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An Urgent Need to Map Biodiversity

The scientific imagination has been stirred by a call for complete sequencing of the human genome (The Scientist, October 20, 1986, pp. 11-12). The prospect is attractive because it offers an Everest-like goal, the entrainment of new advances in high technology, and the promise of practical applications in medicine. A close parallel exists in the mission envisioned by other biologists to describe and characterize the remainder of life on Earth. Where the genome project will search inwardly to ma

By | February 9, 1987

The scientific imagination has been stirred by a call for complete sequencing of the human genome (The Scientist, October 20, 1986, pp. 11-12). The prospect is attractive because it offers an Everest-like goal, the entrainment of new advances in high technology, and the promise of practical applications in medicine.

A close parallel exists in the mission envisioned by other biologists to describe and characterize the remainder of life on Earth. Where the genome project will search inwardly to map several billion base-pairs comprising 100,000 to 300,000 genes, the biodiversity project will explore outwardly to encompass the still largely unknown millions of species of animals, plants and microorganisms on which human existence depends.

A recent tabulation places the number of described species at about 1.6 million (a large majority of which are insects and plants). But the actual number believed to exist ranges from four million to more than 30 million. Each species in turn is composed of millions or even billions of base-pairs. Those portions that make a species unique are also very old. The average life of a species—or "clade," a set of closely related species derived from a single ancestral stock—is from one to 10 million years according to taxonomic group.

Two Major Goals

The study of biodiversity, or systematics in the broad sense, has hitherto been conducted in a largely piecemeal fashion. Many researchers closest to the subject believe that the time has come to define its larger mission more clearly. Two primary goals of such a project stand out. The first is the measure of biological diversity and its rate of change. The second is the unraveling of homology and its implications for the branching patterns of evolution.

The first goal, a dynamic map of diversity on a worldwide scale, is the more urgent. It will provide the entrée to a largely unknown biological process, and the answer to a central question: why 30 million species and not 40 million, or only 2,000, or as many as one billion? After all, the diversity of eukaryotic organisms is spread across more than 1,018 organisms, so a vast array of species numbers is conceivable.

We have no idea whether there is something peculiar about the conformation of the planet or the mechanisms of evolution itself that has led to the amount of diversity actually in existence. "Hot spots" of disproportionately high diversity of plants and animals occur within the more extensive tropical forests and marine benthic environments. We need to know their contents and limits, as well as the peculiarities of their evolution at the species level. For the effective design of parks and reserves, information is needed on the minimum habitat area that can. sustain given levels of diversity for a long period of time.

Biodiversity is in fact one of Earth's most important and least utilized resources. For example, we have come to depend completely on fewer than one percent of living plant species for our existence, with the remainder waiting largely untested and fallow. In the course of history, people have utilized about 7,000 species of plants for food, with emphasis on wheat, rye, maize and about a dozen other highly domesticated species. Yet at least 75,000 edible species exist, and many of these are potentially superior in yield and nutritive quality to the crop plants in widest use. Others are potential sources of new pharmaceuticals (as many as one in 10, for example, may contain anticancer compounds), fibers and petroleum substitutes.

Running Out of Time

Unlike human genetics and other biological disciplines, systematics has a time limit. Much of the diversity is being lost through extinction caused by the accelerating destruction of natural habitats. This is especially the case in the tropical moist forests, where more than half the species are thought to exist. Each year, about one percent of these forests, or some 10 million hectares (an area roughly equal to Switzerland and the Netherlands combined) is permanently destroyed.

Although extinction rates are difficult to estimate, they appear to approach or exceed 1,000 times the average level in past geological time. Much of the tropical forest, and with it many thousands of species of plants and animals, is destined to disappear during the next 30 years. Thus, humanity is locked into a race in which systematics will play a crucial role. We must hurry to acquire the knowledge on which a wise policy of conservation and development can be based for centuries to come.

The global biodiversity survey can be advanced very far during the next one or two decades at a small fraction of the cost of most other Big Science efforts. Complete floristic surveys of entire islands and continents, for example, can be based substantially on the efforts of native collectors followed by the low-cost study of specimens in herbaria and greenhouses. By improving computer-aided techniques in data storage and analysis, the cost-effectiveness can be steadily increased.

Not all of the benefits will be purely practical or scientific. In the midst of this effort, it should be kept in mind that the museum collections and biogeographIc data acquired will in many cases serve, like Mayan codices, as a rare and irreplaceable record of part of man's heritage.

Wilson is Frank B. Baird Jr. Professor of Science at Harvard University, Cambridge, MA 02138.

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