Top 6 Types of Natural Resources | Ecology

The following points highlight the top six types of natural resources. The types are: 1. Soil 2. Water 3. Land 4. Energy 5. Marine 6. Mineral.

Natural Resources: Type # 1. Soil:

Land is a major constituent of the lithosphere and the source of many minerals essential to man and other organisms. It forms about one-fifth of the earth’s surface, covering about 13, 393 million hectares.

About 36.6 per cent of the land area is occupied by human dwellings and factories, roads and railways, deserts and dunes, glaciers, polar ice marshes, rocks and mountains. About 30 per cent of the total land mass is under forests, approximately 22 per cent is occupied by meadows and pastures and only 11 per cent is arable land (i.e., suitable for growing crops).

The surface layer of the land is called soil. About four-fifths of the land area is covered by soil. Soil is composed of inorganic particles, organic matter, air, water and a variety of organisms. It takes hundreds of years for the development of soil horizons having different physico-chemical properties.

The physical properties of soil depend on its texture, structure, bulk, density, porosity and water retentivity. The salt content, pH, and organic and inorganic nutrients like nitrogen, phosphorus and potassium determine its chemical properties. The topography, climate and biotic factors control the conditions of the soil.

Human activities often create worldwide problems. Soil erosion, salinisation, water-logging, and acidification and alkalisation of soil by erroneous human activities are the great dangers to the land resources.

Construction of dams, roads, and railways, urban encroachment and industrialisation and mining activities are responsible for causing depletion of productive land.

Soil Erosion:

The word ‘erosion’ literally means ‘to wearing away’. In soil erosion, fertile soil surfaces are detached and removed from their original places and are deposited at some other places.

According to Fox (1950), the soil erosion covers a wide range of physical and chemical actions, such as removal of soluble matters, chemical changes, disintegration by frost or by rapid changes of temperature, attrition by dust charged wind, scouring by silt laden currents, alternate impact and succession by storm waves, land-slides and so on. Thus, soil erosion is the removal of top soil by movement of water and air.

Human activities accelerate soil erosion by removing natural plant cover. From croplands in India, millions of tons of top soil are eroded into sea each year. Deforestation, undesirable forest biota, and mechanical practices by man are important factors which cause soil erosion. Erosion causes a significant loss of soil fertility by transporting organic matter and nutrients that are essential part of the soil.

The eroded soil, which gets into streams, rivers and lakes in the form of sediments, affects water quality and the habitats of aquatic organisms.

There are several serious effects of soil erosion, which are as follows:

a. Due to uprooting of trees, scarcity of timber and fuel-wood.

b. Loss of soil stability and fertility.

c. Shortage of fodder.

d. Destruction of cropable land in plains.

e. Formation of sand dunes.

f. Greater frequency of floods and threat to communication channels.

g. Silting of river beds, lakes and dams.

h. Higher temperature and lower rainfall.

However, abundant plant cover significantly reduces soil erosion.

Depletion of Soil Fertility:

If the rate of removal or loss of components is greater than the rate of addition, the soil will naturally less fertile. Leaching is an important factor which makes the soil poor in its resources. In this process minerals and organic substances are removed from the top layer of soil by rain water.

Biological agencies are also active in causing loss of resources from the soil. Cultivation of crops regularly year after year makes the soil less productive. In cultivation there are little chances for the compensation of lost nutrients of the soil by way of death and decay of the vegetation which grows on it.

On the other hand, when natural vegetation is removed to develop agricultural systems, as in many parts of India, not only the nutrients stored in vegetation are removed, the organic matter and nutrients accumulated in the soil are also lost. From agricultural systems, nutrients are exported through crop harvest, thus depleting soil fertility.

Leguminous plants, however, compensate the loss of nitrogenous compounds because bacteria (rhizobia, etc.) inhabiting in their root nodules fix considerable amount of free atmospheric nitrogen into its compounds, such as ammonia, nitrites, nitrates, etc.

Soil Conservation:

The main aims of soil conservation are:

(i) To protect the soil from erosion, and

(ii) To maintain the productive capacity of the soil.

