the animal life of the earth.
Although modern man seldom remembers the fact, he could not exist without the plants that
harness the sun’s energy and manufacture the basic foodstuffs he depends upon for life. Our
attitude toward plants is a singularly narrow one. If we see any immediate utility in a plant we
foster it. If for any reason we find its presence undesirable or merely a matter of indifference,
we may condemn it to destruction forthwith. Besides the various plants that are poisonous to
man or his livestock, or crowd out food plants, many are marked for destruction merely
because, according to our narrow view, they happen to be in the wrong place at the wrong
time. Many others are destroyed merely because they happen to be associates of the
unwanted plants.
The earth’s vegetation is part of a web of life in which there are intimate and essential relations
between plants and the earth, between plants and other plants, between plants and animals.
Sometimes we have no choice but to disturb these relationships, but we should do so
thoughtfully, with full awareness that what we do may have consequences remote in time and
place. But no such humility marks the booming ‘weed killer’ business of the present day, in
which soaring sales and expanding uses mark the production of plant-killing chemicals. One of
the most tragic examples of our unthinking bludgeoning of the landscape is to be seen in the
sagebrush lands of the West, where a vast campaign is on to destroy the sage and to substitute
grasslands. If ever an enterprise needed to be illuminated with a sense of the history and
meaning of the landscape, it is this. For here the natural landscape is eloquent of the interplay
of forces that have created it. It is spread before us like the pages of an open book in which we
can read why the land is what it is, and why we should preserve its integrity. But the pages lie
unread.
The land of the sage is the land of the high western plains and the lower slopes of the
mountains that rise above them, a land born of the great uplift of the Rocky Mountain system
many millions of years ago. It is a place of harsh extremes of climate: of long winters when
blizzards drive down from the mountains and snow lies deep on the plains, of summers whose
heat is relieved by only scanty rains, with drought biting deep into the soil, and drying winds
stealing moisture from leaf and stem. As the landscape evolved, there must have been a long
period of trial and error in which plants attempted the colonization of this high and windswept
land. One after another must have failed. At last one group of plants evolved which combined
all the qualities needed to survive. The sage—low-growing and shrubby—could hold its place
on the mountain slopes and on the plains, and within its small gray leaves it could hold
moisture enough to defy the thieving winds. It was no accident, but rather the result of long
ages of experimentation by nature, that the great plains of the West became the land of the
sage.
Along with the plants, animal life, too, was evolving in harmony with the searching
requirements of the land. In time there were two as perfectly adjusted to their habitat as the
sage. One was a mammal, the fleet and graceful pronghorn antelope. The other was a bird, the
sage grouse—the ‘cock of the plains’ of Lewis and Clark. The sage and the grouse seem made
for each other. The original range of the bird coincided with the range of the sage, and as the
sagelands have been reduced, so the populations of grouse have dwindled. The sage is all
things to these birds of the plains. The low sage of the foothill ranges shelters their nests and
their young; the denser growths are loafing and roosting areas; at all times the sage provides
the staple food of the grouse. Yet it is a two-way relationship. The spectacular courtship
displays of the cocks help loosen the soil beneath and around the sage, aiding invasion by
grasses which grow in the shelter of sagebrush. The antelope, too, have adjusted their lives to
the sage. They are primarily animals of the plains, and in winter when the first snows come
those that have summered in the mountains move down to the lower elevations. There the
sage provides the food that tides them over the winter. Where all other plants have shed their
leaves, the sage remains evergreen, the gray-green leaves—bitter, aromatic, rich in proteins,
fats, and needed minerals—clinging to the stems of the dense and shrubby plants. Though the
snows pile up, the tops of the sage remain exposed, or can be reached by the sharp, pawing
hoofs of the antelope. Then grouse feed on them too, finding them on bare and windswept
ledges or following the antelope to feed where they have scratched away the snow.
And other life looks to the sage. Mule deer often feed on it. Sage may mean survival for winter-
grazing livestock. Sheep graze many winter ranges where the big sagebrush forms almost pure
stands. For half the year it is their principal forage, a plant of higher energy value than even
alfalfa hay. The bitter upland plains, the purple wastes of sage, the wild, swift antelope, and the
grouse are then a natural system in perfect balance. Are? The verb must be changed—at least
in those already vast and growing areas where man is attempting to improve on nature’s way.
