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Criteria for sustainable livestock production: a proposal for implementation
Agricultl~. r~cosyszem~ Environment ELSEVI ER
R er
Agriculture.Ecosystemsand Environment53 (1995) 219-229
Criteria for sustainable livestock production: a proposal for implementation J . d e W i P , J . K . O l d e n b r o e k a ' * , H . v a n K e u l e n b, D . Z w a r f f *,gLO Institute for Animal Science and Health, Research Branch Zeist, P.O. Box 501, 3700 AM Zeist, The Netherlands bDLO Research Institute for Agrobiology and Soil Fertility. P.O. Box 14, 6700 AA Wageningen, The Netherlands CDepartmentof Tropical Animal Husbandry, Wageningen Agricultural University, p.o. Box 338. 6700 AH Wageningen, The Netherlands
Accepted23 November 1994
Abstract After discussing some general problems in measuring sustainability, an identification of measurable criteria for the major agroecological problems is proposed, derived from explicit issues of unsustainability. The proposed criteria are briefly discussed. Factors which might influence the effect of inclusion of livestock in an agricultural system on each criterion are also discussed. it is argued that identification of livestock-specific criteria is impossible because of the large heterogeneity of livestock production systems and the non-linear relation between livestock-specific criteria and agroecological criteria. Therefore, a systemspecific analysis is needed to assess the overall effect of livestock inclusion in an agricultural system on each of the proposed general criteria for sustainability. These are: demand and supply of consumable livestock products; potential human population supporting capacity; land area utilized for agriculture; degree of equity in food distribution; variability of production; net annual soil losses; nutrient balances and losses; water availability and utilization; soil organic matter; fossil energy and drug utilization. Such a system-specific analysis will also allow formulation of measurable criteria for other objectives, and an assessment of trade-offs between the criteria. Recognition of such trade-offs, together with the reduced acceptability of external effects (both in time and space), might appear to be the most important notion of the sustainability concept. geywords: Sustainability,Livestockproduction;Agro-ecologicalcriteria
1. Introduction Sustainability has become a buzz-word in almost every part of society since the report of the World Commission on Environment and Development 'Our Common Future' (1987). Though easily used in casual conversation, it appears difficult to implement sustainability (Redclift, 1987; Francis et al., 1990). Sustainability of livestock productio,, systems (LPS) has also received ample attention (e.g. Marshall, 1992; Kaas* Corresponding author.
0167-8809/95/$09.50 © 1995Elsevier Science B.V. All fights reserved SSDI 0167- 8809 ( 94 ) 005/9-6
schieter et ai., 1992a), mainly dealing with policies and strategies aiming at its improvement. Assessment of the degree of success is seriously hampered by lack of explicitly defined objectives. The objective of this paper is to identify measurable criteria for sustainable livestock production. It will hardly address the body of knowledge on strategies promoting sustainability and that on technologies for sustainable livestock production. The criteria will be derived from explicit but complex issues of unsustainability, such as land scarcity, soil degradation, inefficient use of resources, environmental pollution, and
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declining biodiversity (Durning and Brough, 1991; Rifkin, 1992). As these problems are mainly related indirectly to LPS, the possibilities for an appropriate classification of LPS as a basis for identification of livestock-specific criteria (e.g. mortality, animal productivity) will also be examined, which would facilitate the evaluation of livestock projects. First, some general issues associated with measuring sustainability are discussed. Then, a proposal is presented for implementation of sustainability of LPS and the associated measurable criteria. Subsequently, the possibilities for system classification and identification of livestock-specific criteria are discussed. Finally, the multidimensienai concept of sustainability will be readdressed, to identify some key elements for its operational use.
2. Problems in measuring sustainabflity 2. I. Interpretations o f sustainability
Although the term sustainable agricuiture is singular in form, it comprises a multidimensional concept, referring to such diverse motivations as saving rare breeds, preventing soil degradation by impoverished nomads and reducing effluent production in intensive pig or poultry units. Originally emphasizing the importance of ecological constraints, it now includes economic, social and cultural dimensions, as in the Food and Agriculture Organization (FAO, 1992) definition: "Sustainable development is the management and conservation of the natural resource base, and the orientation of technological and institutional change in such a manner as to ensure the attainment and continued satisfaction of human needs for present and future generations. Such sustainable development (in agriculture, forestry and fisheries sectors) conserves land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially accephable.'" Such complex definitions, combining incomparable objectives, tools and current problems with no clear hierarchy, are problematic for practical application. In this paper, attention will be focussed on ecological and environmel;tal problems vis-a-vis the production of human food (characterized by Harrington (1992) as the 'sustainable growth' interpretation). Socioeco-
nomic issues are not di.seus.ced here as iadependent criteria of sustainability, not because they are unimportant but because: ( ! ) ecological problems are at the origin of the concept of sustainability (Adams, 1990); (2) the relation between socioeconomic conditions and sustainability is not unequivocal---problemsmay occur in both low and high income situations (Ltlt, 1991 ); (3) such issues have been discussed extensively elsewhere (e.g. Chambers, 1988; Chambers et al., 1989; Netherlands Development Corporation ( N I ~ ) , 1991, !993; Vosti et al., 1991 ). The multidimensionality of sustainability will be returned to in the last part of this paper. 2.2. T i m e d i m e n s i o n
In principle, sustainability implies lasting indefinitely, hence dynamic processes are highly important. However, the quantitative relations among many characteristics are only partially understood. For instance, soil erosion results in reduced land productivity, but to what extent has hardly been quantified. The required research is often long-term, while answers are needed at short notice. Hence, predictions of the future are wrought with differences in opinion about future technical possibilities. The resulting problems for the present research system (Funtowicz and Ravetz, 1990) are illustrated in the discussions on global wanning (Reifsnyder, 1989 ). Therefore, political decisions are needed on the degree of risk we are willing to take, which includes both the probability of an event and its possible consequences. For reasons of simplicity and to facilitate the decision-making process, it is proposed to assess the impact of an activity on each criterion indi':idually. These can than be compared and weighed in a multicriteria analysis (as explained in the last section of this paper). The degree of sustainability for natural resources could be expressed in terms of their 'longevity', by dividing proven resource reserves by present resource use intensity. The acceptable 'longevity' should be based on the probability of substitution of a specific resource, with long time frames (e.g. more than 1000 years) in case of (effectively) irreversible consequences (like net soil loss, extinction of species), and shorter ones for resources with higher probabilities of substitution (e.g. soil nitrogen).
J. de Witet al. /Agriculture. Ecosystemsand Environment 53 (1995) 219-229 2.3. Unit and scale of measurement
To assess the impact of an activity on sustainability, criteria are needed. Though at the risk of neglecting characteristics that arc less easily measured, measurability is a prerequisite to implement these criteria and to avoid a priori definitions of sustainability (Harrington, 1992). Many of the objections against measurable criteria will probably disappear with the realization that they can be expressed in various ways (binary/discrete, ordinal/ranking and cardinal/continuous) and that quantification is hardly more than approximations with a higher level of precision. Cardinal and, to a lesser degree, ordinal measures have the advantage tha~ differences in the degree of sustainability can be identified and facilitate assessment of trade-offs among different attributes of sustainability. In quantifying characteristics, attention should be paid to the units in which they arc expressed, particularly for efficiency parameters. Livestock productivity can be expressed per animal, per kilogram metabolic weight, per hectare, per kilogram of nitrogen input, etc., each unit relating to a different objective and/or different system boundary. For instance, productivity per kilogram metabolic weight is a fair indicator of biological efficiency per animal unit, and may increase by reducing the number of animals per hectare. However, if land is scarce, productivity per hectare is also important, which could decrease if animal numbers are reduced (Jones and Sandland, 1974).
