1. The environment and its functions
The environment is the total planetary inheritance: all biotic elements (plants, animals, micro-organisms, people) and abiotic elements (air, water, sunlight, soil minerals) and the links between them.
Four functions
- Supplies resources: renewable (forests, fish, groundwater) and non-renewable (coal, petroleum, ores).
- Assimilates waste: breaks down and absorbs what production and consumption throw away.
- Sustains life: genetic diversity and biodiversity keep ecosystems working.
- Provides aesthetic services: scenery, clean rivers, mountains that people enjoy.
| Biotic (living) | Abiotic (non-living) |
|---|---|
| Plants and trees | Air |
| Animals, birds, fish | Water |
| Micro-organisms in soil and water | Sunlight |
| Human beings | Soil minerals, rocks |
Key terms
- Biotic elements
The living parts of the environment.
- Abiotic elements
The non-living parts of the environment, such as air, water and sunlight.
2. Limits: absorptive capacity, carrying capacity and the crisis
- Absorptive capacity: how much degradation (waste, pollution) the environment can take in and neutralise.
- Carrying capacity is maintained only if (a) resources are extracted within their rate of regeneration and (b) wastes stay within the absorptive capacity.
- Renewable resources last if used within regeneration; non-renewable ones run out with use.
Why there is a crisis now: in earlier times, supply of environmental resources and services was far greater than demand. Population growth, industrialisation and higher consumption have reversed this: demand now exceeds supply, and overuse has reduced supply further.
| Renewable | Non-renewable | |
|---|---|---|
| Meaning | Replenished by nature; usable again if use stays within regeneration | Formed over very long periods; exhausted with use |
| Examples | Forests, fish, groundwater, solar and wind energy | Coal, petroleum, natural gas, metal ores |
| Risk | Exhausted if used faster than it regenerates | Runs out; substitutes needed |
Key terms
- Absorptive capacity
The ability of the environment to absorb degradation.
- Carrying capacity
The ability of the environment to keep supporting life, which holds when extraction stays within regeneration and waste within absorptive capacity.
- Renewable resource
A resource replenished by nature, exhausted only if used faster than it regenerates.
- Non-renewable resource
A resource exhausted by use, such as coal or petroleum.
3. State of India's environment and the cost of degradation
India has rich soil, rivers, forests, minerals and biodiversity, but faces serious threats (stated here without statistics):
- Land degradation: loss of forest cover, shifting cultivation without enough fallow, overgrazing, unsustainable fuelwood and fodder use, excessive agrochemicals, and poor irrigation management causing waterlogging and salinity.
- Loss of biodiversity as forests and wetlands shrink.
- Air pollution, mainly in cities, from vehicles, industry, thermal power and burning of waste.
- Water pollution of rivers and groundwater from sewage, industrial effluents and farm run-off.
Opportunity cost: spending on treating pollution-related illness, on lost workdays and on cleaning rivers or reclaiming land is money not available for schools, roads or jobs. India set up pollution control boards (the Central Pollution Control Board dates from 1974) to monitor and regulate pollution.
| Threat | Main causes | Who is hurt |
|---|---|---|
| Land degradation | Deforestation, overgrazing, agrochemicals, waterlogging | Farmers, through lower yields |
| Loss of biodiversity | Shrinking forests and wetlands, poaching | Everyone: weaker life-support |
| Air pollution | Vehicles, industry, power plants, burning waste | City dwellers' health |
| Water pollution | Sewage, industrial effluents, farm run-off | People who drink and fish |
| Cost (imagined family, a year) | Working | ₹ |
|---|---|---|
| Medicines for stomach illness | — | 3,600 |
| Wages lost | 4 days × ₹600 | 2,400 |
| Water filter and boiling fuel | — | 1,800 |
| Total cost of dirty water | 7,800 |
Key terms
- Land degradation
A fall in the quality and productivity of land through erosion, salinity, waterlogging or chemical damage.
- Opportunity cost of degradation
The best alternative use of the money and resources spent on coping with environmental damage.
4. Global warming and ozone depletion
Global warming: a gradual rise in the average temperature of the earth's lower atmosphere, caused by more greenhouse gases (carbon dioxide, methane and others) from burning fossil fuels and from deforestation. Likely effects: melting glaciers and polar ice, rising sea levels, more extreme weather, damage to farming, and the spread of tropical diseases.
Ozone depletion: thinning of the ozone layer in the stratosphere, mainly by chlorofluorocarbons (CFCs) and halons. More ultraviolet radiation then reaches the earth, raising the risk of skin cancer and cataract and harming plankton and crops.
