Grazing management

Farmers make grazing management decisions based on subjective criteria and previous experience (Golluscio et al., 1999). Paddocks are grazed continuously (year-round), except on high altitude ranges grazed in summer (Borrelli and Oliva, 1999). Vast areas, with few paddocks, restrict the possibilities of controlling grazing, especially when paddocks include grazing sites with contrasting forage availability (e.g. meadows and arid steppes) (Golluscio et al., 1999).

Determining stocking rates is the most important decision in developing a grazing plan (Heady and Child, 1994). The National Institute for Agricultural Technology (INTA), Argentina, with the aid of GTZ (Deutsche Gesellschaft für Technische Zusammenarbeit), developed range evaluation methods, based on satellite imagery and field measurements, which provide objective information for the formulation of sound grazing plans. Improved management is based on adaptive management that consists of a planning-execution-monitoring -evaluation cycle (Borrelli and Oliva, 1999).

Traditional management caused continuous overgrazing in most of the region, which in turn led to general degradation (Oliva, Rial and Borrelli, 1995; Consorcio DHV, 1999). Del Valle (1998) estimated that 65 percent of Patagonia was seriously degraded, 17 percent was moderately degraded and only 9 percent was lightly affected. In no area was grazing impact negligible. The DHV report estimated that 75 percent of Patagonian meadows were severely degraded (Consorcio DHV, 1999). A few small-scale farmers have adopted the recommended practices, with good results in terms of both animal production and rangeland conservation (Borrelli and Oliva, 1999).

Sheep management

Severe winters and the importance of spring forage growth relative to other seasons led to a farming pattern of autumn mating and spring lambing. Shearing was traditionally done between November and January, but with increasing pre-lambing shearing (due to gains in lamb and ewe survival and wool quality), dates have shifted to September-October. Tally Hi and Bowen shearing promoted by PROLANA (SAGPyA, 2001) are now widespread. Sheep are eye-shorn two or three times annually, and lamb tails are generally docked during marking. Male lambs are castrated and marked shortly before being shipped to the abattoir. Scabies (sarcoptic mange) is the commonest sheep disease (Robles and Olaechea, 2001) but its impact is limited to a few areas and so the use of veterinary products to treat it is almost unnecessary.

Sheep breeds and genetic improvement

There are two dominant sheep breeds: Merino and Corriedale. Each is used in production systems with different relative emphases on wool or lamb production.

Fine-wool production systems

Merino flocks predominate in the provinces of Neuquén, Río Negro, Chubut and northern Santa Cruz, comprising almost 75 percent of all sheep in Patagonia; their distribution closely matches the distribution of drier environments, where meat production is limited by nutritional constraints and farming is oriented to fine wool production (mean fibre diameter: 20.5 microns). On these farms, wool sales can represent up to 80 percent of total farm income (Méndez Casariego, 2000). Patagonian Merinos were selected from old Argentine Merino strains, improved by the introduction of Australian Merino, mainly in the past three decades. The Argentine Merino Breeder Association (AMBA) has implemented a genetic improvement programme, including progeny testing of rams, with INTA's technical support There are about 50 Merino studs with pedigree records and several open nucleus flocks, which are inspected by AMBA (Mueller, 2001).

Lamb and fine-crossbred-wool production systems

Grass steppe rangelands of southern Santa Cruz and northern Tierra del Fuego have higher forage production and are therefore more suitable for meat production. In this area, Corriedales introduced in the mid-twentieth century have been very successful. Local stud breeders provide superior rams to commercial farmers. A progeny testing service for top sire evaluation is being conducted under INTA-GTZ direction and funding. Many meat breeds (Texel, Southdown and Hampshire Down) are being introduced to improve lamb traits such as growth rate, low carcass fat and improved carcass conformation (Mueller, 2001).

TABLE 4.3.
Vegetation shifts under grazing in Patagonia.

NOTES: (1) The order in which species appear is associated with their status in the plant community.

SOURCE: The table is a synthesis of state-and-transition catalogues developed for different biozones of Patagonia and compiled in Paruelo et al., 1993.

Evolution of patagonian grasslands over the last 40 years

Patagonian vegetation is generally described as having few adaptations to cope with grazing by domestic ungulates, since the entire region is thought to have evolved under conditions of light grazing by native ungulates (Milchunas, Sala and Lauenroth, 1988). Although this notion has recently been challenged by Lauenroth (1998), there is general consensus that vegetation throughout most of Patagonia has been modified significantly by sheep over the last century, particularly in the last 40-50 years (Golluscio, Deregibus and Paruelo, 1998; Paruelo et al., 1993).

