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close this bookAnimal Husbandry - Initial Environmental Assessment Series No. 2 (NORAD, 1994)
close this folderPart I: General account
close this folder3 Possible environmental impacts
View the document(introduction...)
View the document3.1 Overgrazing and soil erosion
View the document3.2 Pollution of air, soil and water
View the document3.3 Special impacts of livestock-based industries and transportation
View the document3.4 Loss of valuable genes
View the document3.5 Infection pressure and diseases, and impacts of medication
View the document3.6 Other ecological impacts, and consequences for landscapes
View the document3.7 Social impacts
View the document3.8 Impacts of other existing or planned activities


In this survey, both direct and indirect environmental impacts are dealt with. It is often difficult to distinguish clearly between these two types of impacts. Causes of direct environmental impacts can be linked to certain features of the project as such. Indirect environmental impacts can result from other types of activities and processes which the project generates, ea. industrialization and urbanization. Indirect environmental impacts can also occur if the project alters socio-cultural conditions in the local community, ea. by migration or changed power structures.

This survey also presents recommendations for mitigative measures that can reduce prospective environmental impacts.

3.1 Overgrazing and soil erosion

Overgrazing is a widespread problem in many developing countries. The most serious impact is reduced feed supply, so that the growth and production of the animals are hindered. In areas where pastures are the communal property of a village or district, the risk of overgrazing is particularly great. A reform or new legislation can be required in order to make the utilization of communal land more efficient. A fee per grazer could be introduced, for example, as well as a quality grading system for meat. Should mitigative measures of this kind be called for, one also has to make assessments of socio-cultural conditions and consequences for, and of, these (cf. chapter 3.7). Land tenure (see also chapter 2).

Impacts of overgrazing can be illustrated by an example in which 100 hectares of good pasture caters for 40 -100 cattle. 1 hectare is presupposed to yield 5.0 tons of grass and the maintenance requirement per animal is 24.6 MJ.

Impacts of overgrazing

This simple table shows that by an increase of the number of animals by 50 per cent from 40 to 60, most of the growth is lost. By doubling the number of animals from 40 to 80, nothing is left for growth and production. The animals lose weight instead of putting on weight. Research shows that cattle, goats and sheep graze on different plants and that the yield can be increased by letting different animal species graze together on the same land. In pastures under stress, only plant species that tolerate intense grazing will remain. Should there be a lack of feed, it is particularly important to adjust the number of animals according to the sustainability of the range. Since the plant production is dependent on the climate, however, this can be difficult. Should, for example, the expected precipitation fail to come, an unforeseen scarcity of feed may result. An emergency solution could be to move the animals to another area containing more feed, or transport feed to the animals. In areas with unstable precipitation, it may be necessary to take precautions by ensuring feed reserves in some way, ea. by means of standing hay or preserved feed.

Overgrazing and animal tracks can cause soil erosion, especially in steep terrain or in areas with much vulnerable vegetation and great seasonal differences in precipitation. Nevertheless, the risk of soil erosion in connection with grazing, especially extensive forms, seems to be generally less than previously assumed. Perennial plants in fields or pastures provide better protection against erosion than field plants that only partially cover the soil, and only in certain periods of the year. A measure for protecting exposed areas could be periodical or protracted enclosures. In some places, ea. in Tanzania, enclosure of pastures is practiced in order to keep them in reserve for periods of crisis.

Increased surface run-off will occur together with increased soil erosion, because the soil's capacity to retain water is dependent on the plant cover. This will lead to a reduced feeding of ground-water, and a reduced water flow in streams and rivers, so that erosion problems may also emerge here. A problem related to erosion is silting. Eroded matter being carried with the water in streams and rivers may cause a reduction in water quality and unwanted deposits and sediments in other parts of the watercourse. The supply of nutrients may exceed the natural level and thus contribute to eutrophication and overgrowing of water sources, so that breeding areas for fish may be damaged. Eroded matter which is retained in artificial reservoirs will be sedimented there. It will thereby reduce the longevity of the reservoir as well as the production capacity of any prospective power plant. Erosion, sediment transportation and depositing are complex processes, and the impacts of encroachments (ea. pastures) can be hard to predict. A precautionary attitude, therefore, is important in the planning and implementation of projects. (More about soil erosion, see booklet 7 Water supply).

