Pesticides and Pollution

Table of Contents

Cover Page

Title Page

Editors’ Preface

Author’s Preface

CHAPTER ONE

INTRODUCTION

CHAPTER TWO

AIR POLLUTION

CHAPTER THREE

WATER POLLUTION

CHAPTER FOUR

RADIATION

CHAPTER FIVE

POLLUTION OF THE OCEAN AND THE SHORE

CHAPTER SIX

HERBICIDES AND WEED CONTROL

CHAPTER SEVEN

FUNGICIDES

CHAPTER EIGHT

INSECTICIDES AND INSECT CONTROL

CHAPTER NINE

SUBSTANCES USED TO CONTROL OTHER INVERTEBRATE PESTS

CHAPTER TEN

THE CONTROL OF VERTEBRATE PESTS

CHAPTER ELEVEN

THE FUTURE – IMPROVEMENT OR DISASTER?

Bibliography

Appendix

Index

Plates

Copyright

About the Publisher

EDITORS’ PREFACE

The New Naturalist series, now some way beyond its half century of volumes and its quarter century of years, has had much cause for gratitude to the senior officers of our kingdom’s Nature Conservancy who have so valuably contributed to its books and its task.

It could be expected that a servant of a statutory body, when discussing problems of conservation and ecology of political, economic and social moment (as nearly all such problems are) might adopt a somewhat statutory tone of voice. None of our Natural Conservancy authors has yet done so; nor has Dr. Mellanby, who handles in this book what can be vulgarly described (if it is not mixing a biological metaphor) as the hottest potato in the nature business. The impact of modern industry’s chemical products (themselves the products of vastly expensive and brilliant research) upon our environment—the air we breathe, the water we drink, the food we eat, and the animals and plants with which we try peacefully to coexist—is a subject so vast, so emotion-rousing, so socially provoking that almost anybody could be forgiven for approaching it with fearful frenzy on the one hand, or with careful dissemblance or even dissimulation on the other. Not so Mellanby: this is a calm book, and a deeply thought-out book, and patently a balanced book: the kind of book we expected from the leader of one of the finest teams of ecological analysts in the country. Of course we knew it would be so, when we persuaded the Director of the Monks Wood Experimenal Station to write it.

Kenneth Mellanby’s approach is magnificently lucid, the more so because of his deft use of illuminative detail, alternating with wise generalisations that show the deepest understanding of the history of pollution and the eternal struggle of man against predators and pests. He has had to specialise in being general: be not only historian but geographer, physiographer, chemist and physicist as well as biologist to arrive at a sense of proportion and balance, and a true evaluation of the present tides and streams of wastes and poisons, their natural history, control, cause, cure and care.

This book has been written without fear or favour, and with the fairest analyses of mistakes and successes. It persuades us of the need for everybody’s deeper understanding of the problems involved, and that our human stock, with the increase of its population and its civilised wants, has courted risks, certainly invited disasters and suffered a few—and yet may have succeeded in arriving at a point of common-sense confidence in a clean (or cleanish) planet in the predictable future. The planet is presently a pretty dirty one: but some clever ecologists and conservationists have voices that are now being heard, and may be heeded before it is too late.

All books on pesticides and pollution must be compared with the late Rachel Carson’s classic Silent Spring of 1963, which started the general public of all the educated world wondering. Kenneth Mellanby’s book is not of the same genre, and it would have been most inappropriate if it had been. Miss Carson’s book was a chamber of horrors, and, as regards the insecticidal events of its time, as every responsible naturalist (including Dr. Mellanby) would agree, accurate. It did a power of good. This book, we predict, will do further good; for it does the next thing. It does not say how awful! for this has already been said, and in Rachel Carson’s context justifiably. It says how does the business really work, and what next? and proceeds to spell it out, in a masterly style and depth that we are proud to be associated with.

THE EDITORS

AUTHOR’S PREFACE

In this book I have tried to deal with the subject of environmental pollution in Britain in an objective way. The public, and particularly those members of the public who are interested in the conservation of wild life, are very familiar with many types of pollution, but they cannot always judge their importance. Sometimes atomic radiation seems to be all-important, particularly when questions of military strategy are discussed. Our many fishless rivers are clear evidence of the serious effects of the pollution of fresh water, and every year our newspapers have pictures of dead seabirds covered with oil on our beaches. Great publicity has been given to agricultural chemicals. The remarkable impact of Rachel Carson’s Silent Spring has suggested that insecticides are the greatest danger. I have deliberately avoided dealing with this book in the text, not because I underrate its contribution to the subject, but because I think that the time has come to try to look at all sides of the problem. Rachel Carson, when dealing with insecticides and herbicides, was careful to give us the facts as they applied to the United States, but she selected her facts, and gave us an advocate’s case. At the time, this was a useful service to science, and equally selective rejoinders from the chemical industry have done little to reassure the public. Other and more objective books on the effects of pesticides are listed in the bibliography. One of my main tasks has been to try to fit pesticides into the general picture of pollution from all sources.

