Grazing management: new technologies for old problems

John W. Walker and Ken C. Hodgkinson

Texas A&M Research and Extension Center, 7887 US Highway 87 North, San Angelo, Texas 76901, USA; CSIRO Wildlife and Ecology, GPO Box 284, Canberra ACT 2601, Australia

Keywords: plant-animal interface, range improvements, stocking rate

Literature on rangeland grazing management is being published at an accelerating rate, even though the use of rangelands for domestic stock production is increasingly questioned on conservation and sustainability grounds in the USA and Australia (Fleischner, 1994, Grigg, 1995). This is because the vast areas classified as rangelands provide a wealth of non-pastoral services (Holechek et al., 1989) and (or) intrinsic values (Johnson, 1992). The economic and cultural worth of these services often exceeds that of domestic stock production. Whether these rangeland areas continue to be used for pastoral businesses, it is important that the grazing of them be managed so that the basic soil, natural biota and water resources are sustained.

Much recent literature on grazing management, particularly literature from the arid to subhumid regions, is at a theoretical level (eg. Westoby et al., 1989). This is in part because adaptive management research to determine appropriate management practices for extensively managed rangelands is now only beginning at the operational scale. Simulation modelling and decision support systems are currently the only way to explore the many possible management alternatives. Grazing managers do not just adopt a new grazing system but rather they adapt a suite of management changes in conjunction with implementing a new grazing system. Savory and Butterfield (1999) are correct in stating that grazing management may not be researched in the manner of normal biological research. There is a need to develop principles that can be integrated using simulation modelling into grazing management systems. Business schools have extensively studied management practices of successful businesses by interviewing managers and observing how successful businesses are operated (Peters & Waterman, 1982), not by setting up replicate corporations based on different management principles and collecting data on them over a number of years. However, even while modelling approaches are being developed and validated, there is a need now for some practical guidelines for grazing management. Thus for the present and foreseeable future common sense and rule of thumb solutions to grazing management problems may be the most useful. This paper will make some practical recommendations for managing grazing on rangelands. In doing so, we will confine ourselves to the arid to subhumid rangeland areas that are managed on ecological principles rather than the more humid areas where agronomic practices are widely practiced (McMurphy et al., 1990). We focus on pastoral businesses. Some of discussion though will be relevant to people of nomadic pastoral systems.

The challenge in preparing this paper has been to develop new ideas, or combine old ideas in new ways, that offer some different ways of looking at the topic of grazing management. This is particularly daunting considering that the subject has been written about since biblical times. Over 4,000 papers have been written on the subject since 1970, and at least five synoptic books were published in the last 10 years, whereas we are limited to a few thousand words. The enormity of this task leads one to prayer (with apologies to Reinhold Neibuhr): Successful grazing managers will be the ones that have the serenity to accept the things they cannot change, the courage to change the things they can, and the wisdom to know the difference.

Things we must accept. Abiotic factors, such as climate, edaphic and topographic, which structure and maintain rangeland ecosystems, determine the limits to grazing management and cannot be changed. All herbivores (domestic or wild) are highly selective in their grazing patterns in space and time and at many scales, and by choosing to graze some areas and (or) plants and avoiding others, herbivores affect the composition and stability of plant communities and the landscapes on which they are based. Furthermore, the inability to simultaneously optimise both the interception and conversion of solar energy into primary production and the efficient harvest of primary production by herbivores is a biophysical limitation that limits carrying capacity on rangelands and cannot be changed (Briske & Heitschmidt, 1991). Social and economic factors often limit the ability of graziers to change grazing management but we consider these are not fixed impediments (albeit, change may be very slow).

Things we can change. Management options that can almost always be changed if one has the courage and resources to do so include species of livestock, season or timing of grazing and stocking rate. It is interesting that the things that can readily be changed include three of the four principles of grazing management referred to in almost every paper ever written on this topic. The fourth grazing management principle is distribution, which usually requires a substantial investment to modify, at least in areas where livestock distribution is managed primarily by fencing. However, distribution can be affected to some extent by modifying the first three principles. Furthermore, in nomadic pastoral systems distribution is the management principle that has the greatest flexibility and can be used to take advantage of temporal and spatial diversity.