3. Sustainability: implementation of ecological criteria To avoid definition problems of sustainability, that have governed a major part of the discussion, criteria will be derived from explicit issues of unsustalnability, such as food shortages, land scarcity, soil degradation and desertifieation, inefficient use of resources (energy, nutrients and water), deforestation, environmental pollution, and decline in biodiversity (Alexandratos, 1988; Durning and Brough, 1991; Rifkin, 1992). This elaborate process is discussed subsequently. Table 1 gives the proposed measurable criteria, the sustainability problems to which they relate and
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the factors which influence the contribution of LPS to these problems. 3.1. Food shortages
Projections for the year 2000 suggest a gap between demand and supply in milk. Also the assumed increases in meat production per animal seem problematic ( Alexandratos, 1988 ). Although livestock products are valuable for vulnerable groups like children, the elderly and the sick, they are not indispensable and vegetarian diets are possible (Spedding et al., 1981 ). Therefore, both supply and demand of consumable livestock products are proposed as criteria, implying that the need for increased livestock production should be weighed against possible trade-offs like higher nutrient losses or a reduction in natural areas. If the undesirable effects of increased supply are too strong, the a_emand for consumable livestock products should be restricted, by influencing factors like population g~owth, income elasticity of demand or livestock product prices. If a higher supply of consumable livestock products is found to be desirable, special attention should be given to the following. (!) Farm-gate prices of livestock products: are they remunerative? (2) Objectives of livestock farmers: objectives other than the production of consumable livestock products (e.g. manure, investment, security, draught power) are often highly important (Behnke, 1985; Crotty, 1980); measures aimed at increasing production of consumable livestock pioducts are likely to fail if no alternatives for these objectives are developed. (3) Available feed resources: the often abundant low quality feeds result in maximum production per hectare at relatively low animal production levels (Jones and Sandland, 1974; Zemmelink et al., 1992). The net effect of LPS on total human food production--or potential population supporting capacity (PPSC) of an area (FAO, 1984)--is proposed as a criterion, because livestock often competes with food crop production for the same resources, but on the other hand often providing critical inputs to arable farming. In general, livestock production systems are inefficient food producers compared to arable farming systems ($pedding et al., 1992). However, a small increase in the PPSC is likely if livestock uses biomass (less suitable for human consumption) or land not suitable for food crop production, or if important positive crop-
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Table I Criteria for mea.~uring sustainability of liv~tock systerns, the sustainability problems to which they relate and factors that may influence the effect of livestock inclusion in agricultural system on each criterion (De Wit. 1993) Criterion
Related sustaianbility problem
factors influencing the effect of livestock
Supply and demand of consumable livestock product
None (these are related to other objectives)
-
Potential ( human ) population supporting capacity (PPSC)
Food shortage Land scarcity
( ! ) Land suitability for arable farming versus livestock production (2) Staple food characteristics ( 3 ) Crop-livestock interactions
Land area utilized for agriculture
Soil degradation Deforestation Declining biodiversity Global warming
As above for PPSC
Degree of equi:y in food distribution
Food shortage
( I ) Income elasticity of demand for consumable livestock products (2) Location and nature of feed processing
Variability
Temporary food shortages and risk of low returns Correiation and variation of yields and product prices of livestock production versus other production activities
Net annual soil loss
Soil degradation Water availability
( I ) Effect of feed production and utilization on soil cover (2) In case of feed production on rows: length of slope: height of. and distance between, wind breaks
Nutrient (N, Pand K) balances
Soil degradation
( I ) Management of manure and urine (2) Effects on erosion and S O M (3) Soil type (4) Export of nutrients in products
Nntrieu~ lasses
Efficient energy and nutrient resource use
As nutrient balances, except (4)
Water availability
Efficient nutrient resource use Receding groundwater depth
Mainly effect on soil cover and SOM content
Water utilization
Same as water availability
Proposlion of feed from irrigated land
5oil organic matter (SOM)
Soil degradation Influences erosion, nutrient balanccs/lusses and water availability
( I ) Prednction of indigestible organic matter (2) Difference between total biomass production and ~ttilization
Fossil energy utilization
Efficient energy use Global warming
Balance between provision of energy and required energy (particularly off-farm for fertilizer production feed processing, transportation,etc.)
Drug utilization
Harmful effects on wildlife, biological control agents and/or humans
( I ) Level of intensification ( 2 ) Genetic resistance of breeds
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livestock interactions exist (Kaasschieter et ai., 1992b). The degree of equity in food distribution is suggested as a criterion, because malnutrition and starvation are often associated with unequal distribution as much as by inadequate production (Amartya Sen, 1981; World Resources Institute (WRI), ~990). It may be influenced via income, price and land tenure policies. The degree of equity in food distribution could be negatively affected by livestock production if it uses food grains and/or land suitable for food crop production. However, the impact is highly dependent on the income elasticity of demand for consumable livestock products. LPS may affect food distribution via the place and nature of feed processing which is strongly influencing the relative price ratios of different feeds and thus the level of competition. Variability is proposed as another criterion because risk of low returns is a major problem in many agricultural systems, resulting in temporal starvation or migration. Variability can be expressed, in principle, in coefficients of variation of, and correlation coefficients between, different farm activities. Livestock production is often considered a major risk-reducing activity by carrying over food or wealth from periods of surplus to periods of scarcity, by using a failed crop, or as a security against inflation (Nordblom, 1988). However, the potential advantage of livestock, in terms of shock absorption, may be difficult to realize because disinvestment often takes place if crop prices are high and animal prices low or if crop prices are low and animal prices are high (Sandford, 1989). 3.2. Land scarcity
Arable land availability is projected to decline from the present 0.28 ha per capita to 0.17 ha in 2025, with major problems in Asia where it will decline to 0.09 ha (WRI, 1990). The FAO (1991a) gives a similar estimate of 0.15 ha in 2050. The decline in arable land availability per capita is a major concern for sustainable agriculture, because expansion of the cultivated area mainly takes place on marginal lands with inherently low production capacity, that are vulnerable to (virtually irreversible) degradation. Land hunger is also a major cause of declining biodiversity and global warming, because of the conversion of natural areas into agricultural land. The effects of land shortage are often
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aggravated by insecure land tenure regulations for the lalger part of the agricultural labour force (FAO, 1991c). Thus, the land area utilized for agriculture is proposed as a measurable criterion. The overall effect of including livestock in an agricultural system is affected by similar factors as the PPSC of ~.region. If part of the livestock feeds is not produced regionally but imported, the total land area should include the area on which the 'imported' feed i~ grown. However, if the imported feed mainly consistz of crop by-products, arbitrary imputed values may be applied, for instance based on the monetary value of these by-products relative to the main product. 3.3. Soil degradation
Roughly 40% of the arable land and 21% of the grazing land is estimated to be affected by 'human induced degradation' (OIdeman et al., 1991). A major part of 'desertification' is often blamed on livestock production, especially by pastoral societies. Overgrazing does take place, but doubts have been expressed on the role of livestock in irreversible soil degradation (Behnke and Scoones, 1992). The occurrence of soil degradation, of which desertification is an extreme case, is less controversial, particularly in ecosystems with high rainfall because of erosion or soil nutrient depletion, though in some cases trampling seems important. In most developing countries soil nutrient depletion is a major form of soil degradation. It is, for instance, projected that the annual deficit for Sub-Saharan Africa in 2000 will be on average 26 kg of N, 7.5 kg of P205 and 18 kg of K20 per ha (Stoorvogel and Smaling, 1990). For a region in South Mall it was estimated that the losse~ of nutrients in some cropping systems almost equalled the value of the produced crops at present prices (Van der Pol, 1992). Export of nutrients results from erosion, products sold, leaching and denitrification. Volatilization is not considered important because the major part will be deposited nearby. Imports can be via organic and chemical fertilizers, biological fixation of nitrogen, and natural deposition. Nutrient balances can be equilibrated via increased imports and/or reduced losses. The net effect of LPS on nutrient balances (particularly nitrogen and potassium ) is related to factors such as management of manure and especially urine, effects on erosion and soil organic matter
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(SOM), and the export of nutrients in products sold. Erosion is another form of soil degradation. (In addition to the rate of erosion, its nature is also of imperlance, because of differential effects on soil properties like nutrients and SOM.) Annual soil losses of O.l to more than 100 t h a - i have been measured (Pimentel et al., 1987 ), and the annual rates of soil formation are estimated at 0.3-80 t h a - ~, with the highest rates for volcanic soils in high rainfall areas. Erosion is influenced by many factors, some of which could be affected by livestock such as soil cover, length of the slope, distance between windbreaks. Net annual soil losses should be assessed independently from nutrient balances because of incomplete restoration possibilities of the unfavourable structure of the eroded soils. Water erosion can also cause major problems downstream, e.g. flooding and reservoir siltation. On the other hand, part of the eroded material may be deposited nearby, thus reducing the negative impact of soil erosion on larger land units. 3.4. Water resources