3.2 Pollution of air, soil and water

Manure can pollute air by the emission of smell, ammonia and methane. Besides ammonia and hydrogen sulphide (H2S), the most noticeable smelling substances are some cyclic chemical compounds. Ammonia in large concentrations can do damage to the vegetation. H2S gas developing in a manure cellar can, in cases of carelessness and bad ventilation, cause poisoning that may harm, and at worst kill, animals and humans. Smell of manure is normally more unpleasant than harmful. If wet manure is sprayed over fields, ea. by means of watering equipment, fine drops (particles) can float with the wind and be a nuisance for the surroundings.

Methane (CH4) is a gas that is produced in manure and ferments without the supply of air (biogas), but it is also produced in the rumina of ruminants during anaerobic fermentation. As for monogastrics such as pigs and poultry, methane is virtually not produced in the intestinal canal. Methane is a natural greenhouse gas with an impact on the greenhouse effect that is approximately 8 times stronger than that of carbon dioxide (CO2). Methane contributes about lo per cent to the total global heating caused by greenhouse gases. Approximately 15 per cent of the total amount of methane emitted to the atmosphere is produced by domestic animals (ruminants). The rest of the methane derives from rice fields, earth gas, swamps, land fills and wild ruminants. Some therefore contend that approximately 1.5 per cent of the global heating caused by greenhouse gases can be traced back to livestock.

Careful utilization of livestock manure can be difficult if the areas are limited. Pollution may be the result if the amount of manure in an area exceeds the amount that can be utilized by plants and soil. The growth of aquatic plants and algae will increase when excessive nutrients run into ditches, streams and other surface-water sources. This will cause the oxygen in the water to be consumed, and death of fish will ensue. If the pollution becomes a more or less permanent state, the watercourse may gradually overgrow - eutrophication. Phosphorus is generally the minimum factor for the growth of algae in freshwater, whereas nitrogen is the prime limiting nutrient in seawater. Another consequence of large amounts of manure is that the nitrogen may seep down through layers of soil and finally reach the ground-water. As a consequence the level of nitrates in the ground-water may exceed the danger level (see also booklet 7 Water supply). Flies and other insects propagate quickly in manure and can be a nuisance to the surroundings.

In many developing countries, the problem is too little manure rather than too much. In connection with intensive animal husbandry for industrial production of livestock products, however, problems of too much manure per area unit may arise. With regard to such projects, care should be taken to ensure that the manure is spread over a sufficiently large area. The need of a spreading area (minimum area per animal manure unit) will vary according to climate, soil type, plant growth and the feed contents of nutrients, especially nitrogen (N) and phosphorus (P). One animal manure unit can be reckoned as equivalent to the release of P (or N) of ea. a cow (one standard cow) per year. The number of animals per animal manure unit regarding other domestic animals will depend on the amount they release. The capacity of the animals to bind N and P in the body, and thereby traces of this in the livestock produce, is limited in proportion to the contents in the feed. It is important, therefore, that the feed does not contain much more than what the animals can make use of. As for the ruminants, which need carbohydrates in order to synthesize protein, it is important that one pays attention to the carbohydrate/N balance and tries to make it as optimal as possible. This is different with monogastrics. They have a lesser capacity to break down phytate, which is the compound to which most of the phosphorus in grain and other kinds of feed is bound. Consequently, the contents of phosphorus in the feed must be higher than would have been necessary if the physic phosphorus had been more easily accessible. A preparation has recently been developed containing the enzyme phytase. When it is mixed into the feed, the digestibility of physic phosphorus increases so much that it becomes unnecessary to add unorganic phosphorus to, for example, pig and poultry feed.

Fertilization of fish ponds by means of livestock manure may cause pollution of watercourses (see booklet 5 Aquaculture).

Despite these potential negative impacts, it should be stressed that livestock manure, if applied with care, in most cases will benefit the environment. This is both due to the contents of plant nutrients and to the fact that manure can also be used to produce biogas, thereby contributing to saving forests and other sources of energy.

3.3 Special impacts of livestock-based industries and transportation

Different types of livestock-based industries are listed in chapter 1.2. Below is a brief survey of expected environmental impacts. These should be considered prior to the projects. For a more thorough presentation of environmental impacts of industrial projects, see booklet 9 Industry and energy.