Both engineering and biological methods have been used to check the soil erosion but it is still without a plausible check. In India, we are aware of advancing deserts of Rajasthan, and erosional losses, floods, etc., in other parts of the country.

The problem has received the attention of forest ecologists, soil scientists and engineers these days. With the result several soil and crop management practices have been evolved which can minimise erosion and reduce nutrient depletion of agricultural soils.

Such practices include:

(i) Conservation tillage,

(ii) Organic farming,

(iii) Crop rotation (especially cereals with legumes),

(iv) Contour ploughing, and

(v) Strip-cropping terraces, etc.

(i) Tillage Conservation:

Many researches support the view that in dry areas, shallow ploughing gives comparatively good crop yields. Shallow ploughing removes the weeds and enables the soil to absorb water. Deep ploughing often leads to soil erosion but in the areas where rainfall is sufficiently high, deep ploughing (up-to 15 to 30 cm deep) is effective in removing weeds and increasing crop yields.

In contrast to conventional tillage, conservational tillage incorporates residues from previous crops into the soil, thus increasing the organic matter which in turn improves soil moisture and nutrients.

There are two kinds of conservation tillage:

(i) Reduced tillage, and

(ii) No-tillage.

The efforts to improve erosion-affected soils are summarised in two steps. They are:

(i) Stabilising the soil to prevent further erosion, and

(ii) Restoration of soil fertility.

For soil stabilization, seeding of base ground with plants that can survive adverse conditions is required. For this purpose usually drought resistant grasses are grown. Such plants eventually establish vegetation cover on the soil, preventing further erosion.

(ii) Organic Farming:

With increasing addition of detritus, the soil organic matter, nutrient and moisture levels improve. Application of bio-fertilizers is also useful for enhancement of soil fertility. Various organic farming measures that provide increased organic input to soil have long-term beneficial effects on soil fertility.

Humus is formed by the accumulation of partially decayed and partially synthesized organic materials. Humus helps in making the soil granular. It causes air spaces to be formed in the clay soil and increases the water holding capacity of sandy soils. Humus is rich in nutrients and therefore, enhances plant growth. Being black humus absorbs heat and warms up the soil.

Natural Resources: Type # 2. Water:

Water is the major constituent of the hydrosphere and covers four-fifths of the earth’s surface. In fact, water is all around us. Every cubic millimetre of air, even over dry deserts, has water vapour. Water is present in the soil and also hidden in underground pools.

The total volume of water in the hydrosphere is 1.4 billion cubic kilometres (km³), about 97.5 per cent of the earth’s water is found in oceans, which is strongly saline. The rest 2.5 per cent is fresh water, and all of this is not available for direct human use.

Most of the fresh water is frozen as polar or glacial ice (i.e., 1.97 per cent). Remaining fresh water occurs as ground water (i.e., 0.5 per cent), and water in lakes and rivers (0.02 per cent), soil (0.01 per cent) and atmosphere (0.001 per cent). Thus, only a small fraction of fresh water is available for human consumption.

About 84 per cent of the total global evaporation occurs from ocean surface and 16 per cent from land surface.

At any given time the amount of moisture in the air is only enough to meet a total rainfall requirement of ten days. Thus, there is a fast movement of water from ocean and land into the atmosphere, and an average stay time of water in the air is only about ten days.

About 77 per cent of the total rainfall on earth is received on the sea surface (as against 84 per cent evaporation from ocean surface) and 23 per cent on land (as against 16 per cent from land surface). Thus, there is net gain of 7 per cent rainfall water on land, and this excess is returned to the oceans by surface run off through rivers and sub-surface water flows.

However, on global basis, the hydrological cycle is perfectly balanced as the total annual evaporation matches with annual rainfall.

Global water is unequally distributed. Precipitation is seasonal and, therefore, the amount of water in inland bodies is variable. Irregularity in the duration and intensity of rainfall often causes floods or droughts. Scarcity of fresh water results in serious regional disparities. Arid regions suffer perennially from water shortage.

The global distribution of fresh water on our planet is only about 84.4 million cubic km. The global distribution of fresh water on earth’s crust including ground water and water present as vapours in the atmosphere is given in table 13.1.

