Geomorphology is the study of the shape of the Earth. In this book we take this quite literally, and address the shape of the Earth at many scales. We ask why it is spherical, or not quite spherical, why it has a distribution of elevations that is bimodal, one mode characterizing a quite well-organized set of ocean basins, another the terrestrial landscape. At smaller scales, we address why hilltops are convex, why glacial troughs are U-shaped, why rivers are concave up. At yet smaller scales, sand is rippled, beaches are cusped, hillslopes are striped, and mud is cracked. These are some of nature's most remarkable and visible examples of self-organizing systems. Each cries out for both explanation and appreciation.

Goals

We wrote this textbook to provide modern teachers and students of geomorphology with a formal treatment of geomorphic processes that acknowledges the blossoming of this field within the last two decades. It brings together between two covers the background that serves to attach our field with those of geophysics, atmospheric sciences, geochemistry, and geochronology. It honors the heightened importance of geomorphology in understanding the environment and its changes, with an attendant need to pose these problems more formally.

The book is intended to be used in an introductory geomorphology course in which the attention is more on the processes that shape landscapes than on the cataloging of landforms. Most likely such a course will fit into a third and fourth year undergraduate or an introductory graduate curriculum.

RENEWABLE, NONRENEWABLE, AND ENVIRONMENTAL RESOURCES

Economics might be defined as the study of how society allocates scarce resources. The field of resource economics, would then be the study of how society allocates scarce natural resources, such as stocks of fish, stands of trees, fresh water, oil, and other naturally occurring resources. A distinction is sometimes made between resource and environmental economics, where the latter field is concerned with the way wastes are disposed and the resulting quality of air, water, and soil serving as waste receptors. In addition, environmental economics is concerned with the conservation of natural environments and biodiversity.

Natural resources are often categorized as being renewable or nonrenewable. A renewable resource must display a significant rate of growth or renewal on a relevant economic time scale. An economic time scale is a time interval for which planning and management are meaningful. The notion of an economic time scale can make the classification of natural resources a bit tricky. For example, how should we classify a stand of old-growth coast redwood or an aquifer with an insignificant rate of recharge? While the redwood tree is a plant and can be grown commercially, old-growth redwoods may be 800 to 1,000 years old, and the remaining stands may be more appropriately viewed as a nonrenewable resource.

INTRODUCTION AND OVERVIEW

In the preceding chapters I have presented economic models for the management of fisheries, forests, nonrenewable resources, and stock pollutants. For renewable resources and stock pollutants, the possibility of achieving and maintaining a steady state might correspond to the now ubiquitous term sustainability. The term sustainable development became prominent in the lexicon of resource and development agencies following the Earth Summit in Rio de Janeiro in 1992. The United Nation's World Commission on Environment and Development defined sustainable development as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs…. At a minimum, sustainable development must not endanger the natural systems that support life on Earth.”

Since 1992, sustainability has been broadly adopted as a goal by individuals and governments. Making the concept operational and implementing policies that would lead to sustainable lifestyles for individuals and sustainable production and consumption in the global economy have proved difficult. If the global economy critically depends on nonrenewable resources, long-term sustainability may be open to question. Interestingly, the notion of sustainability in a macroeconomic model with a nonrenewable resource was examined by several economists in the early 1970s. Perhaps the most famous article was by Robert M. Solow, entitled, “Intergenerational Equity and Exhaustible Resources,” which appeared in a special symposium issue of the Review of Economic Studies in 1974.

INTRODUCTION AND OVERVIEW

Nonrenewable resources do not exhibit significant growth or renewal over an economic time scale. Examples include coal, oil, natural gas, and metals such as copper, tin, iron, silver, and gold. I noted in Chapter 1 that a plant or animal species might be more appropriately viewed as a nonrenewable, as in Chapter 4, where the stock of old-growth forest was modeled as a nonrenewable resource. In Chapter 2, in the mine manager's problem, I developed a finite-horizon model of a nonrenewable resource to show how Solver might be used to determine the optimal extraction path.

If the initial reserves of a nonrenewable resource are known, the question becomes, “How should they be extracted over time?” Is complete depletion (exhaustion) ever optimal? Is it ever optimal to abandon a mine or well with positive reserves? Does the time path of extraction by a competitive firm differ from that of a price-making monopolist or cartel? If exploration allows a firm to find (acquire) more reserves, what is the optimal risky investment in exploration?

In working through the various models of this chapter, an economic measure of resource scarcity will emerge that is different from standard measures based on physical abundance. From an economic perspective, scarcity should reflect net marginal value (marginal value less the marginal cost of extraction).