· Increased water consumption (both ground water and surface sources), which can affect the supply of water to other users.
· Discharge to air, water and soil.
· Land use conflicts.
· Alterations in social and economic structures in the area.

Surplus of feed can also cause environmental conflicts. This can perhaps be most clearly seen in areas with food industries and other industries that have by-products that are difficult to get rid of except when being used as feed. Such by-products chiefly come from mills, breweries, distilleries, preservation industries, butcheries, fish processing plants, etc. Domestic animals can serve as useful processors of offal and by-products into valuable food products, while at the same time contributing to reducing environmental problems.

Environmental impacts can be considerable in connection with large tanneries. In addition to a great consumption of water, large amounts of waste (skin and hair) can cause pollution. The waste can be utilized as a fertilizer if a mud separator is employed to collect it. Chrome is often used in the tanning process, which may cause considerable pollution problems. From butcheries, byproducts such as blood, entrails, stomach and intestinal contents, bone, etc. can represent serious sources of pollution. If treated in the right way, however, these by-products can yield valuable feed, fertilizers or other products.

Large-scale livestock production requires access to transport (see also booklet 8 Transport). This concerns feed, fertilizers as well as products. Infrastructure such as roads, railway, water installations, electricity and telephone may be necessary in order to make full use of the livestock project. Transportation of live animals has traditionally taken place by herding, partly over long distances. If the flocks are large, such herds can have negative environmental impacts in the form of dust, tracks, etc. In connection with livestock projects, transportation mostly takes place by lorries which results in dust, noise and strains on poor country roads. In the rainy season, it can often be difficult, not to say impossible, to travel outside the main roads. Transportation of live animals requires special care to protect the animals against unnecessary suffering or even death during transport. Livestock products to be stored or transported fresh over long distances in the tropics require refrigeration. Refrigerator and freezing facilities often contain environmentally hazardous CFC gases. There ought to be facilities for tapping such gases when the equipment is disposed of.

Need of transportation can also be an issue in connection with more decentralized projects, especially where livestock production for sale is concerned. The need as well as provision of transport should be taken into consideration already during the planning of the project.

3.4 Loss of valuable genes

Increased efficiency in agriculture and animal husbandry may lead to loss of valuable genes. The focus has particularly been directed towards genetic resources in plants. This is due to the fact that many cultivated plants are self-fertile or clones being marketed as homogeneous lines or hybrids. When these supplant local varieties from a cultivated area, reduced genetic variation and loss of valuable genes may be the result. For a more detailed account of this, "The convention on biological diversity" (UNEP 1992) can be consulted.

In general, the risk of losing genes of domestic animals is smaller, as domestic animals are cross-fertilizers. Loss of genes can happen if imported exotic breeds totally replace local ones. Commercial poultry production is especially vulnerable, because some local poultry breeds are in danger of becoming extinct. Such standardizing of production systems creates a form of monoculture, reducing the possibilities of subsequent alterations, which might be desirable. Experience, by FAO for example, shows that subsistence households and hobby producers often take great interest in local poultry breeds, and that these breeds will therefore be preserved. One should nevertheless note that The World Poultry Science Association has appealed to FAO to take initiatives to preserve genetic resources in poultry. Replacement of local swine breeds by improved swine breeds from the industrialized countries is widespread wherever commercial pork production is established in developing countries. Measures may be called for to preserve local swine breeds. An alternative to preserving local breeds is to improve them by crossing in imported breeds, as well as making selections in the new mixed population under current environmental conditions. Crossing and selection will make it possible to preserve valuable genes in the population, provided they do not have a strongly negative effect on the properties which selection is meant to improve. The frequency of local genes may become lowered, but research has shown that the decline takes place slowly and that loss of important production and resistance properties, being governed by many genes, will not happen for generations. Such improved and upgraded local breeds are also likely to become valuable elements in a three or four breed crossing programme aimed at efficient and economical pork and poultry production in developing countries.

