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ID
Pesticides and
Wildlife
Modern pesticides* have accounted for impressive gains in food
production both here and abroad; they have been responsible for
saving many human lives through control of disease vectors; they have
become components of twentieth-century technology. It is appropn-
ate, however, to examine the evidence of harmful environmental
effects and to weigh the benefit-risk equation in the use of pesticides,
with special reference to their effect on wildlife. It may well be that
the gains sought through pesticide use can be had only at some sacri-
f~ce in wildlife values, but the risks involved should be understood as
fully as possible to provide a basis for establishing policies in the best
public interest.
TH E N EED FOR PESTI Cl DES
Strong pressures-biological, economic, sociological, and esthetic-
favor the use of pesticides. It is extremely important that these influ-
ences be understood if there is to emerge a system of regulating pesti-
cides that strikes a balance between adequate safeguards and undue
restriction.
*As used here, the term "pesticides" includes chemicals employed to kill living organisms that
are considered pests. The major groups of pesticides considered here are insecticides, fungi-
cides, and herbicides. The term "pesticide" may also include chemicals used against pests to
repel, attract, or interrupt a vital function such as reproduction (sterilants). Other chemicals
sometimes considered as pesticides are plant growth regulators, desiccants, and defoliants.
181
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182
Land Use and Wildlife Resources
The Biological Struggle
Man recognizes the need to protect his sources of food and fiber from
the ravages of pests. Similarly, he is concerned with pests that spread
disease and affect his health and comfort. To combat living organisms
he considers harmful, while protecting those he considers beneficial, is
a challenge of great complexity. So-called pest species are to be found
in most of the major groups of living organisms-viruses, bacteria,
fungi, nematodes, insects, birds, mammals, and plants.
All living organisms occur in communities, or ecosystems, inter-
acting and arriving at some kind of balance that is constantly in a state
of flux. To maintain conditions favorable to man requires that he im-
pose many controls. Pesticides are valuable tools in making some of
these adjustments.
The problem is intensified because modern commerce has intro-
duced many pests to new areas where they are not under the restraints
imposed by the biological checks and balances present in their native
habitat. Approximately 50 percent of the pests in the United States
are introduced.
In addition, domesticated varieties of plants and animals are often
selected because of desirable qualities other than their natural resis-
tance to pests. For instance, the McIntosh apple, introduced about
1870, remains a favorite despite its high susceptibility to apple scab, a
fungus disease requiring intensive use of fungicides.
The system of monoculture whereby large numbers of a single spe-
cies are cultivated in close proximity renders the population vulnerable
to attack and subject to violent cyclic fluctuations.
It is evident that modern agriculture, rather than having built-in
biological regulators to hold it in equilibrium, is extremely artificial
and is dependent upon intensive pest-control programs. Chemical pes-
ticides have been very effective as tools in the struggle.
The Need for More Food
Two thirds of the world's inhabitants are underfed, and we are in the
midst of a population explosion that has a potential for doubling the
world population by the year 2000. Every optimistic projection for
overcoming worldwide food shortages is based on the assumption that
the technology responsible for the impressive increase in agricultural
production since about midcentury can be extended to other coun-
tries and that it can be further improved (President's Science Advisory
Committee, 19671. The developed countries of the world have in
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Pesticides and Wildlife
183
creased the use of pesticides chiefly to increase food production, while
developing countries have employed them largely to control vectors of
human diseases. Although pesticides are but one of the numerous ele-
ments of modern agricultural technology, the venous elements interact
in such a way that the withdrawal of any one of them sets off a chain
of limiting effects. Despite the promise of alternative methods of pest
control, they are not likely to account for major reductions in the use
of chemical pesticides in the immediate future.
Public Health
The value of DDT in disease control through the reduction of insect
vectors was dramatically demonstrated during World War II. Since the
war extensive programs in public health have been sponsored by the
World Health Organization (WHO) and other agencies. Because of the
desire to put "first things first," high priorities have been placed on
saving human lives in developing countries and perhaps secondary
priority was given to environmental considerations which, at the
moment at least, did not involve human lives. The sense of responsi-
bility and concern of WHO leadership in the use of DDT is well stated
in the following passage:
The general attitude and feeling of WHO towards the use of DDT is at present
agonizingly ambivalent. On the one hand it is proud of its amazing record, of
having been the main agent in eradicating malaria in countries whose populations
total 550 million people, of having saved about 5 million lives and prevented
100 million illnesses in the first 8 years of its use, of having recently reduced the
annual malaria death-rate in India from 750,000 down to 1,500, and of having
served at least 2 billion people in the world without causing the loss of a single
life by poisoning from DDT alone.
On the other hand WHO is still pressing its search for new compounds with the
view of finding some to validate as DDT substitutes. It has investigated the possi-
bilities of biological control since 1959 and has not Oven up although the outlook
appears so unpromising. It is pushing the development of genetical control, not
only for Culex fatigans in which cytoplasmic incompatibility offers real practical
possibilities, but also for Anopheles gambiae, the principal malaria vector of
Africa. In fact, the bulk of the research promoted by WHO in the past 10 years
has been devoted to the search for substitute materials and methods. And it in-
tends forthwith to repair the omission of not having investigated quantitatively
the fate of the DDT that has been applied to the houses over the years.