The excess water received by land surface, about 41, 000 cubic km has to flow back to sea, it cannot be retained on earth’s surface ordinarily.

Water Use:

On global basis, the water use has increased 4 to 8 per cent per year since 1950 and the consumption rate varies among different countries.

Agriculture sector is the biggest consumer of freshwater. Worldwide, about 70 per cent of total water use is accounted by agriculture.

Following agriculture, power generation (6.2 per cent), and industries (5.7 per cent) are the biggest consumers of fresh water.

Domestic requirement and livestock management taken together consume only 4.3 per cent of the total water drawn.

However, only about 1.1 per cent of fresh water is used for domestic and municipal supplies. The rest of water is consumed by various industries, such as cement, mining, pharmaceutical, detergent and leather industry, etc.

Fisheries, hydro-electric power generation, recreational activities, etc., also require a huge quantity of water, much of which flows down to the sea.

Natural Resources: Type # 3. Land:

Land is a major constituent of the lithosphere and is the source of many materials essential to man and other organisms. Earth’s one fourth area is formed by land which is largely covered with natural forests, grasslands, wetlands arid man made urban and rural settlements along with agriculture.

About 36.6 per cent of the land area is occupied by human dwellings and factories, roads and railways, deserts and; dunes, glaciers, polar ice marshes, rocks and mountains.

About 30 per cent of the total land mass is under forests, approximately 22 per cent is occupied by meadows and pastures and only 11 per cent for agriculture. Low-lying areas covered with shallow water are called wetlands. The wetlands make the transitional zones between terrestrial and aquatic areas.

Grasslands:

The grasslands, also known as rangeland, provide forage and habitat to domestic animals and wildlife. Natural grasslands occur where rainfall is intermediate between that of desert lands and forest lands.

In the temperate zone this generally means an annual precipitation between 10 and 30 inches, depending on temperature, seasonal distribution of the rainfall, and the water- holding capacity of the soil. Tropical grasslands may receive up to 60 inches concentrated in a wet season that alternates with a prolonged dry season. Grasslands are one of the most important of terrestrial ecosystem types.

A well-developed grassland community contains species with different temperature adaptations, one group growing in the cool part of the season {i.e., spring and winter) and another in the hot part (summer). Forbs (i.e., non-grassy herbs) are often important components, and woody plants (trees and shrubs) also occur in grasslands either as scattered individuals (savanna) or in belts or groups along streams and rivers.

In India, the area under various kinds of grass cover, including fallow and waste lands is about 18 per cent of the total land area. While forest cover is about 19 per cent of total land. This means, about 37 per cent of land can be said to be available for grazing.

Uses:

In rural areas of our country, dried hay obtained from grasslands, particularly from tall grasses, is used as fuel or thatching material.

Grass cover is extremely effective in binding soil particles with the help of highly branched fibrous root system, thus significantly reducing soil erosion.

The annual average production of dry grass or hay in India is about 250 million tons.

Large herbivores are a characteristic feature of grasslands.

When man uses grasslands as natural pastures he usually replaces the native grazers with its domestic animals, i.e., cattle, sheep and goats.

Since grasslands are adapted to heavy energy flow along the grazing food chain, such a switch is ecologically sound.

Degradation of Grassland:

However, man has had a persistent history of misuse of grassland resources by virtue of allowing overgrazing and over-plowing. The result is that many grasslands are now man-made deserts. The conversion of grassland (or forest) to desert is called desertification.

Degradation of destruction of grassland is mainly related to overpopulation. To enhance food production, grasslands possessing fertile soils are ploughed and converted to agricultural lands.

In India, grassland areas are frequently overgrazed. For example, the number of animals grazing in the arid and semi-arid regions has been found to be 2 – 10 times greater than the capacity of the grassland to feed the animals.

The lack of plant cover due to overgrazing causes soil erosion. When overgrazing occurs in combination with drought, the deserts are resulted.

Grassland Management:

The important measures of grassland management are:

(i) Protection from Grazing:

This allows recover of severely damaged vegetation.

(ii) Use of Rotational Grazing:

While some areas are closed to grazing, allowing the plane cover to recover, grazing is permitted in other selected areas.

