Class 8 Science Chapter 12: How Nature Works in Harmony

Elephants in a Sugarcane Field

In Assam, Chhattisgarh, Jharkhand, Odisha and West Bengal, elephants sometimes walk out of the forest and into farms. They are not lost. When the plants they feed on grow scarce and the waterholes dry up, they go looking, and a field of bananas or sugarcane is food. Crops are damaged and sometimes people and cattle are hurt.

The Chain Behind It

Pull the story backwards and it is a chain. Rainfall and temperature change, so the plants change. Trees are felled for roads and buildings, so the forest shrinks and dries. The forest is the elephants' home, and when a home gets smaller its occupants move. The animals did not choose to come near us; the forest came apart.

Corridors

Wildlife ecologists have marked corridors across the country - strips of land that join one large forest to another, so an animal can cross between them without walking through a village. It is a repair made by understanding the chain rather than by fencing the symptom.

What a Habitat Is

A habitat is simply the place where an organism lives. That sounds too simple to be useful until you notice how small a habitat can be: the bark of a single tree is a habitat, and so is a pond, a farm, a forest or one old banyan.

Two Kinds of Component

Stand in any habitat and list what you can see. Some of it is alive - fish, grass, birds, trees - and some of it is not: water, soil, air, sunlight, temperature. The living things are called the biotic components and the non-living things the abiotic components.

Both Lists Matter

A fish in a pond needs both. Its food comes from small living things round it around it, which is biotic. The oxygen it breathes is dissolved in the water, which is abiotic. Take either list away and nothing survives, which is why both are counted as components of the habitat rather than one being the setting for the other.

A Pond Is Crowded

A pond is not only fish. Frogs, turtles, snakes, dragonflies, mosquitoes, snails and ducks live there, and so do algae, diatoms, duckweed and lotus. Every one of them is interacting with the others and with the water, the mud and the light.

What a Habitat Provides

Four things, and a habitat that is short of any of them supports less life: space to grow in, shelter, oxygen and food. Different habitats offer these in different amounts and in different forms, which is why some organisms live in water and others on land.

Why Not Everything Lives Everywhere

Every organism needs particular conditions. A fish needs oxygen dissolved in water and cannot take it from the air; a cactus needs long dry spells that would kill a water lily. So the question "why does this live here?" always has the same shape of answer: because here is what it needs.

The Same Habitat, Different Conditions

Here is the part that is easy to miss. A forest can be warm by day and cool by night. A rodent active in the daytime and a snake that comes out after dark share one habitat and yet meet quite different conditions in it. The habitat is one; the experience of it is not.

Different Organisms, Different Uses

For the same reason, two organisms in one habitat may use the same resources quite differently - at different hours, at different heights, in different quantities. That is a large part of how so many kinds manage to live in one place without constantly getting in each other’s way.

Living Together Without Clashing

This is what is meant by saying that organisms coexist in harmony. It does not mean nothing is eaten and nothing competes. It means the conditions and the resources are divided up finely enough that many kinds can be supported at once.

Looking at Two Habitats Side by Side

Compare a pond with a forest and two things come out. Both have a biotic list and an abiotic list - that is the similarity. And both lists are different in each - that is the difference. Those two sentences together are most of what this topic is about.

Why Any of This Matters

Because the elephant story is the same idea read backwards. The abiotic components changed - rainfall, temperature - and the biotic ones followed: fewer plants, less food, animals on the move. Nothing in a habitat can be altered on its own.

What to Carry Forward

A habitat is where an organism lives, and it can be as small as a piece of bark. Its components are biotic and abiotic. A habitat provides space, shelter, oxygen and food. And two organisms sharing one habitat can still live in quite different conditions inside it.

Scenario:

A school is given money to improve the pond in its grounds. The committee clears the duckweed and the algae because they look untidy, concretes the muddy edges so nobody slips, and cuts back the reeds along one side. The water looks much clearer afterwards and everyone is pleased. Within three months the fish are fewer, the frogs have gone and the pond smells. A pupil is asked to explain what happened, and begins by saying that nothing living was removed except some weeds.

