The earth provides an abundance of goods essential to human life, including food, timber, fuel, fiber, and medicine, to name a few. Some highlighted examples follow.

Food. Humans have spent most of their existence as hunter-gathers, dependent on

Table 1

Three Methods of Categorizing the Value oof Biodiversity

Meffe and Carroll




Economic Values

Basic Values

Goods: food, fuel, fiber, medicine

Direct economic: consumptive (local) use; productive (market) use

Utilitarian: basic needs

Services: pollination, recycling, nitrogen fixation

Indirect economic: nonconsumptive (protection of water and soil resources regulation of climate; waste disposal; species relationships; recreation and ecotourism; education and science; environmental monitoring)

Naturalistic: discovery and recreation

Information: genetic engineering, applied biology, pure science

Option value: potential for future economic benefit

Ecologist—Scientific: knowledge

Psycho-spiritual: aesthetic beauty, religious awe, scientific knowledge

Existence value: amount people will pay to prevent species extinction

Aesthetic: beauty, inspiration

Symbolic: communication Humanistic: connection to nature Moralistic: spiritual reverence Dominionistic: dominance over nature Negativistic: alienation from nature

Sources: Kellert, Stephen R. 1996. The Value of Life: Biological Diversity and Human Society. Washington, DC: Island; Meffe, Gary K., and C. Ronald Carroll. 1997. Principles of Conservation Biology, 2d ed. Sunderland, MA: Sinauer Associates; Primack, Richard B. 1998. Essentials of Conservation Biology, 2d ed. Sunderland, MA: Sinauer Associates

Sources: Kellert, Stephen R. 1996. The Value of Life: Biological Diversity and Human Society. Washington, DC: Island; Meffe, Gary K., and C. Ronald Carroll. 1997. Principles of Conservation Biology, 2d ed. Sunderland, MA: Sinauer Associates; Primack, Richard B. 1998. Essentials of Conservation Biology, 2d ed. Sunderland, MA: Sinauer Associates wild plants and animals for survival. Around 10,000 years ago the first plants were cultivated, marking a fundamental shift in human history. Biodiversity continued to play a central role, providing the original source of all crops and domesticated animals. And today people still depend upon biodiversity to maintain healthy, sustainable agricultural systems. World crop exports alone were worth an impressive $432 billion in 2000, according to the Food and Agriculture Organization (FAO). Unlike agriculture, in which wild species have been domesticated, the world's marine fisheries are still dominated by wild-caught fish, representing 73.7 percent of the 125.2 million tons produced in 1999, according to the FAO.

Although humans have used more than 12,000 wild plants for food, twenty species now support much of the world's population (Burnett, 1999). It is still unclear why certain species were cultivated and not others. Of all the plants that we depend upon, none are more important than the grass family, Gramineae. The grass family includes the world's principal staples: wheat, rice, and corn (maize). Rice and corn formed the basis of civilizations in the Far East and the Americas, while wheat (together with barley) formed the basis of the civilizations of the Near East.

Wheat (Triticum sp.) is believed to have been one of the earliest cultivated plants, being highly suited for the making of bread because of the amount and quality of its gluten. Natural hybridization between different types of wild grasses helped produce the first wheat strains. For example, einkorn wheat and a goat grass hybridized to produce "emmer." Later, emmer would form a hybrid with another wild grass to produce the so-called bread wheats. Each of these hybridizations brought new characteristics that made wheat more suitable for cultivation. The grains of wild wheat tended to fall out of the sheath indi vidually, which was useful for seed dispersal but not for harvesting. Modifications to wild wheat eventually created a plant that could no longer spread its own seeds without the help of humans and whose grains were easy to gather. Bread wheat was also unique for its plump grains. Hybridization with grass species that were not used for food created the qualities we revere today in common bread wheat. The stories for rice and corn and other species with a long history of cultivation are similar.

Less familiar wild plants exist that could be important foods in the future. For example, peachpalm (Guilielma gasipaes, Arecaceae) from Central America produces one of the most balanced foods for human nutrition, being composed of an ideal mixture of carbohydrates, protein, fat, vitamins, and minerals. Peachpalm can produce more protein and carbohydrate per hectare than corn (Viet-meyer, 1996). Even among species related to our common staples, only a handful are currently in cultivation. There are 235 species of potatoes, but only seven are cultivated. Sorghum, emmer, and spelt were once widely grown grains, but they have been largely replaced by wheat. However, because of their unique environmental adaptations—sorghum, for example, can be grown in climates that do not support wheat—these grasses may become more important in the future.

Wood and Forest Products. The worldwide production of timber and related products is a multibillion-dollar industry. Wood is used to construct homes and furniture; it is also made into mulch, chipboard, paper, and packaging. The wood from each tree species has unique characteristics suitable for different purposes: white ash is used for baseball bats; locust and cedar, both very rot-resistant, are valued as fence posts; Brazilian rosewood is favored for guitars; and black walnut has been used for gunstocks because of its strength and decay resistance. Fabric manufacturers harvest wood for its fiber, using wood cellulose to make Tencel and rayon. Other useful tree products include cork, rubber, latex, and resins, as well as fruits, nuts, and oils. According to the World Resources Institute, 63 percent of all harvested wood is used as fuel, either burned directly or after being converted to charcoal

Medicine. According to the World Health Organization, about 80 percent of the world's population still use plants as a primary source of medicine, and many Western medicines were developed from a plant or animal source: 57 percent of the 150 most commonly prescribed drugs originate from living organisms (Grifo et al., 1997). For example, the antibiotic penicillin is derived from a fungus (Pen-cillium notatum) that is a common bread mold. Aspirin and common acne medicines are derived from salicylic acids, first taken from the bark of willow trees (Salix sp.). Although these drugs are now synthesized more efficiently than extracted from the wild, we still depend on the chemical structures in nature to guide us in developing and synthesizing new drugs.

Some drugs are still synthesized in whole or in part from wild sources. For example, Taxol, a potent drug used to fight ovarian and breast cancers, was first derived from the bark of the Pacific yew (Taxus brevifolia). In fact, the bark of six trees (each of at least 13.2 cm in diameter) was needed to produce enough Taxol for only one cancer patient; stripping the bark killed the trees. Fortunately, researchers found that the leaves of the European yew (Taxus bac-cata), a close relative of the Pacific yew, produce a similar chemical substance that can be used to produce Taxol both sustainably and less expensively. At this time the production of Taxol remains partially dependent on wild sources.

A less well known, more recent example of how we depend upon nature comes from the biotechnology industry. The polymerase chain reaction (PCR) is used in genetic research to replicate and manipulate DNA in large quantities over short periods of time. PCR has revolutionized genetic engineering, bringing it into the realm of industry and opening new possibilities for improved health and agriculture. The special enzymes used to catalize PCR withstand extremely high temperatures and originate, appropriately enough, in the hot springs of Yellowstone National Park. Needless to say, scientists are now researching these and other extreme environments to identify other enzymes that could be of help to the biotechnology industry.

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