The writer of a book like this needs to call on many others for help. Over a good many years I have discussed these problems with scientists from many countries, and I have tried to digest their views and the contents of their publications. The question of pesticides must have special mention. I have been fortunate in being able to discuss these problems with Dr. N. W. Moore, head of the Nature Conservancy’s Toxic Chemicals and Wild Life Section at Monks Wood Experimental Station, and with the members of his team. Dr. Moore was the first scientist in Britain to organise research work on this subject, and he and his colleagues have made major contributions towards the understanding of their problem. I have received immense help from them at all stages and have taken up a great deal of their time in detailed discussion. I hasten to add, however, that they are in no way to blame for any faults in my presentation of the subject.

The editors of this series have given valuable help. Sir Julian Huxley originally suggested that I should write this book, and made useful proposals as to its contents. Sir Dudley Stamp also gave me much encouragement, and the most courteous application of the spur whenever I fell behind my schedule. Without this I would never have finished the book. He read the manuscript and I shall treasure the appreciative letter he wrote me about it not long before his untimely death.

As I have already said, I have tried to make this book an objective account of pollution. I fear that I shall be attacked from all sides. In discussions I have been accused of exaggerating the dangerous effects of industrial processes and of beneficial agricultural chemicals. I have also been told that I play down the dangers of these substances. So long as the attacks do indeed come from these different quarters I shall not feel that I have entirely failed in my objective.

CHAPTER ONE INTRODUCTION

This book is essentially an account of the way in which man is unintentionally contaminating his environment. This is a world-wide problem, but for the most part I am restricting my scope to consider the situation in Britain. I do this for two reasons, first because this treatment seems appropriate to a volume in the New Naturalist series, and secondly because although the problem is more acute in these small, developed and densely populated islands than in many other parts of the world, it is possible that what we do can help and guide others, and serve as a warning to prevent damage in the countries at present undeveloped which might otherwise accompany their economic development.

I think it is quite logical to bring together in one book the effects on our environments and on our wild life of pollutions which arise from urban conditions and from industry, and the rather special case of pesticides, which have recently been shown to constitute such an important contribution to environmental pollution. In all cases we are dealing with effects which were not deliberately planned by those who produce them. Pollution, including radiation, has grown as a side effect of the increase in human population, and of increased material productivity. Pest control began in quite a different way, but it is the side effects of modern pesticides, substances which could only have been produced and developed in an industrial system, and which may be effective weapons when properly used, which are causing so much concern.

In this book I have attempted to review the present situation, show how it has arisen, and discuss how man may either continue to pollute the earth and to impoverish it by destroying and restricting its flora and fauna, or alternatively may control his own activities for the benefit of posterity. The situation is serious. Much irremediable damage has already been done. On the other hand, we have learned how to avoid the worst types of pollution. Public opinion is strongly in favour of controlling pollution, and we are not so dogmatically in favour of eradicating any forms of life we consider to be “pests” as perhaps we used to be. If mankind is prepared to make a determined effort, to support much more research to make that effort effective, our descendants may not be condemned to live on an impoverished planet devoid of so much of the varied life which has made it so interesting and so beautiful. There is one other point which should be noted. Some pollutions, particularly from insecticides, seem to be harmful to wild life but not, as yet, to man. Air pollution is more often seen to damage plants than to harm man. Perhaps we should look upon these as useful “early warning” systems, and use the opportunity to reduce the chances of future damage to our own species.

Man deliberately alters the face of the earth, to a degree to which no other species of animal has aspired. He builds cities, factories and roads which wipe out wild life over large areas. He does this quite intentionally, assuming that the gain far outweighs the loss, though his pollution of the surrounding countryside with domestic and industrial effluents is not intentional. However, important as are the effects of urban and industrial development, it is as a farmer that man has the most profound effects on the landscape, and on the plants and animals which live there. An excellent account of these changes is given in Man and the Land by Sir Dudley Stamp. Farmers destroy the natural vegetation, and substitute wide areas of alien plants grown in monoculture. They deliberately try to get rid of plants which compete with their crops – that is, weeds. They try to destroy animals which eat their crops and so reduce the amount harvested – that is, pests. As agriculture has developed, new methods of dealing with weeds and pests have been discovered and put into use. To-day we are all conscious of the fact that chemical controls have been developed, and that poisonous substances are widely used to achieve control. We know that these poisons may kill birds and other forms of wild life, and we fear that they may endanger human health. However, we tend to forget that these possible toxic side effects may be less catastrophic to wild life than are the ecological effects of “traditional” agriculture.

