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some degree of potency. A much higher percentage yield pharmaceuticals and other
natural products of potential use as well as basic scientific information. If we dismiss
beardtongues and louseworts, we may be doing ourselves a considerable disservice.
Simple prudence dictates that no species, however humble, should ever be allowed
to go extinct if it is within the power of humanity to save it. Take another—even
repugnant—example, the leech. We would certainly be better off without these
miserable bloodsuckers, right? Wrong. The medicinal leech of Europe has proved to
be of great value to modern medicine. To prevent the blood of its victims from
clotting, it secretes a powerful anticoagulant called hirudin. This substance is used to
treat contusions, thrombosis, hemorrhoids and other conditions in which clotting
blood can be painful or dangerous. Thousands of lives are saved annually by hirudin.
The leech uses a second substance, the enzyme hyaluronidase, to disperse cells and
hasten the penetration of hirudin. Surgeons adapt this material in the same way to
spread injected drugs and anesthetics. Leeches also contain antibiotics and substances
that enlarge the diameter of blood vessels, which might someday lead to a cure
for migraine headaches. Medicinal leeches are now the basis of a $4 million annual
business. They are so much in demand that the European species is threatened by
overcollecting in its natural habitat.
With the aid of other specialists (my own special group is ants), I have estimated
the total number of kinds of plants, animals, and microorganisms known to science
to be about 1.4 million. By “known to science” we mean characterized anatomically
and given a scientific name, such as Canis familiaris for the domestic dog, Hirudo
medicinalis for the European medicinal leech, and Homo sapiens for humans. But
the actual number of kinds is estimated to fall somewhere between 10 million and
80 million, depending on the statistical method used and the degree of conservativeness
on the part of the scientist making the estimate. The truth is that we don’t
know even to the nearest order of magnitude the amount of diversity. In other words,
we cannot say whether the figure is closer to 1 million, 10 million or 100 million.
When scientists fail to make a measurement to the nearest order of magnitude,
it is fair to surmise that the subject is still poorly known. The truth is that life on
planet earth has only begun to be explored. Every time I go to a rainforest site in
Central or South America, I find new species of ants within several hours of searching.
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