International response: Montreal Protocol (1987) on ozone-depleting substances; Kyoto Protocol (1997) on emission cuts by industrialised countries; Paris Agreement (2015), under which every country prepares its own plan to limit warming.
| Agreement | Year | Deals with |
|---|---|---|
| Montreal Protocol | 1987 | Phasing out ozone-depleting substances such as CFCs |
| Kyoto Protocol | 1997 | Emission cuts for industrialised countries |
| Paris Agreement | 2015 | National plans by all countries to limit warming |
Key terms
- Greenhouse gases
Gases such as carbon dioxide and methane that trap heat in the atmosphere.
- Ozone layer
A layer in the stratosphere that filters out most ultraviolet radiation.
5. Sustainable development and Daly's principles
Meaning (paraphrasing the Brundtland Commission, 1987): development that meets the needs of the present generation without reducing the ability of future generations to meet their own needs. It does not mean zero growth; it means growth that respects carrying capacity.
Herman Daly's principles (paraphrased):
- Keep population at a level within the carrying capacity.
- Make technology input-efficient, not input-consuming.
- Harvest renewable resources no faster than they regenerate.
- Deplete non-renewable resources no faster than renewable substitutes are created.
- Correct the inefficiencies caused by pollution.
| Principle (paraphrased) | What it means in practice |
|---|---|
| Population within carrying capacity | Numbers the environment can support |
| Input-efficient technology | More output from fewer resources |
| Renewables: harvest within regeneration | Catch, fell or pump no more than nature replaces |
| Non-renewables: deplete no faster than substitutes appear | Build solar or wind as coal is used up |
| Correct pollution | Treat waste; fix inefficiencies |
| Step | Working (imagined village bamboo grove) | Result |
|---|---|---|
| Sustainable limit | Equal to yearly regrowth | 800 poles |
| Present demand | Poles cut now | 1,000 poles |
| Cut needed | 1,000 − 800 | 200 poles |
| As a percentage | 200 ÷ 1,000 × 100 | 20 per cent |
Key terms
- Sustainable development
Development that meets present needs while leaving future generations able to meet theirs.
- Input-efficient technology
Technology that produces more output from fewer resources.
6. Strategies for sustainable development
- Non-conventional energy: solar photovoltaic cells, wind turbines and mini-hydel plants on hill streams.
- Cleaner fuels: LPG and gobar gas in rural kitchens (less smoke, fewer trees cut; slurry as manure); CNG in urban transport (cleaner air).
- Traditional knowledge: mixed cropping and manure in farming, medicinal plants, climate-suited housing, tanks and step-wells for water.
- Biocomposting: earthworms and composting turn organic waste into manure.
- Biopest control: neem-based sprays and natural predators (owls, snakes, birds) instead of chemical pesticides.
Growth and care for the environment can go together when costs of degradation are counted and resources are used within nature's limits.
| Source | How it works | Best suited to |
|---|---|---|
| Solar (photovoltaic) | Cells turn sunlight into electricity | Rooftops, schools, remote villages |
| Wind | Turbines turn wind into electricity | Windy coasts and ridges |
| Mini-hydel | Small turbines on stream flow | Hilly areas, nearby villages |
| Switch | Where | Gain |
|---|---|---|
| Firewood → LPG or gobar gas | Rural kitchens | Less smoke indoors; fewer trees cut |
| Diesel → CNG | City buses and autos | Cleaner city air |
| Area | Traditional practice | Why it is sustainable |
|---|---|---|
| Farming | Mixed cropping, natural manure | Soil stays fertile; fewer pests |
| Health | Medicinal plants | Local, low-waste remedies |
| Housing | Local materials, climate-suited design | Less energy for cooling or heating |
| Water | Tanks, step-wells, check dams | Rainwater stored and recharged |
Key terms
- Mini-hydel plant
A small hydroelectric plant using the flow of a stream to supply nearby areas.
- Biopest control
Controlling pests with plant products and natural predators instead of chemicals.
- Biocomposting
Turning organic waste into manure, often with earthworms.
Exam tips
Common mistakes
- Listing three functions of the environment instead of four, or leaving out aesthetic services.
- Giving only one condition for carrying capacity.
- Saying renewable resources can never run out: they can, if used faster than they regenerate.
- Mixing up global warming (greenhouse gases) and ozone depletion (CFCs, halons), or the agreements for each.
- Defining sustainable development without mentioning future generations.
- Naming a strategy without explaining how it helps.
How marks are usually awarded
- 1 mark: one correct option or term.
- 3 marks: three distinct points (about 60–80 words).
- 5 marks: five points, each explained (about 100–120 words); evaluation questions need both sides and a judgement.
Data in SOYL practice are imagined; check every figure in a case before you calculate.