The Importance of Preserving Biodiversity

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ILLUSTRATION: FOTOLIA/DANIELLE BONARDELLE
Noting that humanity could benefit in unexpected ways from plants and animals that haven't been studied, ecologists Anne and Paul Ehrlich argued for the importance of preserving biodiversity.

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.

Medicinal Plants

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.

Tiny Miracle-Workers

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.

Animal Surrogates

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.