In 2011 i enjoyed reading The Sea Around Us by Rachel Carson [1].
Many times i've heard of Silent Spring and seen it referenced. So i was excited to find it recently in a little free library. Reading this book felt stimulating because of its clarity, brisk pace, and the large amount of information. Even though it was published in 1962 and some of the details have changed, much of it still feels relevant.
The author spent some time frankly discussing man-made carcinogens. I thought it was interesting that she died of cancer 2 years after this book was published. She was writing about damage to the planet Earth, but she may as well have been writing about damage to her own body. For good or ill we as a species share the fate of our planet.
What follows are quotes that i found interesting, plus comments within square brackets.
Every writer of a book on many diverse facts owes much to the skill and helpfulness of librarians.
I am pessimistic about the human race because it is too ingenious
for its own good. Our approach to nature is to beat it into
submission. We would stand a better chance of survival if we
accommodated ourselves to this planet and viewed it
appreciatively instead of skeptically and dictatorially.
--E. B. White
[ In chapter 1, the author gives a fable to represent environmental destruction, depicting a "before and after" contrast between a lush, fertile environment and a desolate, polluted one. At some point the popular consensus (in the USA) shifted and decided that outdoor house cats were a bad idea. Later, the popular consensus shifted and decided that outdoor children are also a bad idea. This shift to indoor living can only heighten our disconnect from nature.
Once i drove with a friend and her daughter through a clear cut. My friend thought it was a shame. Her daughter replied: "What's the big deal? It will just grow back."
On a hike in northern California, i went through an old-growth preserve, bordered by a monoculture that grew back after a clear cut. When i walked across the border of the preserve, the contrast was as stark as going from Earth to Mars. Yes, both forests contained trees, but the similarity ended there. The monoculture was thick like weeds, and the trees looked crowded, skinny, and ill-favored. It was dry and looked like a fire hazard, in contrast to the cool, moist fairyland that i had just traveled through.
It takes centuries for a forest to progress through its stages and become old-growth. I've read that never in human history have we "grown back" an old-growth forest. Our attention doesn't span centuries. No, it won't "just grow back"! ]
Certain rocks gave out dangerous radiation; even within the light of the sun, from which all life draws its energy, there were short-wave radiations with power to injure. Given time--time not in years but in millennia--life adjusts, and a balance has been reached. For time is the essential ingredient; but in the modern world there is no time.
The rapidity of change and speed with which new situations are created follow the impetuous and heedless pace of man rather than the deliberate pace of nature.
Some would-be architects of our future look toward a time when it will be possible to alter the human germ plasm [DNA] by design. But we may already be doing so now by inadvertence, for many chemicals, like radiation, bring about gene mutations. It is ironic to think that man might determine his own future by something so seemingly trivial as his choice of insect spray.
All this is not to say there is no insect problem and no need of control. I am saying, rather, that control must be geared to reality, not to mythical situations, and that the methods employed must be such that they do not destroy us along with the insects.
The problem whose attempted solution has brought such a train of disaster in its wake is an accompaniment of our modern way of life.
Under primitive agricultural conditions the farmer had few insect problems. Those arose with the intensification of agriculture... Nature has introduced great variety into the landscape, but man has displayed a passion for simplifying it. Thus he undoes the built-in checks and balances by which nature holds the species within bounds.
In new territory, out of reach of the restraining hand of natural enemies that kept down its numbers in its native land, an invading plant or animals is able to become enormously abundant. Thus it is no accident that our most troublesome insects are introduced species.
[This is] an era dominated by industry, in which the right to make a dollar at whatever cost is seldom challenged. When the public protests, confronted with some obvious evidence of damaging results of pesticide applications, it is fed little tranquilizing pills of half-truth. It is the public that is being asked to assume the risks that the insect controllers calculate. The public must decide whether it wishes to continue on the present road, and it can do so only when in full possession of the facts.
[No consent without informed consent.]
This industry is a child of the Second World War. In the course of developing agents of chemical warfare, some of the chemicals created in the laboratory were found to be lethal to insects. The discovery did not come by chance: insects were widely used to test chemicals as agents of death for man.