Wisdom to know the difference. Ability of graziers to change the way they manage livestock and other herbivores is, in part, dependent upon the availability of technologies to make the desired changes. This is where the wisdom to understand which constraints are amenable to technological improvements and which are less likely to result in improvements becomes important. That we have found it convenient to modify a prayer, often used by people with addictions, to serve as an aid in understanding grazing management reflects our perception of the strength with which some members of the range science profession cling to inappropriate paradigms of grazing management. For instance while grazing systems are less effective than stocking rate for enhancing both vegetation and livestock production (Van Poollen & Lacey 1979) rotational grazing still seems to be the cornerstone of much policy from government agencies (Malechek 1984).

The purposes of grazing management is to minimise the adverse impacts of domestic livestock and other herbivores that comprise the total grazing pressure on the natural resources of soil and biota and to maximise the probability that the grazing enterprise will be sustainable. This statement does not imply that grazing is not sustainable or that grazing is not an important ecological force in many rangeland ecosystems (Milchunas et al., 1988). However, at the level of individual plants, defoliation decreases production in the vast majority of instances (Jameson, 1963) and in most instances the purpose of grazing management is to ameliorate this negative effect and maintain a competitive balance among the plant assemblage.

There are now multiple desired outcomes for a sustainable grazing enterprise (Walker, 1995), and this trend is likely to increase. The goals of grazing management may include control of undesirable vegetation (Olson and Lacey, 1994), enhancing wildlife habitat (Mosley, 1994), reduction of fire hazard, maintenance of biodiversity (Landsberg et al., 1999), animal traction, manure, banking livestock capital and, of course, for the profitable production of food and fibre. Herbivores, including domestic livestock, highly select the plants and plant parts they graze (Leigh & Mulham, 1966) and the parts of the landscape they favour for grazing (Landsberg & Stol, 1996, Roshier & Nicol, 1998). Plants are the victims of defoliation, overcompensation notwithstanding, and suffer through reduction in the plant's resource capturing ability. Ultimately, such reduction impairs the ability of rangeland plants to survive times of resource scarcity (Hodgkinson, 1996). Ecosystem functioning may also change under the impact of grazing and other anthropomorphic influences. For example, the chance of fire may be greatly reduced (Hodgkinson & Harrington, 1985) and competitive relationships among plant species may be altered because of elevated atmospheric CO2 that has resulted from the burning of fossil fuels (Polley, 1997).

Development of a grazing management strategy for a pastoral enterprise requires definition of the desired outcomes and of the inherent constraints. From these the solution space of the problem can be defined and management can then adjust the stocking rate, grazing season, livestock species and distribution of grazing animals. It should be recognised that any time domestic livestock are grazed, decisions relative to livestock species, timing of grazing and stocking rate have to be made, either consciously or unconsciously. Improving grazing distribution, however, normally requires the investment in capital improvements such as fencing or water development. Stocking rate is usually considered the most important factor as well as the most abused factor in grazing management. The importance of season of grazing is dependent upon the climate of an area and whether cross fencing is in place that would allow the implementation of a grazing management system. Existing conditions in many areas dictate that on a large percentage of grazing lands, season of grazing is not a factor that can be managed readily. However, resting from grazing to foster plant recovery and seed production, and in some cases to prevent accelerated mortality of domestic stock due to forage and water shortage, is desirable in ecosystems of non-seasonal rainfall. This can be achieved by lease grazing or agistment, stock sale or feeding of livestock on forage reserved within the property.