A major constraint in rain-fed agriculture is soil moisture availability during part of the year. This can be alleviated by irrigation, but large-scale irrigation often results in rapid increase in groundwater depth. For instance, annual groundwater table declines of 14 m have been reported from India and China (Brown et at., 1985). Water availability and water utilization are proposed as separate criteria because they are affected differently by livestock production. Water availability will be affected mainly by effects of livestock on soil cover and SOM, and water utilization is mainly affected by the amount of water used for irrigation of forage crops. Other water-related issues, such as the distribution of water points and the design of water lifting devices, are not considered separately because they rank much lower in the hierarchy of objectives, strategies and tools. 3.5. Energy resources
Most of the production increases in the recent past have been largely the result of increased use of external fossil energy. This has been associated with a decrease in overall output-input ratio for energy, from roughly
> I0 in low input systems to < 2 in high input systems (Bayliss-Smith, 1982; Pimentel et at., 1990). It should be noted that energy balance calculations are fraught with difficulties, because they require arbitrary imputed values for inputs like necessary infrastructure, imported feeds, plant/am'mal breeding, etc. Fossil energy consumption should be examined critically, because proven fossil energy reserves remain limited (e.g. 41 years at 1988 consumption rates for oil; WRI, 1990) and because of their contribution to global wanning. Livestock production usually increases fossil energy consumption mainly via utilization of inputs and processing of the products, bat may decrease it because of energy supplied by animals in the form of draught power and/or dung as fuel. 3.6. Nutrient resources
The main problem nutrient is phosphorus, of which the proven economically exploitable reserves were estimated at approximately 85 years at 1985 production rates (Helsel, 1987). Nitrogen reserves are almost inexhaustible, because of its abundant availability in the air. However, the production and utilization of nitrogen fertilizer requires large amounts of fossil energy. Because nutrients are indispensable for biomass production, and insufficient application may cause soil degradation, total losses of nitrogen, phosphorus and potassium are proposed as indicators for efficient use of mineral resources and energy. 3. Z Soil organic matter (SOM)
SOM is added as a separatecriterion, as an important control variable for erosion, nutrient balances and losses and water availability. The overall effect of livestock inclusion in an agricultural system on SOM is relatively uncertain, partly because of inadequate characterization of SOM composition. Animal digestion is not likely to affect the amount of effective SOM per unit of original biomass. Therefore, the overall effect of livestock production on SOM will depend mainly on the quantity of "indigestible' organic matter that is produced. Total SOM is important in relation to the infiltration capacity, because of its effect on rate of water flow and soil fauna.
J. de Wit et al. /Agriculture. Ecosystems and Environment 53 (1995) 219-229 3.8. Environmental pollution
Environmental pollution is mainly associated with intensive systems, still rare in Third World countries. It consists mainly of (1) groundwater pollution by minerals, which is directly related to the criterion of regional nutrient balances, and (2) drugs, i.e. veterinary products and, especially, pesticides. Utilization of drugs (both veterinary products and pesticides) is problematic, because of their residues and derivatives which can destroy natural pest controlling organisms or contaminate drinking water and food. It has been estimated that approximately 3.7 million people worldwide are exposed annually to high pesticide levels ( Jeyaratnan, 1990). Utilization of pesticides has been strongly promoted by subsidies, which in some countries were over 80% (Repetto, 1985). Livestock inclusion in an agricultural system may lead to reduced drug use through the potential to widen crop rot.-aions, thereby limiting the need to apply pesticides. Specification of the type of drug is needed because of the wide variation in active ingredients and their effects. An additional area of concern is the increasing resistance to drugs. A limitation in drug use is possible via choice of appropriate breeds, the use of vaccines and management techniques. The contribution of livestock in developing countries to other environmental problems like global warming via methane is small (approximately 1.5% of global warming; based on FAO, 1991b) though rising. Reduction can mainly be realized through lower ruminant numbers. The contribution via CO2 emission during respiration is negligible as it cannot exceed the amount fixed by the plants eaten. The emission of CO2 associated with the conversion of forest areas into agricultural and grazing land was estimate.A to contribute around 12-14% to global warming (Winpenny, 1991). This effect is sufficiently covered by the earlier proposed criterion of the land area utilized for agriculture. 3.9. Deforestatiot,
Livestock pn3duction is estimated to contribute approximately 9% directly to total annual deforestation, mainly in Latin America (Prance, 1986). Indirectly, via the claim of LPS on land resources resulting in increased land hunger, the contribution of LPS to deforestation is higher and also relevant to other con-
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tinents. Thus, the land area utilized for agriculture is a sufficient criterion for deforestation. 3.10. Biodiversity
High biodiversity is seen as useful or essential in the future, for example as a source of genetic resistance to yet unknown diseases or as a source of new medicines. However, it is estimated thin the rate of extinction of species is roughly 106 times their rate of origin (May, 1988). Moreover, extinction of species may be regarded as problematic in its own right, because of 'intrinsic values'--i.e, values resulting from the mere existence of species, not from human advantage. In general, agricultural sy.~;temshardly contribute to global biodiversity. Thus, on!~ytwo dozen plant species, of which 14 belong to two families, are of particular importance for food production (Jackson, 1984). Also the diversity in other species (e.g. soil organisms, insects) is poor in agricultural systems in comparison with natural climax ecosystems. Therefore, this aspect seems sufficiently covered by the earlier proposed criterion of the land area utilized for agriculture (as a complement to the area reserved for natural areas). Another issue, often discussed under the heading of hiodiversity, is the genetic diversity of species used in agriculture. Concerns have been expressed about the worldwide loss of breeds and genes in livestock species. Though important in animal breeding, this criterion is impossible to measure, because of inadequate characterization of these breeds and their desired traits (Henson, 1992). Biodiversity is sometimes also linked to stability. However, equating diversity with functional complexity, which in turn results in stability, is oversimplistic (Goodman, 1974; Pimm, 1991). The relation between diversity and stability is further complicated by the multiple meanings of stability, which include resilience, persistence, resistance and variability, none of them having a simple relation with diversity (Pimm, 1991). Except for variability, these characteristics are virtually impossible to measure. 4. System classification: a discussion of the possibility for identification of livestock-specific criteria The variables proposed as criteria for sustainability are influenced by various factors related to the size and
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nature of LPS, their relation to other production activities, and local ecological conditions. Hence, no atte.~apts have been made to assess the effect of livestock inclusion in an agricultural system on each of the criteria. To evaluate these effects a system classification seems indispensable (Kaasschieter et al., 1992a). One possible system classification distinguishes pustoral, mixed and intensive LPS (Kaasschieter et al., 1992a), mainly based on crop-livestock interactions, i.e. independent, complementary and competitive systems. However, these systems are not defined unequivocally, i.e. livestock fed crop residues are only complementary in terms of land resources, but may be competitive on the basis of labour utilization. Moreover, this classification neglects differences in agroecological conditions. For instance, pastoral systems ~.ahilly areas will score differently on the criterion for net annual soil losses from pastoral systems in temporarily flooded areas. Therefore, a system classification based on crop-livestock interactions must also take into account agroecological conditions (FAO, 1984). Both classification criteria neglect differences in input utilization, in demand patterns and social relations, both within families and between gender groups, which result in a vast array of (multiple) production goals and systems. Therefore, a socioeconomic classification seems indispensable (Crotty, 1980; Behnke, 1985). Again, the intensity of livestock production may be an important factor for LPS classification. For instance, grazing land of which only 30% of the available biomass is used as feed will score much better on erosion than that where 80% is used. Many more factors can be identified as important for evaluating LPS as illustrated in the last column in Table 1. The resulting matrix of possible combinations becomes extremely large, even when only a limited number of classes are distinguished per criterion. Hence, defining stereotype LPS may be a helpful z,.arting point, but they are too broad and imprecise to allow their evaluation in terms of the different sustalnability criteria. Identification of livestock-specific criteria eventually becomes impossible us the variables, which serve as indicators for sustainability, simultaneously act as feedback mechanisms which (partly) control the pressure of animals on the natural resources. That holds for indicators such as animal productivity, mortality rates
or changes in herd composition. Increasing livestock l:reductivity can in some situations be a tool to promote sustainability, while in others it may aggravate sustainability problems, depending on system-specific characteristics. Therefore, evaluation of LPS for sustainability should not be based on livestock-specific criteria but on general criteria, as elaborated in this paper.