Epidemics of arsenic poisoning involving whole populations over long periods are on record. Arsenic contaminated environments have also caused sickness and death among horses, cows, goats, pigs, deer, fishes, and bees; despite this record arsenical sprays and dusts are widely used. In the arsenic-sprayed cotton country of southern United States beekeeping as an industry has nearly died out.
[See also my notes at the end of the section on Chapter 5, which are highly relevant to arsenic poisoning.]
Modern insecticides are still more deadly. The vast majority fall into one of two large groups of chemicals. One, represented by DDT, is known as the "chlorinated hydrocarbons." The other group consists of the organic phosphorus insecticides, and is represented by the reasonably familiar malathion and parathion.
The fact that the suburbanite is not instantly stricken has little meaning, for the toxins may sleep long in his body, to become manifest months or years later in an obscure disorder almost impossible to trace to its origins.
There are vast gaps in our knowledge of how dieldrin is stored or distributed in the body, or excreted, for the chemists ingenuity in devising insecticides has long ago outrun biological knowledge of the way these poisons affect the living organism. However there is every indication of long storage in the human body, where deposits may lie dormant like a slumbering volcano, only to flare up in periods of physiological stress when the body draws upon its fat reserves.
Parathion is one of the most widely used of the organic phosphates. It is also on of the most powerful and dangerous. A chemist, thinking to learn by the most direct possible means the dose acutely toxic to human beings, swallowed a minute amount, equivalent to about .00424 ounces. Paralysis followed so instantaneously that he could not reach the antidotes he had prepared at hand, and so he died.
Yet some 7,000,000 pounds of parathion are now applied to fields and orchards of the United States... The amount used on California farms alone could, according to one medical authority, "provide a lethal dose for 5 to 10 times the whole world's population."
The common salad bowl may easily present a combination of organic phosphate insecticides. Residues well within the legally permissible limits may interact [with each other in dangerous ways.]
While the results of weed killers such as sodium arsenite or the phenols are grossly obvious, some other herbicides are more insidious in their effects. For example, the now famous cranberry-weed-killer aminotriazole, or amitrol, is rated as having relatively low toxicity. But in the long run its tendency to cause malignant tumors in the thyroid may be far more significant for wildlife and perhaps also for man.
A disturbing example of [surface water contamination] seems to be building up on the national wildlife refuges at Tule Lake and Lower Klamath, both in California. These refuges are part of a chain including also the refuge on Upper Klamath Lake just over the border in Oregon. All are linked, perhaps fatefully, by a shared water supply, and all are affected by the fact that they lie like small islands in a great sea of surrounding farmlands--land reclaimed by drainage and stream diversion from an original waterfowl paradise of marshland and open water.
These farmlands around the refuges are now irrigated by water from Upper Klamath Lake. The irrigation waters, recollected from the fields they have served, are then pumped into Tule Lake and from there to Lower Klamath. All of the waters of the wildlife refuges established on these two bodies of water therefore represent the drainage of agricultural lands. It is important to remember this in connection with recent happenings.
In the summer of 1960 the refuge staff picked up hundreds of dead and dying birds at Tule Lake and Lower Klamath. Most of these were fish-eating species--herons, pelicans, grebes, gulls. Upon analysis they were found to contain insecticide residues identified as toxaphene, DDD, and DDE. Fish from the lakes were also found to contain insecticides; so did samples of plankton. The refuge manager believes that pesticide residues are now building up in the waters of these refuges being conveyed there by return irrigation flow form heavily sprayed agricultural lands.
Although the California Department of Public Health professed to see no hazard, nevertheless in 1959 it required that the use of DDD in the lake be stopped.
[See the introduction in Myths of the Modocs [2] for a sympathetic view of the indigenous people of this area.]
It is an extraordinary fact that the deliberate introduction of poisons into a reservoir is becoming a fairly common practice. The purpose is usually to promote recreational uses... When sportsmen of an area want to "improve" fishing in a reservoir, they prevail on authorities to dump quantities of poison into it to kill the undesired fish, which are then replaced with hatchery fish more suited to the sportsmen's taste. The procedure has a strange, Alice-in-Wonderland quality.
[Still doing it. In 2014 i camped at Diamond Lake just a few days after the USFS poisoned the lake. There were warning signs all over the place.]