Deterioration of grazed vegetation has usually been demonstrated by replacement of palatable grasses by unpalatable woody plants (Bertiller, 1993a). The severity of plant life-form replacements varies among biozones, depending on abiotic constraints within each ecosystem (Sala, Lauenroth and Golluscio, 1997; Perelman, León and Bussacca, 1997). The process of plant species replacement has been described for most of Patagonia's bio-zones following the conceptual model of “states-and-transitions” proposed by Westoby, Walker and Noy Meir (1989) for non-equilibrium rangeland ecosystems (Table 4.3). According to this model, plant communities shift between alternative steady states rather than progressing in a linear manner toward a predictable climax. Shifts in vegetation composition (transitions) are produced by particular combinations of biotic and abiotic stressors. In Patagonia, transitions in the plant community are frequently close-to-irre-versible and involve not only a reduction in forage biomass for livestock but also a decrease in water-use efficiency that leads to an overall decline in ANPP (Aguiar et al., 1996). In some instances, degradation involves permanent physical changes in soils, resulting in shifts in the soil texture of superficial layers (Oliva, Bartolomei and Humano, 2000).

Although alternative steady states of vegetation in Patagonia have been described with a reasonable level of detail, the factors that trigger transitions from one state to another have not been tested under controlled experimental conditions (Bertiller, 1993b). Overestimation of carrying capacity, uneven distribution of sheep in large pastures and year-long continuous grazing have been suggested as possible factors responsible for vegetation degradation over the last 50 years (Golluscio, Deregibus and Paruelo, 1998).

An analysis of peak sheep numbers in the province of Santa Cruz shows that pioneering sheep farmers did overestimate the carrying capacity of the system. This is especially true of operations on the semi -deserts of the central plateau (Unit Kg 11 in Figure 4.5), where stocking rates were consistently 60 percent above the estimated carrying capacity (Oliva et al., 1996) and the current sheep population has fallen well below the expected carrying capacity of the system (Cibils, 2001). Most of the variability in sheep numbers between 1931 and 1960 on the drier grass steppes north of the Straits of Magellan can be explained by the variation in MAP (r² = 0.97, p = 0.02; Cibils and Coughenour, 2001), a variable that has been shown to relate linearly to ANPP (Sala et al., 1988; Paruelo and Sala, 1995). After 1970, this relation disappears, giving way to a second period in which sheep numbers decrease despite an apparent phase of overall increase in MAP (Cibils and Coughenour, 2001). Interestingly, 1960-1970 was the driest decade in the century; there could have been a breaking point in the system sometime around or after this decade as a consequence of excessive stocking combined with prolonged droughts that caused a significant shift in the relation between rainfall (or ANPP) and sheep numbers (Cibils and Coughenour, 2001).

The spatial distribution of sheep grazing in very large pastures is very uneven and primarily related to the distribution of watering points (Lange, 1985). Sheep densities at a given point within a pasture can vary from 8 to 0.02 times the mean density assigned to the whole pasture (Lange, 1985). Although there have been few efforts to measure grazing distribution in Patagonian-type pastures, there is circumstantial evidence that confirms the occurrence of the grazing patterns described by Lange (1985). Heterogeneous grazing distributions generate local areas of degradation that can trigger severe erosion, particularly when highly-affected areas are sensitive sites, such as riparian meadows (Borrelli and Oliva, 1999; Golluscio, Deregibus and Paruelo, 1998).

Because sheep are selective grazers, continuous year-long grazing tends to intensify the pattern of uneven utilization. Grazing systems have been tested at several sites in the grass -steppe biome as a possible means of attenuating the undesired effects of sheep selectivity. The results of these trials, in terms of both animal production and range condition trend, were mostly comparable to the continuous moderately grazed system (Borrelli, 1999; Anchorena et al., 2000, but see also Paruelo, Golluscio and Deregibus, 1992). In most cases, the application of flexible moderate stocking rates (even in year-long grazing schemes) may be the most reasonable way to manage Patagonia's steppes for long-term sustainability.

