Whenever populations die out and species become extinct, the most serious consequence is the loss of the ecosystem services the creatures formerly helped provide ... but that's far from being the only serious repercussion of extinction. Few people, for instance, are aware of the enormous direct economic (and other) benefits Homo sapiens derives from its living companions on this global spaceship, and even fewer realize that the potential benefits are greater still! This range of direct and indirect, known and unknown benefits underline the importance of preserving biodiversity.
Many examples of the direct "pluses" that Earth's flora and fauna provide us with can be found in the field of medicine. In 1955, Paul's father died after a grim, 13-year battle with Hodgkin's disease, a leukemia-like disorder. Just after his death, Canadian scientists discovered that an extract of the leaves of a periwinkle plant from Madagascar caused a decrease in the white blood cell count of rats. When chemists at Eli Lilly & Co. analyzed the periwinkle's leaves, they discovered a large number of alkaloids—poisonous compounds evolved by the plant to fend off predators and parasites.
Two of the alkaloids, vincristine and vinblastine, have since proved effective in the treatment of Hodgkin's disease. Indeed, with radiation combined with these and other drugs, it's now usually possible to control—or even cure—this kind of cancer. Thus a chemical that was later found in a plant species could have greatly prolonged Bill Ehrlich's life ... and it's now available to aid the 5,000 to 6,000 people, in the U.S. alone, who contract this disease each year.
As one measure of the economic value of the discovery, the world sales of vincristine, in 1979, totaled $35 million. (The drug is also used to fight a variety of other cancers, including several that afflict children and one form of leukemia.) Had the periwinkle become extinct before the 1950's, of course, humankind would have suffered a great loss ... although no one would even have realized it.
Furthermore, vincristine is just one example of the contributions made by plants to human health. There is evidence that Neanderthal people made medicinal use of plants, and many "folk" or "herbal" remedies derived from them are based not on superstition, but on the truly efficacious chemicals that plants contain.
This fact will come as no surprise, however, to folks who remember that the Peruvian Indians long cured malaria with an extract of the bark of Cinchona trees, which are members of the coffee family. The substance's active ingredient, quinine, became the main drug used against the disease—worldwide—for a century. And even the antimalarial drugs now in use have molecules whose design was inspired by the chemical structure of quinine.
Plants aid human beings—especially those in industrial countries—in the battle against another major group of killers, too: the diseases of the heart and circulatory system. Reserpine, from Rauwolfia (a group of plants related to the periwinkle), is widely used in the control of high blood pressure. Digitalis (foxglove), a member of the snapdragon family, is the source of a key medicine used in the treatment of chronic heart failure. (It stimulates the heart to pump blood more effectively with a smaller expenditure of energy.)
Entire books have been written on the plant products human beings use as medicines, and the examples given here barely hint at the many anticancer drugs, painkillers, diuretics, dysentery treatments, antiparasite compounds, dentifrices, ulcer cures, laxatives, and so on that Homo sapiens has obtained from plants alone. In fact, chemicals from flora are major—or sole—ingredients in about a quarter of all the prescriptions written annually in the United States.
Perhaps even more dramatic are the contributions of the lower plants and bacteria that have provided humanity with antibiotics. (Antibiotics also have been found in higher plants, and these may become an important future source of medicine, but none is used medicinally yet.)
The impact on human health of this medical breakthrough can hardly be appreciated by anyone born since World War II, but the fears that—before that time—were associated with a wide variety of injuries and diseases have largely disappeared. War wounds and surgical operations were much less likely to kill after antibiotics became available for infection control. Scourges such as bubonic plague, tuberculosis, epidemic typhus, typhoid fever, scarlet fever, diphtheria, bacterial pneumonia, syphilis, and gonorrhea—the whole spectrum of diseases caused by bacteria—could, with the discovery of these "miracle" medicines, be treated more effectively.