In the name of progress the land management agencies have set about to satisfy the insatiable
demands of the cattlemen for more grazing land. By this they mean grassland—grass without
sage. So in a land which nature found suited to grass growing mixed with and under the shelter
of sage, it is now proposed to eliminate the sage and create unbroken grassland. Few seem to
have asked whether grasslands are a stable and desirable goal in this region. Certainly nature’s
own answer was otherwise. The annual precipitation in this land where the rains seldom fall is
not enough to support good sod-forming grass; it favors rather the perennial bunchgrass that
grows in the shelter of the sage.
Yet the program of sage eradication has been under way for a number of years. Several
government agencies are active in it; industry has joined with enthusiasm to promote and
encourage an enterprise which creates expanded markets not only for grass seed but for a large
assortment of machines for cutting and plowing and seeding. The newest addition to the
weapons is the use of chemical sprays. Now millions of acres of sagebrush lands are sprayed
each year. What are the results? The eventual effects of eliminating sage and seeding with
grass are largely conjectural. Men of long experience with the ways of the land say that in this
country there is better growth of grass between and under the sage than can possibly be had in
pure stands, once the moisture-holding sage is gone. But even if the program succeeds in its
immediate objective, it is clear that the whole closely knit fabric of life has been ripped apart.
The antelope and the grouse will disappear along with the sage. The deer will suffer, too, and
the land will be poorer for the destruction of the wild things that belong to it. Even the livestock
which are the intended beneficiaries will suffer; no amount of lush green grass in summer can
help the sheep starving in the winter storms for lack of the sage and bitterbrush and other wild
vegetation of the plains. These are the first and obvious effects. The second is of a kind that is
always associated with the shotgun approach to nature: the spraying also eliminates a great
many plants that were not its intended target. Justice William O. Douglas, in his recent book My
Wilderness: East to Katahdin, has told of an appalling example of ecological destruction
wrought by the United States Forest Service in the Bridger National Forest in Wyoming. Some
10,000 acres of sagelands were sprayed by the Service, yielding to pressure of cattlemen for
more grasslands. The sage was killed, as intended. But so was the green, lifegiving ribbon of
willows that traced its way across these plains, following the meandering streams. Moose had
lived in these willow thickets, for willow is to the moose what sage is to the antelope. Beaver
had lived there, too, feeding on the willows, felling them and making a strong dam across the
tiny stream. Through the labor of the beavers, a lake backed up. Trout in the mountain streams
seldom were more than six inches long; in the lake they thrived so prodigiously that many grew
to five pounds. Waterfowl were attracted to the lake, also. Merely because of the presence of
the willows and the beavers that depended on them, the region was an attractive recreational
area with excellent fishing and hunting.
But with the ‘improvement’ instituted by the Forest Service, the willows went the way of the
sagebrush, killed by the same impartial spray. When Justice Douglas visited the area in 1959,
the year of the spraying, he was shocked to see the shriveled and dying willows—the ‘vast,
incredible damage’. What would become of the moose? Of the beavers and the little world
they had constructed? A year later he returned to read the answers in the devastated
landscape. The moose were gone and so were the beaver. Their principal dam had gone out for
want of attention by its skilled architects, and the lake had drained away. None of the large
trout were left. None could live in the tiny creek that remained, threading its way through a
bare, hot land where no shade remained. The living world was shattered. . . .
Besides the more than four million acres of rangelands sprayed each year, tremendous areas of
other types of land are also potential or actual recipients of chemical treatments for weed
control. For example, an area larger than all of New England—some 50 million acres—is under
management by utility corporations and much of it is routinely treated for ‘brush control’. In
the Southwest an estimated 75 million acres of mesquite lands require management by some
means, and chemical spraying is the method most actively pushed. An unknown but very large
acreage of timber-producing lands is now aerially sprayed in order to ‘weed out’ the hardwoods
from the more spray-resistant conifers. Treatment of agricultural lands with herbicides doubled
in the decade following 1949, totaling 53 million acres in 1959. And the combined acreage of
private lawns, parks, and golf courses now being treated must reach an astronomical figure.