(iii) Removal of Unwanted Plants:

This includes removal of woody bushes or shrubs and weeds, which usually adversely affect the productivity of grasses.

(iv) Conservation of Soil and Water:

This may be done by reducing loss of soil and water from the grassland.

(v) Use of Controlled Burning:

This promotes recycling of nutrients stored in dried mulch and to reduce woody species invasion. Grassland Types of India

The tropical grasslands of India may be classified a follows:

(i) Xerophilous Grasslands:

They are found in dry regions of North West India under semiarid conditions.

The common examples are:

Andropogon contortus, Cenchrus ciliaris, C. barbatus, etc.

(ii) Mesophilous Grasslands:

Also known as ‘savannahs’ they are extensive grassy plains typically occurring in moist deciduous forests of Uttaranchal.

The dominant species are:

Sacchamm munja, Saccharum narenga, etc.

(iii) Hygrophilous Grasslands:

These are called wet ‘savannahs’ adapted to wet soil.

Wetlands:

Wetlands are low-lying areas, usually covered by shallow water and have characteristic soil and water tolerant vegetation. Wetlands may be either freshwater or salt water.

Wetlands occupy almost 6 per cent of the world’s land surface and provide crucial environmental services. Now-a-days the wetlands are increasingly threatened by agriculture, pollution and construction of dams, etc.

Freshwater Wetlands:

Freshwater wetlands include:

(i) Marshes (where grass-like plants dominate), and

(ii) Swamps (where trees or shrubs dominate),

(iii) Riverine, periodically flooded forests found in lowlands along streams.

Wetland plants are highly productive and provide food and habitat to support a wide variety of organisms.

Areas lying in the immediate vicinity of the rivers of North India supporting tamarisks, acacias, phragmites, saccharum, typha, arundo form this habitat. The areas are subject to summer flooding but often get dried up by May. Very few permanent swamps exist. Vast areas rendered waterlogged in canal irrigated areas also form good habitat for waterfowl.

In the stabilised areas occur hog deer and nilgai. Waterfowl winter in these areas and also use these areas as staging points; large reservoirs created on rivers have also formed good habitats for wildlife.

Wetlands help control flooding by holding excess water, and the flood water stored in wetlands then drains slowly back into the rivers providing a steady flow of water throughout the year.

Wetlands also serve as groundwater recharging areas. They are helpful in cleaning and purifying water runoff.

Freshwater wetlands also provide important commercial products, such as rice, black berries, blue berries, etc.

Moreover, they also provide sites for fishing, boating, nature study, etc.

Freshwater wetlands are often drained, dredged and filled up for housing and industrial purposes.

Finally, it is significant that rice culture, one of the most productive and dependable of agricultural systems yet devised by man, is actually a type of fresh-water marsh ecosystem. The flooding, draining, and careful rebuilding of the rice paddy each year has much to do with the maintenance of continuous fertility and high production of the rice plant, which itself is a kind of cultivated marsh grass.

Saltwater Wetlands:

Coastal wetlands are also known as saltwater wetlands. They include highly productive estuaries which provide food and habitat for a large number of marine organisms. Between the seas and the continents lie a belt of diverse ecosystems that are not just transition zones but have ecological characteristics of their own.

Whereas physical factors such as salinity and temperature are much more variable near shore than in the sea itself, food conditions are so much better that the region is packed with life.

Along the shore live thousands of adapted species that are not to be found in the open sea, on land, or in freshwater. The word ‘estuary’ (Latin, aestus = tide) refers to a river mouth or coastal bay where the salinity is intermediate between the sea and freshwater and where tidal action is an important physical regulator. Estuaries and inshore marine waters are amongst the most naturally fertile in the world.

Tidal action promotes a rapid circulation of nutrients and food, and aids in the rapid removal of the waste products of metabolism. A diversity of plant species and life forms provides a continuous photosynthetic carpet despite variable physical conditions.

Mangrove swamps are coastal wetlands in tropical regions which contain certain trees and shrubs growing best in the intertidal zone. As mangroves expand into the ocean, other plants colonise the soil left behind. Mangrove roots provide habitat for oysters, crabs and other marine organisms. However, the coastal wetlands are also being destroyed for coastal development and agricultural lands.