It's astonishing that—in spite of all the already known benefits—systematic investigations of the medical usefulness of plant species have barely begun. For example, conservationist Norman Myers estimates that only about 2% of our world's quarter-million species (approximately) of flowering plants have even been tested for alkaloids, and no single plant species has yet been thoroughly screened for all of its possible beneficial effects.
If humanity is ever to take advantage of the potential medical bonanza available in plants and micro-organisms, heroic efforts must be made to maintain their diversity. Even a species studied thoroughly today and declared medically "useless" should be preserved against the possibility that future generations will disagree with us about that lack of value. After all, Penicillium notatum—-the source of penicillin—would have been "useless" at the time of the American Civil War, because the role of germs in causing disease was not then understood. Therefore, when the species-rich tropical rain forests are destroyed, both we and our descendants stand to lose many untapped treasures forever.
The medical gifts that society has received from nature are by no means restricted to plant chemicals. Substances of animal origin have medical uses, as well. For example, cytarabine—derived from a sponge—is valuable in the treatment of leukemia, and the venom of a Malayan pit viper (a relative of the rattlesnake) is commonly employed as an anticoagulant to prevent the formation of blood clots, which—among other things—can cause heart attacks.
The major contribution of many species of animals, however, has been their availability as tools for experimentation. Rats, mice, rhesus monkeys, and chimpanzees (among others) have been used in very large numbers as surrogates for human beings in a variety of medical experiments and for the evaluations of numerous suspected toxins and cancer-causing agents. It's less well known that exotic species of wild animals—such as elephants, armadillos, and cottontop marmosets—often play similar roles.
It is, of course, impossible to predict the animal species that hold the greatest potential for rendering medical aid to humanity. The promise of beneficial drugs from immobile marine animals, which—like plants—have evolved complicated chemical defenses, seems enormous. But there's simply no way to know which animals will be in demand in future laboratories. Again, the only sensible strategy is to prevent extinctions wherever possible.
Future Food Sources
The most important role of other species in supporting humanity is as sources of food. Yet this area hasn't been examined any more thoroughly than has that of medical potential. For example, only about 3,000 kinds of plants (about one percent of the total number of higher plant species) have ever been utilized by people for food, and—of those—only a paltry 150 or so have been grown commercially to any extent.
This does not mean, however, that many of the currently unexploited species couldn't provide badly needed nourishment. Wheat, for instance, doesn't grow well in the tropics, partly because the fungus that causes wheat rust thrives in warm, humid climates and thus excludes one of the three great cereal crops from some of the hungriest parts of the world. But in those same regions, there are many potential crops of known value and numerous other plants that might help to feed humanity, but whose potential for development remains untested.
As a single example, there's a plant group called eelgrasses, which grow entirely under the sea and which could become an important substitute for traditional grains in densely populated seacoast regions. The Seri Indians of Mexico's west coast have long made flour from the seeds of one species. Here, then, is a potential crop that would need no fresh water, fertilizer, or pesticides to be successfully cultivated.
The plants that were the ancestors of wheat, barley, and rye still grow in Israel. However, these unimpressive, scruffy grasses show little sign of the potential that selective breeding has brought to fruition. There's no question that among the millions of populations and species of plants now threatened with extinction are many "Cinderella" equivalents to the forebears of today's major crops .... but they may be doomed to disappear without ever getting to "the ball."
Even fewer animals have been domesticated than plants. Virtually all of the domestic meat consumed by humanity comes from just nine groups of livestock: cattle, pigs, sheep, goats, water buffalo, chickens, ducks, geese, and turkeys. Yet cattle, for example, are very unsatisfactory domestic animals for the semiarid regions of Africa. They don't thrive in the climate, and their need to trek long distances to water leads to degradation of the land as well as to eventual desertification.
It would be much more sensible to herd gazelles in such regions, as the antelopes can take advantage of a far wider range of native vegetation; can obtain water from their food, and thus avoid having to travel to it; and would cause less deterioration of the environment. There are—of course—economic, social, and environmental problems to solve before native animals can be herded on a large scale in Africa, but unless the species of the area are preserved, such options will disappear.