The chemical weed killers are a bright new toy. They work in a spectacular way; they give a
giddy sense of power over nature to those who wield them, and as for the long-range and less
obvious effects—these are easily brushed aside as the baseless imaginings of pessimists. The
‘agricultural engineers’ speak blithely of ‘chemical plowing’ in a world that is urged to beat its
plowshares into spray guns. The town fathers of a thousand communities lend willing ears to
the chemical salesman and the eager contractors who will rid the roadsides of ‘brush’—for a
price. It is cheaper than mowing, is the cry. So, perhaps, it appears in the neat rows of figures in
the official books; but were the true costs entered, the costs not only in dollars but in the many
equally valid debits we shall presently consider, the wholesale broadcasting of chemicals would
be seen to be more costly in dollars as well as infinitely damaging to the long-range health of
the landscape and to all the varied interests that depend on it.
Take, for instance, that commodity prized by every chamber of commerce throughout the
land—the good will of vacationing tourists. There is a steadily growing chorus of outraged
protest about the disfigurement of once beautiful roadsides by chemical sprays, which
substitute a sere expanse of brown, withered vegetation for the beauty of fern and wild flower,
of native shrubs adorned with blossom or berry. ‘We are making a dirty, brown, dying-looking
mess along the sides of our roads,’ a New England woman wrote angrily to her newspaper. ‘This
is not what the tourists expect, with all the money we are spending advertising the beautiful
scenery.’
In the summer of 1960 conservationists from many states converged on a peaceful Maine
island to witness its presentation to the National Audubon Society by its owner, Millicent Todd
Bingham. The focus that day was on the preservation of the natural landscape and of the
intricate web of life whose interwoven strands lead from microbes to man. But in the
background of all the conversations among the visitors to the island was indignation at the
despoiling of the roads they had traveled. Once it had been a joy to follow those roads through
the evergreen forests, roads lined with bayberry and sweet fern, alder and huckleberry. Now all
was brown desolation. One of the conservationists wrote of that August pilgrimage to a Maine
island: ‘I returned...angry at the desecration of the Maine roadsides. Where, in previous years,
the highways were bordered with wildflowers and attractive shrubs, there were only the scars
of dead vegetation for mile after mile...As an economic proposition, can Maine afford the loss
of tourist goodwill that such sights induce?’ Maine roadsides are merely one example, though a
particularly sad one for those of us who have a deep love for the beauty of that state, of the
senseless destruction that is going on in the name of roadside brush control throughout the
nation.
Botanists at the Connecticut Arboretum declare that the elimination of beautiful native shrubs
and wildflowers has reached the proportions of a ‘roadside crisis’. Azaleas, mountain laurel,
blueberries, huckleberries, viburnums, dogwood, bayberry, sweet fern, low shadbush,
winterberry, chokecherry, and wild plum are dying before the chemical barrage. So are the
daisies, black-eyed Susans, Queen Anne’s lace, goldenrods, and fall asters which lend grace and
beauty to the landscape. The spraying is not only improperly planned but studded with abuses
such as these. In a southern New England town one contractor finished his work with some
chemical remaining in his tank. He discharged this along woodland roadsides where no spraying
had been authorized. As a result the community lost the blue and golden beauty of its autumn
roads, where asters and goldenrod would have made a display worth traveling far to see. In
another New England community a contractor changed the state specifications for town
spraying without the knowledge of the highway department and sprayed roadside vegetation
to a height of eight feet instead of the specified maximum of four feet, leaving a broad,
disfiguring, brown swath. In a Massachusetts community the town officials purchased a weed
killer from a zealous chemical salesman, unaware that it contained arsenic. One result of the
subsequent roadside spraying was the death of a dozen cows from arsenic poisoning.
Trees within the Connecticut Arboretum Natural Area were seriously injured when the town of
Waterford sprayed the roadsides with chemical weed killers in 1957. Even large trees not
directly sprayed were affected. The leaves of the oaks began to curl and turn brown, although it
was the season for spring growth. Then new shoots began to be put forth and grew with
abnormal rapidity, giving a weeping appearance to the trees. Two seasons later, large branches
on these trees had died, others were without leaves, and the deformed, weeping effect of
whole trees persisted. I know well a stretch of road where nature’s own landscaping has
provided a border of alder, viburnum, sweet fern, and juniper with seasonally changing accents
of bright flowers, or of fruits hanging in jeweled clusters in the fall. The road had no heavy load
of traffic to support; there were few sharp curves or intersections where brush could obstruct
the driver’s vision. But the sprayers took over and the miles along that road became something
to be traversed quickly, a sight to be endured with one’s mind closed to thoughts of the sterile
and hideous world we are letting our technicians make. But here and there authority had
somehow faltered and by an unaccountable oversight there were oases of beauty in the midst
of austere and regimented control—oases that made the desecration of the greater part of the
road the more unbearable. In such places my spirit lifted to the sight of the drifts of white
clover or the clouds of purple vetch with here and there the flaming cup of a wood lily.