5. The concept of sustainabillty reconsidered It has been argued that a system-specific analysis is indispensable because livestock affects agricultural systems in many ways, even when only agroecological criteria are considered. Moreover, trade-offs among different criteria are likely, for instance: ( 1 ) using more chemical fertilizer is a powerful tool to balance nutrient deficits, but will negatively affect fossil energy utilization and nutrient losses; (2) artificial insemination and subsequent high selection pressure on a few productive traits may be effective tools to increase the supply of livestock products, but it will also present a major threat to genetic diversity in farm animals; (3) inclusion of a grass Icy may result in a smaller area required to provide sufficient SOM us compared to legumes. However, only legume-based systems can become self-sufficient in nitrogen (Schiere, 1992). Trade-offs are even more likely, if other objectives (e.g. poverty alleviation, equity, rural employment or even animal welfare and product quality) are added (Van Pelt et al., 1992). This recognition of trede-offs is one of the key elements in implementing sustainability. Many problems occur simultaneously at present; preventing or solving one problem may create or aggravate other problems. This has serious implications: (1) statements such as "this is more sustainable than that" are senseless in themselves, because the important question is, how does the activity score on each of the criteria.'?; (2) sustainability is not a discrete concept ( as questioned by Harrington, 1992) but a continuous one; (3) the chances for success will decrease with the increasing number of objectives, when the "success' of development programmes directed to increase intragenerational equity is already modest. Contrary to economic techniques, in which subjective choices on the value of different outputs and resources are implicit in
J. de Wit et al. ~Agriculture, Ecosystems and Environment 53 (1995) 210-229
the analysis, multicriteria analysis techniques, such as multiple goal linear programming (De Wit et al., 1988), make the choices among different objectives explicit (P~try, 1990) by expressing trade-offs between different objectives, each in their own unit. Prospects for multicriteria analysis o f LPS are given by Schiere (1992). Trade-offs are system-specific because both technical coefficients and objectives vary. Differences in objectives are, however, restricted because of the emphasis on sustainability in relation to future generations. Consequently, all effects, including 'external' effects, should be included in the analysis and decisionmaking process. This is a second key element in implementing sustainability: reduced acceptability o f external effects. Ultimately, this reduction may imply an 'environmental utilization space' (Opschoor, 1992) equal for each person on earth (Buitenkamp et al., 1992), although exchange of its various components among groups and individuals is possible, as implied by the proposed trade in manure production quota in The Netherlands.
6, Conclusions Explicit identification o f issues o f unsustainability is a helpful starting point for implementation o f sustainability. Most of the major agroecological problems can then be translated into measurable criteria. Such a deduction method doe~ not pretend to define the ultimate state of sustainability, but allows addition of criteria when new problems are identified. Identification of livestock-specific criteria is impossible because LPS are too heterogeneous to develop a generally applicable system classification, and because the relation between livestock-specific criteria and agroecological criteria is not unequivocal. Hence, a system-specific analysis is indispensable to assess the effects of livestock inclusion in an agricultural system on the various agroccological criteria. This also facilitates formulation o f measurable socioeconomic criteria, and it is indispensable to assess trade-offs among different criteria. Recognition of such trade-offs, together with the reduced acceptability of external effects (both in time and space), could be the most important notion in implementation of the sustainability concept.
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Acknowledgements Special thanks are expressed to the FAO, which sponsored the study that served as a basis of this article, and to J.B. Schiere who is a major source o f the ideas expressed here,
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Netherlands Development Cooperation. 1993. Sustainable land use. Sectoral Polity Document No. 2. Netherlands Development Cooperation. The Hague, 66 pp. Nordblom, T.L., 1988. The immmaoce of crop residues as feed resources in West-Asia and Nor~-Africa. In: J.D. Reed, B.S. Capper and PJ.H. Ne~e (Editors). Plant Breeding and the Nutritive Value of Crop Residues. proceedings of a workshop held at ILCA, Addis Ababa. Ethiopia. 7-10 December 1987. ILCA, Addis Ababa, pp. 41-64. Oldeman, L.R., van Engelan, V.W.P. and Pulles, J.H.M., 1991. The Extent of Human-induced Soil Degradetion. ISRIC, Wageningee, 7 pp. Opschoor, J.B., 1992. Sustainable development: the economic process and economic analysis. In: LB. Opschoor (Editor). EnvL-onmental Economy and Sustainable Development. Wolters-Noordhoff,Groningen` pp. 25-52. P~.try, F.. 1990. Who is afraid of choices? A proposal for multicriteria analysis as a tool for decision-making support in development plaaning..L Int. Dev.. 2: 209-231. Pimentci, D.. Alien, J., i3~rs. A., Guinand" L., Linder, R., McLaughlin, P., Mcero B., Musonda, D.o Perdne, D., Poisson, S., Siebetl, S., Stoner, K., Salazar, R. and Hawkins. A., 1987. World agriculture and soil erosion. BioScieoce, 37: 277-283. PimenteLD.. Dazhong. W. aad Giampietro. M.. 1990.Technological changes in energy use in U.S. agricultural production. In: S.R. Glies~man (Editor), Agrnecology; Researching the Ecological Basis for Sustainable Agriculture. Ecological Studies, Vol. 78. Springer-Verlag, New York, pp. 305-321. Pimm. S.L., 1991. The Balance of N~ure? Ecological Issues in the Conservation of Species and Communities. University of Chicago pre~. USA. 434 pp. Prance. G.T., 1986. Tropical Rain Forests and the World Atmosphere. Westview Press, Boulder, CO, 105 pp. Redclift. M.R., 1987. Sustainable Development: Exploring the Contraclictions. London. Methuen` 221 pp. Roifsnyder, W.F., 1989. A tale often fallacies: the skeptical enquirer's view of the carbon dioxide/climaZecontroversy. Agrie. Forest Meteorol.. 47: 349-371. Repetto, R., 1985. Paying the Price: Pesticide Subsidies in Developing Countries. World Resources Institute. Washington, DC, 33 pp. Rifkin, J., 1992.Beyond Beef. The Rise and Fall of the Cattle Culture. Penguin, New York. 353 pp. Sandford, S.G., 1989. Crop residne-livestnek relationships. In: ICRISAT, Soil. Crop and Water Management Systems for Rainfed Agriculture in the Sudano-Sabalian Zone. Proceedings of an international workshop, 1i-16 January 1989, Niamey, Niger, pp. 169-182. Schiere. J.B., 1992. Aspects of modelling for susteinable crop-livestock integration. In: N.M.N. ibrahim, R. De Jong, J. van Binchem and Haft Pemomo (Editors). Livestock and Feed Development in the Tropics. Proceedings of a seminar, 21-25 October 1991. Malang, Indonesia. pp. 433-443. Spedding, C.R.W., 1992. Constraints and pressures on livestock farming systems. In: BJ. Marshall (Editor). Sustainable Livestock Fanning into the 21st Century. CAS Paper 25, Reading, pp. 51-60.