Ongoing research, management, restoration and biodiversity maintenance activities

Research activities

A review of abstracts of both poster and oral presentations of current research in the arid and semi -arid ecosystems and published in the proceedings of recent meetings of the Argentine Ecological Association (April 2001 meeting) and the Argentine Association for Animal Science (October 2000 meeting) was undertaken to assess research trends. Approximately 30 percent of research in Patagonia is in the Monte region, close to 40 percent on the shrub and shrub-grass steppes and about 20 percent on the Patagonian grass steppe. The remaining 10 percent is regional-scale, greenhouse or riparian meadow (Plate 4.6) research. A common feature of the results reviewed is the relative scarcity of manipulation experiments; most results are derived primarily from observation-type studies. The most frequent issue is the influence of grazing by domestic herbivores on a number of vegetation and soil variables (over 30 percent of studies reviewed). Next come studies on the influence of water or nitrogen on ecosystems (13 and 10 percent of reviewed studies, respectively) and, thirdly, research on the impact of fire on ecosystems (10 percent of current studies). Research and surveys on wildlife account for 9 percent of abstracts, and studies of ecosystem processes such as primary productivity and decomposition are 9 and 5 percent of all studies, respectively. Satellite image analysis or simulation modelling are only used in about 4 percent of ongoing research activities.

Plate 4.6
Winter view of a riparian meadow or mallin.

V.A. DEREGIBUS & M.F. GARBULSKY

Grazing (mostly by sheep) is currently being studied in relation to its effect on: vegetation structure in the shrub-dominated ecosystems of Patagonia at either patch or landscape scale (Ares, Bertiller and Bisigato, 2001b; Cecchi, Distel and Kröpfl, 2001; Ciccorossi and Sala, 2001; Ghersa et al., 2001; Ripol et al., 2001); overall community plant diversity or population genetic diversity of endangered plant species at local spatial scales (Aguiar, Premoli and Cipriotti, 2001; Cesa and Paruelo, 2001; Cibils et al., 2000); riparian meadow productivity (Collantes, Stoffella and Pomar, 2001; Golluscio et al., 2000; Utrilla et al., 2000); the demography of native dominant tussock grasses (Weber et al., 2000; Oliva, Collantes and Humano, 2001); interspecific relations between shrubs (Cipriotti and Aguiar, 2001); shrub crown shapes (Siffredi and Bustos, 2001); soil nitrogen mineralization rates in relation to changes in vegetation composition (Anchorena et al., 2001); shrub recruitment in relation to soil compaction (Stofella and Anchorena, 2001); and microphytic crusts in the Monte shrub steppes (Silva et al., 2001). Finally, grazing is also currently being researched in relation to herbivore diets and lambing rates at regional scales (Hall and Paruelo, 2001; Pelliza et al., 2001). Water is the single most important factor regulating processes such as primary and secondary productivity in Patagonian ecosystems. Nitrogen dynamics is closely tied to moisture availability. Although there has been much research in the past decades addressing the use of water by different life forms (Sala, Lauenroth and Golluscio, 1997, and references therein), only recently have studies begun to address issues related to the joint effects of water and nitrogen. One of the few ongoing manipulative field experiments is being conducted in this area, studying the effects of drought on productivity and N mineralization, using rain shelters in the shrub steppe ecosystem (Sala, Yahdjian and Flombaum, 2001). Current studies on the influence of water (alone) include: effects of water deficit on the germination of an endangered grass species (Flombaum et al., 2001); simulation of competition for water and light in Festuca tussocks growing in a grass-forest ecotone (Fernández, Gyengue and Schlichter, 2001); effects of stem flow on soil water content beneath shrubs (Kröpfl et al., 2001); and Poa ligularis response to defoliation and water stress in a greenhouse experiment (Sáenz and Deregibus, 2001). Currently, nitrogen dynamics are being studied in relation to: the effect of litter nitrogen content of different plant life forms on soil N fractions in the grass-steppe ecosystems (Sain, Bertiller and Carrera, 2001) and the Monte shrub steppes (Carrera et al., 2001); effects of levels of soil nitrogen fractions on the segregation of male and female Poa ligularis individuals (Bertiller, Sain and Carrera, 2001); soil nitrogen mineralization rates in relation to grazing (Anchorena et al., 2001); decomposition rates of litter with different nitrogen content (Semmartin et al., 2001); and nitrogen use efficiency (together with water use efficiency) of 26 species of plants from Patagonian ecosystems (Golluscio, Oesterheld and Soriano, 2001).