... a study made in Holland in the early 1950's provides support for the view that polluted waterways may carry a cancer hazard. Cities receiving their drinking water from rivers had a higher death rate from cancer than did those whose water came from sources presumed to be less susceptible to pollution, such as wells.
The thin layer of soil that forms a patchy covering over the continents controls our own existence and that of every other animal on the land. Without soil, land plants as we know them could not grow, and without plants no animals could survive.
The problem that concerns us here is one that has received little consideration: What happens to these incredibly numerous and necessary inhabitants of the soil when poisonous chemicals are carried down into their world, either introduced directly as soil "sterilants" or borne on the rain that has picked up a lethal contamination as it filters through the leafy canopy of forest and orchard and cropland? Is it reasonable to suppose that we can apply a broad-spectrum insecticide to kill the burrowing larval stages of a crop-destroying insect, for example, without also killing the "good" insects whose function may be the essential one of breaking down organic matter? Or can we use a non-specific fungicide without also killing the fungi that inhabit the roots of many trees in a beneficial association that aids the tree in extracting nutrients from the soil?
Seemingly moderate applications of insecticide over a period of years may build up fantastic quantities in soil.
Arsenic provides a classic case of the virtually permanent poisoning of the soil. Although arsenic as a spray on growing tobacco has been largely replaced by the synthetic organic insecticides since the mid-40's, the arsenic content of cigarettes made from American-grown tobacco increased more than 300 per cent between the years 1932 and 1952. Later studies have revealed increases as much as 600 per cent. Dr. Henry S. Satterlee, an authority on arsenic toxicology, says that although organic insecticides have largely been substituted for arsenic, the tobacco plants continue to pick up the old poison. For the soils of tobacco plantations are now thoroughly impregnated with residues of a heavy and relatively insoluble poison, arsenate of lead. This will continue to release arsenic in a soluble form. The soil of a large portion of the land planted with tobacco has been subjected to "cumulative and well-nigh permanent poisoning," according to Dr. Satterlee. Tobacco grown in the eastern Mediterranean countries where arsenical insecticides are not used has shown no such increase in arsenic content.
[Cotton was another southern crop heavily dosed with arsenic.
I read about repeated arsenic scares in baby food, caused by USA-grown rice [3]. Rice is used in many baby foods because it is inexpensive and easy to digest. I read that rice is often grown in former cotton-growing parts of the south. I read that federal rules require 7 years without using conventional pesticides before land can qualify for organic farming. This begs several questions.
"Although the of lead arsenic-containing pesticides has long been stopped, large areas land remain contaminated." --Wikipedia [4]
I read that in the USA, rice is mainly grown in Arkansas, California, Louisiana, Mississippi, Missouri, and Texas. All of these states have a history of growing cotton, with the last 3 being the largest producers. Rice from these states has twice as much arsenic compared to rice grown in California [5]. I read that the USA has some of the most relaxed rice regulations in the world, and India has some of the most stringent. So i was not surprised to read that rice grown in India and Pakistan has the least arsenic.
Arsenic is mostly deposited in the outer layers, so brown rice has much more arsenic than white rice does. ]
A practical example was provided recently by the parks in a city in Holland. The roses were doing badly. Soil samples showed heavy infestations by tiny nematode worms. Scientist of the Dutch Plant Protection Service did not recommend chemical sprays or soil treatments; instead, they suggested that marigolds be planted among the roses. This plant, which the purist would doubtless consider a weed in any rosebed, releases an excretion from its roots that kills the soil nematodes. The advice was taken; some beds were planted with marigolds, some left without as controls. The results were striking. With the aid of the marigolds the roses flourished; in the control beds they were sickly and drooping. Marigolds are now used in many places for combating nematodes.
In the same way, and perhaps quite unknown to us, other plants that we ruthlessly eradicate may be performing a function that is necessary to the health of the soil.
An outstanding example in the field of controlling unwanted plants is the handling of the Klamath weed problem in California. Although the Klamath weed, or goatweed is a native of Europe (where it is called St. Johnswort), it accompanied man in his westward migrations, first appearing in the United States in 1793 near Lancaster, Pennsylvania. By 1900 it had reached California in the vicinity of the Klamath River, hence the name locally given to it. By 1929 it had invaded some two and one half million acres.
