Now back to the main point: the environmental aspects of the way we use materials. Use is too weak a word; it sounds as though we have a choice: use, or perhaps not use? We don’t just "use" materials, we are totally dependent on them. Over time this dependence has progressively changed from a reliance on renewable materials—the way mankind existed for thousands of years—to one that relies on materials that consume resources that cannot be replaced.
As little as 300 years ago, human activity subsisted almost entirely on renewables: stone, wood, leather, bone, natural fibers. The few nonrenewables— iron, copper, tin, zinc—were used in such small quantities that the resources from which they were drawn were, for practical purposes, inexhaustible. Then, progressively, the nature of the dependence changed (see Figure 1.2). Bit by bit nonrenewables displaced renewables until, by the end of the 20th century, our dependence on them was, as already said, almost total.
Dependence is dangerous; it is a genie in bottle. Take away something on which you depend—meaning that you can’t live without it—and life becomes difficult. Dependence exposes you to exploitation. While a resource is plentiful, market forces ensure that its price bears a relationship to the cost of its extraction. But the resources from which many materials are drawn, oil among them, are localized in just a few countries. While these compete for buyers, the price remains geared to the cost of production. But if demand exceeds supply or the producing nations reach arrangements to limit it, the genie is out of the bottle. Think, for instance, of the price of oil, which today bears little relationship to the cost of producing it.
Dependence, then, is a condition to be reckoned with. We will encounter its influence many times in subsequent chapters.