Livestock-Environment Interactions:
Pollution

The main environmental impacts of livestock production are on soil, water, air, flora, fauna and non-renewable resources. Soil features are affected by nutrient contamination, by trampling and by erosion. Groundwater can be polluted with nitrates and pesticides. Surface water may be threatened by eutrophication. Toxic residues in food are also a threat to human health. Air pollution has an impact on habitats and on Global Climate Change.

Livestock-Environment Interactions Nutrient Balance Increasing Intensification Waste Products References and Further Reading

The nature of livestock and environment interactions is dictated mostly by the type of production system. These production systems are themselves evolving in response to population pressure, resource availability, social and economic forces, and importantly - marketing opportunities and constraints. Three main production systems are distinguished (Seré and Steinfeld, 1996) although in practice there is a gradual change from grazing through mixed to industrial systems.

Mixed farming systems in general do not add new nutrients to the system. Instead, with constant and long-term removal of products, both crops and livestock, there is in many cases a net reduction in nutrients. The key to sustainable agricultural production is the maintenance of Nutrient Balance. See in Steinfeld et al. (1997) for further details.

Most mixed farming systems of the developing world have a negative nutrient balance. Deficits are partially covered by a flow of nutrients from grazing areas to cropland. As population pressure increases, the crop/grazing land ratio changes, with more land being taken up by crops - leaving smaller areas for extensive livestock grazing. If other sources of nutrients are not available, the problem of nutrient balance increases. This is typically the case with many mixed farming systems in the tropics (Steinfeld et al. 1997).

Because of transport costs and market infrastructure, industrial livestock production systems are normally found close to urban areas. They import feeds from outside the system and produce large quantities of manure and other wastes - leading to excessive nutrient imbalances.

Brandjes et al. (1996) refer to unbalanced systems in the Netherlands with excessive Nitrogen surplus mostly resulting from mineral fertilizers and imported feed, with only 16% being removed in the form of livestock products. The remainder represents a potential source of environmental pollution. The opposite case is represented by an example from Southern Mali, where farmers effectively derive a large part of their income from soil nutrient depletion or soil mining.

Manure management should aim at reducing the negative effects (lower nutrient losses) and maximizing the positive effects (plant nutrient supply and organic matter supply to the soil) of manure. A more balanced nutrient management will result with less burden on the environment.

Expansion of agricultural area and intensification are two ways to increase agricultural output in order to meet the demands of an increasing human population. An expansion of area given over to growing crops inevitably introduces the possibility of conflict with the land requirements for keeping livestock - resulting in an overall loss of available grazing land.

At the same time, there is an increase in the demand for livestock products, and the consumption of livestock products is currently growing at a faster rate than the increase in world population (see Changing Demand for Livestock Products). The greater part of the increase in livestock production has come from, and will continue to come from increased productivity through intensification.

Industrial-scale livestock production arises where the demand for animal products increases too rapidly for land-based systems to respond. Initially the process id from more extensive systems, through more intensive mixed farming systems, and ultimately to industrial-scale livestock production where production is divorced from the surrounding land.

The process of intensification is complex, but tied closely to urbanization. As incomes rise, particularly in urban areas, consumers seek greater variety in their diets. Demand for livestock products rises rapidly, an effect which is driven by the rapid growth in per capita incomes, particularly in East and South East Asia. At the same time population growth has led to increases in the number of consumers, particularly in urban zones. The high rates of growth in meat supply, and consumption, per capita recorded in all regions except North Africa and the Near East, are significant and form the basis of the so-called "'Livestock Revolution". If the growth in consumer demand continues at the same rate, livestock producers are faced with rapidly expanding urban markets.

The rapid changes in supply and consumption of meat are accompanied by shifts in the types of meat contributing to the total. Over the past ten years, while consumption per head of bovine and sheep and goat meat has remained more or less steady in all regions of the developing world (with the exception of Latin America where beef consumption rose by 1% annually), poultry meat consumption has risen annually by over 6.5% in South Asia, and by nearly 6% in Latin America. Significant increases in consumption of eggs are also recorded for all regions except Africa. Hence it can be argued that the rapid increases in consumption of livestock products have largely stemmed from a shift towards consumption of poultry products.

Urban markets are also the conduits for international trade, which has increased at an accelerating rate over time. Trade in livestock products has expanded since the development of refrigerated shipping at the end of the 19th Century. Today, domestic livestock producers, in most countries, face market competition from imported products. Local producers must achieve comparable quality standards at no higher price in order to compete. At the same time, some developing country livestock producers are able to compete in world markets, so the country becomes a net exporter.