Organisms have evolved many adaptations to cope, with tidal cycles, thereby enabling them to exploit the many advantages of living in an estuary. Some animals such as fiddler crabs, have internal ‘biological crops’ that help to time their feeding activities to the most favourable part of the tidal cycle.

Wetland Conservation:

Conservationists and trained marine environmental engineers have become alarmed by the needless destruction of coastal resources. Ultimately it may be necessary to set up some kind of conservation plan so that the use of such areas by man can be placed on a sound ecological basis.

Some wetland conservation programmes are as follows:

(i) Preparation of wetland inventories

(ii) Identification of wetlands of critical importance for their protection.

(iii) Checking waste disposal in wetlands

(iv) Reduction of excessive inflow of nutrients and silt into wetlands from surrounding uplands by keeping them under plant cover.

Natural Resources: Type # 4. Energy:

The energy crisis is a global problem today. The survival of the man will be difficult if the energy problem is not solved on the priority basis. Future energy needs of rapidly expanding human population will demand the exploitation of most energy resources. The energy consumption is maximum in developed countries as Compared to developing nations.

The nineteenth century industrial societies used fossil fuels, and the daily per capita energy utilisation jumped to 70, 000 kcal. Today we require energy for agriculture, industry, transport, communication, comfort and defence.

The per capita energy consumption per day in the USA has reached about 2,50,000 kcal. People in other countries use far less energy. It is as low as 10,000 kcal in several developing countries. However, it is increasing fast with rapid industrialisation.

Today the world’s energy resources have reached a critical stage. The reasons are many. First, the worlds almost total dependence on the fossil fuels-coal, petroleum and natural gas has caused such depletion that these fuels may last only another few centuries.

Today, 30 per cent of the world’s population, living in industrialised countries, consumes about 80 per cent of the global energy. On the other hand the poorer nations rely more on firewood for cooking and heating and animal power for transport.

(i) Non-Renewable Energy Resources:

Such resources include various fossil fuels and nuclear energy. Fossil fuels include petroleum products, natural gas and coal. While nuclear energy is mainly obtained from the nuclear fission of the uranium.

The world reserves of fossil fuels and uranium are limited and will eventually be depleted. It is estimated that the stock of the mineral oil will be depleted in twenty first century, if it continues to be used at present rate.

However burning fossil fuels for energy has negative environmental consequences, such as global warming, air pollution, acid rain and oil spills. Now, this has become necessary to minimise use of non-renewable energy resources, and to replace them with renewable resources.

(ii) Renewable Energy Resources:

Such energy resources are regenerated by natural processes so that they could be used indefinitely.

Renewable energy generally causes much less negative environmental impact than fossil fuels or nuclear energy. However, the generation of renewable energy is often more expensive than energy produced by fossil fuels or nuclear energy. With the advancement of technology, the costs of renewable energy are expected to decrease.

The most important renewable energy is solar energy, while other resources of renewable energy are hydropower, wind geothermal energy, ocean waves and tidal energy,

Solar Energy:

There are two types of solar energy:

(i) Direct solar energy, and

(ii) Indirect solar energy.

Direct solar energy is the radiant energy, while indirect solar energy is obtained from materials that have previously incorporated the sun’s radiant energy.

Solar energy can be used for direct heating and alternatively the heat converted into electricity, i.e., thermal electric generation. Solar thermal pumps have been developed and are being tested under actual field conditions. Photovoltaic cells convert direct solar energy into electricity.

However, a back-up system is required to store and generate electricity when solar power is not operative at night or during cloudy days. Solar photovoltaic panels, cookers, heaters and solar battery driven cars are being made and are in use.

Biomass Energy:

Among various energy resources, where solar energy is utilised indirectly, biomass energy is most important one. This is detained from those materials whose origin can be traced to photosynthesis, e.g., live plant material and dried residues, freshwater and marine algae, agricultural and forest residues, such as straw, husks, corn cobs, bark, sawdust, roots, animal wastes, etc.