Klamath weed, quite unlike such native plants as sagebrush, has no place in the ecology of the region and no animals or other plants require its presence. On the contrary, wherever it appeared livestock became "scabby, sore-mouthed, and unthrifty" from feeding on this toxic plant. Land values declined accordingly, for the Klamath weed was considered to hold the first mortgage.
In Europe the Klamath weed, or St. Johnswort, has never become a problem because along with the plant there have developed various species of insects; these feed on it so extensively that its abundance is severely limited. In particular, two species of beetles in southern France, pea-sized and of metallic color, have their whole beings so adapted to the presence of the weed that they feed and reproduce only upon it.
It was an event of historic importance when the first shipments of these beetles were brought to the United States in 1944, for this was the first attempt in North America to control a plant with a plant-eating insect. By 1948 both species had become so well established that no further importations were needed. Their spread was accomplished by collecting beetles from the original colonies and redistributing them at the rate of millions a year. Within small areas the beetles accomplished their own dispersion, moving on as soon as the Klamath weed dies out and locating new stands with great precision. And as the beetles thin out the weed, desirable range plants that have been crowded out are able to return.
A ten-year survey completed in 1959 showed that control of the Klamath weed had been "more effective than hoped for even by enthusiasts," with the weed reduced to a mere 1 per cent of its former abundance. This token infestation is harmless and is actually needed in order to maintain a population of beetles as protection against a future increase in the weed.
The citizen who wishes to make a fair judgment of the question of wildlife loss today is confronted with a dilemma. On the one hand conservationists and many wildlife biologists assert that the losses have been severe and in some cases catastrophic. On the other hand the control agencies tend to deny flatly and categorically that such losses have occurred, or that they are of any importance if they have. Which view are we to accept?
In Toledo, Ohio, a similar experience caused the Superintendent of Forestry, Joseph A. Sweeney, to take a realistic look at the results of spraying. Spraying was begun there in 1953 and continued through 1959. Meanwhile, however, Mr. Sweeney had noticed that a city-wide infestation of the cottony maple scale was worse after the spraying recommended by "the books and the authorities" than it had been before. He decided to review the results of spraying for Dutch elm disease for himself. His findings shocked him. In the city of Toledo, he found, "the only areas with any control were the areas where we used some promptness in removing the diseased or brood trees. Where we depended on spraying the disease was out of control. In the country where nothing has been done the disease has not spread as fast as it has in the city. This indicates that spraying destroys any natural enemies."
"We are abandoning spraying for the Dutch elm disease. This has brought me into conflict with the people who back any recommendations by the United States Department of Agriculture but I have the facts and will stick with them."
And New York state today has a most impressive record of containing and suppressing the disease. Yet it has not relied on spraying. In fact, its agricultural extension service does not recommend spraying as a community method of control.
The key to a healthy plant or animal community lies in what the British ecologist Charles Elton calls "the conservation of variety." What is happening now is in a large part a result of the biological unsophistication of past generations. Even a generation ago no one knew that to fill large areas with a single species of tree was to invite disaster.
Each of the recurrent exposures, no matter how slight, contributes to the progressive buildup of chemicals in our bodies and so to cumulative poisoning. Lulled by the soft sell and the hidden persuader, the average citizen is seldom aware of the deadly materials with which he is surrounding himself; indeed, he may not realize he is using them at all.
So thoroughly has the age of poisons become established that anyone may walk into a store and, without questions being asked, buy substances of far greater death-dealing power than the medicinal drug for which he may be required to sign a "poison book" in the pharmacy next door.
The mores of suburbia now dictate that crabgrass must go at whatever cost. Sacks containing chemicals designed to rid the lawn of such despised vegetation have become almost a status symbol. These weed-killing chemicals are sold with brand names that never suggest their identity or nature. To learn that they contain chlordane or dieldrin one must read exceedingly fine print placed on the least conspicuous part of the sack. The descriptive literature that may be picked up in any hardware or garden-supply store seldom if ever reveals the true hazard involved in handling or applying the material. Instead, the typical illustration portrays a happy family scene, father and son smilingly preparing to apply the chemical to the lawn, small children tumbling over the grass with a dog.
The ultimate answer is to use less toxic chemicals so that the public hazard from their misuse is greatly reduced. Such chemicals already exist: pyrethrins, rotenone, ryania, and others derived from plant substances.