Analysis:

Three of the four things a habitat must provide were taken away, and most of them were not obvious. The duckweed and algae were biotic components and also the base of the food supply. So clearing them cut the food the small animals lived on and the fish fed on in turn. The reeds were shelter, and without them the frogs had nowhere to hide. Concreting the edges removed the mud, which looks like a cosmetic change and is not: the mud was an abiotic component that many small living things lived in. Only space to grow was left intact. The pupil’s sentence is the error worth naming - weeds are living things, and in a pond they are the part everything else is built on.

Activity:

Look at a pond or a water tank near you and list what in it is biotic and what is abiotic before anything is cleared.

Title:

Try it at home: two habitats, two lists

Safety:

Go in a group with your teacher or an adult, do not put your hands into water you cannot see the bottom of, and touch no animal.

What You Notice:

Both habitats turn out to have a living list and a non-living one. And the contents of both lists differ between them. The afternoon visit usually adds names to the living list, which is the clearest sign that one habitat can offer different conditions at different hours.

The bark of one tree counts as a habitat, with its own living things and its own conditions, which means a single forest holds thousands of habitats inside it.

A pond holds algae, diatoms, duckweed and lotus as well as fish, frogs, turtles, snakes, dragonflies, snails and ducks - the plant list is as long as the animal one.

Elephant corridors are mapped by wildlife ecologists rather than drawn on a plan, because the route has to be one the animals already use.

Bio is alive, a-bio is not — The prefix does the work. Biotic names the living part of a habitat and abiotic the part that is not alive, and every component belongs to exactly one list.

Food, oxygen, shelter, space — The four things a habitat has to supply. If you can name all four you can say why a particular organism lives where it does.

One Fish, or Many?

Look into a pond and you rarely see a single fish of a kind. You see a group of them. A group of organisms of the same kind, living in one habitat at one time, is called a population. The words "same kind" and "at one time" are both doing work in that sentence.

Counting a Population

You can measure one. Mark out a square a metre on each side in a garden, choose a kind of plant, and count the individuals inside the square. Twenty of one plant and five of another in the same square means two populations of very different sizes sharing one patch of ground.

What If Only One Kind Lived There?

Suppose a habitat held just one kind of organism. Every individual would need exactly the same food, the same water and the same space at the same time. The result would be competition, and before long scarcity. Variety is not decoration; it is part of how a habitat keeps working.

A Community

Different populations sharing one habitat make up a community. All the plants, all the animals and all the microorganisms of a place, taken together, are its community - which means a community is built entirely out of biotic components.

A Flower, in Passing

Since the next idea runs through flowers, it is worth naming their parts. A flower carries a stalk, green sepals shaped like small leaves, coloured petals, and the two parts used in reproduction - the female carpels and the male stamens. Stamens burst and release a yellow dust called pollen.

Who Carries the Pollen

Wind, water, insects, bats and birds carry pollen from the stamens of one flower to the carpels of the same or another flower. That carrying is pollination, and without it there would be no fruit and no seed.

Two Ponds

Now the experiment. Researchers watched two ponds: pond A had fish and a great many flowering plants around it; pond B had no fish and fewer flowering plants. The puzzle is why the presence of fish in the water should have anything to do with flowers on the bank.

Counting the Dragonflies

Pond A, with fish, had fewer dragonflies than pond B. The reason is direct: fish eat dragonfly larvae, so a pond with fish grows fewer dragonflies. Nothing surprising yet.

Following the Chain Upward

But dragonflies eat flies, bees and butterflies. Fewer dragonflies therefore means more bees, flies and butterflies - and those insects are pollinators. More pollinators means more pollen moved from flower to flower, which means more seeds. That is why flowers beside a pond with fish may set more seed.

Direct and Indirect

Two kinds of effect are at work here. The fish eat the larvae directly. The fish affect the flowers indirectly, through two steps in between. A direct effect is easy to see; an indirect one has to be traced, and it can be just as large.

So Overfishing Reaches the Bank

Read the chain backwards and a practical question appears. If people take too many fish out of pond A, dragonflies increase, pollinators fall, and the flowers on the bank set less seed. An action taken in the water changes the plants on the land.

Three Kinds of Interaction

Sort the interactions in any habitat and there are three sorts. Between a living thing and a non-living one: earthworms live in moist soil. Between two non-living ones: sunlight raises the day temperature, and makes water evaporate faster. And among living things: a frog eats insects, or two kinds compete for the same larvae.

