Forests: Our Lifeline

"The word forest is derived from a Latin word foris which means "out of doors", i.e., it is a land which lies beyond those areas enclosed for agriculture or parkland and is not fenced. Such an area is generally composed of trees and other forms of life."

1.0Introduction

About one-third of the world's land surface is covered with forests. Forests are different from one another depending upon where they are located. Climate, topography (physical features) and soil type are some of the main factors that determine the type of trees and animals that grow and thrive in a forest. The current forest cover of the world is shown in the figure given below.

2.0Forest profile

In a forest, many different trees like those of teak, sal, shisham, kachnar, amla, neem, palash, khair and bamboos are found. In addition to trees, shrubs, herbs, climbers and creepers are present in a forest. A forest area may have a dense growth of trees. The forest floor is quite dark as the sun is not able to penetrate through the leaves of the trees.

Such a shaded forest floor provides habitat for the growth of mosses, lichens and other shadeloving plants. The branches of trees in a dense forest form a cover or roof over the other plants in the forest. Such a cover or roof formed by the tree branches in the upper regions is called a canopy. The branchy part of a tree above the stem is known as the crown of the tree. Shapes and size of the crown differs in different trees. Based on the height of trees, different horizontal layers are created in the forest.

These horizontal layers present at different heights below the canopy are known as understorey. Tall trees form the canopy, followed by small trees and shrubs, which form the understorey, and the herbs or ground flora which forms the lowest layer of the understorey. The forest floor seemed dark coloured and was covered with a layer of dead and decaying leaves, fruits, seeds, twigs and small herbs. The decaying matter was moist and warm. It is warm because of the metabolic activities being processed by the micro-organisms. Heat generated during this process gets trapped inside the layers & hence decaying substance is always warm.

3.0Uses of forest

(i) They are the main sources of food to all living beings, as the plants are the producers of food. (ii) They also provide us wood, fuel, clothing (fibre), shelter, medicines, paper, rubber, vegetable oil and many other useful things. (iii) They provide home and protection to wildlife. (iv) They regulate earth's temperature and water cycle. (v) Forests help in bringing good rainfall. (vi) Plants help to purify water in the soil. Roots allow slow movement of water in the soil. The gradual movement of water helps in its purification. (vii) They help in regulating the balance of ${\mathrm{CO}}_2$ and ${\mathrm{O}}_2$ in the atmosphere and check global warming. This is because plants release oxygen and use ${\mathrm{CO}}_2$ during the day through the process of photosynthesis. (viii) They check air pollution and contribute to purification of air. (ix) They prevent erosion of soil by water and wind. Roots of trees bind the soil together. (x) They save the hill slopes from landslides. (xi) They reduce the intensity of floods. If trees are not present, rain hits the ground directly and may flood the area around. Forest acts as a natural absorber of rainwater and allows it to seep down in the soil through the roots. Forests thus also help in maintaining the water table. (xii) Forests not only help in controlling floods but also help in maintaining the flow of water in the streams so that we get a steady supply of water. (xiii) They are a source of recreation and tourism. (xiv) Forests also control the noise pollution. The trees absorb the noise of the nearby traffic.

Useful plants and plant products

• Food (i) Cereals : Rice, wheat, maize, barley, etc. (ii) Pulses : Moong, gram, pea, urad, arhar, etc. (iii) Vegetables : Onion, potato, spinach, brinjal, radish, carrot, beetroot, etc. (iv) Fruits : Mango, apple, banana, grapes, pineapple, orange, etc. (v) Beverages: Tea, coffee, etc. (vi) Sugar: Sugarcane and sugarbeet (vii) Spices : Turmeric (haldi), pepper, chilli, clove (loung), etc. (viii) Oil seeds: Groundnut, coconut, mustard, etc.
• Clothing: We also get fibre from plants such as cotton, jute, linen, hemp, flux and ramie, which grow in forests.
• Medicines: Most of the medicines are obtained from plants. E.g., Quinine - Bark of Cinchona (cure for malaria)
• Timber or wood: [Furniture, housing, ship etc.] Trees such as sal, mahogany, teak and rosewood. We also get firewood from trees.
• Paper: Wood pulp of bamboos and eucalyptus.
• Rubber: For tyres, shoes, mattresses etc.
• Resins, Bamboo, Cane: Forests are also a source of resins (used to make varnish and paint); latex (used to make rubber); bamboo (useful as fodder and serves as an important raw material for the manufacture of paper and pulp, basket and other smallscale industries); and cane (used to make walking sticks, furniture, baskets, picture frames, screens and mats).
• Fuel
• Ornamental and landscape purposes A number of plants are grown in gardens and other places for aesthetic beauty.
• Oils: Many varieties of grasses such as lemon grass, vanilla, kewra, and khus are the sources of several kinds of essential oils. Sandalwood, eucalyptus and pine also give us oil, which can be extracted from the wood of these trees. These oils are used in making soaps, cosmetics, incenses, medicines and as an essence for flavour and smell in bakeries and confectioneries.
  