Choice of species of livestock is an underutilized management tool at the present time. The selection of the species of livestock best adapted to a particular environment is often the simplest solution to grazing management problems. However, many graziers are reluctant to make such changes often for cultural reasons but also because of the presence of predators. In the USA, the impact of grazing on riparian areas, one of the biggest grazing management problems, has resulted in a large part from using inappropriate species of livestock (Kauffman & Krueger 1984). Overgrazing of riparian areas affects biodiversity and water quality and is caused primarily by a distribution problem. Whereas ribbon fencing of riparian areas is a solution that has been used in some areas, a much simpler solution is to change from cattle to sheep or goats, which prefer uplands to riparian areas (Glimp & Swanson, 1994). The current riparian grazing problems largely resulted from the decline in the USA sheep industry and subsequent conversion to cattle grazing. Unfortunately, evaluating the appropriate species of livestock, which should be the first consideration in developing a grazing management plan, is seldom considered. Control of undesirable plants is another example of a problem that often is best solved by changing species of livestock. It is a truism that plants dominating an area are the ones avoided by the dominant herbivores in the system. Whereas determining the dietary preferences of grazing livestock is often difficult, determining the plants that are avoided is typically much easier. If a species of livestock exists that has a preference for the undesirable plant, changing livestock species is an easy solution. Classic examples include the use of sheep or goats to control leafy spurge (Euphorbia eusla L.; Johnson & Peake, 1960) or gorse (Ulex europaeus L.; Radcliffe, 1985). Finally, if the management goal is to maximise profit and minimise risk, then mixed species grazing, which has been shown to accomplish this objective under a wide array of price ratios (Connolly & Nolan, 1976), should be implemented. However, except for a few areas where it is the cultural norm this practice is used rarely (Walker, 1994).

Poor spatial distribution is the cause of many problems associated with grazing livestock (Holechek et al., 1989). Just as diet selection is a spatially hierarchical problem so too are distribution problems (Stuth, 1991). Furthermore, uneven distribution is caused by characteristics of both the grazing animal as well as the plant community or landscape. Distribution of livestock occurs at many levels and affects and is affected by livestock species, season of use and stocking rate. Many overgrazing problems are actually species of livestock or season of grazing problems and are in a sense manifested as distribution problems. Examples include overgrazing of riparian areas or grazing prior to range readiness, both of which can cause adverse impacts at very low grazing intensities. Carrying capacity in large pastures with poor livestock distribution is lower than on similar areas with good distribution. Poor distribution may buffer the effect of changes in stocking rate on livestock performance compared to the classic response curve where animals are well distributed (Stafford Smith, 1996). Fencing and water development have traditionally been used to improve distribution and the benefits from infrastructure development can be modelled.

Grazing systems are based on manipulation of spatial and temporal distribution of livestock grazing pressure. Because grazing systems involve rotating animals among pastures they de facto determine at some level the distribution of livestock. There is good evidence that any production benefits that result from implementing grazing systems arise from improved distribution and increased carrying capacity (Hart et al., 1993) rather than altered foraging behaviour (Gammon & Roberts, 1978) or increased primary production (Heitschmidt et al., 1987). While most research on animal distribution has been conducted at the paddock level, the effect of meta-scale distribution that involves transportation systems and grazing livestock only during those seasons or years with adequate precipitation deserves more consideration in non-equilibrium areas as a means of achieving sustainable systems.

In contrast, when non-pastoral goals such as maintenance of biodiversity become important grazing management objectives, practices that improve livestock distribution may not be implemented because they conflict with the other objectives. In Australia's rangelands, 38% of understory plants, 15% of overstory plants, 23 % of seed bank plants, 23% of birds, 22% of reptiles and 26% of ants substantially decrease, or are locally eliminated, around water points (Landsberg et al., 1997). Ensuring that parts of paddocks are ungrazed or lightly grazed would meet biodiversity objectives at the local scale. The challenge is to devise and implement strategies that will strike a balance between the needs of the pastoral industry and the needs of the vulnerable elements of Australia's rangeland biodiversity.

