The Green Revolution at Higher Level: Different examples from SL: IR8 rice, world cereal output on the same land, Indonesia's planthopper crisis and sub-Saharan Africa. At HL, link this to the economics and ethics of farming (HL.b) and to high-tech farming today (5.2.16).
Practise this as you read
- Explain how each input raised yields.
- Evaluate the Green Revolution: benefits and costs.
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More food from the same fields: The Green Revolution (also called the Third Agricultural Revolution) began in the 1950s and 1960s. New high-yielding varieties were grown with irrigation, synthetic fertilizer and pesticides, so poorer countries could grow far more food and improve their food security.
The points to remember
- When: the 1950s and 1960s, spreading through Asia and Latin America.
- What: high-yielding crops plus irrigation, synthetic fertilizer and pesticides.
- Aim: more food per hectare, to increase food security as populations grew.
- Criticized for its environmental, economic and sociocultural consequences.
- It did not happen in all developing countries.
Remember it as: New seeds, plus water, plus fertilizer, plus spray.
Example (HL): IR8, the 'miracle rice'. In 1966 the International Rice Research Institute in the Philippines released IR8, a short rice that could take heavy fertilizer without falling over. With irrigation it often doubled the rice harvested from each hectare.
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Each part of the package removed a limiting factor. Together they raised the yield: the crop harvested from each hectare.
Seeds
- IR8 had short, stiff stems and ripened in about 130 days, so two crops a year were possible.
Water
- Canals and pumps kept the paddies flooded in the dry season, so water no longer limited growth.
Fertilizer
- Nitrogen fertilizer raised yields because the short stems did not collapse under the heavier grain.
Sprays
- Insecticides protected the dense, uniform fields from pests such as the brown planthopper.
The points to remember
- High-yielding varieties: more grain per plant, short stems, faster growth, more harvests a year.
- Irrigation: water is no longer the limiting factor.
- Synthetic fertilizer: soil nutrients are no longer limiting.
- Pesticides: less of the crop lost to pests and weeds.
- Machines: more work on bigger areas with fewer people.
- Soil conservation methods cut soil degradation on the more intensively used land.
- So production rose far faster than the area farmed.
The Green Revolution's supporters point to what it achieved for people and for land.
The points to remember
- More food: cereal harvests in Asia rose fast and famines were avoided.
- Food security: countries that imported grain became self-sufficient.
- Cheaper food: bigger harvests lowered grain prices for poor buyers.
- Land spared: more food from the same area, so less forest was cleared for farms.
- Incomes: farmers who could afford the package earned more; rural jobs in trade grew.
Remember it as: More food, less hunger, less land.
Example (HL): land spared and Indonesia. One study estimated that without the new varieties, between about 18 and 27 million more hectares would have been farmed by 2004. Indonesia, once the world's largest rice importer, grew enough rice for itself by 1984.
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The same inputs that raised yields put pressure on water, soil and wildlife.
The points to remember
- Groundwater pumped faster than rain refills it: water tables fall.
- Irrigation in dry areas leaves salt behind: salinization; poor drainage causes waterlogging.
- Fertilizer runs off into rivers: eutrophication; soils lose organic matter.
- Pesticides kill non-target species, poison people and breed resistant pests.
- Monocultures of a few varieties: old local varieties lost, less genetic diversity.
- More burning of crop waste and fuel: air pollution and greenhouse gases.
Remember it as: Water down, salt up, runoff out, resistance in.
Example (HL): Indonesia's brown planthopper. Heavy insecticide spraying in the 1970s and 1980s killed the spiders and other predators of the brown planthopper, while the pest itself became resistant. Outbreaks destroyed huge areas of rice. In 1986 Indonesia banned 57 insecticides on rice and trained farmers in integrated pest management.
Critics also point to who gained, who lost, and who was left out.
Economic
- Seed, fertilizer, pesticide and pumps must be bought every year.
- Farmers with land, credit and irrigation gained most; small farmers fell into debt.
- Machines replaced landless labourers.
Sociocultural
- Gaps between rich and poor farmers, and between regions, grew.
- Traditional knowledge and local seeds were lost.
- Diets narrowed: wheat and rice replaced millets and pulses.
The points to remember
- It did not happen in all developing countries.
- Much of sub-Saharan Africa missed out: rain-fed farms, little irrigation.
- Its main crops (cassava, sorghum, millet) had few new varieties at first.
- Poor roads, little credit, and high fertilizer prices held it back.
Example (HL): sub-Saharan Africa. Between the 1960s and 2000, cereal yields in South Asia roughly doubled, while in sub-Saharan Africa they stayed at about 1 tonne per hectare, and the population grew much faster than the harvest.
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Plants need nitrogen, but most of it is in the air as a gas they cannot use. The Haber-Bosch process fixes it into fertilizer.
The points to remember
- Higher yields depended on fixing nitrogen into synthetic fertilizer.
- The hydrogen comes mostly from natural gas, and the process needs high heat and pressure.
- So fertilizer production is fossil-fuel dependent and releases carbon dioxide.
- Tractors, pumps and pesticides add more oil and electricity use.
- If gas becomes scarce or costly, fertilizer and food prices rise.
Remember it as: Gas in, ammonia out, food up, carbon up.
Example (HL): the carbon cost of ammonia. Making one tonne of ammonia from natural gas releases about 2 tonnes of carbon dioxide. Ammonia making uses about 1-2% of the world's energy, yet the fertilizer it produces helps feed around half of the world's people.
How this comes up: Paper 1 gives graphs of farm output and fertilizer use, then asks you to explain how output rose while fewer people worked on farms [4].
Read both figures together: Figure 2 shows one of the reasons for the change in Figure 1.
Figure 1 shows farm output and the number of farm workers in the United States from 1950 to 1980. Figure 2 shows nitrogen fertilizer use.
With reference to Figures 1 and 2, explain how farm output increased while the number of farm workers decreased.
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