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Spedding, C.R.W., WaJsingham,J.M. and Hoxey, A.M,, 1981. An Introduction to Agricultural Systems. Academic Press, London, 383 pp. Stoorvogel, J.J. and Smaling. E.M.A.. ! 990. Assessment of soil nutrient depletion in Sub-Saheran Africa, 1983.-2000. Report 28. Vol. 1, Winand Staring Centre, Wageningen. 173 pp. Van der Pol. F., 1992. Soil mining. An unseen contr;hution to farm income in Southern Mall Bulletin 325. Royal Tr~plcal Institute. Amsterdam, 48 pp. Van Pelt, MJ.F., Kuyvenboven, A. and Nijkamp, P., 1992. Sustainability, efficiency and equity: project appraisal "n ccounmic development strategies. In: A.G. Colombo (Editor), Environmental Impact Assessment. ECSC. EEC, EAEC, Brussels and Luxembourg, pp. 287-312. Vosti. S.A., Reardon, T. and yon Urff, W. (Editors). 1991. Agricultural Sustainability, Growth and Poverty Alleviation: Issues and
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Criteria for sustainable livestock production: a proposal for implementation J . d e W i P , J . K . O l d e n b r o e k a ' * , H . v a n K e u l e n b, D . Z w a r f f *,gLO Institute for Animal Science and Health, Research Branch Zeist, P.O. Box 501, 3700 AM Zeist, The Netherlands bDLO Research Institute for Agrobiology and Soil Fertility. P.O. Box 14, 6700 AA Wageningen, The Netherlands CDepartmentof Tropical Animal Husbandry, Wageningen Agricultural University, p.o. Box 338. 6700 AH Wageningen, The Netherlands
Accepted23 November 1994
Abstract After discussing some general problems in measuring sustainability, an identification of measurable criteria for the major agroecological problems is proposed, derived from explicit issues of unsustainability. The proposed criteria are briefly discussed. Factors which might influence the effect of inclusion of livestock in an agricultural system on each criterion are also discussed. it is argued that identification of livestock-specific criteria is impossible because of the large heterogeneity of livestock production systems and the non-linear relation between livestock-specific criteria and agroecological criteria. Therefore, a systemspecific analysis is needed to assess the overall effect of livestock inclusion in an agricultural system on each of the proposed general criteria for sustainability. These are: demand and supply of consumable livestock products; potential human population supporting capacity; land area utilized for agriculture; degree of equity in food distribution; variability of production; net annual soil losses; nutrient balances and losses; water availability and utilization; soil organic matter; fossil energy and drug utilization. Such a system-specific analysis will also allow formulation of measurable criteria for other objectives, and an assessment of trade-offs between the criteria. Recognition of such trade-offs, together with the reduced acceptability of external effects (both in time and space), might appear to be the most important notion of the sustainability concept. geywords: Sustainability,Livestockproduction;Agro-ecologicalcriteria
1. Introduction Sustainability has become a buzz-word in almost every part of society since the report of the World Commission on Environment and Development 'Our Common Future' (1987). Though easily used in casual conversation, it appears difficult to implement sustainability (Redclift, 1987; Francis et al., 1990). Sustainability of livestock productio,, systems (LPS) has also received ample attention (e.g. Marshall, 1992; Kaas* Corresponding author.
0167-8809/95/$09.50 © 1995Elsevier Science B.V. All fights reserved SSDI 0167- 8809 ( 94 ) 005/9-6
schieter et ai., 1992a), mainly dealing with policies and strategies aiming at its improvement. Assessment of the degree of success is seriously hampered by lack of explicitly defined objectives. The objective of this paper is to identify measurable criteria for sustainable livestock production. It will hardly address the body of knowledge on strategies promoting sustainability and that on technologies for sustainable livestock production. The criteria will be derived from explicit but complex issues of unsustainability, such as land scarcity, soil degradation, inefficient use of resources, environmental pollution, and
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declining biodiversity (Durning and Brough, 1991; Rifkin, 1992). As these problems are mainly related indirectly to LPS, the possibilities for an appropriate classification of LPS as a basis for identification of livestock-specific criteria (e.g. mortality, animal productivity) will also be examined, which would facilitate the evaluation of livestock projects. First, some general issues associated with measuring sustainability are discussed. Then, a proposal is presented for implementation of sustainability of LPS and the associated measurable criteria. Subsequently, the possibilities for system classification and identification of livestock-specific criteria are discussed. Finally, the multidimensienai concept of sustainability will be readdressed, to identify some key elements for its operational use.
2. Problems in measuring sustainabflity 2. I. Interpretations o f sustainability
Although the term sustainable agricuiture is singular in form, it comprises a multidimensional concept, referring to such diverse motivations as saving rare breeds, preventing soil degradation by impoverished nomads and reducing effluent production in intensive pig or poultry units. Originally emphasizing the importance of ecological constraints, it now includes economic, social and cultural dimensions, as in the Food and Agriculture Organization (FAO, 1992) definition: "Sustainable development is the management and conservation of the natural resource base, and the orientation of technological and institutional change in such a manner as to ensure the attainment and continued satisfaction of human needs for present and future generations. Such sustainable development (in agriculture, forestry and fisheries sectors) conserves land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially accephable.'" Such complex definitions, combining incomparable objectives, tools and current problems with no clear hierarchy, are problematic for practical application. In this paper, attention will be focussed on ecological and environmel;tal problems vis-a-vis the production of human food (characterized by Harrington (1992) as the 'sustainable growth' interpretation). Socioeco-
nomic issues are not di.seus.ced here as iadependent criteria of sustainability, not because they are unimportant but because: ( ! ) ecological problems are at the origin of the concept of sustainability (Adams, 1990); (2) the relation between socioeconomic conditions and sustainability is not unequivocal---problemsmay occur in both low and high income situations (Ltlt, 1991 ); (3) such issues have been discussed extensively elsewhere (e.g. Chambers, 1988; Chambers et al., 1989; Netherlands Development Corporation ( N I ~ ) , 1991, !993; Vosti et al., 1991 ). The multidimensionality of sustainability will be returned to in the last part of this paper. 2.2. T i m e d i m e n s i o n
In principle, sustainability implies lasting indefinitely, hence dynamic processes are highly important. However, the quantitative relations among many characteristics are only partially understood. For instance, soil erosion results in reduced land productivity, but to what extent has hardly been quantified. The required research is often long-term, while answers are needed at short notice. Hence, predictions of the future are wrought with differences in opinion about future technical possibilities. The resulting problems for the present research system (Funtowicz and Ravetz, 1990) are illustrated in the discussions on global wanning (Reifsnyder, 1989 ). Therefore, political decisions are needed on the degree of risk we are willing to take, which includes both the probability of an event and its possible consequences. For reasons of simplicity and to facilitate the decision-making process, it is proposed to assess the impact of an activity on each criterion indi':idually. These can than be compared and weighed in a multicriteria analysis (as explained in the last section of this paper). The degree of sustainability for natural resources could be expressed in terms of their 'longevity', by dividing proven resource reserves by present resource use intensity. The acceptable 'longevity' should be based on the probability of substitution of a specific resource, with long time frames (e.g. more than 1000 years) in case of (effectively) irreversible consequences (like net soil loss, extinction of species), and shorter ones for resources with higher probabilities of substitution (e.g. soil nitrogen).
