Over the next 40 years, the demand for staple foods in developing countries will grow at 2.5 percent per year (WORLD BANK, 1992). However, the United Nations Conference on Environment and Development (UNCED) increased the awareness amongst policy-makers and scientists of the need to consider the impact of agricultural production on the environment. The development of strategies to meet the increased demand for food should, therefore, be based on a sound understanding of the impact of different types of production systems on the environment. This series of studies on the “Interactions between Livestock Production Systems and the Environment” was commissioned to provide this understanding.
Increased production can be achieved either through intensification, or the exploitation of new agricultural land. It is estimated that only 25 percent of the projected increase, mostly in sub-Saharan Africa and Latin America, can be met through the exploitation of new agricultural land. Intensification is, therefore, a key process in meeting the increased demand. In the industrialised world, intensification has led to specialisation. However, specialisation throughout the entire agricultural economy does not appear to occur until labour scarcity arises out of non-agricultural demand for labour e.g. BINSWANGER (1986). Labour shortages have forced farmers to adopt labour-saving technologies leading to the increased use of tractors, threshers and agricultural chemicals, and the decreased use of draught animals and manure, resulting in specialisation to make efficient use of the increased inputs. Whilst population pressure has led to the development of specialised dairy, poultry and pig production systems in South-East Asia to provide meat and milk for urban populations (DEVENDRA, 1986), the majority of farmers do not have access to these markets and continue to produce a mixture of crop and livestock products, mainly for subsistence. In sub-Saharan Africa, population pressure is also leading to expanding crop-livestock systems (WINROCK INTERNATIONAL, 1992). In Nigeria, for example, nomadic pastoralists have been settling and taking up cropping on a regular basis over the last two decades. Also, a number of arable farmers in the sub-humid zone are increasingly investing in livestock. Thus, these mixed farming systems are likely to make an increasing contribution to meeting food demand in developing countries in the forseeable future, and the impact of these systems on the environment provides the focus for this particular study.
Mixed farming systems are already long-established in the developed countries of the temperate zones e.g. NEWTON (1982), JASIOROWSKI and QUICK (1987) and SERE (1994). In family farms in Europe and the USA sheep, beef and dairy cattle are integrated with cropping; manure is collected and applied to arable land, and crop residues and by-products utilised as animal feed. Straw from cereal crops is much used for livestock bedding. These farms make significant contributions to agricultural production in the different countries.
The Terms of Reference for the study asked for the identification of indicators by which to measure the impact of these systems on the environment, both technically and socio-economically. Technical indicators need to take account particularly of the effects on plant species, soil and water. McINTIRE et al.(1992) published a detailed review of crop-livestock systems, and it is the aim of this report to analyse the interactions referred to by these and other authors, as part of the process of identifying quantifiable indicators, giving examples of how these may be applied. It has been recognised that some indicators are of more importance globally (e.g. biodiversity) than at the level of the production system, and many of these global indicators are being identified in other studies in the series. Cross-reference is made to these reports in the text. First, however, the links between this particular study and the “building blocks” of the studies i.e. the defined Livestock Production Systems will be described, to put this component in perspective relative to the overall project.