Biomass also includes biodegradable organic wastes from industries, such as sugar mills, breweries, etc. About half of the world’s population depends upon biomass as their main source of energy for domestic use.

In India, fuel wood is still a major source of energy for domestic purposes, at least in rural areas. Biomass fuel may be solid, liquid or gas. This is burned to release its energy. Solid biomass includes wood, charcoal, animal dung and peat.

Biomass can be converted to liquid fuels, such as methanol (methyl alcohol) and ethanol (ethyl alcohol), which can be used in internal combustion engines of automobiles. Gasoline mixed with 10-20 per cent ethanol can be used in conventional gasoline engines.

Biogas:

Biomass in the form of animal waste and hydrophytes, such as Eichhornia can be converted into biogas in biogas digesters by using the process of anaerobic microbial decomposition. This is a clean anaerobic fuel whose combustion produces less pollutants than other combustible energy resources. The biogas is composed of 60 per cent methane and 40 per cent carbon dioxide.

Energy Plantations:

Production of biomass for energy requires sufficient area of land and water. Fuel wood has been the primary energy source for mankind from the beginning of civilization and still continues to be the main source of energy in the developing countries, particularly in rural areas. Plant based energy is obtained through energy plantations which can produce biomass from sleeted species of trees in the shortest possible time at a low cost.

These plants yield solid, liquid or gaseous fuel through burning, gasification, digestion, etc. Such plantations can be raised in both hills and plains particularly on marginal land. It has been calculated that about four tons of dry matter can be obtained in 0.25 ha land, which is sufficient for an average family.

Some important plants for energy plantation, which are extensively grown in India are Leucaena leucocephala, Casuarina, poplar tree and Eucalyptus.

Petroplants:

Also called hydrocarbon plants are known to yield liquid hydrocarbons the substitute for liquid fuels. The hydrocarbons present in such plants can be converted into petroleum hydrocarbons of high molecular weight.

Jatropha curcas tree yields 2 kg of seed oil per plant/year. The oil obtained from this plant is expected to replace the conventional diesel fuel. These plants can easily be grown in arid regions and other waste lands.

Other Renewable Resources of Energy:

Among other renewable resources of energy some are important which are mentioned here:

(i) Hydropower:

Hydroelectric power is the most important and widely used resource of renewable energy. This is generated from water. Water falling from a height turns turbines at the bottom of dams to generate electricity.

Hydropower produces approximately one-fourth of the worlds electricity, and is usually cheaper than electricity produced by thermal power plants. India has big potential for hydroelectric power generation. The energy obtained from hydropower is widely used in agriculture, industry, transport, domestic sectors, etc.

However, building a dam to hold the water results in several environmental problems, such as submergence of plant and animal habitats and displacement of people.

(ii) Wind Energy:

The wind can also be exploited as a source of energy in different ways. When fans are rotated by the action of wind, its energy can be used for generation of electricity. National Aeronautics Limited, Bangalore is engaged in research and development of power generation through wind mills. In many states wind mills have been set up for irrigation purposes.

However, harvesting wind energy is possible only in the areas that receive fairly continual winds, such as islands, coastal areas and mountain passes. Wind energy may be converted into mechanical and electrical energy.

Now a days, wind energy is being used for pumping water is rural areas. According to an estimate, about 20,000 mw electricity can be generated in India from wind alone.

(iii) Tidal Energy:

The difference in the level of water between high tide and low tide can be used to generate electricity.

(iv) Geothermal Energy:

Heated groundwater flowing upward as hot water or steam, or as hot springs, can be used to turn turbines and generate electricity is geothermal power plants.

(v) Ocean Waves Energy:

Ocean waves, produced by winds, possess the potential to turn a turbine and generate electricity.

The present critical energy position demands an organised effort at all levels from individual practices to international action. Considerable amount of energy can be saved by reducing wastage and using energy efficient devices.

Some of such measures are:

(i) Reduction in man’s dependence on fossil fuels and development of newer alternative sources of energy.

(ii) Preparation of smokeless and efficient chulhas (wood stoves).

(iii) Improvement and expansion of sources of solar energy. Solar photovoltaic panels, cookers, heaters, and solar-battery driven cars need to be improved technically and made cost-effective.