J. de Witet al. /Agriculture. Ecosystemsand Environment 53 (1995) 219-229 2.3. Unit and scale of measurement
To assess the impact of an activity on sustainability, criteria are needed. Though at the risk of neglecting characteristics that arc less easily measured, measurability is a prerequisite to implement these criteria and to avoid a priori definitions of sustainability (Harrington, 1992). Many of the objections against measurable criteria will probably disappear with the realization that they can be expressed in various ways (binary/discrete, ordinal/ranking and cardinal/continuous) and that quantification is hardly more than approximations with a higher level of precision. Cardinal and, to a lesser degree, ordinal measures have the advantage tha~ differences in the degree of sustainability can be identified and facilitate assessment of trade-offs among different attributes of sustainability. In quantifying characteristics, attention should be paid to the units in which they arc expressed, particularly for efficiency parameters. Livestock productivity can be expressed per animal, per kilogram metabolic weight, per hectare, per kilogram of nitrogen input, etc., each unit relating to a different objective and/or different system boundary. For instance, productivity per kilogram metabolic weight is a fair indicator of biological efficiency per animal unit, and may increase by reducing the number of animals per hectare. However, if land is scarce, productivity per hectare is also important, which could decrease if animal numbers are reduced (Jones and Sandland, 1974).
3. Sustainability: implementation of ecological criteria To avoid definition problems of sustainability, that have governed a major part of the discussion, criteria will be derived from explicit issues of unsustalnability, such as food shortages, land scarcity, soil degradation and desertifieation, inefficient use of resources (energy, nutrients and water), deforestation, environmental pollution, and decline in biodiversity (Alexandratos, 1988; Durning and Brough, 1991; Rifkin, 1992). This elaborate process is discussed subsequently. Table 1 gives the proposed measurable criteria, the sustainability problems to which they relate and
22!
the factors which influence the contribution of LPS to these problems. 3.1. Food shortages
Projections for the year 2000 suggest a gap between demand and supply in milk. Also the assumed increases in meat production per animal seem problematic ( Alexandratos, 1988 ). Although livestock products are valuable for vulnerable groups like children, the elderly and the sick, they are not indispensable and vegetarian diets are possible (Spedding et al., 1981 ). Therefore, both supply and demand of consumable livestock products are proposed as criteria, implying that the need for increased livestock production should be weighed against possible trade-offs like higher nutrient losses or a reduction in natural areas. If the undesirable effects of increased supply are too strong, the a_emand for consumable livestock products should be restricted, by influencing factors like population g~owth, income elasticity of demand or livestock product prices. If a higher supply of consumable livestock products is found to be desirable, special attention should be given to the following. (!) Farm-gate prices of livestock products: are they remunerative? (2) Objectives of livestock farmers: objectives other than the production of consumable livestock products (e.g. manure, investment, security, draught power) are often highly important (Behnke, 1985; Crotty, 1980); measures aimed at increasing production of consumable livestock pioducts are likely to fail if no alternatives for these objectives are developed. (3) Available feed resources: the often abundant low quality feeds result in maximum production per hectare at relatively low animal production levels (Jones and Sandland, 1974; Zemmelink et al., 1992). The net effect of LPS on total human food production--or potential population supporting capacity (PPSC) of an area (FAO, 1984)--is proposed as a criterion, because livestock often competes with food crop production for the same resources, but on the other hand often providing critical inputs to arable farming. In general, livestock production systems are inefficient food producers compared to arable farming systems ($pedding et al., 1992). However, a small increase in the PPSC is likely if livestock uses biomass (less suitable for human consumption) or land not suitable for food crop production, or if important positive crop-
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Table I Criteria for mea.~uring sustainability of liv~tock systerns, the sustainability problems to which they relate and factors that may influence the effect of livestock inclusion in agricultural system on each criterion (De Wit. 1993) Criterion
Related sustaianbility problem
factors influencing the effect of livestock
Supply and demand of consumable livestock product
None (these are related to other objectives)
-
Potential ( human ) population supporting capacity (PPSC)
Food shortage Land scarcity
( ! ) Land suitability for arable farming versus livestock production (2) Staple food characteristics ( 3 ) Crop-livestock interactions
Land area utilized for agriculture
Soil degradation Deforestation Declining biodiversity Global warming
As above for PPSC
Degree of equi:y in food distribution
Food shortage
( I ) Income elasticity of demand for consumable livestock products (2) Location and nature of feed processing
Variability
Temporary food shortages and risk of low returns Correiation and variation of yields and product prices of livestock production versus other production activities
Net annual soil loss
Soil degradation Water availability
( I ) Effect of feed production and utilization on soil cover (2) In case of feed production on rows: length of slope: height of. and distance between, wind breaks
Nutrient (N, Pand K) balances
Soil degradation
( I ) Management of manure and urine (2) Effects on erosion and S O M (3) Soil type (4) Export of nutrients in products
Nntrieu~ lasses
Efficient energy and nutrient resource use
As nutrient balances, except (4)
Water availability
Efficient nutrient resource use Receding groundwater depth
Mainly effect on soil cover and SOM content
Water utilization
Same as water availability
Proposlion of feed from irrigated land
5oil organic matter (SOM)
Soil degradation Influences erosion, nutrient balanccs/lusses and water availability
( I ) Prednction of indigestible organic matter (2) Difference between total biomass production and ~ttilization
Fossil energy utilization
Efficient energy use Global warming
Balance between provision of energy and required energy (particularly off-farm for fertilizer production feed processing, transportation,etc.)