Timing of defoliation may adversely affect a plant's ability to replace tissue, reproduce and compete for resources. There are times when a plant can be grazed safely and there are other times when grazing will raise the probability of the plant's dying or its growth being impaired (Blaisdell & Pechanec, 1949). Animal grazing preferences vary seasonally and interact with seasonal plant responses. In temperate climates with strong seasonal differences in temperature and elevation, seasonal grazing practices have evolved to meet stock and natural resource requirements. Properties with contrasting soil types, such as floodplains and runoff landscapes, also are a form of seasonal grazing based on flooding patterns. Timing of grazing, for whatever reason, will affect stocking rate because grazing at sensitive times will reduce primary production and community stability unless grazing levels are low. In areas with large elevation differences, phenological development may vary by 60 to 90 days between the valley floor and the alpine grasslands. Grazing management accommodates these differences in phenological development as livestock are moved up the mountain following the green (Burkhart, 1996). Similarly, in Australian rangelands, where properties are large and rainfall is irregular in space and time, such as in semi-arid woodlands, livestock may be moved to a paddock(s) where high rainfall from a convective storm has generated a pulse of plant growth (Martin, 1978; Hodgkinson & Freudenberger, 1997). Tactical grazing, particularly in semi-arid areas, is a management option that is underutilised. It is time to reevaluate the appropriateness of continuous grazing in Australian rangelands, and elsewhere (Holmes 1996). The economic and ecological implications of grazing selected rangeland areas only during the seasons or years with adequate precipitation for plant requirements needs urgent evaluation.

Landscape degradation and adverse vegetation change from overgrazing was one of the primary factors leading to the development of the discipline of range science. While the importance of proper stocking rate is well recognised and techniques for assessing the problem are available, overgrazing is still a major problem in many areas. However, it is more of a problem of wrong mental models than inadequate technology and there are several factors that tempt graziers to exceed the carrying capacity of a property. These factors include the variable and unpredictable nature of precipitation coupled with the overly optimistic attitude of graziers who gamble on the ending of drought. Unfortunately, in many arid areas, probability of a drought is greater than the probability of above normal precipitation (Riggio Bomar & Larkin 1987). Sometimes government policies inadvertently provide incentives that encourage overgrazing (Foran & Stafford Smith 1991; Holechek & Hess, 1995). Overgrazing occurs even though analysis demonstrates that maximum net economic returns will occur below the maximum sustainable level of livestock off-take per unit area (Buxton & Stafford Smith 1996). Financial crisis is another factor tempting graziers to push stocking to the limit. Pastoral businesses facing insolvency are greatly tempted to increase stocking rates in an effort to sustain their operation until commodity prices or climate take a favourable turn. Properties located in the more arid regions with lower carrying capacities tend to be less profitable because of higher fixed cost (Holechek & Hawkes, 1993). Thus the temptation to overgraze is often greatest in the areas that are the most vulnerable. Carrying capacity and the appropriate stocking rate cannot be determined until the decisions relative to species of livestock, season of use and distribution have been made. Although the correct stocking rate is dependent upon these other three factors, the overall success of the system will be dependent upon setting the appropriate stocking rate. In general when stocking rate is too high, the system will not be sustainable even if the other components of grazing management are correct.

In addition to interacting among themselves, the four principles of grazing management and consequently grazing systems also interact with the environment. We will attempt to postulate how differences in rangeland ecosystems affect their response to grazing management. Several different models to describe how evolutionary history of grazing, precipitation, stability and (or) resilience affect response to grazing have been proposed (Westoby et al., 1989; Milchunas et al., 1988; Tainton et al., 1996). For the purpose of this paper we will consider equilibrium versus non-equilibrium continuum. Equilibrium systems are those that may change in plant species composition in response to grazing, but when grazing pressure is reduced, will return to their former composition. These systems typically have a long evolutionary history of grazing, are not susceptible to invasion by undesirable plants, either woody or herbaceous, and can be managed using Clementsian models of succession. Non-equilibrium systems are those that never reach a steady state and are controlled primarily by abiotic factors such as precipitation and fire. These systems typically have a short evolutionary history of grazing, are prone to invasion by undesirable plants and are best managed using the state and transition model of community dynamics.