Such plants are ‘weeds’ only to those who make a business of selling and applying chemicals. In
a volume of Proceedings of one of the weed-control conferences that are now regular
institutions, I once read an extraordinary statement of a weed killer’s philosophy. The author
defended the killing of good plants ‘simply because they are in bad company.’ Those who
complain about killing wildflowers along roadsides reminded him, he said, of antivivisectionists
‘to whom, if one were to judge by their actions, the life of a stray dog is more sacred than the
lives of children.’ To the author of this paper, many of us would unquestionably be suspect,
convicted of some deep perversion of character because we prefer the sight of the vetch and
the clover and the wood lily in all their delicate and transient beauty to that of roadsides
scorched as by fire, the shrubs brown and brittle, the bracken that once lifted high its
proudlacework now withered and drooping. We would seem deplorably weak that we can
tolerate the sight of such ‘weeds’, that we do not rejoice in their eradication, that we are not
filled with exultation that man has once more triumphed over miscreant nature.
Justice Douglas tells of attending a meeting of federal field men who were discussing protests
by citizens against plans for the spraying of sagebrush that I mentioned earlier in this chapter.
These men considered it hilariously funny that an old lady had opposed the plan because the
wildflowers would be destroyed. ‘Yet, was not her right to search out a banded cup or a tiger
lily as inalienable as the right of stockmen to search out grass or of a lumberman to claim a
tree?’ asks this humane and perceptive jurist. ‘The esthetic values of the wilderness are as
much our inheritance as the veins of copper and gold in our hills and the forests in our
mountains.’ There is of course more to the wish to preserve our roadside vegetation than even
such esthetic considerations. In the economy of nature the natural vegetation has its essential
place. Hedgerows along country roads and bordering fields provide food, cover, and nesting
areas for birds and homes for many small animals. Of some 70 species of shrubs and vines that
are typical roadside species in the eastern states alone, about 65 are important to wildlife as
food. Such vegetation is also the habitat of wild bees and other pollinating insects. Man is more
dependent on these wild pollinators than he usually realizes. Even the farmer himself seldom
understands the value of wild bees and often participates in the very measures that rob him of
their services. Some agricultural crops and many wild plants are partly or wholly dependent on
the services of the native pollinating insects. Several hundred species of wild bees take part in
the pollination of cultivated crops—100 species visiting the flowers of alfalfa alone. Without
insect pollination, most of the soil-holding and soil-enriching plants of uncultivated areas would
die out, with far-reaching consequences to the ecology of the whole region. Many herbs,
shrubs, and trees of forests and range depend on native insects for their reproduction; without
these plants many wild animals and range stock would find little food. Now clean cultivation
and the chemical destruction of hedgerows and weeds are eliminating the last sanctuaries of
these pollinating insects and breaking the threads that bind life to life.
These insects, so essential to our agriculture and indeed to our landscape as we know it,
deserve something better from us than the senseless destruction of their habitat. Honeybees
and wild bees depend heavily on such ‘weeds’ as goldenrod, mustard, and dandelions for pollen
that serves as the food of their young. Vetch furnishes essential spring forage for bees before
the alfalfa is in bloom, tiding them over this early season so that they are ready to pollinate the
alfalfa. In the fall they depend on goldenrod at a season when no other food is available, to
stock up for the winter. By the precise and delicate timing that is nature’s own, the emergence
of one species of wild bees takes place on the very day of the opening of the willow blossoms.
There is no dearth of men who understand these things, but these are not the men who order
the wholesale drenching of the landscape with chemicals.
And where are the men who supposedly understand the value of proper habitat for the
preservation of wildlife? Too many of them are to be found defending herbicides as ‘harmless’
to wildlife because they are thought to be less toxic than insecticides. Therefore, it is said, no
harm is done. But as the herbicides rain down on forest and field, on marsh and rangeland, they
are bringing about marked changes and even permanent destruction of wildlife habitat. To
destroy the homes and the food of wildlife is perhaps worse in the long run than direct killing.