  Soil Erosion
• Other uses (i) Plants prevent soil erosion by wind or water. Removal of plants (deforestation) leads to soil erosion. Plants serve the purpose of binding the soil with the help of their roots. (ii) Certain plants like legumes enrich soil fertility.

4.0Interdependence of plants and animals

Living organisms are all interconnected and form a biotic community or biota. Forests help to conserve the diverse life forms or living organisms around the world. Plants prepare their own food and are called producers (autotrophic nutrition). Animals cannot produce their own food and have to consume plants or other animals to live and grow. Therefore, they are called consumers. Consumers may be herbivores or carnivores. Herbivores are animals which eat only plants. Some animals eat only other animals. They are called carnivorous animals. There is another category of animals called omnivorous animals. These animals eat both plants and animals.

Food chain and food web: All animals depend on plants for food directly or indirectly. For example, a rat eats grains and plants, a snake eats a rat, which is in turn eaten by an eagle. It is like a chain that exists in nature. Such a chain is called a food chain. Green plants are called the producers as they can produce their own food. Animals are called consumers since they cannot produce their own food and depend on plants and other animals for food.

When plants and animals die, their bodies breakdown (with the help of decomposers such as bacteria and fungi) and become a part of the soil. This makes the soil fertile helping in the growth of plants. These plants again become food sources for the animals. Thus, the food chain goes on and on. They exist everywhere, be it in the ocean, the grassland, desert or the mountain.

Food chain

Several food chains that exist in nature are interconnected. For example, a rat and a hen both eat grains. Both of them can be eaten by a cat. A cat can be eaten by a bigger animal such as a wolf. But a wolf can also eat a hen and a rat directly. There also exists a more complex representation of energy flow in nature. We call such a representation a food web, as it appears like a web that a spider spins.

Trophic levels : The distinct sequential steps in the food chain where transfer of energy occurs are referred to as different trophic levels.

Scavengers and decomposers

You might have seen vultures or crows eating dead animals. Animals that eat dead animals are called scavengers.

Dead plants and animals, fallen leaves, left-over food material rot after some days. This process of rotting is called decomposition. Certain living organisms like bacteria and fungi help in this process. Such organisms are called decomposers. Decomposers break down the organic matter of dead organisms into simple nutrients in the soil. This matter is called humus. From the soil, the nutrients are again absorbed by the roots of plants. In this way, cycling of nutrients takes place. Thus, a forest is a dynamic living entity as it consists of living organisms of different kinds performing different roles.

Balance in nature

For a living thing to survive, it must exist in a certain proportion and allow other living things to exist. Living things cannot afford to exist without any check. For instance, if there are too many lions, they will kill all the deer. On the other hand, if there are too many deer, they will eat too much grass and not leave any grass for the other animals. Thus, different living organisms must exist to survive.

5.0Dependence of animals on plants

Animals depend upon plants in various ways: For Food: All animals depend for their food directly or indirectly on green plants. For Oxygen: Plants give out oxygen during the process of photosynthesis. The oxygen, so liberated, is used by animals and plants for their respiration.

For Shelter: Some animals depend on plants for shelter. They make their homes in holes of the trees. Some birds build their nests in the trees. Many insects like grasshoppers, moths, ants, beetles etc, live in trees. Monkeys also live on trees.

6.0Dependence of plants on animals

For Carbon dioxide: Plants need carbon dioxide to prepare food through photosynthesis. This carbon dioxide comes from animals during respiration.