Management of equilibrium systems is fairly straightforward because these systems respond to change in total grazing pressure. Outcomes must be described and criteria established to monitor progress. A grazing management plan could be developed based on manipulating livestock species, grazing season, distribution and stocking rate to accomplish goals. For instance, if maximum sustainable production of livestock products is the objective and distribution is not considered a problem, then year-long continuous grazing using sheep and cattle at a variable stocking rate tied to annual precipitation would be appropriate. Decision support systems are currently available to monitor and adjust stocking rate to match animal demand with primary production (Stuth & Lyons, 1993). In equilibrium ecosystems, management to maintain the correct stocking rate is the most important factor of grazing management. This can be done with a simple rotation or even continuous grazing system. Season or timing of use, livestock species and distribution can be adjusted to increase carrying capacity or accomplish other management objectives such as multiple use. Multiple use objectives will complicate the grazing management of equilibrium systems, but in many cases there is commonality of states that meet different objectives. For example, grazing management that retains all palatable plant species will probably meet both biodiversity and sustainable production goals.

Non-equilibrium systems are more difficult to manage because even in the absence of livestock they may be unstable, particularly if invasion by undesirable plant and animal species is a problem. Invasion by woody plants is a widespread problem, which although potentially accelerated by grazing, typically will also occur in the absence of grazing (Archer, 1996). Fire is the best tool for controlling woody plant invasion, but the ability to use this tool is dependent upon grazing systems to accumulate and manage grass fuel levels. In these systems grass production will usually need to be managed both as forage and as fuel (Kothmann et al.,1997). Because of the tendencies of non-equilibrium systems to cross thresholds to less productive seral states, grazing systems that have been shown to advance succession will have the greatest potential for maintaining plant communities in the desired vegetation state. Grazing systems with these capabilities are ones with long deferment periods such as the Merrill 3 herd 4 pasture, high intensity low frequency (non-selective grazing) and rest-rotation grazing. Because of the long deferment periods and resultant increased grazing intensity on the grazed units, these types of systems tend to be very sensitive to stocking rate particularly as it affects animal performance. Another advantage of grazing systems with long deferment periods is that they are the ones best adapted to accumulate the grass fuel required for a successful prescribed fire program.

We have purposely avoided discussing grazing systems per se, because there is no evidence to indicate that they provide any advantage other than the flexibility that cross fencing and grouping of animals provide for managing livestock distribution and timing of grazing. However, as we learn more about how timing may be used to provide either rest or grazing pressure at critical times to accomplish vegetation management goals this flexibility will be increasingly important. Likewise when prescribed fire becomes an integral part of the grazing management plan the flexibility of multiple pastures to manage grass as forage or fuel becomes very important.

Before turning to new technologies for improving management of rangelands it should be noted that in most instances today where rangelands are being grazed by domestic livestock in an unsustainable manner, the root cause is not a lack of theory or technology on grazing management. In most cases we believe the principles discussed above can be applied to alleviate most of the problems associated with grazing by domestic livestock. Graziers can be expected to make rational decisions from their point of view. Where grazing management is poor the theory may be wrong or incomplete or it may apply to only part of a system being managed. Other factors such as social and economic ones may override consideration of grazing and/or uncontrolled feral and native herbivores may limit the ability to manage grazing.