What an Ecosystem Is

Put it together. The biotic components of a habitat and its abiotic components, interacting with one another, make an ecosystem. It is the interaction that is being named, which is why an ecosystem is more than a list of what is present.

Big, Small, and Overlapping

Ecosystems come in all sizes. Aquatic ones include ponds, rivers and lakes; terrestrial ones include forests, farms and even one large banyan or mango tree. A farm is a human-made ecosystem. They overlap, too: a river running through mountains, forest, grassland and farmland is several ecosystems touching at once.

From an Individual Upward

So there is a ladder. One organism is an individual. Many of its kind in one place at one time are a population. Several populations together are a community. The community plus the non-living surroundings it interacts with is an ecosystem. And the dependence runs both ways - plants release oxygen, roots hold soil in place, and leaves keep moisture and cool the air.

Scenario:

A village pond is used for washing and for a small amount of fishing, and mustard is grown in the field beside it. A committee decides to take out almost all the fish in one season to raise money for a new pump. The following year the mustard field yields noticeably less seed, and the farmers blame the weather, which was much as usual. One member points out that there are far more dragonflies over the pond than anybody remembers. And another says dragonflies have nothing to do with mustard.

Analysis:

The dragonflies are the link, and the chain has three steps. Fish eat dragonfly larvae, so while the fish were there the dragonfly population was held down. Removing the fish removed that check, which is why there are now so many dragonflies - and that part is a direct effect. Dragonflies eat flies, bees and butterflies, so more dragonflies means fewer of those insects. Those insects are the pollinators that carry pollen from a stamen of one mustard flower across to a carpel of another. And without enough of them fewer flowers are pollinated and fewer seeds are set. So the mustard yield fell because of a decision taken in the water, two steps away. It is the same study the chapter describes, read backwards: ponds with fish had more seeds nearby, so a pond stripped of fish has fewer.

Activity:

Count the dragonflies over a pond and the bees on a nearby flowering plant on the same morning, and repeat it a month later.

Title:

Try it at home: count a population in one square metre

Safety:

Mark the square where you have permission to, do not pull any plant up to count it, and touch no animal.

What You Notice:

Each kind you counted is a population. So your square holds four of them and together they are part of that patch’s community. The month-later count is usually different, which is why a population is always recorded at a particular time.

Bats carry pollen as well as insects and birds do, which is why some flowers open only after dark.

A square just one metre on each side is enough to measure a plant population, which makes this one of the few pieces of ecology you can do with a piece of string.

A single large banyan or mango tree is counted as a terrestrial ecosystem in its own right, because so much lives on and in it.

One, many, mixed, and the setting — The ladder in four words. An individual is one. A population is many of one kind. A community is many kinds mixed. An ecosystem is the community plus the non-living setting it works with.

Fish, larvae, pollinators, seeds — The two-pond chain in order. Each arrow is easy; it is the length of the chain that hides the result.

Who Makes the Food

Start with the plants. A green plant makes its own food by photosynthesis, so it does not have to find any. Organisms that can do this are called producers, or autotrophs - auto meaning self and troph meaning food. Every chain of eating begins with them.

Who Has to Find It

Nothing else can. An animal, a fungus or a microbe cannot make food inside itself and must take it from other organisms. Such organisms are consumers, or heterotrophs, from hetero meaning other. Deer, leopards, crows and mushrooms are all heterotrophs, however different they look.

Three Kinds of Consumer

Sort the consumers by what they eat. Those that eat only plants and plant products are herbivores - a deer, a hare. An animal that takes only other animals is a carnivore - a leopard. Those that eat both are omnivores, and crows, foxes and mice belong here.

A Food Chain

Write the eating down as a line and you have a food chain: a simple sequence showing who eats whom. A hare eats the grass, and a leopard then takes the hare. The arrows run in the direction the food travels, from the eaten to the eater.

A Longer One

The same grassland gives a longer chain: grass, then a grasshopper, then a frog, then a snake, then an eagle. Five links, and each link depends on the one before it. Remove the grass and every animal above it is in trouble.

Trophic Levels

Each position in a chain has a name - a trophic level, from the same troph. Producers such as green plants occupy the first level. A hare or a deer, eating only plants, is at the second. Small carnivores such as frogs are at the third, and large carnivores like tigers or vultures at the next.