Man has existed for hundreds of thousands of years, but it is only within the last ten thousand that he has had any considerable ecological effect, and only within the last millenium that he has really begun to change the whole appearance of the earth’s surface. Until about 8,000 B.C. man was a hunter and a gatherer of wild plants, with no domestic animals and no crops. Life, as Hobbes has said, was “nasty, brutish and short.” Man had little effect on his environment. He ate fruit and berries, and helped to disperse the seeds as do birds and animals to-day. His waste-products were probably dispersed over the land and helped to fertilise it. When he died his remains decayed and the nutrients were returned to the system. The nastiness of his life was probably made worse by pollution, even at that stage of his development, and pests contributed to its shortness. Some animals are naturally clean. They excrete in recognised latrines some distance from their usual resting places, and they do not leave the decaying remains of food in inconvenient places. Other animals, and primitive man was probably one of them, are not so hygienic, and if he lived in a cave it probably stank disgustingly. Even when he buried his dead he sometimes did so beneath his dwelling, just where decay would be most objectionable. Under these conditions many diseases must have been rife.

Early man probably thought of the larger carnivores as the most serious pests. He competed with them for animal food when he became a hunter, and he himself formed a part of their prey. At first he did little positive to control these pests; his main object was to avoid them. Later, but long before he became a farmer, man in some parts of the world learned to trap and hunt even the most ferocious wild animals, and he probably accelerated the extinction of several species. Recent work on the so-called “Pleistocene overkill” goes so far as to suggest that man exterminated nearly half the larger mammals in Africa some 50,000 years ago, and that in North Africa (where man arrived much later) he similarly killed off at least sixty per cent of the species of large mammals around 10,000 B.C. If these conclusions are finally substantiated, they will have a profound effect on ecological thinking. Early man probably paid little attention to the smaller insect pests, lice, bugs and fleas, from which he no doubt suffered. He did not realise that these were not only a nuisance, but were also the carriers of diseases which were far more deadly than all the lions and tigers and snakes which he so greatly feared. At this stage man was simply an animal, competing with other animals, and doing little to upset the uneasy balance of nature.

There were cases where hunters profoundly changed the landscape. It is likely that North American Indians deliberately burned the forest, and so encouraged grassland which could maintain larger herds of buffalo. This could be considered an early example of wild life conservation! It must also have had profound effects on all the other animals and plants in the region. Incidentally, at a much later date, when the prairies were cultivated to grow cereal crops, the buffaloes became “pests” and were almost completely exterminated.

Primitive man suffered from pests and pollutions, even if he was not always aware of this. When he became an agriculturalist, he recognised the fact. Settled agriculture, with the growing of some crops, has gone on in parts of the world for perhaps ten thousand years, but extensive farming has only existed for about five thousand years. Arable farming is essentially a process where certain plants are encouraged, and others, which would compete with them, are discouraged. The unwanted plants are pests or weeds.

It is difficult to find a satisfactory definition of a pest, other than to describe it as a plant or animal living where man does not want it to live. The same animal may sometimes be treated as economically valuable, at other times as a dangerous competitor. Thus mink, escaped from fur farms in England, where they are prized, are considered as dangerous pests in other parts of the country. The same plant may be a valued crop at one time and a weed at another; an obvious example is the potato, for a few tubers, accidentally left in the soil when this crop is harvested, are troublesome weeds in cereals grown in succeeding years.

A great part of the energy expended in arable farming goes in weed control. Ploughing, harrowing and cultivation are all means of reducing weeds and their growth, as well as of making conditions suitable for planting crops. It is therefore somewhat ironic that weeds are important largely because man has produced conditions in which they flourish. Most weeds were rare plants before man became a farmer, and some are now uncommon or even extinct except on farm land. The history of weeds and their development has been fully described by Sir Edward Salisbury in his masterly book Weeds and Aliens, to which any interested reader must refer.

At different times farmers have used different methods of weed control, and different species of plant have been economically important. When wheat and other corn crops were sown broadcast, hand weeding was the only practicable method. When drilling in rows was introduced in the eighteenth century, it became much easier to keep crops clean. At the same time improved methods of separating crop from weed seeds were devised, so that sowing did not itself greatly contaminate the ground. Thus with clean seed and properly planted crops, cheap labour and comparatively simple horse-drawn machines kept the fields clean. At the end of the nineteenth century there was no serious weed problem for the good farmer in most parts of Britain. As agricultural wages rose, mechanisation was introduced, and some farming processes were improved, but many crops became weedier and weedier, so that different rotations had to be developed, not always with success. In recent years the situation, for the farmer, has been saved by the introduction of selective weedkillers. These have revolutionised agriculture, but have produced their own problems, as will be seen in chapter 6.

