Unwelcome Harvest

Agriculture and pollution

Gordon R. Conway, Jules N. Pretty

• Publisher: Routledge
• Year: 2013
• ISBN:
  9781134063659
• Edition: 1
• Topic: Law
• Subtopic: Environmental Law
• Index: Law

Agriculture Pollutes: pesticides can destroy wildlife and some are toxic to humans; some fungicides and herbicides cause cancer. Nitrates result in the contamination of drinking water and produce the risk of the blue-baby syndrome in infants and of stomach cancer in adults. Agriculture produces methane, ammonia, nitrous oxide and the products of burning off, all of which add to the world's problems of acid rain, depletion of the ozone layer and global warming.

This book, which focuses on the UK, the USA and Third World countries, is the first comprehensive review of agriculture and pollution: it examines the facts and assesses the relative dangers of each pollution problem. It also considers the effects of pollution on agriculture itself crop yields are depressed and livestock damaged by various forms of pollution from all sources.

The authors offer solutions to these apparently overwhelming problems, and describe existing technology which would allow us to deal with them.

Originally published in 1991

1 Introduction to Agriculture and Pollution

Industrial activity has always resulted in pollution. But agriculture, for most of its history, has been environmentally benign. Even when industrial technology began to have an impact in the eighteenth and nineteenth centuries, agriculture continued to rely on natural ecological processes. Crop residues were incorporated into the soil or fed to livestock, and the manure returned to the land in amounts that could be absorbed and utilized. The traditional mixed farm was a closed, stable and sustainable ecological system, generating few external impacts.

Since the Second World War this system has disintegrated. Farms in the industrialized countries have become larger and fewer in number, highly mechanized and reliant on synthetic fertilizers and pesticides. They are now more specialized, so that crop and livestock enterprises are separated geographically. Crop residues and livestock excreta, which were once recycled, have become wastes whose disposal presents a continuing problem for the farmer. Straw is burnt since this is the cheapest and quickest method of disposal. Livestock are mostly reared indoors on grain and silage on farms whose arable land is insufficient to take up the waste.

Coincident with these changes, growing urbanization and population densities, coupled with increased affluence, have intensified the conflicts over land use. Urban populations have become reliant on agricultural catchments for their drinking water, are demanding uncontaminated food, and are increasingly valuing the countryside for attributes other than food and fibre production. Amenity, recreation and nature conservation are now important products of the countryside in their own right. Hiking, horse-riding, angling and camping are pursuits followed by millions. Thus, not only has the potential for contamination increased, so have the consequences, because of the greater value we now place on our environment.

Similar changes are beginning to occur in many parts of the Third World. The advent of new high-yielding cereal varieties as part of the Green Revolution, together with intensification of export crop agriculture, have resulted in a dramatic growth of pesticide and fertilizer use. Pollution problems are already apparent and are likely to grow in importance in the next few years. Although the use of the countryside for leisure is confined, at present, to a very few urban dwellers, many Third World countries are developing strong conservation movements among whose concerns are the effects of agriculture on wildlife.

The nature of pollution

At its most inclusive, the term pollution encompasses all unwanted effects of human or natural activities. According to this definition an unsightly farm building would be classified as “aesthetic pollution”. However, in this book we use the term as more commonly and narrowly defined whereby a pollutant is a substance (e.g. a chemical compound or waste material) or an energy (e.g. noise) which produces unwanted effects. It is usual to restrict the term pollutant to substances or energies created by human beings while recognizing that, under certain conditions, natural processes generate “pollutants”, for example the sulphur dioxide given off during a volcanic eruption. It is also useful to make a distinction between a contaminant, which is any substance or energy introduced by human beings into the environment, and a pollutant, which is a contaminant that is causing, or liable to cause, damage or harm.¹

The primary environmental contaminants produced by agriculture are agrochemicals, in particular pesticides and fertilizers. These are deliberately introduced into the environment by farmers to protect crops and livestock and improve yields. Contamination is also caused, though, by the various wastes produced by agricultural processes, in much the same way as occurs in industry. The wastes comprise straw, silage effluent and livestock slurry, and, in the Third World, the wastes from on-farm processing of agricultural products such as oil palm and sugar. From the immediate environment of the farm contamination spreads to food and drinking water, to the soil, to surface and groundwaters and to the atmosphere, in some instances reaching as high as the stratosphere (Table 1.1).

Table 1.1 The principal pollution problems caused by agriculture

Contaminant or Pollutant	Consequences
Contamination of water
Pesticides	Contamination of rainfall, surface and groundwater, causing harm to wildlife and exceeding standards for drinking water
Nitrates	Methaemoglobinaemia in infants; possible cause of cancers
Nitrates, phosphates	Algal growth and eutrophication, causing taste problems, surface water obstruction, fish kills, coral reef destruction; and illness due to algal toxins
Organic livestock wastes	Algal growth, plus deoxygenation of water and fish kills
Silage effluents	Deoxygenation of water and fish kills; nuisance
Processing wastes from plantation crops (rubber, oil palm)	Deoxygenation of water and fish kills; nuisance
Contamination of food and fodder
Pesticides	Pesticide residues in foods
Nitrates	Increased nitrates in food; methaemoglobinaemia in livestock
Contamination of farm and natural environment
Pesticides	Harm to humans; harm to humans; nuisance
Nitrates	Harm to plant communities
Ammonia from livestock and paddy fields	Disruption of plant communities; possible role in tree deaths
Metals from livestock wastes	Raised metal content in soils
Pathogens from livestock wastes	Harm to human and livestock health
Contamination of atmosphere
Ammonia from livestock manures and paddy fields	Odour nuisance; plays role in acid rain production
Nitrous oxide from fertilizers	Plays role in ozone layer depletion and global climatic warming
Methane from livestock and paddy rice	Plays role in global climatic warming
Products of biomass burning (cereal straw, forests, savannas)	Enhances localized ozone pollution of troposphere; plays role in acid rain production, ozone layer depletion and global climatic warming; nuisance
Indoor contamination
Ammonia, hydrogen sulphide from livestock wastes	Harm to farm worker and animal health Odour nuisance
Nitrogen dioxide from silage in silos	Harm to farm worker health

The assessment of pollution

Pollution assessment is a complicated process. Ideally it requires an understanding of the components and linkages of a chain that stretches from underlying causes, through effects, to perceptions and costs (Figure 1.1). Once this is fully understood, it is then possible to seek out and implement appropriate preventative or control measures. But ...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• Glossary for Units of Measurement
• List of tables, boxes and figures
• Preface
• 1. Introduction to Agriculture and Pollution
• 2. Pesticides and the Environment
• 3. Pesticides and Human Health
• 4. Fertilizers and the Environment
• 5. Fertilizers and Health
• 6. Farm Wastes
• 7. Agriculture as a Global Polluter
• 8. The Impact of Air Pollution on Agriculture
• 9. The Impact of Land and Water Pollution on Agriculture
• 10. The Control of Pollution
• 11. Agriculture Without Pollution
• Index