Industrial livestock production systems emit large quantities of waste, resulting in excessive loading of manure on the limited land areas within reasonable distances of the production facilities. Globally, Steinfeld et al. (1997) estimated that pig and poultry industries produce 6.9 million tons of nitrogen per year, equivalent to 7 percent of the total inorganic nitrogen fertilizer production in the world.

In these areas of high animal concentrations, excess nitrogen and phosphorus leaches or runs off into drainage and groundwater, damaging aquatic and wetland ecosystems, and polluting water supplies for human consumption.

The return of nutrients to the land by the application of manure causes problems due to high water content and high transport cost. While it is difficult to generalize, transport beyond 15 kilometres is often uneconomical. In addition, mineral fertilizers, often a cheaper, more available and more practical source of nutrients, further reduce the demand for nutrients from manure, turning the latter into "waste".

These nutrient surplus situations also result in high concentrations of heavy metals. These are contained in livestock feed as growth stimulants (e.g. copper and zinc), or simply as pollutants (e.g. cadmium). If the addition to the soil of heavy metals exceeds uptake by crops, this will most likely have a negative impact on soil flora and fauna, eventually leading to human and animal health risks (Bos and de Wit, 1996). Regulations to reduce the heavy metal content of animal feed are now in place in most OECD member countries. An absence of regulations in many developing countries is likely to result in problems in the future.

Nitrate is a potential human health threat especially to infants, causing the condition known as methaemoglobinaemia, also called "blue baby syndrome". Nitrate is converted in the gut to nitrite, which then combines with haemoglobin to form methaemoglobin, thus decreasing the ability of the blood to carry oxygen.

Removal of these and other agricultural pollutants from water sources intended for human consumption is expensive. Moreover, it is not normally the polluter that pays for this - resulting in artificial subsidies for those industrial livestock production systems causing some of the greatest pollution problems. For example, approximately 70-80% of the UK's nitrate input to the water environment comes from diffuse sources, with agricultural land as the main source. It is only recently that the scale of the costs involved has begun to be appreciated. Pretty et al. (2000), for example, estimated the total external environmental costs of agriculture in the UK was £2.3 billion in 1996. The approximate annual costs of treating drinking water for pesticides were about £120 million, for phosphate and soil £55 million, for nitrates £16 million and for micro-organisms £23 million. Monitoring water supplies and supplying advice on pesticides and nutrients costs were around £11 million and off-site damage from soil erosion was put at £14 million.

National policies tend to favour the growth of industrial systems, whilst at the same time effectively discouraging land-based systems (perhaps unintentionally). Industrial systems in many countries have benefited from policy distortions which have given these systems a competitive edge over land-based systems. In many developing countries there are subsidies on feed and on energy. With energy being a major direct and indirect cost in industrial production systems, policies often favour industrial landless systems over land-based production systems.

Processing and Slaughter House Wastes

As well as manure and other waste from animal production, the processing of animal products also results in environmental damage when it is concentrated and unregulated. This is particularly the case in urban and peri-urban environments in many developing countries.

Slaughtering requires large amounts of hot water and steam for sterilization and cleaning, and the resulting waste water is the main cause of pollution. A concentration of organic compounds in waste water leads to a biological oxygen demand (BOD). Waste water includes fats, oils, proteins, carbohydrates and other biodegradable compounds, and breakdown of these substances requires oxygen. Waste water usually contains additional insoluble organic and inorganic particles or suspended solids.

Effluent from tanneries may be discharged into sewers, or into inland surface waters, or even used for irrigation (Verheijen et al., 1996). High concentrations of salt and hydrogen sulphide present in tannery wastewater have a negative impact on water quality. Suspended matter such as lime, hair, fleshings, etc. make the surface water turbid and settle to the bottom, thereby affecting fish. Chromium tannin is toxic to fish and other aquatic life. When mineral tannery waste water is applied on the land, the soil productivity is adversely affected and some part of the land may become completely infertile. Due to infiltration, groundwaters are also adversely affected.

Discharge from dairies is often an issue in the developed world where most milk is processed at an industrial scale. In developing countries, home or village processing or consumption of processed milk is much more common. In Africa, it is estimated that 80-90 percent of milk is home processed or consumed raw whereas for Latin America, this share averages about 50 percent (FAO, 1990). Again, waste water production from milk processing is the major environmental concern, mainly resulting from cleaning operations.

In principle, the production of waste water does not necessarily lead to environmental problems if animal product processing is carried out on a small scale and is not concentrated in a given area.