Biodiversity: A New Challenge

Biodiversity: A New Challenge
		by *Edward T. LaRoe* National Biological Service
Resource managers at many state and federal agencies are in the middle of a fundamental change in the practice and objectives of conservation. Traditional management has been directed toward maintaining, usually for harvest purposes, populations of individual species such as ducks, deer, or salmon. Increasingly, however, resource managers are recognizing the critical importance of conserving biological diversity, or biodiversity.
In its simplest terms, biological diversity is the variety of life at all levels: it includes the array of plants and animals; the genetic differences among individuals; the communities, ecosystems, and landscapes in which they occur; and the variety of processes on which they depend. Conserving biological diversity poses dramatic new problems for comprehensive inventory and monitoring: what should be measured or monitored?
Biodiversity is important for many reasons. Its value is often reported in economic terms: for example, about half of all medicinal drugs (Keystone Center 1991; Wilson 1992) come from--or were first found in--natural plants and animals, and therefore these resources are critical for their existing and as yet undiscovered medicinal benefits. Additionally, most foods were domesticated from wild stocks, and interbreeding of different, wild genetic stocks is often used to increase crop yield. Today we use but a small fraction of the food crops used by Native cultures: many of these underused plants may become critical new food sources for the expanding human population or in times of changing environmental conditions.
But biodiversity has an even greater importance: it is the great variety of life that makes existence on earth possible. As a simple example, plants convert carbon dioxide to oxygen during the photosynthetic process; animals breathe this fresh air, releasing energy and providing the second level of the food chain. In turn, animals convert oxygen back to carbon dioxide, providing the building blocks for the formation of sugars during photosynthesis by plants. Microbes (fungi, bacteria, and protozoans) break down the carcasses of dead organisms, recycling the minerals to make them available for new life; along with some algae and lichens, they create soils and improve soil fertility.
Biodiversity provides the reservoir for change in our life-support systems, allowing life to adapt to changing conditions. In a natural population, for example, some individuals will be more resistant to drought or disease or cold; as the environment changes, from season to season, year to year, or over longer periods, and as plagues come and go, these differences among individuals allow at least some members of the population or species to survive and reproduce. This diversity is the basis not only for short-term adaptation to changing conditions, but also for long-term evolution as well.
Like air, water, and soils, biological diversity is part of the capital upon which all life depends. The need for this diversity is greatest in times of environmental stress when plants, animals, and microbes must develop new characteristics or strategies for survival. As we look at the problems of the globe today--global climate change, decreases in the ozone shield and increasing ultraviolet radiation, losses of natural habitats, and pervasive pollution in our streams and oceans--we must recognize that we, as a form of life on earth, need the ability to change in order to cope with new stresses.
Humans cannot survive in the absence of nature. We depend on the diversity of life on earth for about 25% of our fuel (wood and manure in Africa, India, and much of Asia); more than 50% of our fiber (for clothes and construction); almost 50% of our medicines; and, of course, for all our food (Miller et al. 1985). As previously stated, biodiversity produces other benefits: plants produce oxygen for our atmosphere; microbes break down wastes, recycle nutrients, and build the fertility of our soils. One reason our highways are not littered with the carcasses of dead dogs, cats, skunks, armadillos, and deer is biodiversity, in the form of the many scavengers and microbes that we don't often think about, but which play an essential role in the cycle of life. Even species often viewed as "repulsive," such as vultures and maggots, play critical roles in our lives.
Some people believe that because extinction is a natural process, we therefore should not worry about endangered species or the loss of biodiversity. Certainly extinction is natural; it usually occurs as newer forms of life evolve. But under the forces of population growth, technology, and special interests, humans have driven the rate of extinctions today to about 100 times--two orders of magnitude--the natural rate. Even worse, the rate of extinction is still increasing and will be 100 to 1,000 times faster yet in the next 55 years (Miller et al. 1985); scientists today predict that between now and 2030, half the expected lifetime of a child born today, the Earth will lose between a quarter and a third of all existing species. And this is in the absence of new forms of life to replace them. The last time Earth lost this large a share of its life was 65 million years ago when it may have collided with an asteroid; the impacts of humans on our planet today may have been last equaled by the collision of two heavenly bodies (Wilson 1992).
Scientists cannot honestly say that we need all species that exist today for humans to survive; but as a general rule, the more diversity is diminished, the less stable ecosystems become and the greater the fluctuations that occur in plant and animal populations. The more diversity we lose, the more our quality of life and economic potential are diminished, and the greater the risk that we will cause a critical part of the cycle of life to fail.
If humans were allowed to cause the extinction of other species, who would determine which species? If we had been asked 60 years ago what life we could let become extinct, who among us would have insisted that we preserve the lowly mold that was penicillin, the first of the series of antibiotics that have today so changed the quality of our lives? And who, only 5 years ago, would have identified the need to preserve the Pacific yew, which today yields taxol, one of the greatest new hopes in our arsenal against cancer?

References
Keystone Center. 1991. Biological diversity on federal lands, report of a Keystone policy dialogue. The Keystone Center, Keystone, CO. 96 pp.	Miller, K.R., J. Fortado, C. De Klemm, J.A. McNeely, N. Myers, M.E. Soule, and M.C. Trexler. 1985. Issues on the preservation of biological diversity. Pages 337-362 in Robert Repetto, ed. The global possible. Yale University Press, New Haven. Wilson, E.O. 1992. The diversity of life. Belknap Press of Harvard University Press, Cambridge, MA. 424 pp.