Our Dependence on Biodiversity

Our lives depend on biodiversity in ways that are not often appreciated. A case in point is agriculture. Society has learned a tremendous amount about techniques to maximize crop yields, both in temperate climates such as the grain belt of the U.S. and Canada, and in subtropical and tropical environments, where the "green revolution" that gained initial momentum in the 1960s vastly increased yields of rice and other crops. In both cases, the advances relied in part on biodiversity, and specifically on the availability of diverse strains of cereal grains capable of responding positively to heavier applications of fertilizer. The need continues, for we are still learning how to sustain tropical agriculture and to minimize adverse environmental impacts of fertilizers and pesticides while maintaining high yields, and how to sustain the highly-managed agro-ecosystems on which we more and more depend.

Much of today's world is also dependent on wild resources, of which the best known examples are probably marine fisheries. The industrial nations of the world support large and technologically- advanced fleets whose sole purpose is to harvest wild fish for human consumption, either directly or indirectly as fishmeal for fertilizers, cattle feed, and aquaculture. Averaged globally, people derive about 16 percent of their total animal protein from marine fisheries. Many developing nations also support a combination of open-ocean fishing industries and intensive coastal and local fisheries, upon which coastal populations depend both for food and for their economic livelihood. About a sixth of the world's population, much of it in the developing world, derives more than a third of their total protein from marine fisheries.

Our long-standing dependence on the natural world for wood is another example that is still much in evidence around the world. Only a small fraction of the timber that is cut in the U.S., for instance, is harvested from plantations: most is taken from natural forests that are not intensively managed. Worldwide, an even greater fraction comes from trees grown in the wild: by far the most important source is unmanaged or lightly managed forest stands. The use of wood for fuel, while of little consequence in technologically advanced countries like our own, is an abiding staple in many developing nations, and the twin demands for shelter and fuel have led to extensive deforestation in many parts of the world, such as Madagascar and Indonesia.

Four out of every five of the top 150 prescription drugs used in the U.S. have had their origins in natural compounds. An example is aspirin--a derivative of salicylic acid which was first taken from the bark of willow trees. Today aspirin and many other drugs are synthesized more efficiently than they can be extracted from the wild, but they were first discovered in naturally occurring compounds, which then formed the basis for subsequent improvement. The process of discovery still continues. For example, taxol, a promising anti-cancer drug, was first extracted from a tree found in the wild: the Pacific yew. The chemical substance from which taxol came has since been discovered in close relatives of that species, thus reducing pressures for harvesting what is already a small population.

Other economic gains derive from our interaction with the natural world, of which the best known example may be the economic value of tourism. Much, although obviously not all vacation travel comes under the rubric of "eco-tourism," driven by a desire to see and experience the natural world. The total economic activity generated by tourists of this kind has been recently estimated by the United Nations at nearly $230 billion each year. Even on regional and local scales, the revenue generated by tourism can be substantial, and a major component of local and regional economies (Table 1).

Each of the activities cited above provides resources and economic gains for citizens in all societies. Yet each is at risk due to the continued erosion of the resource on which they are based, which is biodiversity. In what follows we review what is known of the forces that are reducing biodiversity and some of the possible consequences of this loss, and suggest areas in which additional research and policy analyses are most needed.

The Winds of Change
The recent Global Biodiversity Assessment of the United Nations Environment Program (UNEP) has identified four major causes of the present decrease in biodiversity, and a fifth which may yet prove to be important