Counting the Numbers

Now count rather than name. In a crop field of millet, mice and eagles, the millet plants are many, the mice fewer, the eagles fewest. Arrange the numbers with the largest at the bottom and the smallest at the top and the shape you get is a pyramid.

Why a Pyramid and Not a Column

The shape is not decoration. It takes a great many millet plants to keep a smaller number of mice alive, and a great many mice to keep a very small number of eagles. Each level supports a smaller one above it, which is why the top of a chain is always thinly populated.

Chains Do Not Stay Separate

Real eating is untidier than a line. A mouse may be taken by an owl, a snake or a fox. A grasshopper is eaten by a bird, a frog and a mouse. So the chains of an ecosystem cross one another constantly.

A Food Web

Those crossing chains, taken together, make a network called a food web. It is the same information as the chains and it is a truer picture, because it shows that most organisms are connected to several others rather than to one.

Why the Web Matters

A web is harder to break than a line. If one prey animal becomes scarce, a predator in a web may have something else to turn to, while a predator at the end of a single chain has nothing. Variety in a web is a kind of insurance.

What Happens to the Dead

Organisms grow, function, and die, and they leave waste and dead matter behind all their lives. Walk through a forest after the rains and you may see mushrooms - small umbrella-shaped fungi - growing on dead wood. They are feeding on it.

Decomposers

Fungi and bacteria break the complicated substances inside dead plants and animals down into simple ones, and that returns important nutrients to the soil. The process is decomposition and the organisms that carry it out are decomposers, or saprotrophs, from sapro meaning rotten.

Not Only Microbes

Small insects do this work too. Look at animal droppings - elephant dung, for instance - and you will find beetles and flies breaking it down and putting its nutrients back into the soil. Plants then grow in that soil, and much of what feeds a plant there came from exactly this process.

Nothing Is Wasted

That is the sentence to keep. The nutrients in every dead leaf and every carcass are returned and used again. There is no waste in nature in the sense we mean the word - only material on its way back to the soil and up into the next generation of plants. It is worth noticing how different that is from what we do with our own waste, which mostly leaves the cycle rather than rejoining it. A forest floor has no heap of old leaves from previous years because the decomposers have already taken them apart, and the plants growing there are built partly out of what those leaves used to be.

Scenario:

A fruit orchard has an old barn where barn owls have nested for years. The barn is pulled down to make a shed, and the owls leave. Within two seasons the orchard has far more mice than before, and the mice are stripping bark from the young trees. The owner buys poison for the mice. A neighbour warns him that the snakes and the foxes in the hedge will eat the poisoned mice, and that he will then have even fewer animals eating mice than he has now. The owner replies that mice are the problem and the owls were only one bird.

Analysis:

Both of the neighbour’s points follow from reading the orchard as a web rather than a chain. A mouse there is prey for owls, snakes and foxes. So removing the owls took away one of three checks and the mouse population rose - that is why the bark is being stripped. The web is what made the orchard resilient in the first place, because losing one predator did not leave the mice unchecked altogether. Poison is the part that would do real damage. The snakes and foxes feeding on poisoned mice are taking the poison in with their food, so the remaining two checks would weaken as well. And the mice would end up with fewer predators than before the barn came down. The owner’s sentence - that the owls were only one bird - is exactly the mistake. In a web every connection is one of several, and the value of the others is what you lose by poisoning along the chain.

Activity:

Draw the orchard as a web with the mouse in the middle, and mark which arrows the poison would reach.

Title:

Try it at home: build a food web from your own plate

Safety:

This is a paper activity, so the only care needed is to check your facts before drawing an arrow.

What You Notice:

Every arrow you can draw traces back to a producer, because nothing else makes food. Once you add the other eaters your lines stop being a chain and start being a web, which is the truer picture. And your own name turns out to be one node in it rather than the top of a line.

Many migratory birds come to India each winter, and besides pollinating and spreading seeds along their route they eat insect pests, which helps farmers without any cost to them.

Demoiselle Cranes spend the winter months at a lake at Khichan, in Jodhpur district, which is one of the best known gatherings of migratory birds in the country.

A mushroom growing on a dead log is not decorating it; it is feeding on it, which is why mushrooms appear after the rains when the wood is soft.

Auto is self, hetero is other — Autotrophs make their own food; heterotrophs take it from others. Troph means food in both words, and in trophic level and saprotroph as well.