For Pollination: In some plants, pollination is brought about by insects, birds and bats. Without pollination, formation of seeds in these plants would not be possible. For Seed dispersal: Seed dispersal in many plants is through animals and even man. Fruits are eaten by animals such as the birds who carry them to distant places. Finally, the seeds are passed out in their egested waste without any damage.

Some seeds possess spines or hooks which enable them to stick to the body of animals and thereby helping them being carried from one place to the other. Finally, man himself is a great disseminator of seeds, especially of those which he uses, for his food and other needs.

7.0If forests disappear

We have learnt how forests are important to all living beings on the Earth. But what if these forests get destroyed? With the increase in human population, there have been ever-rising demands for converting forests into residential and agriculture areas. As a result, lots of trees are being felled and forests have been cleared, thus destroying the habitat of several species of animals and plants. Such large-scale falling of trees is called deforestation. Deforestation is the permanent destruction of forests and woodlands. (i) If forests get destroyed, global climate and local weather may change drastically. This will result in the loss of many species of animals and plants and biological diversity. (ii) Large amounts of greenhouse gases such as carbon dioxide are released into the atmosphere due to deforestation. (iii) Natural resources such as timber, medicinal plants, fruits and nuts are depleted due to deforestation. (iv) Deforestation can cause severe flooding, soil erosion, landslide, etc., affecting our day-to-day life. Our forests need to be protected from further depletion.

Afforestation: Large-scale planting of trees in deforested areas or for commercial purposes is called afforestation.

8.0Conservation of forests

Prevention of further depletion of forests is called conservation of forests. Few measures that could be followed to conserve our forests are given below :- (i) Afforestation: People living near forest areas should be made aware of the damages caused by felling of trees. They should be encouraged to cut branches, twigs, and leaves of the trees to meet their everyday requirements instead of chopping down the fullgrown trees. Government and communities should take steps to plant trees on a large scale. Trees that will meet the basic requirements of fuelwood, fodder and timber should be planted instead of falling the existing ones. (ii) Planned cultivation: People should be made aware that a forest should not be cleared of all its trees and converted to an agricultural land, as this can lead to soil erosion. (iii) Prevent illegal logging: Illegal logging has led to the decrease of a lot of trees over the years. The Indian government has laid out rules to prevent illegal logging by making it punishable under law. (iv) Prevent overgrazing: Provision of sufficient pasture should be made, especially in areas adjoining forests, to prevent overgrazing of growing plants by cattle. (v) Protection from forest fires: Forest fires can occur as a result of careless human activities, such as debris burning and campfires and lightning. These might cause damage to nearby housing and agricultural land. Forest fires are considered beneficial for plants but they might have devastating effects on the animal life and people living nearby. These forest fires can be prevented by being careful in burning debris. Fire retardants and water bombs are also used to prevent forest fires.

9.0Building Concepts

Explain why there is no waste in a forest?

• The forest floor is often littered with fallen decaying leaves, twigs, fruits and seeds. It is dark coloured and many saprophytic micro-organisms like fungi and bacteria grow on dead and decaying matter. They convert the dead plants and animals to humus and thereby return the nutrients to the soil.

How does forests help in purifying air?

• Forests are rich in plants and animals. All plants and animals take in air to survive. As we know, green plants take in carbon dioxide of the air to manufacture their own food (photosynthesis) and release oxygen as a by-product. Forests also serve as a sink for carbon dioxide given out by plants and animals during respiration, produced by burning coal and petroleum, given out as a result of volcanoes and other natural disasters. Thus, forests help to maintain the levels of oxygen and carbon dioxide of the air. Forests, especially rainforests, are referred to as the 'green lungs' of the Earth.

10.0SOME BASIC TERMS

• Canopy: Cover or roof formed by the tree branches in the upper regions is called a canopy.
• Crown : The branchy part of a tree above the stem is known as the crown of the tree.
• Decomposers : Living organisms like bacteria and fungi which help in the process of decomposition, such organisms are called decomposers.
• Deforestation : Large-scale falling of trees is called deforestation.
• Humus : Decomposers break down the organic matter of dead organisms into simple nutrients in the soil. This matter is called humus.
• Seed dispersal : Process of transportation of seeds to new places for germination.
• Soil erosion : Removal or thinning of top layer of soil is called soil erosion.
• Understorey : Horizontal layers present at different heights below the canopy are known as understorey.