In short, WHO has been working towards a progressive transfer away from DDT
in public health operations. But the problem is to effect this transfer without jeop-
ardizing the large amount of human life and health which is at stake, and without
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Land Use and Wildlife Resources
making control so expensive, complicated and uncertain that the developing coun-
tries will lose heart in their operations against diseases transmitted by disease vec-
tors. Certainly an attempt to force the pace by advocating the immediate discon-
tinuation of the use of DOT would be a disaster to world health.*
Economic Stress
In a free enterprise system the entrepreneur can adopt any legal means
to protect his investment and insure a favorable competitive position.
Indeed, his success is measured in terms of his ability to do this. In re-
sponse to this well-known economic pnnciple, modern agriculture
seeks to adopt all measures that can enhance its efficiency. This means
converting to large production units, using hybrid seed, and adopting
mechanization to reduce labor and insure timely cultivation and har-
vesting. Pesticides have proven their worth as elements in modern tech-
nology, and sound economics dictates that they be used, for example,
in weed control, or insect control as a substitute for more costly hand
operations.
Similarly, the economic pressure favors using the least expensive
pesticide. Although the trend is away from persistent pesticides, they
are often chosen as less costly than unstable ones requiring more ap-
plications, but having less potential for environmental pollution.
All trends in modern agriculture suggest that these economic pres-
sures will increase. If so, the regulations governing the use of such
components of the technology web as pesticides need to be re-
examined and clear guidelines established.
The present regulatory system places the responsible agricultural
producer in the difficult position of choosing between practices that
are economically sound and legally acceptable, but that may well be
harmful to environmental quality-a matter he understands only
vaguely and for which he recognizes no direct responsibility-and
more expensive, less environmentally troublesome measures.
Standards of Quality
The Amencan public has come to expect high standards of quality
and, in response to this expectation, regulatory agencies have estab
*World Health Organization, Vector Biology and Controh 1969. The present place of DDT in
world operations for public health. Statement presented at the symposium "The Biological
Impact of Pesticides in the Environment,~' at Oregon State University, Corvallis, August 19,
1969.
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Pesticides and Wildlife
fished exacting standards that producers must meet to qualify for
marketing grades and to avoid condemnation. Thus, more is involved
than the grower's desire to produce attractive fruits and vegetables.
The housewife would be reluctant to buy wormy apples, nor would
wormy apples qualify for existing marketing grades. Again, though the
housewife is unlikely to detect fragments of aphids on broccoli, the
Food and Drug Administration of the Department of Health, Educa-
tion, and Welfare has established tolerance limits for insect fragments.
To meet these the grower resorts to control programs of which chemi-
cal control is the most effective. The Food and Drug Administration is
also charged with responsibility for establishing residue tolerances for
pesticides (discussed later in this chapter). Purity standards that insure
freedom of food products from insect fragments, excrete of rats, and
other extraneous filth is in the best public interest; these standards
must be realistically established; however, undue emphasis on the use
of pesticides is to be avoided. In terms of human health and environ-
mental quality, a few more insect fragments may be the lesser of two
evils.
When the foregoing factors are considered, it is evident that pesti-
cides are an indispensable component of our technology for producing
food and fiber and protecting man's health and comfort. All responsi-
ble studies agree with this conclusion. The choice is not whether pes-
ticides will be used, but which ones and under what circumstances.
185
ASSESSMENT OF TH E PESTICI DE PROD LEM
Chemical pest control in the modern sense began around the middle of
the last century. Sulfur was used against powdery mildew of grapes in
1821; Paris green was successfully used to control an outbreak of
Colorado potato beetle in 1867; and the fung~cidal properties of
Bordeaux mixture, which is still used, were discovered in 1883.
Reservations about effectiveness and concern for hazard to non-
target organisms were expressed early in the development of chemical
pest control. An editorial in the first number of the Practical Ento-
mologist, October 30, 1 865 (Entomological Society of Philadelphia,
1 865 ), raised doubts as to the value of chemical pesticides in insect
control and suggested the importance of biological studies. In 1894 it
was proven that arsenicals killed bees when sprayed on fruit trees in
bloom, and in 1903 a tolerance for arsenicals on foods was established
by the British.
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186
Land Use and Wildlife Resources
The era of the synthetic organic pesticides began with the develop-
ment of DDT as an insecticide in 1939. The effectiveness of DDT was
highlighted through its use during and after World War II to control
vectors of human diseases
After World War II, the chemical industry, government, and universi-
ties joined forces in adapting DDT and related compounds to peacetime
uses. The discovery of many new synthetic compounds followed. This
was augmented by equally rapid developments in formulation and
methods of application. Thus, in a matter of a decade or so, synthetic
organic pesticides became commonplace in agriculture, in industry, and
in the home. Indeed, by 1962 some 500 compounds, in more than
54,000 formulations, were registered for use as pesticides in the United
States.