The irony of this all-out chemical assault on roadsides and utility rights-of-way is twofold. It is
perpetuating the problem it seeks to correct, for as experience has clearly shown, the blanket
application of herbicides does not permanently control roadside ‘brush’ and the spraying has to
be repeated year after year. And as a further irony, we persist in doing this despite the fact that
a perfectly sound method of selective spraying is known, which can achieve long-term
vegetational control and eliminate repeated spraying in most types of vegetation. The object of
brush control along roads and rights-of-way is not to sweep the land clear of everything but
grass; it is, rather, to eliminate plants ultimately tall enough to present an obstruction to
drivers’ vision or interference with wires on rights-of-way. This means, in general, trees. Most
shrubs are low enough to present no hazard; so, certainly, are ferns and wildflowers.
Selective spraying was developed by Dr. Frank Egler during a period of years at the American
Museum of Natural History as director of a Committee for Brush Control Recommendations for
Rights-of-Way. It took advantage of the inherent stability of nature, building on the fact that
most communities of shrubs are strongly resistant to invasion by trees. By comparison,
grasslands are easily invaded by tree seedlings. The object of selective spraying is not to
produce grass on roadsides and rights-of-way but to eliminate the tall woody plants by direct
treatment and to preserve all other vegetation. One treatment may be sufficient, with a
possible follow-up for extremely resistant species; thereafter the shrubs assert control and the
trees do not return. The best and cheapest controls for vegetation are not chemicals but other
plants.
The method has been tested in research areas scattered throughout the eastern United States.
Results show that once properly treated, an area becomes stabilized, requiring no respraying
for at least 20 years. The spraying can often be done by men on foot, using knapsack sprayers,
and having complete control over their material. Sometimes compressor pumps and material
can be mounted on truck chassis, but there is no blanket spraying. Treatment is directed only to
trees and any exceptionally tall shrubs that must be eliminated. The integrity of the
environment is thereby preserved, the enormous value of the wildlife habitat remains intact,
and the beauty of shrub and fern and wildflower has not been sacrificed. Here and there the
method of vegetation management by selective spraying has been adopted. For the most part,
entrenched custom dies hard and blanket spraying continues to thrive, to exact its heavy
annual costs from the taxpayer, and to inflict its damage on the ecological web of life. It thrives,
surely, only because the facts are not known. When taxpayers understand that the bill for
spraying the town roads should come due only once a generation instead of once a year, they
will surely rise up and demand a change of method.
Among the many advantages of selective spraying is the fact that it minimizes the amount of
chemical applied to the landscape. There is no broadcasting of material but, rather,
concentrated application to the base of the trees. The potential harm to wildlife is therefore
kept to a minimum. The most widely used herbicides are 2,4-D, 2,4,5-T, and related
compounds. Whether or not these are actually toxic is a matter of controversy. People spraying
their lawns with 2,4-D and becoming wet with spray have occasionally developed severe
neuritis and even paralysis. Although such incidents are apparently uncommon, medical
authorities advise caution in use of such compounds. Other hazards, more obscure, may also
attend the rise of 2,4-D. It has been shown experimentally to disturb the basic physiological
process of respiration in the cell, and to imitate X-rays in damaging the chromosomes. Some
very recent work indicates that reproduction of birds may be adversely affected by these and
certain other herbicides at levels far below those that cause death. Apart from any directly toxic
effects, curious indirect results follow the use of certain herbicides. It has been found that
animals, both wild herbivores and livestock, are sometimes strangely attracted to a plant that
has been sprayed, even though it is not one of their natural foods. If a highly poisonous
herbicide such as arsenic has been used, this intense desire to reach the wilting vegetation
inevitably has disastrous results. Fatal results may follow, also, from less toxic herbicides if the
plant itself happens to be poisonous or perhaps to possess thorns or burs. Poisonous range
weeds, for example, have suddenly become attractive to livestock after spraying, and the
animals have died from indulging this unnatural appetite. The literature of veterinary medicine
abounds in similar examples: swine eating sprayed cockleburs with consequent severe illness,
lambs eating sprayed thistles, bees poisoned by pasturing on mustard sprayed after it came
into bloom. Wild cherry, the leaves of which are highly poisonous, has exerted a fatal attraction
for cattle once its foliage has been sprayed with 2,4-D. Apparently the wilting that follows
spraying (or cutting) makes the plant attractive. Ragwort has provided other examples.