Wide at the bottom — Many millet plants, fewer mice, fewest eagles. Numbers fall as you climb a chain, which is why the drawing is a pyramid and never a column.

One Change Does Not Stay One Change

Pollution reaches a pond and many of its plants die. That is the whole of the first event, and the rest of it follows from there. Fewer plants means less oxygen produced in the water. Less oxygen means the fish population drops.

Following It Out of the Pond

Fish are consumers, so fewer fish means fewer things eating insects, and the insects multiply. Insects do not stay over the water; they spread to the farmland nearby. The farmers there now have a pest problem and reach for pesticides, which bring harms of their own to the soil and the water. One dose of pollution, and the consequences are still arriving.

Why This Is Called a Cascade

Each step is small and reasonable on its own. Nobody decided that pond pollution should lead to pesticide on a field. The chain did it, one sensible link at a time, which is exactly why a change made in one place has to be thought about in several.

Frog Legs, in the 1980s

A real case. In the 1980s India exported frog legs in quantity, particularly of the Indian bullfrog, and the harvesting was on a large scale. Frog populations fell sharply, which is the obvious and intended cost.

What Nobody Had Priced In

Frogs eat insects. With far fewer frogs, agricultural pests rose, and farmers answered with more synthetic pesticides. Those pesticides damaged the soil and the water and harmed the environment and the health of people. The Government of India forbade the frog-leg trade to stop any further ecological damage.

Balance, and What Kind of Thing It Is

An ecosystem is in balance when the dealings between its organisms and their surroundings keep populations and resources steady. The word steady is doing careful work here, because this balance is dynamic rather than fixed - it holds by constant adjustment, not by nothing happening. Natural events can disturb it and so can human ones. The pond and the bullfrog are both examples of the human kind, and they are the kind this chapter keeps returning to, because they are the kind we can choose not to make.

Competition

Feeding is not the only interaction. Organisms also compete for the resources they share - food, water, physical space, sunlight. Competition sounds destructive, and it is in fact one of the things that keeps an ecosystem steady.

Why Competition Helps

It controls population size. Without it, one kind could multiply until it crowded out the rest, and the result would be imbalance rather than abundance. A check on growth is not a problem to be solved; it is part of how the system holds.

Three Named Relationships

Besides competition there are three relationships worth naming, and the way to tell them apart is to ask who gains and who loses.

Mutualism

Both organisms benefit. A honeybee visits a flower: the bee gets nectar and the flower gets pollinated. Each of them leaves the encounter better off, which is why mutualism is the easiest of the three to remember.

Commensalism

One benefits and the other is unaffected. An orchid growing on a tree branch gets physical support and a place in the light; the branch is neither helped nor harmed by it. Nothing is being taken from the tree.

Parasitism

One benefits and the other is harmed. A tick on a dog feeds on the dog’s blood and the dog gets skin irritation. The tick gains and the dog loses, which is the whole difference from the orchid.

Telling the Three Apart

Ask two questions in order. Does the first organism gain? Does the second one gain, lose, or neither? Both gain is mutualism. One gains, the other neither is commensalism. One gains, the other loses is parasitism.

Johnsingh, and Why Prey Matter

A.J.T. Johnsingh was an Indian wildlife biologist who studied forests through the eyes of the animals in them, and was a pioneer of modern tracking methods. Working in Bandipur National Park in Karnataka, he showed that predators such as tigers and leopards depend on prey animals such as the deer and the wild boar - and that a predator survives only where its prey is plentiful, so a predator’s survival.

Protect the Deer

That finding changes what protection means. Guarding a tiger from hunters is not enough if the deer and wild boar it lives on are disappearing, because a predator cannot survive a shortage of prey however well it is watched itself. So protecting the deer is a way of protecting the tiger, and the whole food web of a reserve has to be looked after rather than its most famous animal. Johnsingh’s work inspired a generation of younger people to study wildlife and to guard the forests of India and the variety of life in them.

Scenario:

A lake used for fishing becomes choked with water weed, and the municipality sprays a weedkiller to clear it. The weed dies back in a fortnight and the surface looks clean. Over the next two months the fish catch falls sharply, and mosquitoes over the lake become bad enough that the nearby colony complains. The municipality proposes spraying an insecticide next. A science teacher at the local school objects that the second spray is the first mistake repeated, and that the council should look at what the weeds were doing before they were killed.