Other Essential (and Potential) Products
Finally, consider some of the myriad other "gifts" that human beings have received—or might receive—from various species. Wood comes to mind immediately. Many trees produce timber, but different varieties produce lumber of rather different characteristics. White pine wouldn't make good spars for an airplane wing, and balsa wouldn't make a decent piano sounding board. Even within a single species, different populations may have diverse growth characteristics and wood quality.
As you might imagine, there's been far too little exploration into the potential of tropical trees, and many species doubtless have as-yet-undiscovered desirable properties. Furthermore, today's desirable quality may not be yesterday's or tomorrow's. A few centuries ago, for instance, British naval surveyors valued oaks with low, spreading crowns from which they could obtain properly shaped pieces for crucial parts of ships. Now, however, that particular tree form is entirely wrong for most uses of oak.
Other inedible products that humanity derives from plants include natural rubber (superior, in many applications, to artificial types), tanning agents, dyes, fibers (such as cotton, flax, and hemp), natural pesticides (such as pyrethrum and rotenone), perfumes, lotions (witch hazel), waxes, gums, cosmetics, meat tenderizers, preservatives, gutta-percha (used for insulation and waterproofing), turpentine, candles, soap substitutes, fertilizers, brooms, and rattan furniture.
Then, too, many plants yield valuable oils. Those derived from safflowers, soybeans, peanuts, and olives are used in cooking. Linseed, soybean, and flax oils are ingredients in paints and varnishes. And, in addition to its well-known use as a laxative, castor oil is a fine lubricant of machinery. Plant materials are also widely utilized in the manufacture of products that range from plastics to explosives.
Animals, too—although not nearly so rich a source of goods as are plants—supply a wide range of products used in commerce including wool, shellac, musk, silk, down, sperm oil, and leathers. Many of these have qualities that are difficult (or impossible) to emulate with synthetics.
At the risk of sounding like a broken record, we must reiterate that the potential for extracting useful products from plants and animals seems barely to have been tapped. For example, some tropical plant species produce an oil that shows promise of providing a renewable source of a low-sulfur petroleum substitute. With appropriate genetic improvement, "gasoline farms" may someday supply a significant fraction of our fuels.
Although this idea may seem strange at first glance, one need only recall that all fossil fuels were originally plant hydrocarbons. They were "processed" by geological action over millions of years into coal, natural gas, and oil. There's no theoretical reason why Homo sapiens can't short-circuit the plant-to-gasoline sequence by starting with plants especially rich in hydrocarbons ... no reason except, of course, the possibility that the very best plant sources may be unrecognized species and populations that are being pushed toward extinction at this very moment.
In other words, the destruction of Earth's flora and fauna that's proceeding today may be, unbeknown to us, wiping out species that hold secrets which might help to cure cancer, feed the burgeoning human population, or solve the energy crisis. The loss of these benefits alone would be a high price to pay for our cavalier treatment of fellow living beings.
EDITOR'S NOTE: For further information on direct benefits from other species, see Extinction by Paul and Anne Ehrlich (Random House, 1981, $15.95), upon which this column is based.
Paul Ehrlich (Bing Professor of Population Studies and Professor of Biological Sciences, Stanford University) and Anne Ehrlich (Senior Research Associate, Department of Biological Sciences, Stanford) are familiar names to ecologists and environmentalists everywhere. As well they should be. Because it was Paul and Anne who—through their writing and research—gave special meaning to the words "population," "resources," and "environment" in the late 1960's. (They also coined the term coevolution, and did a lot to make ecology the household word it is today.) But while most folks are aware of the Ehrlichs' popular writing in the areas of ecology and overpopulation (most of us—for instance—have read Paul's book The Population Bomb), far too few people have any idea of how deeply the Ehrlichs are involved in ecological research (research of the type that tends to be published only in technical journals and college textbooks). That's why it pleases us to be able to present these semi-technical columns by authors/ecologists/educators Anne and Paul Ehrlich.