How did new seeds, fertilizers and machines multiply crop yields, and what did that progress cost the environment?
Topic 5.3 The Green Revolution: describe the methods and benefits of the Green Revolution and explain its environmental costs.
A focused answer to APES Topic 5.3, covering the Green Revolution, high-yield crop varieties, fertilizers, pesticides, irrigation and mechanisation, its benefits for food supply, and its environmental costs, with a worked yield-increase calculation.
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What this topic is asking
The College Board (Topic 5.3) wants you to describe the methods and benefits of the Green Revolution and explain its environmental costs. This is the starting point for the agriculture topics that follow.
What the Green Revolution was
Benefits
Environmental costs
Monoculture (growing one crop over a large area) is especially important: a pest adapted to that crop can spread fast because there are no resistant plants to stop it.
Why this matters
The Green Revolution defines the trade-off at the heart of Unit 5: more food versus environmental harm. Its methods reappear in the topics on agricultural impacts (Topic 5.4), irrigation (Topic 5.5) and pest control (Topic 5.6), and its costs motivate the sustainable agriculture alternatives (Topic 5.15). It also connects to the nitrogen and phosphorus cycles (Topics 1.5 and 1.6) through fertilizer pollution.
Try this
Q1. Identify one method used to increase yields during the Green Revolution. [1 point]
- Cue. High-yield crop varieties (also acceptable: synthetic fertilizers, pesticides, irrigation, mechanisation).
Q2. Explain why monoculture increases the risk of a pest outbreak. [2 points]
- Cue. Monoculture grows a single, genetically uniform crop over a large area, so a pest adapted to that crop has unlimited identical hosts and no resistant plants to slow it, allowing it to spread rapidly.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AP 2021 (style)4 marksSection II (FRQ). (a) Describe two methods used in the Green Revolution to increase crop yields. (b) Identify one major benefit of the Green Revolution. (c) Explain one environmental cost of the increased fertilizer use it brought. (d) Explain why monoculture, common in Green Revolution agriculture, increases vulnerability to pests.Show worked answer →
A 4-point FRQ on the Green Revolution.
(a) Describe (1 point): any two of high-yield crop varieties, synthetic fertilizers, chemical pesticides, expanded irrigation, and mechanisation.
(b) Identify (1 point): greatly increased food production, helping feed a growing population and reducing famine.
(c) Explain (1 point): heavy synthetic fertilizer use causes nutrient runoff into waterways, leading to eutrophication and algal blooms, and can acidify or degrade soils.
(d) Explain (1 point): monoculture plants a single genetically uniform crop over large areas, so a pest adapted to that crop can spread rapidly with no resistant plants to slow it.
Markers reward two valid methods, the food-supply benefit, a real fertilizer cost (eutrophication), and genetic uniformity for pest vulnerability.
AP 2019 (style)1 marksSection I (multiple choice). Which of the following was NOT a typical feature of the Green Revolution? (A) High-yield crop varieties (B) Increased use of synthetic fertilizers (C) Reduced reliance on irrigation (D) Greater mechanisation. Justify your choice.Show worked answer →
A 1-point MCQ on the Green Revolution. The answer is (C).
The Green Revolution increased reliance on irrigation, not reduced it; expanded irrigation was one of its defining features. (A), (B) and (D) were all central methods (high-yield seeds, synthetic fertilizers and mechanisation). The trap is that all four sound plausible; the Green Revolution expanded irrigation rather than reducing it.
Related dot points
- Topic 5.4 The Impact of Agricultural Practices: explain how tillage, fertilizer use, overgrazing and other farming practices degrade soil and water.
A focused answer to APES Topic 5.4, covering how tillage, fertilizer use, overgrazing, and confined animal feeding degrade soil and water through erosion, nutrient runoff, salinisation, desertification and waste, with a worked nutrient-loading calculation.
- Topic 5.5 Irrigation Methods: compare the main irrigation methods and explain the problems of salinisation, waterlogging and aquifer depletion.
A focused answer to APES Topic 5.5, covering flood (furrow), spray, drip and other irrigation methods, their water efficiency, and the problems of salinisation, waterlogging and aquifer depletion, with a worked irrigation-efficiency calculation.
- Topic 5.15 Sustainable Agriculture: describe sustainable farming practices that conserve soil and water and maintain long-term productivity.
A focused answer to APES Topic 5.15, covering sustainable agriculture practices (crop rotation, contour ploughing, terracing, no-till, cover crops, strip cropping, agroforestry, rotational grazing) and how each conserves soil and water and maintains productivity, with a worked erosion-reduction calculation.
- Topic 5.6 Pest Control Methods: compare chemical and biological pest control and explain the pesticide treadmill and the evolution of pesticide resistance.
A focused answer to APES Topic 5.6, covering chemical pesticides, their benefits and costs, biological control, the pesticide treadmill, pesticide resistance through natural selection, and broad-spectrum versus narrow-spectrum pesticides, with a worked resistance calculation.
- Topic 1.5 The Nitrogen Cycle: describe the steps of the nitrogen cycle and explain how nitrogen fixation, the role of bacteria and human activities move nitrogen between reservoirs.
A focused answer to APES Topic 1.5, covering nitrogen fixation, nitrification, assimilation, ammonification and denitrification, the central role of bacteria, and how synthetic fertilizer alters the cycle, with a worked nitrogen-input question.
Sources & how we know this
- AP Environmental Science Course and Exam Description — College Board (2020)