5.3 The Green Revolution

Starting in the 1940s in Mexico and spreading to India, Pakistan and much of Asia and Latin America in the 1960s, the Green Revolution transformed farming. Plant scientist Norman Borlaug developed short-stemmed, disease-resistant wheat that produced much more grain. He won the Nobel Peace Prize in 1970 for his role in reducing hunger. Similar high-yield rice varieties followed.

• High-yield varieties: crops bred to produce more grain per plant, often with short, sturdy stems that don't fall over under heavy grain heads.
• Synthetic fertilizers: nitrogen made by the Haber-Bosch process, plus phosphorus and potassium, to feed those high-yield crops.
• Pesticides and herbicides: to protect large fields of a single crop.
• Irrigation: high-yield varieties need reliable water.
• Mechanization: tractors, harvesters and other machines replaced much human and animal labor.

Food production rose dramatically, and grain yields in many countries roughly doubled or more within a few decades. Countries that had faced famines, like India, became able to feed their growing populations. Food became cheaper. Machinery let fewer workers farm more land, which raised efficiency and profits for many farms. Because each hectare produced more, less new land had to be cleared for farms than would otherwise have been needed.

A monoculture is a large area planted with one crop variety. It's efficient to plant, spray and harvest. But because all the plants are genetically similar, a single pest or disease can spread through the whole crop. In 1970, a fungal disease called southern corn leaf blight destroyed about 15% of the U.S. corn crop, largely because most of the corn shared the same vulnerable genetic trait.

• Fossil fuel use: machinery runs on fuel, and making synthetic nitrogen fertilizer takes large amounts of natural gas.
• Water use: more irrigation led to depleted aquifers, waterlogging and salinization.
• Pollution: fertilizer runoff causes eutrophication; pesticides harm wildlife and can contaminate water.
• Soil degradation: heavy machinery compacts soil, and intensive tilling increases erosion.
• Monoculture and lost genetic diversity: farmers planted huge areas of a single high-yield variety, replacing many local varieties.
• Social effects: the expensive inputs favored larger farms that could afford them.

Today, genetically modified (GM) crops, whose genes have been changed, often by adding a gene from another organism, to resist pests or herbicides, continue the push for higher yields. They raise many of the same tradeoffs: higher production versus concerns about reduced genetic diversity and pest resistance. Sustainable agriculture (topic 5.15) tries to keep high yields while lowering these costs.