It was at this point that Rachel Carson's Silent Spring appeared
(Carson, 19621. The combination of timing, her literary skill, the popu-
lar cause she espoused, and the misgivings that had already arisen
touched off a great debate. This debate extended throughout govern-
ment, the scientific community, the chemical industry, and agriculture
and conservation organizations, and provided a public forum whereby
the advantages and disadvantages, the gains and the losses, the facts
and the fantasies could be aired.
This controversy led to numerous investigations. Of these, five are
especially pertinent to the impact of pesticide use on wildlife:
i. The President's Science Advisory Committee's (PSAC) Panel on
the Use of Pesticides began a study of the problem in the summer of
1962. This group's report is of particular interest because it represents
the first official pronouncement after the outbreak of the pesticide
controversy (President's Science Advisory Committee, 19631. The
theme of the report, simply stated, is that the use of pesticides must
be continued to insure adequate supplies of food and fiber, but that
their use may endanger beneficial plants and animals as well as man
himself. The report recommended:
a. assessment of the level of pesticides in man and his environment;
b. development of measures to allow greater safety in pesticide use;
c. research on safer and more specific methods of pest control;
d. amendments to strengthen public laws governing the use of pesti-
cides; and
e. public education of pesticide benefits and hazards.
2. At about the same time, the Subcommittee on Reorganization
and International Organization of the Committee on Government
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187
Operations began its study entitled "Inter-Agency Coordination in
Environmental Hazards (Pesticides)" under the chairmanship of Sena-
tor Abraham Ribicoff. Hearings continued for 15 months and massive
testimony was compiled on many aspects of the problem. The hearings
served not only as a fact-finding forum, but also as a public sounding
board for the diverse interests represented by the many witnesses. The
final report of the subcommittee (United States Senate, 1966) was re-
leased in August, 1966.
Particularly significant is the broad ecological context within which
the committee viewed the pesticide issue. The following is indicative of
. .
its view:
The public debate over pesticides is but one facet of a wider debate which reflects
a greater sensitivity to the fundamental questions raised by the continuing and
accelerating pace of man's modification of his total environment. Pesticides are
but one factor and we are increasingly aware that our environment is being altered
even more dramatically by air and water pollution, atomic fallout and the popula-
tion explosion.
As we come to appreciate more keenly the significance of this fast accelerating,
irreversible alteration of our environment, we recognize the need for stock-taking
and the necessity of endeavoring to take into account all the multitude of complex
relationships between man and his natural and artificial surroundings.
3. In a comprehensive report titled "Restoring the Quality of Our
Environment," the PSAC Environmental Pollution Panel (President's
.,
Science Advisory Committee, 1965) considered pollution in its broad-
est context and made more than a hundred specific recommendations.
The philosophy of the panel was based on the assumption that pollu-
tion is a by-product of a technological society and that pollution prob-
lems will grow with increases in population and improved living stand-
ards unless drastic counter-measures to reduce it are taken.
The panel offered some sweeping recommendations that placed
problems of pollution in a new perspective. The report stated that free-
dom from pollution should be recognized as a human right, that respon-
sibility for pollution control rests with the polluter, and that the pol-
luter should bear the cost of pollution abatement and pass it on to the
consumer as part of the cost of operation. Finally, the need for con-
sidering all pollution as a single problem was stressed; the responsibility
for leadership in pollution abatement should be assumed by the federal
government.
The study by the PSAC Environmental Pollution Panel was attuned
to the needs of the times and the report provides a broad blueprint for
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Land Use and Wildlife Resources
constructive action. The philosophy, recommendations, and much of
the material in the appendixes of that report are relevant to the ques-
tion of land use and wildlife.
Although the approach was different, the recommendations growing
out of the Ribicoff hearings (United States Senate, 1966) agree essen-
tially with those of the Environmental Pollution Panel report. This is
not surprising since the counsel of many of the same individuals or
agencies was sought by the two groups in the course of their investiga-
tions.
4. In early 1966, a symposium on "Scientific Aspects of Pest Con-
trol," sponsored by the National Academy of Sciences-National Re-
search Council (1966) was held in Washington, D.C. The objective was
to bring together the current scientific knowledge of the various aspects
of pest control, and communicate it not only to the scientific com-
munity, but to lay leaders, the press, and government policymakers
as well.
The symposium provided an opportunity for review of the progress
made on the recommendations of the PSAC Panel almost 3 years ear-
lier. It was a unique experiment in seeking to bridge the communication
gap between persons developing specialized knowledge and persons
responsible for translating that knowledge into broad policy and future
environmental quality goals.
5. The most recent report was by the Committee on Persistent Pesti-
cides, which was established by the National Academy of Sciences-
National Research Council (1969b) at the request of the U.S. Depart-
ment of Agriculture. This report is of special interest because it ad-
dresses the problem of persistent pesticides as they relate to wildlife.