While forecasting the future may at first appear to be of doubtful value in a rapidly changing world there are certain inevitable futures with a relatively high degree of certainty. Such futures are based on events that have already occurred. For instance if a ball is dropped, that it will hit the ground is a near certainty. Other highly probable futures include 1) a world population that will increase by nearly 40% in the next 25 years from the current 5.9 billion to 8.2 billion people; 2) the continual trend for increasing microprocessor capacity and all associated information technology; 3) the increasing ability to alter all biological organisms by changing their genetic code, and 4) there will be a new generation of rangeland owners and managers. What is more questionable is when, and in what form, these trends will impact upon rangeland management. The effect of population growth on rangeland management will depend upon the ability to expand food production at an equal or greater rate. Most-science based organisations predict only local and isolated food shortages in the foreseeable future (CAST, 1998), dissenting opinions notwithstanding (Brown et al., 1998). If food supplies continue to be adequate and living standards continue to rise then we believe that rangelands will increasingly be valued for production of non-food goods, particularly in areas where highly variable abiotic conditions limit profitability.

Agricultural production has demonstrated a long-term trend toward intensification and specialisation. The pressures of global population growth will for the most part ensure that this trend continues. However, rising affluence will ensure demand for niche products such as organically produced food and fibre (Raterman, 1997). Furthermore, in many developed countries the demand for recreational opportunities and better conservation of biodiversity will continue to increase. The largest, healthiest and wealthiest class of retirees in history will create this demand. These three trends (global population growth, demand for organic foods and other "clean, green" products, and recreation) will have a large impact on the types of enterprises that will be most profitable on different rangeland types and will in turn determine what technologies are required.

The intensification trend will cause the production of grazing livestock to shift to more mesic locations with higher production potential that can more profitably employ advanced technologies. Since 1920 the proportion of the USA beef cow herd raised south-west of about 42ºN latitude, 95ºW longitude (ie. Kansas) has decreased approximately 2.5 percentage units per decade, while south-east of those coordinates it has increased 1.4 percentage units per decade (USDA-NASS 1998). This regional shift in production corresponds with a precipitation gradient that is more arid in the west and increasingly humid to the east. Demands for recreation and organic food will cause livestock production on more arid areas, particularly those areas where livestock production involves high risk and low profit, to decrease in importance. In these areas increased emphasis will be placed on recreation and the production of high value animal products that will be produced with minimum inputs. The idea of high value and low input is a paradox to most concepts of modern agriculture but results from the desire by some for naturally grown foods such as "bush tucker" in Australia and apparel from organically labelled fibres in the USA (Nimon & Beghin 1998). However, low input does not necessarily imply low cost particularly when low input results in low production efficiencies in the presence of high fixed cost.

The greatest impediment to this predicted transition is the value systems and personality characteristics of current property owners and managers (Thompson 1995). These characteristics that were important for the successful settlement and development of the current livestock production systems tend to make people with current tenure of the land very resistant to such changes. However, if one accepts the self-evident statement that "the only sustainable agriculture is profitable agriculture" (Ainesworth, 1989) and the trends discussed above continue, eventually economics will either transform people or cause a change in ownership. Then the products and services produced on rangelands will be more congruent with contemporary socio-economic systems. This will also affect the types of information and technology that will be demanded from rangeland ecologists but the principles that can be managed will remain constant (i.e., livestock species, distribution, timing and stocking rate). We will briefly describe technologies that could be developed from existing or impending technologies.

The components necessary to develop many technologies that would improve our ability to manage rangelands are currently available. However, the development of commercial systems using this technology will be relatively slow because the low returns to ranching dictate that such systems will have small markets and low profit margins. The development of barbed wire, an important tool in range management, provides a useful example. Although wire was first produced commercially in the 13th century, and in 1860, 1,500-tons of wire were used in the U.S. for hoop skirts, barbed wire was not invented until 1873. Furthermore, this technology initially met much resistance and wide spread adoption did not occur until the technology was practical and economic.