Drug utilization
Harmful effects on wildlife, biological control agents and/or humans
( I ) Level of intensification ( 2 ) Genetic resistance of breeds
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livestock interactions exist (Kaasschieter et ai., 1992b). The degree of equity in food distribution is suggested as a criterion, because malnutrition and starvation are often associated with unequal distribution as much as by inadequate production (Amartya Sen, 1981; World Resources Institute (WRI), ~990). It may be influenced via income, price and land tenure policies. The degree of equity in food distribution could be negatively affected by livestock production if it uses food grains and/or land suitable for food crop production. However, the impact is highly dependent on the income elasticity of demand for consumable livestock products. LPS may affect food distribution via the place and nature of feed processing which is strongly influencing the relative price ratios of different feeds and thus the level of competition. Variability is proposed as another criterion because risk of low returns is a major problem in many agricultural systems, resulting in temporal starvation or migration. Variability can be expressed, in principle, in coefficients of variation of, and correlation coefficients between, different farm activities. Livestock production is often considered a major risk-reducing activity by carrying over food or wealth from periods of surplus to periods of scarcity, by using a failed crop, or as a security against inflation (Nordblom, 1988). However, the potential advantage of livestock, in terms of shock absorption, may be difficult to realize because disinvestment often takes place if crop prices are high and animal prices low or if crop prices are low and animal prices are high (Sandford, 1989). 3.2. Land scarcity
Arable land availability is projected to decline from the present 0.28 ha per capita to 0.17 ha in 2025, with major problems in Asia where it will decline to 0.09 ha (WRI, 1990). The FAO (1991a) gives a similar estimate of 0.15 ha in 2050. The decline in arable land availability per capita is a major concern for sustainable agriculture, because expansion of the cultivated area mainly takes place on marginal lands with inherently low production capacity, that are vulnerable to (virtually irreversible) degradation. Land hunger is also a major cause of declining biodiversity and global warming, because of the conversion of natural areas into agricultural land. The effects of land shortage are often
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aggravated by insecure land tenure regulations for the lalger part of the agricultural labour force (FAO, 1991c). Thus, the land area utilized for agriculture is proposed as a measurable criterion. The overall effect of including livestock in an agricultural system is affected by similar factors as the PPSC of ~.region. If part of the livestock feeds is not produced regionally but imported, the total land area should include the area on which the 'imported' feed i~ grown. However, if the imported feed mainly consistz of crop by-products, arbitrary imputed values may be applied, for instance based on the monetary value of these by-products relative to the main product. 3.3. Soil degradation
Roughly 40% of the arable land and 21% of the grazing land is estimated to be affected by 'human induced degradation' (OIdeman et al., 1991). A major part of 'desertification' is often blamed on livestock production, especially by pastoral societies. Overgrazing does take place, but doubts have been expressed on the role of livestock in irreversible soil degradation (Behnke and Scoones, 1992). The occurrence of soil degradation, of which desertification is an extreme case, is less controversial, particularly in ecosystems with high rainfall because of erosion or soil nutrient depletion, though in some cases trampling seems important. In most developing countries soil nutrient depletion is a major form of soil degradation. It is, for instance, projected that the annual deficit for Sub-Saharan Africa in 2000 will be on average 26 kg of N, 7.5 kg of P205 and 18 kg of K20 per ha (Stoorvogel and Smaling, 1990). For a region in South Mall it was estimated that the losse~ of nutrients in some cropping systems almost equalled the value of the produced crops at present prices (Van der Pol, 1992). Export of nutrients results from erosion, products sold, leaching and denitrification. Volatilization is not considered important because the major part will be deposited nearby. Imports can be via organic and chemical fertilizers, biological fixation of nitrogen, and natural deposition. Nutrient balances can be equilibrated via increased imports and/or reduced losses. The net effect of LPS on nutrient balances (particularly nitrogen and potassium ) is related to factors such as management of manure and especially urine, effects on erosion and soil organic matter
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(SOM), and the export of nutrients in products sold. Erosion is another form of soil degradation. (In addition to the rate of erosion, its nature is also of imperlance, because of differential effects on soil properties like nutrients and SOM.) Annual soil losses of O.l to more than 100 t h a - i have been measured (Pimentel et al., 1987 ), and the annual rates of soil formation are estimated at 0.3-80 t h a - ~, with the highest rates for volcanic soils in high rainfall areas. Erosion is influenced by many factors, some of which could be affected by livestock such as soil cover, length of the slope, distance between windbreaks. Net annual soil losses should be assessed independently from nutrient balances because of incomplete restoration possibilities of the unfavourable structure of the eroded soils. Water erosion can also cause major problems downstream, e.g. flooding and reservoir siltation. On the other hand, part of the eroded material may be deposited nearby, thus reducing the negative impact of soil erosion on larger land units. 3.4. Water resources
A major constraint in rain-fed agriculture is soil moisture availability during part of the year. This can be alleviated by irrigation, but large-scale irrigation often results in rapid increase in groundwater depth. For instance, annual groundwater table declines of 14 m have been reported from India and China (Brown et at., 1985). Water availability and water utilization are proposed as separate criteria because they are affected differently by livestock production. Water availability will be affected mainly by effects of livestock on soil cover and SOM, and water utilization is mainly affected by the amount of water used for irrigation of forage crops. Other water-related issues, such as the distribution of water points and the design of water lifting devices, are not considered separately because they rank much lower in the hierarchy of objectives, strategies and tools. 3.5. Energy resources
Most of the production increases in the recent past have been largely the result of increased use of external fossil energy. This has been associated with a decrease in overall output-input ratio for energy, from roughly
> I0 in low input systems to < 2 in high input systems (Bayliss-Smith, 1982; Pimentel et at., 1990). It should be noted that energy balance calculations are fraught with difficulties, because they require arbitrary imputed values for inputs like necessary infrastructure, imported feeds, plant/am'mal breeding, etc. Fossil energy consumption should be examined critically, because proven fossil energy reserves remain limited (e.g. 41 years at 1988 consumption rates for oil; WRI, 1990) and because of their contribution to global wanning. Livestock production usually increases fossil energy consumption mainly via utilization of inputs and processing of the products, bat may decrease it because of energy supplied by animals in the form of draught power and/or dung as fuel. 3.6. Nutrient resources
The main problem nutrient is phosphorus, of which the proven economically exploitable reserves were estimated at approximately 85 years at 1985 production rates (Helsel, 1987). Nitrogen reserves are almost inexhaustible, because of its abundant availability in the air. However, the production and utilization of nitrogen fertilizer requires large amounts of fossil energy. Because nutrients are indispensable for biomass production, and insufficient application may cause soil degradation, total losses of nitrogen, phosphorus and potassium are proposed as indicators for efficient use of mineral resources and energy. 3. Z Soil organic matter (SOM)
SOM is added as a separatecriterion, as an important control variable for erosion, nutrient balances and losses and water availability. The overall effect of livestock inclusion in an agricultural system on SOM is relatively uncertain, partly because of inadequate characterization of SOM composition. Animal digestion is not likely to affect the amount of effective SOM per unit of original biomass. Therefore, the overall effect of livestock production on SOM will depend mainly on the quantity of "indigestible' organic matter that is produced. Total SOM is important in relation to the infiltration capacity, because of its effect on rate of water flow and soil fauna.