Parasitic fungi cause a great deal of crop damage. Early man was aware of some of these diseases, and the danger of eating corn made poisonous, for instance, by the fungus causing ergot, particularly in rye. However, many fungus diseases were not recognised as such, and their damage was accepted as a normal risk of farming, until the latter part of the nineteenth century. As shown in chapter 7, many fungus diseases are now controlled with little risk to other forms of life.

Farmers, from neolithic times onwards, were aware of mammalian pests, ranging from deer which damaged their crops to wolves which preyed on their herds. Rats and other rodents were known to consume much of the stored grain, and many ingenious methods of excluding them were devised. Early pest control was in effect hunting; the results were sometimes successful, as in the case of large and slow-breeding animals, and quite ineffective against small mammals which bred rapidly. Brown bears were exterminated in England in Roman times, and in Scotland before the Norman invasion. Wolves continued much longer. They were quite common, particularly in Wales, into the medieval period, and the last survivor is believed to have been killed in 1740; a few lingered on in Ireland for another thirty years.

Pest control in the English countryside has usually been related to game preservation and sport as well as to agriculture. The wolf was clearly too large and voracious an animal to be tolerated, and so it was eliminated. No one to-day seriously suggests its reintroduction, though conservationists (if not the local farmers) are concerned about its future in Spain. The fox, however, is still quite abundant, although it undoubtedly kills poultry. It would be difficult, though not impossible, to exterminate all the hill foxes in the wilder parts of Britain, but a determined effort could get rid of this animal in areas of intensive farming within a couple of years. Foxes may not be deliberately preserved, but they have been tolerated for many years because of fox-hunting, and those naturalists who are opposed to blood sports should realise their debt in this connection. Recent research has shown that foxes live as much on carrion and on small animals and insects as upon poultry and game, so they are likely to continue to survive unless accidentally wiped out by chemicals (see here). Recently foxes have been reported in increasing numbers in suburbia, raiding dustbins and feeding on garbage. These habits will not endear them to the more sentimental members of the public, who may equate garbage-eating foxes with rats. More of the animals are likely to survive, and they may eventually become pests in a new role if they become too common.

Gamekeepers were for a long time the main enemies of carnivorous animals and birds, which they spoke of as “vermin” on the assumption that they lived mainly on game. Most keepers until recently had their “gallows” on which the rotting corpses of stoats, weasels, hawks and owls were hung, presumably pour encourager les autres. Systematic shooting of slow-breeding predatory birds effectively controlled their numbers. In the nineteenth century kites, formerly distributed throughout the country, were eliminated except from a few mountainous areas. A careful investigation by Dr. N. W. Moore shows how the buzzard has fared in the last 150 years. At the beginning of the nineteenth century buzzards were quite common breeding birds over most of Britain. By 1865 they had been exterminated in most of East Anglia and the Midlands, and by 1900 they were only to be found in Cornwall, Wales, the Lake District and Western Scotland. By 1954 the situation had somewhat improved, and the birds had recolonised many of the areas occupied in 1865. This spread was clearly due to the decrease in game preservation during and after the 1914-18 war. If the data for buzzards and the numbers of gamekeepers are mapped side by side, this shows a good negative correlation.

To-day many gamekeepers are more enlightened. Although hawks and other carnivorous birds do eat some game birds, they prey much more on small mammals (mice, voles, etc.) which compete with game for food. Most predators are now themselves legally “preserved,” though they can be shot if caught in the act of taking poultry or game. We may see an improvement in numbers, similar to that manifested by the buzzard between 1900 and 1954, for many other species, if the new danger from agricultural chemicals can be overcome.

Smaller, non-carnivorous mammals and birds do a lot of damage, the amount of which is not always recognised. Rabbits were probably introduced into England by the Normans in the eleventh or twelfth century and were comparatively uncommon, prized as game animals until the nineteenth century. Then, for some reason which we do not yet understand, they suddenly increased in numbers so that a density of twenty animals to an acre was not uncommon, and as many as 100,000,000 carcasses were sold in a year, without noticeably depleting the numbers still at large. It was not until rabbits were wiped out in many areas by myxomatosis in 1954 that the extent of the damage they had done was recognised. Pre-myxomatosis control, by shooting and trapping, was rarely effective, and merely served to “crop” the population. The importance of myxomatosis is discussed in chapter 10.