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CHAPTER 7

Sustaining Terrestrial Resources

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Over 2,000 years ago, people understood that tending to the health of soils is essential to sustaining the welfare of human communities.

Sometime around 2,400 years ago, the Greek philosopher Plato gazed up at the dry, barren hills surrounding his native Athens and came to a startling conclusion about the impact of human agriculture over the preceding centuries. A once-extensive forest had been cleared, and the landscape had subsequently grown parched. “What now remains compared to what then existed,” he wrote, “is like a skeleton of a sick man, all the fat and the soft soil having wasted away, and only the bare framework of the land being left.”

Like a detective, Plato gathered evidence to test his theory by scouting the countryside. He noticed that forests growing some distance from Athens included enormous, old trees and deep, fertile soils. These forests, he reasoned, are what Athens must have been like during some past era. In fact, Plato noticed that in the center of the city where large trees no longer grew, there were buildings with wide, wooden roof beams extracted from these long-lost forests. In addition, he observed that many religious shrines in the area, which ancient Greeks typically sited near perennial springs and streams, had no flowing water nearby. In the past, he reasoned, the combination of forested hills and deep soils would have captured precipitation and slowed its passage through the landscape. Deforestation had increased rates of soil loss, which meant that water rapidly ran off the land during rainstorms.

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“A good part of agriculture is to learn how to adapt one’s work to nature, to fit the crop-scheme to the climate and to the soil. . . . To live in right relation to the natural conditions is one of the first lessons that a wise farmer or any other wise man learns.”

Liberty Hyde Bailey, The Holy Earth, 1915

Athens was hardly unique. The changes Plato noticed in his backyard are just one part of the global story of how humans have altered the world we live in. In the early days of our species, we lived by gathering wild plant materials for food and shelter and hunting wild animals that gave us furs and meat. In other words, we lived entirely off the production of natural ecosystems. Then about 10,000 years ago, human communities around Earth began to domesticate plants and animals, manipulating natural ecosystems to serve our needs.

Managing terrestrial resources through ranching, forestry, and farming has increased the amount of food and forest products (e.g., wood) available to human populations, as well as reduced variation in supplies of these resources. A more reliable food supply increased the rate of human population growth (see Chapter 5, page 130), which led to the development of cities. Forestry cleared land for crops and created pastures for ranching while also supplying building material and fuel. The benefits of agriculture and forestry, however, were accompanied by unsustainable environmental costs as humans irrigated lands, replaced natural vegetation with crops, and cleared forests for land to support human populations. The need for careful management of Earth’s terrestrial resources brings us to the central question of this chapter.

Central Question

How can we produce food and forest products while minimizing environmental impact?