(iv) The use of biogas plants must be encouraged so that agricultural and animal wastes can be used to produce both energy and fertiliser,

(v) Improvement in design, manufacture and maintenance of biogas plants, engines and pumps.

(vi) Generation of hydroelectric, wind and tidal power has to be explored more extensively.

(vii) Programmes for growing fuel wood trees and shrubs under the control and maintenance of local communities have to be implemented in the rural areas of the developing countries.

Natural Resources: Type # 5. Marine:

The oceans cover nearly three-fourth of earth’s surface. Ocean has been the source of many needs of man from the time immemorial. The rapid growth of human population and the advancement of industrialization have exerted great pressure on the resources and the environment of oceans.

Land resources are depleting at tremendous rate and in view of this man has started thinking to exploit the oceanic resources.

Marine resources can be broadly divided into two major categories:

(i) Living resources, such as algae and the animals of the sea,

(ii) Non-living resources, e.g., various kinds of minerals.

Alga Resources:

Marine algae vary greatly in form and range from one-called microscopic phytoplanktons to giant helps, which attain a length of 100 to 150 metres, e.g., Nereocystis, Macrocystis, etc.

Green, blue, red and brown algae are commonly found in oceans. From time immemorial, algae have been widely used as human food. The algae are used as direct source of food by several sea animals and fishes. Marine planktonic diatoms are of fundamental biological importance since all life of sea is dependent upon them.

Since the prehistoric times several sea weeds have been used as direct source of food to human beings. The sea weeds form the most important part of the diet of Japan and China. Suimono is a Japanese preparation of dried fish and several sea weeds. Mitsu is another Japanese preparation which contains sea weeds, fruits, sugars and dried kidney beans.

In many countries, animals are still regularly fed on fresh or processed sea weed (e.g., Laminaria and Fucus).

Marine algae have been used as a manure in many countries because of their high nutrient content. Balanced fertiliser can be made by mixing sheep manure, fish and shells with seaweeds. Seaweeds are a store-house of the important potash, ionic sulphate, microelements and growth substances, besides having every other element and radical required by plants.

Seaweed manure seems to increase disease resistanc to plants.

Agar Extraction:

Mainly red algae, e.g., Gracilaria, Gelidium, etc., are used for the extraction of commercially important agar. Japan produces the largest quantity of agar, and exports to most of the countries of the world.

The agar is used in several ways. It is employed in the preparation of ice creams, jellies, desserts, pharmaceuticals, photography, metal plating, lithography, metallurgy, and also in the manufacture of explosives, detergents, pesticides, in sizing the textiles and clearing many liquids.

It is also used in preparing shaving creams, cosmetics and shoe polishes. The agar has constantly been used in biological laboratories for media preparation for fungal and bacteriological cultures.

Animal Resources:

Fish, molluscs, crustaceans and many mammals found in sea waters are used as human food. Oceans provide an excellent habitat for above mentioned organisms.

Fish:

The bulk of fish and other aquatic animals come from marine habitats. Marine fish provide considerable amount of food throughout the world. Fish are also used for the manufacture of several edible products, such as fish glue, fish meal, fish oil, fish proteins and vitamins.

Economically important fish are generally divided into two categories:

(i) Demersal fish, and

(ii) Pelagic fish.

The demersal fish are found at the sea-bottom, while pelagic fish floating free in the water column.

Fishing activity near the shore-line is carried on by small boats and vessels. This is called coastal fishing. On the other hand a large part of the total annual catch of fish comes from deep waters, and called deep sea fishing. This type of fishing is done by large boats or ships. In developed countries, where fishing is an organised industry, large boats and vessels are used for the purpose.

Molluscs:

They are soft-bodied and shelled animals, (Latin, molluscus = soft bodied). Important molluscs from commercial point of view are the mussel, oyster, clam, etc. Many types of molluscs are used as food.

However, pearl oyster is commercially important. The pearl worn as jewellery is secreted by certain oysters (bivalves). The inner calcareous surface of several bivalve shells is iridescent and pearl-like (nacreous) in appearance.