Analysis:

The teacher is reading the lake as a cascade. The weeds were plants, so they were producing oxygen in the water and they were also the base of its food. Killing them meant less oxygen and less food, so the fish population dropped - which explains the catch. But fish eat insect larvae, so fewer fish left the mosquitoes unchecked, and that explains the complaints from the colony. This is the chapter’s pond cascade almost exactly: plants die, oxygen falls, fish die, insects rise. The proposed insecticide would repeat the error because it treats the last link as the problem. It would also reach the few fish that are left, weakening the one check on mosquitoes that the lake still has. That is the same shape as the frog-leg case, where removing an insect-eater led to more spraying rather than less.

Activity:

Draw the lake as a chain of five boxes and mark where each of the two sprays would act.

Title:

Try it at home: who gains and who loses, in your own street

Safety:

Go with an adult, look rather than touch, and keep well clear of any animal that is not yours.

What You Notice:

The pairs are easy to spot and the names are the hard part, which is the point of filling the middle two columns first. Most of the undecidable ones turn out to need one piece of information: whether the second organism is paying anything at all. That single question separates commensalism from parasitism.

A.J.T. Johnsingh was a pioneer of modern wildlife tracking in India, and his work at Bandipur National Park in Karnataka showed that a predator survives only where its prey is plentiful, so a predator’s survival.

The ban on exporting frog legs was brought in because of the knock-on effect on crops, not only because the frogs themselves were disappearing.

Competition is often described as harmful, but it is one of the things that keeps any one kind from multiplying until it crowds out the rest.

Both, one, or one at a cost — Mutualism: both gain. Commensalism: one gains, the other neither. Parasitism: one gains and the other loses. Ask who gains and who loses and the three sort themselves out.

Bee, orchid, tick — One example each, in the order of the three names. The bee and flower both gain, the orchid gains and the tree does not mind, the tick gains and the dog suffers.

What a Forest Hands Over

Begin with the list, because it is longer than people expect. A forest gives timber, medicines, food, fibres, fertile soil and fresh medicines. An aquatic ecosystem gives water and food. Both also give something harder to price: places that are pleasant to be in and worth going to see.

Why the List Matters

Every item on it is produced by the interactions in the chapter so far - plants releasing oxygen, decomposers making soil fertile, food chains carrying energy upward. The benefits are not a separate topic. They are what a working ecosystem looks like from our side of it.

The Sundarbans

Take one case. The Sundarbans hold the largest mangrove forest in the world, where the Ganges and the Brahmaputra meet, spread across India and Bangladesh. Its forests and rivers are home to a great variety of plants and animals, many of them endangered.

What the Mangroves Do for Us

They slow the waves and the strong winds a storm or a flood brings, which protects the land and the people behind them. The trees also take in carbon dioxide and release oxygen. The Sundarbans were listed by UNESCO as a World Heritage Site in 1987 because of that importance.

And What Is Being Done to Them

Mangrove trees are cut for farmland and for fuelwood. Illegal hunting, and the overuse of forest resources threaten the wildlife. Industrial waste and untreated sewage in the rivers damage both the water and the habitat. The protection the forest gives is being removed by the people it protects.

The Same Story Elsewhere

Ecosystems across India are under similar pressure - rivers, wetlands, grasslands, forests, scrublands and the coasts. The causes repeat: deforestation, the overuse of natural resources, pollution, unsustainable land use and invasive species.

Protected Areas

One answer is to set land or water aside. India has biosphere reserves, national parks, wildlife sanctuaries and community conserved areas, and the point of them is that they protect whole habitats rather than single animals - endangered mammals, birds and rare plants together.

Some of Them by Name

Pirotan Island Marine National Park in Gujarat, Keibul Lamjao National Park in Manipur, and Hemis National Park in Leh. Eaglenest Wildlife Sanctuary in Arunachal Pradesh, Chilika Lake in Odisha, and the Nilgiri Biosphere Reserve in the Western Ghats. Manas National Park in Assam, and Jim Corbett National Park in Uttarakhand. People also make ecosystems of their own.

Ecosystems We Build

Fish ponds, farms and parks are all of them. Designed well they can reduce pollution, support a variety of living things and give people somewhere to go. Unlike a forest, they need human care and management to keep working.

