In addition to its function as a repository for waste (discussed in Part Six), the natural environment is also a source of food and other extractive materials essential for the human economy. Part Seven examines the economics of natural resources that are either biological or geological by their nature and origin.
Chapter 16 examines economic theories and management strategies applicable to biological resources such as fish, forests, and other plant and animal varieties. Biological resources have one distinctive feature that is important for consideration here. That is, while these resources are capable of self-regeneration, they can be irreparably damaged if they are exploited beyond a certain critical threshold. Hence, their use is limited to a certain critical zone. In Chapter 16 only the basic elements of the economics of renewable resources are discussed, and with a primary focus on fishery.
Chapter 17 concerns the economics of nonrenewable resources—resources that either exist in fixed supply or are renewable only on a geological timescale and therefore for all practical purposes are assumed to have zero regenerative capacity. Examples of these resources include metallic minerals like iron, aluminum, copper and uranium; and nonmetallic minerals like fossil fuels, clay, sand, salt and phosphates.