J. de Wit et al. /Agriculture. Ecosystems and Environment 53 (1995) 219-229 3.8. Environmental pollution
Environmental pollution is mainly associated with intensive systems, still rare in Third World countries. It consists mainly of (1) groundwater pollution by minerals, which is directly related to the criterion of regional nutrient balances, and (2) drugs, i.e. veterinary products and, especially, pesticides. Utilization of drugs (both veterinary products and pesticides) is problematic, because of their residues and derivatives which can destroy natural pest controlling organisms or contaminate drinking water and food. It has been estimated that approximately 3.7 million people worldwide are exposed annually to high pesticide levels ( Jeyaratnan, 1990). Utilization of pesticides has been strongly promoted by subsidies, which in some countries were over 80% (Repetto, 1985). Livestock inclusion in an agricultural system may lead to reduced drug use through the potential to widen crop rot.-aions, thereby limiting the need to apply pesticides. Specification of the type of drug is needed because of the wide variation in active ingredients and their effects. An additional area of concern is the increasing resistance to drugs. A limitation in drug use is possible via choice of appropriate breeds, the use of vaccines and management techniques. The contribution of livestock in developing countries to other environmental problems like global warming via methane is small (approximately 1.5% of global warming; based on FAO, 1991b) though rising. Reduction can mainly be realized through lower ruminant numbers. The contribution via CO2 emission during respiration is negligible as it cannot exceed the amount fixed by the plants eaten. The emission of CO2 associated with the conversion of forest areas into agricultural and grazing land was estimate.A to contribute around 12-14% to global warming (Winpenny, 1991). This effect is sufficiently covered by the earlier proposed criterion of the land area utilized for agriculture. 3.9. Deforestatiot,
Livestock pn3duction is estimated to contribute approximately 9% directly to total annual deforestation, mainly in Latin America (Prance, 1986). Indirectly, via the claim of LPS on land resources resulting in increased land hunger, the contribution of LPS to deforestation is higher and also relevant to other con-
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tinents. Thus, the land area utilized for agriculture is a sufficient criterion for deforestation. 3.10. Biodiversity
High biodiversity is seen as useful or essential in the future, for example as a source of genetic resistance to yet unknown diseases or as a source of new medicines. However, it is estimated thin the rate of extinction of species is roughly 106 times their rate of origin (May, 1988). Moreover, extinction of species may be regarded as problematic in its own right, because of 'intrinsic values'--i.e, values resulting from the mere existence of species, not from human advantage. In general, agricultural sy.~;temshardly contribute to global biodiversity. Thus, on!~ytwo dozen plant species, of which 14 belong to two families, are of particular importance for food production (Jackson, 1984). Also the diversity in other species (e.g. soil organisms, insects) is poor in agricultural systems in comparison with natural climax ecosystems. Therefore, this aspect seems sufficiently covered by the earlier proposed criterion of the land area utilized for agriculture (as a complement to the area reserved for natural areas). Another issue, often discussed under the heading of hiodiversity, is the genetic diversity of species used in agriculture. Concerns have been expressed about the worldwide loss of breeds and genes in livestock species. Though important in animal breeding, this criterion is impossible to measure, because of inadequate characterization of these breeds and their desired traits (Henson, 1992). Biodiversity is sometimes also linked to stability. However, equating diversity with functional complexity, which in turn results in stability, is oversimplistic (Goodman, 1974; Pimm, 1991). The relation between diversity and stability is further complicated by the multiple meanings of stability, which include resilience, persistence, resistance and variability, none of them having a simple relation with diversity (Pimm, 1991). Except for variability, these characteristics are virtually impossible to measure. 4. System classification: a discussion of the possibility for identification of livestock-specific criteria The variables proposed as criteria for sustainability are influenced by various factors related to the size and
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nature of LPS, their relation to other production activities, and local ecological conditions. Hence, no atte.~apts have been made to assess the effect of livestock inclusion in an agricultural system on each of the criteria. To evaluate these effects a system classification seems indispensable (Kaasschieter et al., 1992a). One possible system classification distinguishes pustoral, mixed and intensive LPS (Kaasschieter et al., 1992a), mainly based on crop-livestock interactions, i.e. independent, complementary and competitive systems. However, these systems are not defined unequivocally, i.e. livestock fed crop residues are only complementary in terms of land resources, but may be competitive on the basis of labour utilization. Moreover, this classification neglects differences in agroecological conditions. For instance, pastoral systems ~.ahilly areas will score differently on the criterion for net annual soil losses from pastoral systems in temporarily flooded areas. Therefore, a system classification based on crop-livestock interactions must also take into account agroecological conditions (FAO, 1984). Both classification criteria neglect differences in input utilization, in demand patterns and social relations, both within families and between gender groups, which result in a vast array of (multiple) production goals and systems. Therefore, a socioeconomic classification seems indispensable (Crotty, 1980; Behnke, 1985). Again, the intensity of livestock production may be an important factor for LPS classification. For instance, grazing land of which only 30% of the available biomass is used as feed will score much better on erosion than that where 80% is used. Many more factors can be identified as important for evaluating LPS as illustrated in the last column in Table 1. The resulting matrix of possible combinations becomes extremely large, even when only a limited number of classes are distinguished per criterion. Hence, defining stereotype LPS may be a helpful z,.arting point, but they are too broad and imprecise to allow their evaluation in terms of the different sustalnability criteria. Identification of livestock-specific criteria eventually becomes impossible us the variables, which serve as indicators for sustainability, simultaneously act as feedback mechanisms which (partly) control the pressure of animals on the natural resources. That holds for indicators such as animal productivity, mortality rates
or changes in herd composition. Increasing livestock l:reductivity can in some situations be a tool to promote sustainability, while in others it may aggravate sustainability problems, depending on system-specific characteristics. Therefore, evaluation of LPS for sustainability should not be based on livestock-specific criteria but on general criteria, as elaborated in this paper.
5. The concept of sustainabillty reconsidered It has been argued that a system-specific analysis is indispensable because livestock affects agricultural systems in many ways, even when only agroecological criteria are considered. Moreover, trade-offs among different criteria are likely, for instance: ( 1 ) using more chemical fertilizer is a powerful tool to balance nutrient deficits, but will negatively affect fossil energy utilization and nutrient losses; (2) artificial insemination and subsequent high selection pressure on a few productive traits may be effective tools to increase the supply of livestock products, but it will also present a major threat to genetic diversity in farm animals; (3) inclusion of a grass Icy may result in a smaller area required to provide sufficient SOM us compared to legumes. However, only legume-based systems can become self-sufficient in nitrogen (Schiere, 1992). Trade-offs are even more likely, if other objectives (e.g. poverty alleviation, equity, rural employment or even animal welfare and product quality) are added (Van Pelt et al., 1992). This recognition of trede-offs is one of the key elements in implementing sustainability. Many problems occur simultaneously at present; preventing or solving one problem may create or aggravate other problems. This has serious implications: (1) statements such as "this is more sustainable than that" are senseless in themselves, because the important question is, how does the activity score on each of the criteria.'?; (2) sustainability is not a discrete concept ( as questioned by Harrington, 1992) but a continuous one; (3) the chances for success will decrease with the increasing number of objectives, when the "success' of development programmes directed to increase intragenerational equity is already modest. Contrary to economic techniques, in which subjective choices on the value of different outputs and resources are implicit in
J. de Wit et al. ~Agriculture, Ecosystems and Environment 53 (1995) 210-229
the analysis, multicriteria analysis techniques, such as multiple goal linear programming (De Wit et al., 1988), make the choices among different objectives explicit (P~try, 1990) by expressing trade-offs between different objectives, each in their own unit. Prospects for multicriteria analysis o f LPS are given by Schiere (1992). Trade-offs are system-specific because both technical coefficients and objectives vary. Differences in objectives are, however, restricted because of the emphasis on sustainability in relation to future generations. Consequently, all effects, including 'external' effects, should be included in the analysis and decisionmaking process. This is a second key element in implementing sustainability: reduced acceptability o f external effects. Ultimately, this reduction may imply an 'environmental utilization space' (Opschoor, 1992) equal for each person on earth (Buitenkamp et al., 1992), although exchange of its various components among groups and individuals is possible, as implied by the proposed trade in manure production quota in The Netherlands.
6, Conclusions Explicit identification o f issues o f unsustainability is a helpful starting point for implementation o f sustainability. Most of the major agroecological problems can then be translated into measurable criteria. Such a deduction method doe~ not pretend to define the ultimate state of sustainability, but allows addition of criteria when new problems are identified. Identification of livestock-specific criteria is impossible because LPS are too heterogeneous to develop a generally applicable system classification, and because the relation between livestock-specific criteria and agroecological criteria is not unequivocal. Hence, a system-specific analysis is indispensable to assess the effects of livestock inclusion in an agricultural system on the various agroccological criteria. This also facilitates formulation o f measurable socioeconomic criteria, and it is indispensable to assess trade-offs among different criteria. Recognition of such trade-offs, together with the reduced acceptability of external effects (both in time and space), could be the most important notion in implementation of the sustainability concept.
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Acknowledgements Special thanks are expressed to the FAO, which sponsored the study that served as a basis of this article, and to J.B. Schiere who is a major source o f the ideas expressed here,
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