The report reiterates many earlier findings regarding the benefit-risk
features of persistent pesticide use. In addition, it stresses that while
present methods of pesticide regulation adequately protect man's food
supply, "they do not appear to insure the prevention of environmental
contamination."
These five reports provide useful assessments of the relationship of
pesticides and, to a lesser degree, other pollutants to wildlife. Many
other studies have contributed to our knowledge of the problem. Two
committees established by agencies of the federal government in the
late 1 960's undertook to study the relationship of pesticides to human
health and environmental pollution-the Commission on Pesticides and
Their Relationship to Environmental Health, an 11-member committee
appointed by Secretary Finch of the Department of Health, Education,
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Pesticides and Wildlife
and Welfare, and the Environmental Quality Council established by
executive order of President Nixon.
189
In all of these studies the problem of pesticide pollution as it affects
wildlife was recognized. The plea for more research is common to all
of them. Lacking, however, are statements fixing responsibility for
well-being of the ecosystem and specific proposals to reduce inputs of
persistent pesticides to avoid the adverse consequences that are fore-
told in these reports if their use continues unabated.
REGULATING THE USE OF PESTICIDES
The three major concerns in the use of pesticides are: (1) direct poison-
ing of humans and wildlife through accidents or exposure during manu-
facture, transport, storage, or use; (2) toxic residues that may pose a
hazard to the consumer; and (3) environmental pollution arising from
introduction of pesticides in the ecosystem.
The need has long been recognized for legislation to regulate the use
of pesticides and minimize the undesirable effects. The original Federal
Insecticide Act of 1910 controlled the sale of pesticides in the United
States to protect consumers from substandard or fraudulent products.
The concern for human health was first demonstrated with the Federal
Caustic Poison Act of 1927, which regulated the labeling of any dan-
gerous, caustic, or corrosive substance put up in containers suitable for
household use. The present regulatory responsibilities of the U.S. De-
partment of Agriculture and the Department of Health, Education, and
Welfare have been described in detail (National Academy of Sciences-
National Research Council, 1 9 6 6: 3 8 5 -3 9 8 ).
It was not until after World War II, when the variety of pesticides
had greatly increased and commercial use became widespread, that
concern for protection of human health led to the replacement of the
Insecticide Act of 1910 with the Federal Insecticide, Fungicide and
Rodenticide Act of 1947 (FIFRA), administered by the Pesticides Regu-
lation Division of the Department of Agriculture. This law is the basic
federal act governing pesticides in interstate commerce. A 1959 amend-
ment to the FIFRA added nematocides, plant regulators, defoliants,
and desiccants. Further amendments in 1964 (a) eliminated the contro-
versial section of the 1947 act that allowed sale of an unregistered
product when a protest had been filed, (b) required a federal registra-
tion number on each label and conspicuous precautionary labeling of
poisonous and potentially hazardous pesticides and (c) required manu
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Land Use and Wildlife Resources
facturers to remove unwarranted safety claims from the labels. The
1964 act requires:
1. Registration of economic poisons prior to their sale or introduc-
tion into interstate or receipt from foreign commerce;
2. Prominently displayed warnings on the labels of all pesticides with
an LDso of less than 5,000 mg/kg;*
3. The coloring or discoloring of certain economic poisons to pre-
vent their being mistaken for flour, sugar, salt, baking powder, or other
similar articles used in preparing foodstuffs;
4. Prominently displayed statements on the label of the economic
poison to advise the user of potential hazards to man, wildlife, vegeta-
tion, and other nontarget organisms; and
5. Instructions for use to provide adequate protection and to assure
effectiveness of the formulations against stated target organisms.
Besides the above requirements, a three-way agreement was con-
cluded in 1964 between the Departments of Agriculture, of the Interior,
and of Health, Education, and Welfare on the review of pesticide reg-
istration applications relative to considerations of human health and
hazards to wildlife. The Department of the Interior reviews for implica-
tions as to hazard to wildlife all data on compounds submitted to the
Department of Agriculture for registration or re-registration. When a
hazard to wildlife is believed to exist, the Department of the Interior
advises the Department of Agriculture of appropriate action to restrict
use, to require additional warnings, or to eliminate certain use patterns.
In addition to the 1947 FIFRA and its amendments and regulations,
the Federal Food, Drug and Cosmetic Act of 1938 and its "Miller
Amendment" of 1954 (Public Law 83-518) further control the use of
pesticides. This act and its amendments are administered by the Secre-
tary of Health, Education, and Welfare through the Food and Drug Ad-
ministration. They provide that tolerance levels be established for
pesticide residues in raw agricultural commodities upon which pesti-
cides are used. Any raw agricultural commodity may be condemned as
adulterated if it contains a residue of any pesticide that has not been
formally exempted or that is present in excess of the tolerances. This
law is also concerned with the adulteration of foods with insects, insect
fragments, hair, excrete of rodents, and any other extraneous filth that
may offend the sensitivities of consumers or endanger their health.