A Farm Is One of Them

Farming is a major livelihood in India and a farm is a human-made ecosystem, which means it can be managed well or badly. From 1950 to 1965 India was short of food because its crops yielded too little, and the answer transformed farming.

The Green Revolution

From the middle of the twentieth century, tractors, machines, synthetic fertilisers and pesticides raised food production sharply. That period is called the Green Revolution, and it helped make India food secure. The methods, though, are now considered unsustainable.

Three Reasons They Are Unsustainable

Too much synthetic chemical. Too much groundwater drawn out. And growing only one kind of crop for sale, which is called monoculture. Each of the three has turned out to cost something that was not counted at the time. Take the first. Overusing fertiliser lowers fertility, which sounds contradictory until you see how: the friendly microorganisms in the soil decrease and the organic matter called humus falls. Humus binds soil particles together, so without enough of it the soil washes away easily, and the fertility that is lost is the soil itself.

What It Does to the Living Things

The population of natural predators drops, and with fewer predators the pests increase - so more pesticide gets used. Heavy irrigation and repeated ploughing disturb earthworms and snails, which matter for keeping the balance. Some pests also develop resistance, which makes them harder to control at all.

And What Monoculture Costs

Growing the same crop repeatedly reduces the variety of living things and affects pollinators, which food production itself depends on. So a practice adopted to raise yield ends by removing something the yield needs.

The Way Back

Some farmers are therefore turning to organic and natural methods, which aim to use less synthetic fertiliser and to interfere as little as possible with the natural system the field sits in. The idea is not new. The ancient text Vrikshayurveda urges feeding the soil continuously with organic manure such as Kunapa Jala - a liquid manure fermented out of animal and plant waste, which breaks complex substances into simpler ones, exactly as decomposers do.

Scenario:

Two farmers on one road grow the same crop. One has used synthetic fertiliser and pesticide heavily for fifteen years and plants nothing else, and pumps groundwater freely in the dry months. The other uses compost, rotates three crops, and keeps a hedge along one side. Both had similar yields a decade ago. Today the first field yields less than it did, its soil runs off the surface in the first heavy rain, and its pests need a stronger spray every year. The first farmer says the difference must be the weather, since the two fields get the same rain.

Analysis:

The weather is the same, so the difference is in how each field has been managed. And each of the three symptoms has a named cause in this topic. The falling yield and the running soil go together: heavy fertiliser use reduces the friendly microorganisms and lowers the humus. And humus is what binds soil particles, so a field short of it loses its topsoil to the first heavy rain. The stronger spray each year is two things at once. Pesticide reduces the natural predators of the pests, so the pests increase, and some of them develop resistance, which makes them harder to control than before. Planting nothing else is monoculture, which reduces variety and affects the pollinators the crop needs. The second farmer has done the opposite in each case: compost returns organic matter, rotation avoids monoculture, and the hedge keeps habitat for predators and pollinators. The groundwater is the fourth difference and the one neither field can see yet.

Activity:

Compare two patches of soil - one from a flower bed with compost dug in, one from bare ground - by pouring the same water through each and looking at what comes out.

Title:

Try it at home: test two soils for how well they hold

Safety:

Cut the bottles with an adult, and keep the muddy water off anything you cannot wash.

What You Notice:

The composted soil holds more water and lets far less soil through. The organic matter in it - the humus - is binding the particles together. The bare soil drains fast and the water comes out cloudy, which is the same soil loss a field suffers when heavy fertiliser use has lowered its humus.

Complex substances are broken into simpler ones by Kunapa Jala, a fermented liquid made from animal and plant waste, and the ancient text Vrikshayurveda urges feeding the soil with organic manure of that kind.

Keibul Lamjao National Park in Manipur and Pirotan Island Marine National Park in Gujarat are protected areas of very different kinds - one floating on a lake, the other in the sea.

Some pests develop resistance to pesticides, so a field that is sprayed heavily can end up with pests that are harder to control than the ones it started with.

Timber, medicine, food, fibre, soil, air — Six things a forest hands over, and every one of them is produced by the interactions in this chapter rather than by the forest sitting there.

No humus, no hold — Humus binds soil particles together. Overusing fertiliser lowers it, and soil without enough humus washes away.