effective way to arrest landslide.
• The surface drainage control  works are implemented to control the movement of landslide along with rain water and spring flows.

Soil : The thin layer of grainy substance covering the surface of the earth is called soil. It is closely linked to land. Landforms determine the type of soil. Soil is made up of organic matter, minerals and weathered rocks found on the earth. This happens through the process of weathering. The right mix of minerals and organic matter make the soil fertile. The major factors of soil formation are the nature of the parent rock and climatic factors. Other factors are the topography, role of organic material and time taken for the composition of soil formation. All these differ from place to place. Normally it takes hundreds of years to make just one centimetre of soil.

Factors causing Soil degradation : Soil erosion and depletion are the major threats to soil as a resource. Both human and natural factors can lead to degradation of soils. Factors which lead to soil degradation are deforestation, overgrazing, overuse of chemical feritilisers or pesticides, rain wash, landslides and floods.

Methods of soil conservation are
1. Mulching: The bare ground between plants is covered with a layer of organic matter like straw. It helps to retain soil moisture.
2. Contour barriers: Stones, grass, soil are used to build barriers along contours. Trenches are made in front of the barriers to collect water.
3. Rock dam: Rocks are piled up to slow down the flow of water. This prevents gullies and further soil loss.
4. Terrace farming: These are made on the steep slopes so that flat surfaces are available to grow crops. They can reduce surface run-off and soil erosion.
5. Intercropping: Different crops are grown in alternate rows and are sown at different times to protect the soil from rain wash.
6. Contour ploughing: Ploughing parallel to the contours of a hill slope to form a natural barrier for water to flow down the slope.
7. Shelter belts: In the coastal and dry regions, rows of trees are planted to check the wind movement to protect soil cover.

Water : Water is a vital renewable natural resource. Three fourth’s of the earth’s surface is covered with water. It is therefore appropriately called the ‘water planet’. It was in the primitive oceans that life began almost 3.5 billion years back. Even today, the oceans cover two-thirds of the earth’s surface and support a rich variety of plant and animal life. The ocean water is however saline and not fit for human consumption.
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. Only 1 per cent of freshwater 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. Water can neither be added nor subtracted from the earth. Its total volume remains constant. Its abundance only seems to vary because it is in constant motion, cycling through the oceans, the air, the land and back again, through the processes of evaporation, precipitation and run-off. This is referred as the ‘water cycle’.

Consumption of Water : In 1975, the consumption of water for human use was 3850 cukm/year. It soared to more than 6000 cukm/year in the year 2000. An average urban Indian uses about 135 litres of water every day.

Water Conservation : Water pollution can be controlled by treating non-biodegradable effluents suitably before releasing them in water bodies. Forest and other vegetation cover slow the surface runoff and replenish underground water. Water harvesting is another method to save surface runoff. Water is used for irrigating fields. The canals should be properly lined to minimise losses by water seepage. Sprinklers effectively irrigate the area by checking water losses through seepage and evaporation. In dry regions with high rates of evaporation, drip or trickle irrigation is very useful. The valuable water resource can therefore be conserved by adopting these means of conservation.

Biosphere : Natural vegetation and wildlife exist only in the narrow zone of contact between the lithosphere, hydrosphere and atmosphere that we call biosphere. In the biosphere living beings are inter-related and interdependent on each other for survival. This life supporting system is known as the  ecosystem. Vegetation and wildlife are valuable resources. Plants provide us with timber, give shelter to animals, produce oxygen we breathe, protects soils so essential for growing crops, act as shelter belts etc.

Rain water harvesting : It is the process of collecting rain water from roof tops and directing it to an appropriate location and storing if for future use. On an average, one spell of  rain for two hours is enough to save 8,000 litres of water.

Vegetation : The growth of vegetation depends primarily on temperature and moisture. The major vegetation types of the world are grouped as forests, grasslands, scrubs and tundra. In areas of heavy rainfall, huge trees may thrive. The forests are thus associated with areas having abundant water supply. As the amount of moisture decreases the size of trees and their density reduces. In the regions of moderate rainfall short stunted trees and grasses grow forming the grasslands of the world. In dry areas of low rainfall, thorny shrubs and scrubs grow. In such areas plants have deep roots and leaves have thorny and waxy surface to reduce loss of moisture by transpiration. Tundra vegetation of cold Polar Regions comprise of mosses and lichens. Forests are broadly classified as evergreen and  deciduous depending on when they shed their leaves. Evergreen forests do not shed their leaves simultaneously in any season of the year. Deciduous forests shed their leaves in a particular season to conserve loss of moisture through transpiration. These forests are further classified as tropical or temperate based on their location in different latitudes.

Indian Vultures : Vultures in the Indian subcontinent were dying of kidney failure shortly after scavenging livestock treated with diclofenac, a painkiller that is similar to aspirin or ibuprofen.

Forest fire : It is a threat to entire region of fauna and flora. It occurs mainly due to three reasons.
1. Natural fire due to lightening etc.
2. Fire due to heat generated in the litter due to carelessness of people.
3. Purposely caused fire by local inhabitants.
Some Control Measures
1. Prevention of human-caused fires through education.
2. Prompt detection of fires through well co-ordinated network of obsevation points, efficient ground patroling and communication network.

CITES : "Convention on International Trade in Endangered Species of Wild Fauna and Flora" is an international agreement between governments. It aims to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Roughly 5,000 species of animals and 28,000 species of plants are protected. Bears, dolphins, cacti, corals, orchids and aloes are some examples.

Based on Resource and Develpoment Chapter 2 : Land and Water Resources