*LD<;O-Lethal dose for 50 percent of the test populations (a computed, not observed, figure)
reported in milligrams toxicant per kilogram body weight of test species (mg/kg).
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191
These two federal statutes (FIFRA and Miller) in their present form
supplement each other and are interrelated by law and practical op-
eration. Both require stringent evaluation of the safety and effective-
ness of the toxicants. Both are primarily concerned with the protection
of the health of the user, the consumer, and the public in general. Be-
cause both statutes apply to interstate sale of the chemical or com-
modities treated with pesticides, there is no provision for federal
control over the final use of a USDA-registered pesticide. Control of
actual use of pesticides rests with the states. Present pesticide use laws
vary considerably between states. However, many of the states now
have pesticide control boards or panels that include representation
from fish and wildlife groups as well as from agricultural and industrial
interests and that are working in the public's behalf to reduce pollution
by pesticides and to minimize their harmful effects on fish and wildlife.
By 1969, 48 states regulated the marketing of pesticides within their
own borders through labeling or tolerance laws, or both, patterned
after the federal acts. In addition, 37 states regulate the use and com-
mercial application of pesticides, which includes the licensing of com-
mercial applicators. Unfortunately, many states use pesticide laws as a
means of providing additional revenue and exercise little regulatory au-
thority. The need for state legislation and enforcement, in addition to
the federal, is based on two facts: (1) Federal legislation applies only
in interstate commerce, and there are many instances where sale either
of the pesticide or of the agricultural commodity is transacted com-
pletely within a single state; and (2) neither of the two federal laws
(FIFRA and Miller) provides for control of the actual use of a given
chemical.
State legislation frequently deals specifically with the use of toxi-
cants for control of birds, mammals, or fish. In 1967, for example, 12
states prohibited completely the use of poisons for eliminating such
birds as starlings, feral pigeons, or house sparrows, which frequently
become a nuisance. The use of rotenone or other toxicants to control
or eliminate unwanted fish is usually regulated by the state fish and
game laws. The use of these materials ordinarily requires a permit from
the state.
As indicated above, numerous legislative regulations exist at both
state and federal levels designed to control residues and promote safe
use of pesticides. These impose direct legal controls on the manufac-
turer and shipper to insure proper labeling and acceptable standards of
quality. The chief control over the user is the regulations on residue
tolerances that must be met if the commodity is to be safe from con
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197
regards toxicity, stability, and solubility. Information is also needed on
mobility in the ecosystem and on levels in living organisms and com-
ponents of the biosphere.
Toxicity
In seeking chemicals useful as pesticides, the search is for those that
interfere with an essential link in the biochemical chain of events. It is
therefore not surprising that chemicals selected to kill pests also affect
other species. This follows because, in the evolution of organisms, suc-
cessful biochemical processes have been passed on to higher forms with
the result that there is far less diversity in physiological machinery than
in morphology among the countless species of living things. This is well
illustrated by the similarity in biochemical pathways in yeast and man
whereby glucose is converted to pyruvic acid in eight chemical steps;
the same steps occur in a primitive unicellular plant and in a highly
developed mammal.
Despite these similarities there is the apparent contradiction that
differences in susceptibility to a given chemical occur even among
closely related species, and data from one species cannot be extrapo-
lated with certainty to another. The basis for such differential suscep-
tibility may lie in differences in entry, transport, metabolism, excretion,
or action at an active site.
Of the various classes of pesticides currently in general use, insecti-
cides pose a greater hazard to wildlife than do fungicides and herbi-
cides, since the physiological processes of insects have more in com-
mon with those of wildlife than do those of plants and fungi. In addi-
tion, the chlorinated hydrocarbons, the first family of insecticides, are
more stable than are most fungicides and herbicides.
Our concern at this point is chiefly over DDT and its relatives, which
are already widely distributed in the ecosystem. This group is toxic to
a broad spectrum of living organisms through their action as nerve poi-
sons, although the precise manner in which they exert toxicity is not
known.
While focusing chiefly on insecticides of the chlorinated hydrocarbon
class, because they represent our major concern at this time, we should
recognize that substitute pesticides will likely involve some adverse
side-effects. The chief replacements for chlorinated hydrocarbons are
presently organophosphorus and carbamate compounds and, although
these are less stable, they are, in general, also toxic to a broad spectrum
of organisms.
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Chemical Stability
Land Use and Wildlife Resources
The range in chemical stability of pesticides includes those that are bio-
degradable within a few hours following application and those having a
half-life of days or years. The chlorinated hydrocarbons fall in the class
of very stable compounds. Unfortunately, existing knowledge of degra-
dation in soil, water, plants, and animals has many voids. Some persis-
tent pesticides are decomposed photochemically, whereas others are
subject to biological degradation. The sequence of degradation and the
identity and biological activity of the products formed must be known
in order to make meaningful assessments of toxicity and duration of
residency.
The ideal would be to develop compounds that are relatively stable
in soil and water and selectively biodegradable in plants and animals.