Introduction of new cattle, goat and sheep breeds in developing countries generally takes place through crossing with local breeds, not through substitution by new pure breeds. Such crossing and subsequent selection under local environmental conditions will preserve valuable local genes. FAO (1992) has recommended that selection in order to improve and preserve local breeds should take place in a so-called Open Nucleus Breeding System, where it is allowed to cross in animals of the same breeds or of other breeds having the desired properties. In many industrialized countries, a high degree of standardization of cattle breeds over large areas and between countries is taking place. This development, however, is still not common in most developing countries.

3.5 Infection pressure and diseases, and impacts of medication

When localizing a livestock project, the risk of serious diseases should be taken into consideration. Some livestock diseases can be transmitted to humans and wild animals and thus pose a threat to the environment. Generally speaking, the heavier the stocking rate in an area, the greater is the risk that infectious diseases may break out. An area in which a major animal husbandry project is established ought to have a satisfactory veterinary service.

Livestock production in tropical areas is vulnerable to a series of infectious diseases. Bacteria, virus, protozoa and worms which are rare or non-existent in temperate areas exist here. Examples are foot-and-mouth disease (virus), anthrax (bacteria), trypanosomiasis (sleeping sickness, caused by a protozoan) and various intestinal worms. Most of these diseases rarely have dramatic effects in extensive forms of production, but they can strike hard in intensive ones.

Many parasites flourish around water sources and feeding places, and full exploitation of few water points may increase the risk of diseases breaking out. Problems of illness can often occur in connection with a too intensive exploitation of areas in proportion to their capacity. Inadequate or incorrect nutrition or lack of minerals and vitamins can be decisive in regard to the extent of an outbreak of a disease. One should especially be cautious with regard to animals being kept in cages or bins (ea. poultry, pigs, rabbits).

Domestic animals introduced from outside often lack the power of resistance that local species have evolved throughout generations. In addition, pressure of infection may build up in the environment so that also local breeds become vulnerable to diseases. Conversely, local breeds and wild animals might pose a risk to imported breeds, partly by a direct pressure of infection and partly because preventive treatment/vaccination does not always reach the animals of all livestock keepers.

Experience shows that in the cool highlands in the tropics exotic livestock may be introduced or crossed with local breeds to the effect that the production capacity is greatly increased. Many diseases are less troublesome in the highlands and easier to control.

Many of the most common diseases can be controlled by means of a vaccination programme. Examples are vaccination against cattle plague, anthraz and some clostridial infections among various animal species. Vaccination is generally a cheap alternative as compared to drug treatment. Moreover, it is within the reach of many less prosperous livestock keepers. Curative drug treatment may be so expensive that only intensive forms of operation make use of such opportunities. When establishing a veterinary service, it is important to be aware of the limitations of such services when the majority of the livestock keepers are very poor. Preventive treatment by means of chemicals (spraying/cattle dip) also tends to be expensive and beyond the reach of extensive forms of animal husbandry.

Intensive animal husbandry often makes use of large amounts of drugs. In many places, it has been documented that drugs are used inappropriately or in incorrect doses. As a consequence, the desired effect is not achieved. Environmental impacts of medication can be considerable if it is not done safely. Especially two groups of drugs have been focused in this connection: parasiticides that are applied externally to the animal, and antibiotics that are given as injections or through the mouth, on their own or mixed with the feed.

Chemical insecticides being used to fight ticks, flies, horseflies, etc. are either very persistent (not easily broken down) in nature (chlorinated hydrocarbons such as DDT, Lindan) or, if not safely used, extremely poisonous for the users (phosphoric insecticides). Use of these insecticides is still widespread in many developing countries. Remnants of them may spread to the environment and accumulate in the food chain. In some places, high levels of such chemicals have been detected in an important nutrient such as mother's milk (cf. booklet 13 Use of chemical pesticides).

With regard to the antibiotics group (antibiotics and chemotherapeutics), great concern is attached to the development of resistant microbes that can infect humans and cause diseases that may be difficult to treat. For the same reason, treatment of many animal diseases has already become more difficult. If antibiotics are used as a growth-promoting drug, which often happens in connection with industrial modes of animal husbandry, special care must be taken. Much of the antibiotics that are given to animals finally end in the surroundings. This is most evident in connection with fish farming (see booklet 5 Aquaculture), but treatment of mammals will also cause a great deal of the drugs to end in the environment, either in their original form or as converted into other substances that can be equally harmful. It is still unclear how high the risk of establishing resistant environmental bacteria is, and what possible impacts this will have, but there is good reason to be aware of the problem.

