Natural resources, unlike man-made resources, exist independently of human labor. These resources are, however, not unlimited and must be used with care. Some natural resources are called "fund resources" because they can be exhausted through use, like the burning of fossil fuels. Other fund resources such as metals can be dissipated or wasted if they are discarded instead of being reused or recycled. Some natural resources can be used up like fund resources, but they can renew themselves if they are not completely destroyed. Examples of the latter would include the soil, forests, and fisheries.
Because of population growth and a rising standard of living, the demand for natural resources is steadily increasing. For example, the rising demand for minerals, if continued, will eventually deplete the known and expected reserves.
The world's industrialized nations are consuming nonrenewable resources at an accelerating pace, with the United States the world's leading industrial power, ranking first on a per capita basis. With only 5% of the global population, Americans consumes 30% of the world's resources. Because of their tremendous demand for goods, Americans have also created more waste than is generated by any other country. The environment in industrialized countries has been degraded with an ever-increasing volume and variety of contaminants. In particular, a complex of synthetic chemicals with a vast potential for harmful effects on human health has been created. The long-term effects of a low dosage of many of these chemicals in our environment will not be known for decades. The three most important causes for global environmental problems today are population growth, excessive resource consumption, and high levels of pollution. All of these threaten the natural resource base.