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Class 12 Geographical Perspective on Selected Issues and Problems: cheat sheet
CBSE Social Science. Air, water, land and noise pollution, urban waste, rural–urban migration with its push and pull, slums, and land degradation and its remedies.
Key ideas
- Pollution is grouped by medium into air, water, land and noise pollution.
- Air is polluted by burning coal, petrol and diesel, industry and mining; it harms the lungs, nerves and heart, and causes smog and acid rain.
- Industry is the biggest human source of water pollution, with sewage and farm run-off; about a fourth of communicable diseases are water-borne.
- Noise is measured in decibels; traffic is the biggest nuisance.
- Uncollected urban waste breeds flies and rodents and releases methane as it rots; it can be turned into energy and compost.
- People move from villages to cities for jobs (pull) and because of few jobs at home (push); migrants send remittances home.
- Land degradation lowers the productivity of land; wastelands come from natural agents, human action or both, and watershed management helps restore them.
Remember
| Waste uncollected | waste a day × per cent uncollected ÷ 100 (30–50% in many small towns; metros collect about 90%) |
| Waste produced | people × grams each a day ÷ 1,000,000 = tonnes |
| Water-borne cases | about one-fourth of communicable disease cases |
| Remittances in a year | monthly amount × 12 |
| Urban by 2050 | about 68% of the world’s people |
| Polluter pays | those who pollute bear the cost of cleaning up (the Daurala example) |
Watch out
- Forgetting that 1 tonne is 1,000,000 g when converting waste per person.
- Calling gullies and desert sands human-made wastelands (they come from natural agents).
- Measuring noise in hertz instead of decibels.
Worked example
Suppose a town of 20 lakh people produces 450 g of solid waste per person a day, and 50% is collected. How many tonnes are produced and how many left uncollected each day? (1 tonne = 1,000,000 g)
Working: 20 lakh × 450 ÷ 1,000,000; 50% of that
Answer: 900 tonnes produced; 450 tonnes uncollected
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