Current studies on the effects of fire on Patagonian ecosystems mostly include monitoring of vegetation following natural wildfire outbreaks. Such studies include: descriptions of post-burn secondary succession patterns (Ghermandi, Guthmann and Bran, 2001; González et al., 2001; Rafaelle and Veblen, 2001); study of biotic and abiotic (including weather) conditions that promote wildfire outbreaks (Defossé et al., 2001; De Torres Curth, Ghermandi and Pfister, 2001); and effects of wildfires on survival of adult tussocks or seeds in soil seed-banks (Gittins, Bran and Ghermandi, 2001; González, Ghermandi and Becker, 2001). Almost all fire-related studies have been conducted either in the shrub-steppe ecosystems or the steppe-forest ecotones.

Current studies on wildlife in Patagonia include: surveys of animal numbers such as guanaco population numbers in relation to sheep density and forage availability (Baldi, Albon and Elston, 2001); calculations of Rhea densities using improved field methods (Funes et al., 2001); census of migratory bird species in southern Patagonia (Manero et al., 2001); predator-prey relations studying fox and European hare populations and diets of a number of predators of the shrub steppe ecosystems (Donadío et al., 2001; Novaro et al., 2001); habitat use by Rheas (Bellis et al., 2001); and deer reproductive ecology in relation to droughts (Flueck, 2001).

ANPP of Patagonian ecosystems is currently being studied in relation to range condition (Bonvissuto, González Carteau and Moraga, 2001), grazing system (Collantes, Stoffella and Pomar, 2001), competition among plant life-forms (Schlichter, Fernández and Gyenge, 2001), or forage production (Bustos and Marcolín, 2001). Satellite image analysis using NDVI at regional scales continues to be used as a tool to estimate ANPP (Fabricante et al., 2001). Decomposition is being studied at regional scales either along rainfall gradients (Austin and Sala, 2001), or in relation to a species' successional status within the plant community and its litter N content (Semmartin et al., 2001). At local scales, decomposition of forbs is being studied in relation to increased ultravio-let-B radiation, derived from the thinning in the ozone layer at high latitudes in the southern hemisphere (Pancotto et al., 2001).

A number of ongoing research projects include the study of aspects of the biology of a few shrub species, namely: shrub secondary compounds (Cavagnaro et al., 2001; Wassner and Ravetta, 2001); within-genus shrub genetic diversity (Bottini et al., 2001); the effects of pruning or cloning treatments (Arena, Peri and Vater, 2001; Peri, Arena and Vater, 2001); segregation of shrub species in relation to rainfall gradients (Marcolin and Bustos, 2001); allocation patterns or morphological attributes in sympatric shrub species (Stronatti et al., 2001; Vilela, Agüero and Ravetta, 2001); and factors influencing insect herbivory in shrubs (D'Ambrogio and Fernández, 2001; Villacide and Farina, 2001).

A few researchers are studying seed biology or germination dynamics in relation to presence of microphytic crusts (Villasuso et al., 2001), litter accumulation (Rotundo and Aguiar, 2001), plant life-form (Vargas and Bertiller, 2001), or grazing (Oliva, Collantes and Humano, 2001). Finally, there are a small number of studies addressing miscellaneous issues ranging from secondary succession patterns on cultivated rangelands to endophyte fungi in a series of grasses from Patagonia (Cibils, Peinetti and Oliva, 2001; Vila Aiub et al., 2001).

Management activities

The need for management tools to regulate grazing and slow down rates of vegetation deterioration has led to the development of a number of vegetation-based pasture assessment routines over the past decade. Most of these (developed primarily by INTA) are being used in almost all provinces of Argentinian Patagonia, either by government agencies or private consultants (Borrelli and Oliva, 1999; Nakamatsu, Escobar and Elissalde, 2001; Bonvissuto, 2001; Siffredi et al., 2002).

The rangeland assessment methods used in the provinces of Río Negro and Chubut (generally areas of shrub-steppe vegetation) basically involve: the measurement of vegetation cover (forage species cover, in particular); and estimation of ANPP using annual precipitation data (see appendix in Golluscio, Deregibus and Paruelo, 1998). The routine used in Santa Cruz (generally applied to grass -steppes and semi -deserts) involves: the measurement of forage biomass (short-grasses, sedges and forbs); and grass key species stubble heights (Borrelli and Oliva, 1999). The output of all methods is an estimate of sheep carrying capacity. Whereas the biomass-based method involves yearly monitoring, the vegetation-cover-based methods do not. In all cases, however, assessment routines are fairly labour-intensive and therefore, in some instances, their use becomes economically unviable. A number of efforts aim at reducing labour costs by using up-to-date technological tools to facilitate a more widespread adoption of range assessment routines.