Crustaceans:

They include crabs and prawns. They are the dominant arthropods of the sea. Prawns, lobsters and crabs are important economically. They make valuable items of food. India ranks first among the prawn producing countries of the world.

Phytoplankton-feeding, tiny crustaceans form an important link in the food chain of oceans.

Mammals:

Whales, dolphins and porpoises are the economically important mammals found in the sea. The blue whales are the largest animals, some 30 m in length. Whales may be filter- feeders, living on planktons, or may feed on fish.

Whales provide many valuable primary products, such as meat, ivory, skin, and frozen glands. They also produce many secondary products, such as oils, liver oil, etc. Fresh meat of all cetaceans, i.e., whales, dolphins, porpoises, etc., has been used for human consumption.

Minerals in Sea:

The sea is a store house of many valuable minerals. Most abundant elements in sea water are sodium, chlorine, magnesium, and bromine that are commercially extracted from sea water. Phosphorite nodules are also found in sea, which can meet the shortage of phosphate fertilizers.

The sea weeds make a unique supplement for a well-balanced diet. Potassium, sodium and chloride are found in the ionic form in sea weeds. The significance of iodine, as a constituent of food, is that besides being present in organic combination, it is also available in part in the readily available form of the precursor of thyroxine and hence this source of iodine surpasses mineral iodine in drinking water and iodized table salt.

The another micronutrients besides iodine which are important in human metabolism are iron, copper, manganese and zinc and all of them present as the trace elements of sea weeds. The highest copper content is found is Sarconema and Acanthophora. Today, iodine is produced from brown algae (seaweeds) in Japan, France, Norway and Jawa.

Natural Resources: Type # 6. Mineral:

Some mineral elements are essential for the formation and functioning of the living body of all organisms, including man. Most of the essential elements enter animals through food chains and food webs. However, minerals are essential to our industrialised society and daily life. Mineral resources are non-renewable.

The geographical distribution of essential minerals is unequal. Industry, transport, agriculture and defence preparation are making ever-increasing demands on the limited mineral deposits of the world. Depletion of almost all known and easily accessible deposits is anticipated within a few decades.

Moreover, there may be shortage of some crucial elements, such as mercury, silver, gold, platinum, copper, tungsten within next 20 to 100 years. The limited resources of phosphorus which is an essential component of fertilizers may also cause retardation of agricultural growth.

Minerals can be divided into two groups:

(i) Metallic, e.g., iron, copper, gold, silver, platinum, etc., and

(ii) Non-metallic, e.g., sand, stone, salt, phosphates, asbestos, sulphur, corundum, etc.

Mining:

This includes extraction, processing and disposal of minerals. However, mining has adverse effects on environment. This not only disturbs and damages the land, but also pollutes the soil, water and air.

The land that has been destroyed due to mining is known as mine spoil. Such destroyed lands can be reclaimed to a semi-natural condition by revegetation to prevent further degradation.

Conservation of Minerals:

Efforts are being made to check the wasteful and injudicious use of minerals by recycling and adopting more efficient technologies, exploiting untapped deposits and by deep sea-mining. In process of recycling, used and discarded items are collected, remelted and reprocessed into new products, such as iron scraps, aluminium cans, etc.

The problem of high mineral consumption can be minimised by scientific and technological developments. Search for new production processes, designing smaller equipment, use of new raw materials and restrained use of materials have to be intensified. Finding new uses for glass, plastics, ceramics and synthetic fibres and using them as substitutes for exhaustible minerals is in progress.

Some minerals present in products can be recycled, e.g., gold, silver, lead, copper, nickel, steel, zinc, aluminium, etc. However, minerals in several other products are lost through normal use, such as paints containing lead, zinc, chromium, etc.

Recycling and reusing not only renew the mineral resources, but also help in:

(i) Saving land from disruption of mining,

(ii) Reducing the amount of solid waste that is disposeable, and

(iii) Reducing pollution and consumption of energy.

However, to maintain the extended supply of minerals for a longer time, consumers must decrease their mineral consumption.

Durable and repairable products should be encouraged to be used again. Manufacturing industries should use the waste products of one manufacturing process as the raw materials for mother industry.