Such compounds are not beyond the realm of chemical possibility.
Solubility
The solubility properties of a pesticide greatly influence its potential
activity as a pollutant. Those that are water soluble are subject to dilu-
tion within living organisms and within the ecosystem as well as to
chemical reaction with water. The chlorinated hydrocarbons are in-
soluble in water and soluble in lipids. Since lipids occur in all living or-
ganisms, they act as built-in solvents for chlorinated hydrocarbons, thus
imparting to this class of pesticides an affinity for living organisms.
Mobil ity
Pesticides such as DDT have become widely distributed throughout the
biosphere. They have been found beyond points of application in run-
off water (Weaver et al., 1965), in air and rainwater (Abbott et al.,
1965), and in animals from diverse parts of the world. In addition to
pesticides applied as dusts and sprays in the air, additional amounts
enter the air on soil particles and by co-distillation in the evaporation
of water. Their high affinity for colloidal surfaces makes them suscep-
tible to transport on soil particles during soil erosion.
Once circulating in the biosphere they can travel great distances and
be deposited by physical forces that tend to concentrate them in strata
in the biosphere. Such mobility accounts for the general distribution of
DDT in organisms that have not been directly exposed to the pesticide.
This mobility phenomenon as it has been disclosed through continued
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Pesticides and Wildlife
use was not generally anticipated and has, therefore, not been taken
into full account in establishing policy on the use of persistent
pesticides.
Biological Magnification
199
Another factor that bears an important relationship to the effect of
pesticides on wildlife is biological magnification. This is the process
whereby pesticides accumulated in one organism are passed on through
the food chain to other organisms, thus leading to higher concentrations
at each level in the food chain. Each organism eats many organisms
from the lower step in the food chain. A large fish, for instance, feeds
on many smaller fish, which in turn feed on still smaller fish, the small-
est feeding on plankton, which may acquire the initial concentration of
a pesticide introduced into the environment.
A classic example of biological magnification is one that occurred
at Clear Lake, California, after the lake was treated with DDD to con-
trol gnats in 1957 (Hunt and Bischoff, 19604. The level of DDD in the
lake was calculated to be 0.02 ppm. Residue levels of DDD in samples
taken 13 months later were 10 ppm in plankton, 903 ppm in fat of
plankton-eating fish, 2,690 ppm in fat of carnivorous fish, and 2,134
ppm in fat of fish-eating birds. This represents a 1 OO,000-fold increase
in fish-eating birds over levels in lake water after treatment.
Ecosystems are characterized by countless intricate food chains and
the end result of interference in food chain relationships cannot be pre-
dicted. The end result of practices that might interfere with some basic
organism in the food chain such as algae in marine food chains is, there-
fore, viewed with concern.
Another form of biological magnification involves transfer of a pesti-
cide directly from the environment rather than indirectly through the
food chain. Fish, for instance, may acquire DDT from water in contact
with the gills (Holder, 19621.
MONITORING PESTICIDES IN THE EN\/IRONMENT
The need to monitor residues in the environment was stressed by the
President's Science Advisory Committee (19631. The committee spe-
cifically recommended that current pesticide levels and their trends in
man and his environment be determined and that a continuing network
be established to monitor residue levels in air, water, soil, man, and
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Land Use and Wildlife Resources
wildlife In response to this recommendation the interagency Federal
Committee on Pest Control provided guidelines for establishing the
National Pesticide Monitoring Program (NPMP). The findings of NPMP,
as well as the monitoring findings of other agencies, are reported in the
Pesticides Monitoring Journal which began publication in June 1967
under sponsorship of the Federal Committee on Pest Control. This
monitoring program is described in the first issue of the journal (Fed-
eral Committee on Pest Control, 19671.
Phases of the NPMP designed to measure pesticides in humans follow
the levels in selected communities. Pesticides in foods are considered in
terms of average levels in a standard diet as well as in selected compo-
nents of basic diets. These findings provide baselines for determining
changes and also for calculating average values.
Soil monitoring is based on sampling of agricultural, range, and
forest soils. Monitoring of water is based on sampling of rivers at se-
lected sites. Oysters and clams, freshwater fish, waterfowl, and starlings
have been selected as representative substrates for monitoring residues
in wildlife. The importance of comprehensive air monitoring is obvious,
particularly in view of the growing recognition of air as a transport
medium in the movement of pesticides.
It is perhaps too early to judge the adequacy of the monitoring pro-
gram, but it would appear in view of their mobility that persistent pes-
ticides should be monitored on a global scale, with emphasis on the
pattern of pesticide "fallout" in the biosphere.
PESTICIDES IN Wl LDLI FE AND THEI R SIGNIFICANCE
A voluminous literature establishes the fact that persistent insecticides
are widely distributed in the biosphere and occur in a wide variety of
animals throughout the world. A review of some pertinent evidence on
this topic has been provided by Stickel (19681.