[A family member overheard a disturbing conversation at a garden supply store during the "cannabis boom" in Oregon. A new grower was talking with a store employee about about a spider mite infestation. The employee recommended using earwig perimeter treatments. Common perimeter treatments are bifenthrin, cyhalothrin, deltamethrin, and permethrin. These are pyrethrins, one of the "less toxic" pesticides listed in Silent Spring. However, several of them are neurotoxic and carcinogenic. They aren't safe to inhale. For example, cyhalothrin is a restricted use pesticide and it is a violation of federal law to use it in a manner inconsistent with its labelling.]
In addition to making this change to less dangerous agricultural pesticides, we should diligently explore the possibilities of nonchemical methods. Agricultural use of insect diseases, caused by a bacterium highly specific for certain types of insects, is already being tried in California, and more extended tests of this method are underway. A great many other possibilities exist for effective insect control by methods that will leave no residue on foods. Until a large-scale conversion to these methods has been made, we shall have little relief from a situation that, by any common-sense standards, is intolerable.
We are accustomed to look for the gross and immediate effect and to ignore all else. Unless this appears promptly and in such obvious form that it cannot be ignored, we tend to deny the existence of a hazard.
Storage of the chlorinated hydrocarbons, as we have seen, is cumulative, beginning with the smallest intake. The toxic materials become lodged in all the fatty tissues of the body. When these reserves of fat are drawn upon the poison may then strike quickly. [This can happen with the loss of weight during an illness, making illness that much more dangerous.]
The adipose tissue, we are warned, is not merely a place for the deposition of fat, but has many important functions with which the stored poisons may interfere. Furthermore, fats are widely distributed in the organs and tissues of the whole body, even being constituents of cell membranes. It is important to remember, therefore, that the fat-soluble insecticides are in a position to interfere with the most vital and necessary functions of oxidation and energy production.
One of the most significant facts about the chlorinated hydrocarbon insecticides is their effect on the liver.
The whole problem of pesticide poisoning is enormously complicated by the fact that a human being, unlike a laboratory animal living under rigidly controlled conditions, is never exposed to one chemical alone. Between the major groups of insecticides, and between them and other chemicals, there are interactions that have serious potentials.
The power of the organic phosphates, these poisons of the nerve-protecting enzyme cholinesterase, may become greater if the body has first been exposed to a chlorinated hydrocarbon which injures the liver. This is because, when liver function is disturbed, the cholinesterase level drops below normal. The added depressive effect of the organic phosphate may then be enough to precipitate acute symptoms.
During [the prohibition] some medicinal substances were pressed into service as substitutes for liquor. One of these was Jamaica ginger. But the /United States Pharmacopeia/ product was expensive, and bootleggers conceived the idea of making a substitute Jamaica ginger. They succeeded so well that their spurious product responded to the appropriate chemical tests and deceived the government chemists. To give the false ginger the necessary tang they had introduced a chemical known as triorthocresyl phosphate. This chemical, like parathion and its relatives, destroys the protective enzyme cholinesterase. As a consequence of drinking the bootleggers' produce some 15,000 people developed a permanently crippling type of paralysis of the leg muscles, a condition now called "ginger paralysis." The paralysis was accompanied by destruction of the nerve sheaths and by degeneration of the cells of the anterior horns of the spinal cord.
About two decades later various other organic phosphates came into use as insecticides, as we have seen, and soon cases reminiscent of the ginger paralysis episode began to occur.
The insecticide responsible for these cases has been withdrawn from the market, but some of those now in use may be capable of like harm. Malathion (beloved of gardeners), has induced severe muscular weakness in experiments on chickens. This was attended (as in ginger paralysis) by destruction of the sheaths of the sciatic and spinal nerves.
All these consequences of organic phosphate poisoning, if survived, may be a prelude to worse. In view of the severe damage they inflict upon the nervous system, it was perhaps inevitable that these insecticides would eventually be linked with mental disease.
Echoes of this sort of thing are to be found, as we have seen, widely scattered throughout medical literature, sometimes involving the chlorinated hydrocarbons, sometimes the organic phosphates. Confusion, delusions, loss of memory, mania--a heavy price to pay for the temporary destruction of a few insects, but a price that will continue to be exacted as long as we insist upon using chemicals that strike directly at the nervous system.
