DIRECT VALUES
Consumptive Use Value refers to non-market value of resources such as firewood, game meat, etc. Such resources are consumed directly, without passing through a market. They usually are not calculated (but often can be approximated). A study in Malaysia estimated that wild pigs harvested by hunters had a value equivalent to $100 million annually. In Zaire, 75% of animal protein comes from wild sources. In a number of poor countries, firewood and dung are primary energy sources. As these become scarce, women spend most of their day simply collecting fuel wood.
Productive Use Value refers to the commercial value of products that are commercially harvested for exchange in formal markets, such as game meat, timber, fish, ivory, medicinal plants. They are included in national income accounts like the GNP. Estimates are usually made at the production end (sale of timber by the timber harvester to the sawmill), rather than the eventual value of the furniture and houses built from the timber. In developing countries, the commercial value of natural resources usually is a much greater fraction of the national economy than is the case in developed countries.
Much attention has focused recently around alternative uses of the rain forest. Usually, this is the search for valued non-wood products that can be harvested sustainably (fruits such as Brasil nuts, and latex from rubber-tapping).
INDIRECT VALUES
Non-consumptive Use Value refers to all of the "functions" or "services" of natural systems, as well as scientific research, bird-watching, etc. They rarely are included in any national accounting. Table 1 below lists some important ecosystem goods and services.
Option Value refers to the value of retaining options available for the future, such as yet-undiscovered new crops and medicines.
Existence Value refers to the value of ethical feelings for the existence of nature. Many of us attach value to the existence of a species or habitat that we are unlikely ever to see -- mountain gorillas, the deep rainforests of Amazonia, the highlands of Madagascar. This may include the satisfaction of knowing that certain species exist in the wild, or an ethical dimension of responsibility to nature, or future generations, or other peoples. WWF receives donations of $100 million a year on this basis, and it is by no means the only or biggest recipient of such donations.