The mere presence of a pesticide in a living organism does not mean,
per se, that it has a harmful effect. In fact, the tolerances established
for DDT in the human diet are based on the assumption that, at these
levels, DDT will accumulate in the fat, but at levels that are not harmful
to human health.
Unfortunately, diagnosing a cause of mortality as it relates to residue
content in the animal is fraught with difficulty. Much research has been
directed to this question in insect toxicity studies and many anomalies
remain. Such studies are complicated by the fact that the mode of ac
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Pesticides and Wildlife
201
tion of chlorinated hydrocarbons is not precisely known. Even in the
case of organophosphate insecticides, whose mode of action is known
to be generally through the inhibition of cholinesterase of the nervous
system, the relationships between dosage levels, inhibition rates, and
toxicity are not readily established experimentally; these relationships
would be even more difficult to establish in animals taken in their natu-
ral habitats. Despite these considerations, the literature includes many
reports of residue content of tissues or whole bodies of animals on the
assumption that such evidence is diagnostic of pesticide poisoning.
Some meaningful correlations have apparently been established for the
relationship between DDT residue levels in the brain and DDT poison-
ing that do apply to a wide range of species (Bernard, 1963; Dale et al.,
1962; Stickel et al., 19661. Obviously, it will not be possible to regulate
pesticides effectively unless the significance of pesticide levels in living
organisms is better understood.
Levels of pesticide residues in animals are influenced by many vari-
ables, such as contamination of the food supply and the abilities of dif-
ferent species to absorb, metabolize, and excrete the toxicant. In birds,
for instance, raptorial and fish-eating species in general have higher resi-
due levels than do plant-feeding and omnivorous species because of
magnification through the food chain.
The effects of pesticides on living organisms may be acute or chronic.
Acute effects generally become evident soon after treatment, and are
readily apparent by symptoms of abnormal behavior or death. Chronic
effects, on the other hand, are in many cases not readily detected and
may manifest themselves by death or in subtle ways over an extended
time span. Chronic poisoning is of major concern as it might relate to
mortality or physiological disturbance resulting in reproductive impair-
ment or behavioral change. Mortality of wildlife due to pesticide poi-
soning has been reported for a number of species and under varied
circumstances (e.g., Robbins et al., 1951; DeWitt, 1956; Rudd and
Genelly, 1 956; Wallace, 1 959, 1 962; Hunt, 1 960; Hickey, 1 96 1;
Roelofs and Shick, 1962; Rosene, 1965; Ames, 1966; Keith, 19669.
More recently, concern has centered on less obvious effects of pesti-
cide residues, such as reproductive failure. Estrogenic activity of DDT
in mammals and birds has been demonstrated by Bitman et al. (19681.
In both fish and birds, cases of reproductive failure have been estab-
lished. Burdick et al. ( 1964) showed that the reduced hatch of eggs of
lake trout in Lake George, New York, was due to DDT. Similar cases
have been reported elsewhere. Apparently, in the maturation of eggs,
the female draws on fat reserves containing DDT, which is transferred
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Land Use and Wildlife Resources
to lipids in the egg and acts on the embryo as it metabolizes this source
of food in the yolk sac.
The evidence on impaired reproduction in birds by chlorinated hy-
drocarbon residues has been reviewed by Wurster ( 1 968a). DDT ap-
parently stimulates the liver to produce enzymes that act on steroids;
these in turn control metabolism of calcium and its deposition in egg-
shells. Decrease in eggshell weight, resulting in breakage and reproduc-
tive failure, has been cited in the United States and Great Britain
(Ratcliffe, 1967; Hickey and Anderson, 19681. Laboratory studies have
confirmed that DDT may cause reproductive decline through reduction
in eggshell thickness, resulting in mechanical breakage, and through be-
havioral changes, resulting in abandonment of eggs. Retardation in
sexual maturity has also been reported (Jefferies, 19671.
Behavioral responses that could have important survival implications
have been reported for New Brunswick salmon from DDT-sprayed
rivers. Very low doses resulted in increased sensitivity to low tempera-
tures, causing a shift in temperature selection (Ogilvie and Anderson,
19654. Behavioral changes have also been cited in gulls on Lake Michi-
gan where high DDT levels were associated with aggressive behavior and
high egg breakage (Ludwig and Tomoff, 19661. In a study of cowbirds
that were fed DDT, mortality was reported following the stress of dis-
turbance (Sticker, 19651.
While birds and fish are of general interest and are subject to obser-
vation and study with relative ease, some other important components
of the biota are less conspicuous, and possible ill effects may escape de-
tection. For instance, marine algae, which are important components
of marine food chains and which play a major role in total photosyn-
thetic activity, show reduced photosynthesis at low concentrations of
DDT under laboratory conditions (Wurster, 1 968b). It has also been
shown that microorganisms accumulate DDT and dieldrin from soils
and culture media (Chacko and Lockwood, 19671. Changes in such es-
sential components of the ecosystem could have profound biological
implications. Thus, the evidence on wildlife is important not only as it
relates to wildlife directly, but to wildlife as living monitors of the en-
vironment that they share with man.