The biologist George Wald once compared his work on an exceedingly specialized subject, the visual pigments of the eye, to "a very narrow window through which at a distance one can see only a crack of light. As one comes closer the view grows wider and wider, until finally through this same narrow window one is looking at the universe."
So it is that only when we bring our focus to bear, first on the individual cells of the body, then on the minute structures within the cells, and finally on the ultimate reductions of molecules within these structures--only when we do this can we comprehend the most serious and far-reaching effects of the haphazard introduction of foreign chemicals into our internal environment. Medical research has only rather recently turned to the functioning of the individual cell in producing the energy that is the indispensable quality of life. The extraordinary energy-producing mechanism of the body is basic not only to health but to life; it transcends in importance even the most vital organs, for without the smooth and effective functioning of the energy-yielding oxidation none of the body's functions can be performed. Yet the nature of many of the chemicals used against insects, rodents, and weeds is such that they may strike directly at this system, disrupting its beautifully functioning mechanism.
ATP is the universal currency of energy--found in all organisms from microbes to man.
The charging of the battery, in which ADP and a free phosphate group are combined to restore ATP, is coupled to the oxidative process; the close linking is known as coupled phosphorylation. If the combination becomes uncoupled, the means is lost for providing usable energy. The consequences of uncoupling could indeed be disastrous for any organism from embryo to adult: in time it could lead to the death of the tissue or even of the organism.
How can uncoupling come about? Radiation is an uncoupler, and the death of cells exposed to radiation is thought by some to be brought about in this way. Unfortunately, a good many chemicals also have the power to separate oxidation from energy production, and the insecticides and weed killers are well represented on the list.
But uncoupling is not the only way to extinguish the little fires in some or all of the body's billions of cells. We have seen that each step in oxidation is directed and expedited by a single enzyme. When any of these enzymes--even a single one of them--is destroyed or weakened, the cycle of oxidation within the cell comes to a halt. It makes no difference which enzyme is affected. Oxidation progresses in a cycle like a turning wheel. If we thrust a crowbar between the spokes of a wheel it makes no difference where we do it, the wheel stops turning. In the same way, if we destroy an enzyme that functions at any point in the cycle, oxidation ceases. There is then no further energy production, so the end effect is very similar to uncoupling.
The crowbar to wreck the wheels of oxidation can be supplied by any number of chemicals commonly used as pesticides.
Merely by systematically withholding oxygen, experimenters have caused normal cells to turn into cancer cells...
Two of the carbamates are actually used to prevent sprouting of potatoes in storage--precisely because of their proven effect in stopping cell division. Another anti-sprouting agent, maleic hydrazide, is rated a powerful mutagen.
In 1775 Sir Percival Pott declared that the scrotal cancer so common among chimney sweeps must be caused by the soot that accumulated on their bodies. He could not furnish the "proof" we would demand today, but modern research methods have now isolated the deadly chemical in soot and proved the correctness of his perception.
A quarter of a century ago, cancer in children was considered a medical rarity. /Today, more American school children die of cancer than from any other disease./
The late C. P. Rhoads, onetime director of the Sloan-Kettering Institute for Cancer Research, found that test animals exposed to a very potent chemical carcinogen developed no cancer if they had been fed yeast, a rich source of natural B vitamins. A deficiency of these vitamins has been found to accompany mouth cancer and perhaps cancer of other sites in the digestive tract.
Despite the prominence that "magic bullets" and "wonder drugs" hold in the layman's mind, most of the really decisive battles in the war against infectious disease consisted of measures to eliminate disease organisms from the environment. [Such as water sanitation. Prevention is better than cure.]
The chemical agents of cancer have become entrenched in our world in two ways: first, and ironically, through man's search for a better and easier way of life; second, because the manufacture and sale of such chemicals has become an accepted part of our economy and our way of life.
To have risked so much in our efforts to mold nature to our satisfaction and yet to have failed in achieving our goal would indeed be the final irony. Yet this, it seems, is our situation. The truth, seldom mentioned but there for anyone to see, is that nature is not so easily molded and that the insects are finding ways to circumvent our chemical attacks on them.