Livestock ordinarily avoid this plant unless forced to turn to it in late winter and early spring by
lack of other forage. However, the animals eagerly feed on it after its foliage has been sprayed
with 2,4-D. The explanation of this peculiar behavior sometimes appears to lie in the changes
which the chemical brings about in the metabolism of the plant itself. There is temporarily a
marked increase in sugar content, making the plant more attractive to many animals.
Another curious effect of 2,4-D has important effects for livestock, wildlife, and apparently for
men as well. Experiments carried out about a decade ago showed that after treatment with this
chemical there is a sharp increase in the nitrate content of corn and of sugar beets. The same
effect was suspected in sorghum, sunflower, spiderwort, lambs quarters, pigweed, and
smartweed. Some of these are normally ignored by cattle, but are eaten with relish after
treatment with 2,4-D. A number of deaths among cattle have been traced to sprayed weeds,
according to some agricultural specialists. The danger lies in the increase in nitrates, for the
peculiar physiology of the ruminant at once poses a critical problem. Most such animals have a
digestive system of extraordinary complexity, including a stomach divided into four chambers.
The digestion of cellulose is accomplished through the action of micro-organisms (rumen
bacteria) in one of the chambers. When the animal feeds on vegetation containing an
abnormally high level of nitrates, the micro-organisms in the rumen act on the nitrates to
change them into highly toxic nitrites. Thereafter a fatal chain of events ensues: the nitrites act
on the blood pigment to form a chocolate-brown substance in which the oxygen is so firmly
held that it cannot take part in respiration, hence oxygen is not transferred from the lungs to
the tissues. Death occurs within a few hours from anoxia, or lack of oxygen. The various reports
of livestock losses after grazing on certain weeds treated with 2,4-D therefore have a logical
explanation. The same danger exists for wild animals belonging to the group of ruminants, such
as deer, antelope, sheep, and goats. Although various factors (such as exceptionally dry
weather) can cause an increase in nitrate content, the effect of the soaring sales and
applications of 2,4-D cannot be ignored. The situation was considered important enough by the
University of Wisconsin Agricultural Experiment Station to justify a warning in 1957 that ‘plants
killed by 2,4-D may contain large amounts of nitrate.’ The hazard extends to human beings as
well as animals and may help to explain the recent mysterious increase in ‘silo deaths’. When
corn, oats, or sorghum containing large amounts of nitrates are ensiled they release poisonous
nitrogen oxide gases, creating a deadly hazard to anyone entering the silo. Only a few breaths
of one of these gases can cause a diffuse chemical pneumonia. In a series of such cases studied
by the University of Minnesota Medical School all but one terminated fatally. . . .
‘Once again we are walking in nature like an elephant in the china cabinet.’ So C. J. Briejèr, a
Dutch scientist of rare understanding, sums up our use of weed killers. ‘In my opinion too much
is taken for granted. We do not know whether all weeds in crops are harmful or whether some
of them are useful,’ says Dr. Briejèr. Seldom is the question asked, What is the relation between
the weed and the soil? Perhaps, even from our narrow standpoint of direct self-interest, the
relation is a useful one. As we have seen, soil and the living things in and upon it exist in a
relation of interdependence and mutual benefit. Presumably the weed is taking something
from the soil; perhaps it is also contributing something to it. 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. Scientists 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
rose bed, 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. One very useful function of
natural plant communities—now pretty generally stigmatized as ‘weeds’—is to serve as an
indicator of the condition of the soil. This useful function is of course lost where chemical weed
killers have been used. Those who find an answer to all problems in spraying also overlook a
matter of great scientific importance—the need to preserve some natural plant communities.
We need these as a standard against which we can measure the changes our own activities
bring about. We need them as wild habitats in which original populations of insects and other
organisms can be maintained, for, as will be explained in Chapter 16, the development of
resistance to insecticides is changing the genetic factors of insects and perhaps other
organisms. One scientist has even suggested that some sort of ‘zoo’ should be established to
preserve insects, mites, and the like, before their genetic composition is further changed. Some
experts warn of subtle but far-reaching vegetational shifts as a result of the growing use of
herbicides. The chemical 2,4-D, by killing out the broad-leaved plants, allows the grasses to
thrive in the reduced competition—now some of the grasses themselves have become ‘weeds’,
presenting a new problem in control and giving the cycle another turn. This strange situation is
acknowledged in a recent issue of a journal devoted to crop problems: ‘With the widespread
use of 2,4-D to control broadleaved weeds, grass weeds in particular have increasingly become
a threat to corn and soybean yields.’