It is clear from the evidence cited that:
1. Pesticide residues occur very generally in wildlife-in some cases
at high levels.
2. Pesticide residues may in some species cause death, or physiologi-
cal disturbances that result in reduced reproductive potential and be-
havioral changes.
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Pesticides and Wildlife
3. The numbers of some species of wildlife are declining and the
evidence strongly implicates pesticides as a causative factor.
The conclusion seems inescapable that pesticides, as currently em-
ployed, constitute a threat to wildlife, and that future practices for
their use should be formulated with this in mind.
IMPLICATIONS FOR EDUCATION AND RESEARCH
203
The evidence cited above establishes a number of points as the frame-
work for consideration in the future employment of pesticides.
1. During two decades of use, some adverse side-effects of persistent
pesticides on wildlife have become evident.
2. In terms of biological adjustments in the global ecosystem, two
decades has been insufficient to assess the ultimate effect of these
pesticides.
3. No decrease is anticipated in worldwide production and use of
pesticides.
4. Persistent pesticides continue to play an important role in pro-
viding for man's food, fiber, health, and comfort.
5. The replacement of persistent pesticides and adoption of alterna-
tive methods of control are desirable but have proceeded slowly for
lack of economic and other incentives and because so much time is
needed for research on other methods.
6. While pesticide regulations in the United States are believed to
provide adequate safeguards for human health, they are inadequate for
controlling pesticide levels in the environment.
7. Knowledge of the movement of pesticides in the environment,
their degradation, and fate is inadequate.
8. Contamination of the biosphere with pesticides is a worldwide
problem, but no international body is charged with responsibility for
environmental quality.
These conclusions have strong implications for programs in education
and research. While these are somber conclusions, there is encourage-
ment in the national awakening to abuses of the environment and the
need for constructive programs to restore its quality. Central to this
point are the questions, "What level of environmental quality does
society want?" and "What level is it prepared to pay for?"
It seems reasonable to proceed from the premise that knowledge of
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Land Use and Wildlife Resources
the relationship of man to his environment is an essential component
of an educational program at both the secondary and college levels. It
is entirely practical to make such training an integral part of the high
school curriculum and to provide it for college students in the humani-
ties as well as those in the sciences.
Beyond this general need is the special need to provide training for a
cadre of scientists and technicians who can conduct research on the
myriad problems associated with environmental pollution. Challenging
opportunities are available for young people interested in careers in im-
proving environmental quality (President's Science Advisory Commit-
tee, 1965: 39-569.
It is particularly important that narrow specialization be avoided in
training scientists. In retrospect, the failure to consider pest control in
terms of ecological principles accounts for some failures in the tactics
employed in pest control. It is equally clear that interdisciplinary effort
will be required to solve problems of environmental quality and that
receptiveness to such team effort is greatly influenced by the breadth
of training provided.
In addition to more adequate formal education in high schools and
colleges, there is the need for education of the general public on en-
vironmental quality in all its aspects. The pesticide problem is typical
of the kind of issue that will continue to arise in a technological soci-
ety. In the end, society must decide, but our system of informing the
public is rather ineffective in providing a useful fund of knowledge on
which the concerned individual can draw. Furthermore, the existing
options are not made clear and the result is a polarization of opinion
"for" or "against," with little regard for the consequences of either
course. In the present debate on regulating the use of persistent pesti-
cides, no estimates have been provided on the cost of food produced
without benefit of these materials.
In considering the problem of public understanding of the impact of
science and technology, an intriguing proposal has been offered by
Morison (19691:
As for less formal methods for presenting science to adults, we should devise some
analogy that would do for the general public what agricultural extension courses
have done for the farmer and his wife. The average successful farmer, although he
is far from being a pure scientist, has an appreciation for the way science works.
Certainly he understands it well enough to use it in his own business and to sup-
port agricultural colleges and the great state universities that grew out of them.
The important point is that in terms of an informed public, we can
do far better than we have done and an immediate objective should be
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Pesticides and Wildlife
205
that of developing an informed and responsible public to which alterna-
tives may be directed.
We are only beginning to understand the delicate interrelationships
among living creatures in biological communities. Similarly, there are
great voids in our knowledge of cellular functions on which the survival
of the individual organism depends. When these matters are considered,
it should be recognized that most pesticides were developed empirically
rather than by designing a molecule that would induce toxicity in a pre-
dictable manner. Thus, the mode of action of the most intensely stud-
ied insecticide, DDT, is still unknown-a striking example of the kind
of bottlenecks that exist.
It is obvious that a tremendous research effort is needed at the basic
and applied levels, that research is costly, that achievement of research
goals cannot be predicted with accuracy, and that competition for able
young minds is always keen.
It is reassuring, however, to note the progress that can be made in
science and technology, once clear national goals are established. The
success of Apollo 11 in placing men on the moon is a dramatic case in
point. The current public interest in pesticide pollution offers promise
for significant advances in our knowledge through research.
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Representative terms from entire chapter:
pest control