By a process of genetic selection, the insects are developing strains resistant to chemicals. But the broader problem, which we shall look at now, is the fact that our chemical attack is weakening the defenses in the environment itself, defenses designed to keep the various species in check. Each time we breach those defenses a horde of insects pours through.
The stockman's zeal for eliminating the coyote has resulted in plagues of field mice.
The predatory insects of field and forests play the same role as the wolves and coyotes of the Kaibab. Kill them off and the population of the prey insect surges upward.
The trouble is that we are seldom aware of the protection afforded by natural enemies until it fails. Most of us walk unseeing through the world, unaware alike of its beauties, its wonders, and the strange and sometimes terrible intensity of the lives that are being lived around us. So it is that the activities of the insect predators and parasites are known to few.
Thus, through the circumstances of their lives, and the nature of our own wants, all of these have been our allies in keeping the balance of nature tilted in our favor. Yet we have turned our artillery against our friends. The terrible danger is that we have grossly underestimated their value in keeping at bay a dark tide of enemies that, without their help, can overrun us.
If this seems absurd, consider the situation in the citrus groves of California, where the world's most famous and successful experiment in biological control was carried out in the 1880's. In 1872 a scale insect that feeds on the sap of citrus trees appeared in California and within the next 15 years developed into a pest so destructive that the fruit crop in many orchards was a complete loss. Many farmers gave up and pulled out their trees. Then a parasite of the scale insect was imported from Australia, a small lady beetle called the vedalia. Within only two years after the first shipment of the beetles, the scale was under complete control throughout the citrus-growing sections of California. From that time on one could search for days among the orange groves without finding a single scale insect.
Then in the 1940's the citrus growers began to experiment with glamorous new chemicals against other insects. With the advent of DDT and even more toxic chemicals to follow, the populations of the vedalia in many sections of California were wiped out. Its importation had cost the government a mere $5000. Its activities had saved the fruit growers several millions of dollars a year, but in a moment of heedlessness the benefit was canceled out. Infestations of the scale insect quickly reappeared and damage exceeded anything that had been seen for fifty years.
"This possibly marked the end of an era," said Dr. Paul Debach of the Citrus Experiment Station in Riverside. Now control of the scale has become enormously complicated. The vedalia can be maintained only be repeated releases and by the most careful attention to spray schedules, to minimize their contact with insecticides. And regardless of what the citrus growers do, they are more or less at the mercy of the owners of adjacent acreages....
The list of resistant species now includes practically all of the insect groups of medical importance.
Agencies concerned with vector-borne disease are at present coping with their problems by switching from one insecticide to another as resistance develops. But this cannot go on indefinitely, despite the ingenuity of the chemists in supplying new materials. Dr. Brown has pointed out that we are traveling "a one-way street." No one knows how long the street is. If the dead end is reached before control of disease-carrying insects is achieved, our situation will indeed be critical.
With insects that infect crops the story is the same.
Ordinarily resistance takes two or three years to develop... The number of generations produced by an insect population in a year is important.
The hopeful question is sometimes asked, "If insects can become resistant to chemicals, could human beings do the same?" Theoretically they could; but since this would take hundreds or even thousands of years [at our rate of reproduction], the comfort to those living now is slight.
We stand now where two roads diverge. But unlike the roads in Robert Frost's familiar poem, they are not equally fair. The road we have long been traveling is deceptively easy, a smooth superhighway on which we progress with great speed, but at its end lies disaster. The other fork of the road--the one "less traveled by"--offers our last, our only chance to reach a destination that assures the preservation of our earth. [And the preservation of ourselves.]
A truly extraordinary variety of alternatives to the chemical control of insects is available. All have this in common: they are /biological/ solutions, based on understanding of the living organisms they seek to control, and of the whole fabric of life to which these organisms belong.
The "control of nature" is a phrase conceived in arrogance, born of the Neanderthal age of biology and philosophy, when it was supposed that nature exists for the convenience of man. The concepts and practices of applied entomology for the most part date from that Stone Age of science. It is our alarming misfortune that so primitive a science has armed itself with the most modern and terrible weapons, and that in turning them against the insects it has also turned them against the earth. [And against ourselves.]
author: Carson, Rachel, 1907-1964
detail: gopher://gopherpedia.com/0/Silent_Spring
title: Silent Spring