3.6 Other ecological impacts, and consequences for landscapes

When drilling wells to supply ground-water to animals and humans, preliminary surveys have to be made to ensure that the sources are not emptied, or that the water table is not periodically lowered too much. This may have impacts, not only for the water supply, but also for the vegetation in the area. The quality of the ground-water, which may be important to health, should also be examined. See booklet 7 Water supply for a more detailed account of these conditions.

If an animal husbandry project is established near to game reserves and/or national parks, it may be relevant to consider whether a buffer zone ought to be created in the border area. Major land-demanding projects may require that large forested areas are cut. Various types of forest in the tropics, ea. rain forests, are vulnerable to clear-cutting (see booklet 3 Forestry).

Initiatives within animal husbandry may visually alter a landscape. Careful development of operational plants and installations, adaptation and cultivation of landscapes should be considered during the planning and implementation of projects. A project may at best contribute to making a landscape more scenic rather than ruining its contents and quality. Operations may also affect historical relics, burial sites and other objects that are important locally. Preliminary investigations may be required in order to avoid conflicts.

Animal husbandry, especially grazing, is a major factor regarding the development of cultivated landscapes. Such cultivated landscapes can be conservation-worthy and in need of management in order to prevent over-growth or any other alterations. For example, the Masai and their animals grazing on the mountain slopes by the Ngorongoro crater in Tanzania no doubt have great socio-cultural value, not to speak of their importance for tourism. Considering conservation and management, however, it is crucial that other economic and cultural interests do not suffer. Conservation of areas based on traditional forms of animal husbandry must take place in agreement with the local population. Those who may suffer losses on account of the operations should receive an acceptable compensation.

3.7 Social impacts

Initiatives concerning grazing require surveys of existing terms of tenure and privileges tied to the areas. Specific conditions attending communal ownership may create conflicts if initiatives are aimed at making the management more efficient (cf. chapter 2.2).

Conflicts may occasionally arise between forestry and livestock interests. It may be necessary to consider the livestock project against the consequences of a reduction in forested areas, for example. Questions concerning food supplies, subsistence, risk of erosion, local climatic changes and preservation of a biological variety should be considered in this context.

Major projects based on sales of products beyond the local area should not be started until a market survey has been performed. Questions concerning processing, preservation and transportation of the products should also be closely considered. Wherever the conditions are favourable, decentralized livestock projects may have their advantages, ea. better feed supplies, less pressure of infection and better utilization of manure and other by-products. Establishment of cooperatives, cooperative groups, etc. can be advantageous under such conditions.

Major projects may cause the removal of people from their settlement areas, and/or initiate an unintended immigration into the project area by people looking for work or possibilities of trading. In either case, the project ought to assess the need to make provisions for settlement, so as to minimize risks of pollution, spreading of diseases, increased and uncontrolled exploitation of natural resources and social conflicts.

It is important that the establishment of livestock projects takes place in agreement with the local population. Herding is normally carried out by men or young boys who often have a good knowledge of which is the best pasture and where water can be found. In many places, moreover, women are in charge of the family household and health, in addition to having the responsibility for collecting water, feeding and tending the animals. Introduction of new animals may increase the burden of work for women. With regard to milking and the making of milk products, an improved technique can relieve the work pressure, since traditional methods are often time-consuming. If there are insufficient amounts of feed and water near the household, women may have to spend much time collecting feed and water rather far away from their homes. Introduction of draught animals, ea. donkeys, may somewhat alleviate the situation. Experience shows that women and children to a greater extent than men are affected by pollution from fertilizers, as they spend more time near to home and the animals. Pollution of water sources from manure can also be a reason why women will have to collect water from farther away than previously.

3.8 Impacts of other existing or planned activities

Several types of activities in the vicinity of an animal husbandry project can adversely affect the project or reduce its output. Industry and energy production may pollute the area, having a negative impact on grazing, for example, due to fallout of toxic substances or acid rain. Changes in the use of land involving the clearing of land for houses, industry, systems of transportation, etc., can reduce the area available for livestock production.

It is important that new animal husbandry projects take existing environmental problems and land use plans into consideration before they are launched.