Ragweed, the bane of hay fever sufferers, offers an interesting example of the way efforts to
control nature sometimes boomerang. Many thousands of gallons of chemicals have been
discharged along roadsides in the name of ragweed control. But the unfortunate truth is that
blanket spraying is resulting in more ragweed, not less. Ragweed is an annual; its seedlings
require open soil to become established each year. Our best protection against this plant is
therefore the maintenance of dense shrubs, ferns, and other perennial vegetation. Spraying
frequently destroys this protective vegetation and creates open, barren areas which the
ragweed hastens to fill. It is probable, moreover, that the pollen content of the atmosphere is
not related to roadside ragweed, but to the ragweed of city lots and fallow fields. The booming
sales of chemical crabgrass killers are another example of how readily unsound methods catch
on. There is a cheaper and better way to remove crabgrass than to attempt year after year to
kill it out with chemicals. This is to give it competition of a kind it cannot survive, the
competition of other grass. Crabgrass exists only in an unhealthy lawn. It is a symptom, not a
disease in itself. By providing a fertile soil and giving the desired grasses a good start, it is
possible to create an environment in which crabgrass cannot grow, for it requires open space in
which it can start from seed year after year.
Instead of treating the basic condition, suburbanites—advised by nurserymen who in turn have
been advised by the chemical manufacturers—continue to apply truly astonishing amounts of
crabgrass killers to their lawns each year. Marketed under trade names which give no hint of
their nature, many of these preparations contain such poisons as mercury, arsenic, and
chlordane. Application at the recommended rates leaves tremendous amounts of these
chemicals on the lawn. Users of one product, for example, apply 60 pounds of technical
chlordane to the acre if they follow directions. If they use another of the many available
products, they are applying 175 pounds of metallic arsenic to the acre. The toll of dead birds, as
we shall see in Chapter 8, is distressing. How lethal these lawns may be for human beings is
unknown. The success of selective spraying for roadside and right-of-way vegetation, where it
has been practiced, offers hope that equally sound ecological methods may be developed for
other vegetation programs for farms, forests, and ranges— methods aimed not at destroying a
particular species but at managing vegetation as a living community. Other solid achievements
show what can be done. Biological control has achieved some of its most spectacular successes
in the area of curbing unwanted vegetation. Nature herself has met many of the problems that
now beset us, and she has usually solved them in her own successful way. Where man has been
intelligent enough to observe and to emulate Nature he, too, is often rewarded with success.
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
occupied about 100,000 acres of rangeland, and by 1952 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 colour 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 beetle from the original colonies and
redistributing them at the rate of millions a year. Within small areas the beetles accomplish
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.
Another extraordinarily successful and economical example of weed control may be found in
Australia. With the colonists’ usual taste for carrying plants or animals into a new country, a
Captain Arthur Phillip had brought various species of cactus into Australia about 1787,
intending to use them in culturing cochineal insects for dye. Some of the cacti or prickly pears
escaped from his gardens and by 1925 about 20 species could be found growing wild. Having no
natural controls in this new territory, they spread prodigiously, eventually occupying about 60
million acres. At least half of this land was so densely covered as to be useless. In 1920
Australian entomologists were sent to North and South America to study insect enemies of the
prickly pears in their native habitat. After trials of several species, 3 billion eggs of an Argentine
moth were released in Australia in 1930. Seven years later the last dense growth of the prickly
pear had been destroyed and the once uninhabitable areas reopened to settlement and
grazing. The whole operation had cost less than a penny per acre. In contrast, the
unsatisfactory attempts at chemical control in earlier years had cost about £10 per acre.
Both of these examples suggest that extremely effective control of many kinds of unwanted
vegetation might be achieved by paying more attention to the role of plant-eating insects. The
science of range management has largely ignored this possibility, although these insects are
perhaps the most selective of all grazers and their highly restricted diets could easily be turned
to man’s advantage.
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