The only limitation to developing information technologies to improve rangeland management will be the lack of desire to invest resources in this effort. However, such investments will have to be publicly funded because return on investments will be too low to attract private capital. Potential information technology systems might include 1) global positioning systems programmed to contain animals in a desired area through the use of electronic cuing devices, 2) remote sensing for monitoring rangeland condition and to support real time management decisions; and 3) simulation modelling and decision support systems. Continually increasing microprocessor capacity coupled with increased connectivity such as provided by the World Wide Web will ensure that decision support systems and simulation models will become increasingly useful and will be widely adopted. These tools will be integrated with geographic information systems to provide the data bases and parameters necessary to make them user friendly. These tools will improve the ability to make decisions relative to livestock species, timing of grazing and stocking rate. However, a word of caution is appropriate, these modelling tools must place their emphasis on accurate prediction. The argument that extremely complex models offer better understanding of ecosystem processes is not a justifiable excuse for poor prediction (Peters, 1991). The quality of models must be judged by their ability to provide useful management predictions. As John Gardner stated "The society which scorns excellence in plumbing as a humble activity and tolerates shoddiness in philosophy because it is an exalted activity will have neither good plumbing nor good philosophy . . . neither its pipes nor its theories will hold water."

Genetic manipulation, the backbone of the green revolution, will be used to develop animals that are adapted to their particular environment. Most livestock breeds were developed to improve growth rate and (or) fibre production in management systems that minimised environmental constraints in order to maximise the expression of genetic potential. However, in environments with low production potential increasing emphasis will be placed on development of animals that are adapted to the environment with a suite of traits that causes them to have dietary preferences for the plant community, resistance to appropriate diseases and parasites, and tolerance to local climatic conditions. The importance of resistance to adverse environmental conditions have been demonstrated as important traits for affecting cattle production (Frisch & Vercoe, 1991) and the potential for genetic resistance to parasitism is also a possibility (Woolaston & Baker, 1996). Heritability for dietary preferences is less well demonstrated but does exist. Winder et al., (1996) reported heritability exceeding 50% for consumption of some range plants by Brangus cattle. Warren et al., (1983) showed that Spanish goat sire groups differed in their preference for low but not for high palatability shrub species. Heritability for percent composition of those species with significant sire effects was 30%. Juniper consumption by goats has also been shown to have a heritability of 28% (C. A. Taylor unpublished data). Both these are within the range of heritability for body weight and fibre diameter in sheep (Fogarty, 1995) suggesting that genetic changes in diet selection of a magnitude similar to those demonstrated for these production traits, are possible. The potential for using classical selection to produce lines of fruit flies (Drosophila melanogaster) with preferences for high energy or high protein diets has also been demonstrated (Wallin 1998). Previously the major limiting factor for making genetic progress in manipulating diet selection has been the lack of methods for screening populations of livestock species to identify those individuals with phenotypic differences in dietary preferences. However, there are currently several techniques being developed that will overcome this limitation including plant cuticular waxes (Dove 1992) laser-induced fluorescence (Anderson et al.1996) and near infrared reflectance spectroscopy (Walker et al., 1998). Eventually designer livestock adapted to accomplish management objectives and adapted to the environment will be available in much the same manner as has already been done in many crops and in the poultry industry. We believe that these "green livestock" will be the key to transforming what is currently considered by many non-pastoralists as an unsustainable use of rangeland ecosystems, and by some pastoralists as economically unsustainable production systems, into systems that meet the goals of both groups.

Currently, there are many under utilised technologies available that could greatly enhance the management of grazing in rangelands. Therefore, it is important that consideration be given to marketing and technical transfer systems that will increase adoption rates of existing technologies. Similarly, market research should be done to determine probable adoption rate and (or) product attributes that will enhance adoption before scarce research dollars are invested in the development of new technologies. Sustainable management of rangeland ecosystems, which has been demonstrated in many places on several continents, is possible by greater adoption of current technologies. New technologies can be developed that will aid in decision making and provide locally adapted livestock, which hopefully will increase profitability and reduce risk.

We gratefully acknowledge the financial support given by the Murray-Darling Basin Commission to one of us (KCH) to develop tactical management of Total Grazing Pressure.

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