AP® Environmental Science · Unit 5 · Topic 5.3
The Green Revolution
The Green Revolution was a mid-1900s package of high-yield seed varieties, synthetic fertilizer, irrigation, and pesticides that dramatically raised crop yields on existing farmland, but the same inputs that boosted yield also degraded soil and water.
Starting in the 1940s through the 1960s, plant breeders developed high-yield varieties of wheat, rice, and corn bred to put more energy into grain and less into stalk. Those seeds only pay off as part of a package: they need heavy doses of synthetic nitrogen fertilizer, controlled irrigation water on a reliable schedule, and pesticides to protect the dense, uniform plantings from insects and disease. Remove any one piece and yields fall back toward old levels. Put all four together on the same acreage and a country like India or Mexico can multiply its grain output without clearing a single new field, which is exactly why the Green Revolution is treated as a land-use story: it is a way of getting more food per hectare rather than more hectares.
The catch is that yield and environmental damage are not separate dials, they are driven by the same inputs. Irrigation water that does not drain well leaves salts behind as it evaporates, building up soil salinity until the land stops supporting crops. Fertilizer that the plants do not absorb runs off into streams and lakes, feeding algae blooms and eutrophication. Pesticides kill the target insect but also beneficial insects, fish, and birds downstream, cutting biodiversity. So a field can show a tripled yield and a ruined water table at the same time, because both numbers come from the same fertilizer truck and irrigation pipe.
This sets up the back half of the unit: sustainable farming methods like crop rotation, drip irrigation, and integrated pest management try to keep the yield gains while breaking that link to salinization, runoff, and biodiversity loss.
Key terms
- High-yield variety
- A crop strain bred to produce more grain per plant, usually requiring heavy fertilizer and water to reach that potential.
- Salinization
- Buildup of salts in soil, often from evaporating irrigation water, that eventually reduces or stops crop growth.
- Eutrophication
- Excess nutrients, often from fertilizer runoff, causing algae overgrowth and oxygen loss in water bodies.
- Percent change
- The difference between a new value and an old value, divided by the old value, multiplied by 100.
Watch it explained
- How it worksWalk me through high-yield seeds, fertilizer, irrigation, and pesticides working as one package.
- Worked exampleFind the percent yield change when output goes from 1.2 to 3.6 tons per hectare on the same land.
- Common mistakeWhy doesn't a higher yield per hectare automatically mean less environmental damage?
- Going furtherWhat happens to the soil and water under a field after 30 years of green revolution farming?
Check yourself
End of topic.