Scientists at the Universidad de Buenos Aires (IFEVA-UBA) are using Landsat TM image analysis to derive primary productivity estimates from NDVI values to calculate carrying capacity at individual pasture scales (Paruelo et al., 2001). Another approach that is currently being investigated by INTA scientists is the use of either empirical or mechanistic simulation models to predict year-to-year fluctuations in forage availability and adjust animal numbers accordingly. The empirical approach involves the use of seasonal rainfall data to make stocking rate adjustment decisions following within-year patterns of drought or moisture surpluses (Rimoldi and Buono, 2001). The mechanistic approach includes the parameterization of existing mechanistic spatially-explicit models that allow landscape -scale simulation of primary productivity and grazing at a number of different time scales of interest. This approach involves the use of satellite image analysis to calibrate productivity estimates (Ellis and Coughenour, 1996).

In recent years there has been increasing demand for long-term range monitoring tools at scales ranging from individual pastures to landscapes and ecosystems. Current range assessment routines cannot (in most cases) provide useful long-term monitoring information. Furthermore, land uses other than grazing, such as oil extraction or other mining, require the development of tools tailored to the type of environmental disturbance they produce. Landsat TM satellite image analysis has been used over the last decade to make an inventory of the state of Patagonian rangelands (degrees of desertification) in several key areas of the region (del Valle et al., 1995). As the availability of satellite images increases, much of the installed capabilities in research institutes throughout the region will be used as a basis for multi-temporal monitoring of rangelands at regional scales. At smaller spatial scales, Ares et al. (2001a,b) are developing methods of monitoring changes in vegetation structure under grazing at landscape scales in the Monte shrub steppes using aerial photographs and spatially-explicit simulation modelling.

Restoration activities

Restoration activities have traditionally been restricted to the stabilization of sand accumulations in severely eroded areas, using special cultivation techniques and generally involving the seeding of rhizomatous grasses of the genus Elymus (Castro, Salomone and Reichart, 1983). Almost all of these activities have been conducted successfully, by both INTA and the Board of Agriculture (Consejo Argario Provincial) of the Province of Santa Cruz. Although this and other variants of grazing -related restoration activities continue (Magaldi et al., 2001; Becker, Bustos and Marcolín, 2001; Rostagno, 2001), current efforts in this field have mostly shifted toward the reclamation of disturbances associated with the mining and oil industries (Baetti et al., 2001; Ciano et al., 2001).

Currently, restoration activities involve: the developing or adaptation of technologies to promote in situ biodegradation of oil (especially in situations where oil spills affect valuable riparian meadow habitats) (Luque et al., 2000; Nakamatsu et al., 2001b); conducting conservationist tillage in areas of topsoil decapitation (Ciano et al., 2000); and selection of native ruderal species for revegetation of highly degraded environments (Ciano et al., 1998). Shrubs of the genera Atriplex, Grindelia and Tamarix are being used in many current restoration projects, with establishment rates of almost 70 percent (Ciano et al., 2001).

Most land reclamation activities are currently in a region with some of the oldest oil fields of southern Patagonia (northern Santa Cruz and southern Chubut), and lie mostly within the shrub-grass steppes and semi -desert bio-zones. Recently, there has been a rapid growth in the demand for further land reclamation technology by a number of large mining projects in the southern semi-desert biozone (Province of Santa Cruz), a need that is currently being met by local Universities. Mine reclamation will possibly be one of the fastest growing applications of restoration in certain areas of Patagonia during the decades to come.

Biodiversity maintenance

There are 1 378 recorded vascular plant species in arid and semi -arid Patagonia (Correa, 1971), almost all of which are angiosperms and close to 30 percent of which are endemic species. Of all species recorded in the Flora of Patagonia, there are about 340 exotic plants that are restricted to areas surrounding houses, pens and roads, but they are, in all cases, unable to become part of the native steppe plant communities (Soriano, Nogués Loza and Burkart, 1995). Due to its relatively high level of endemism, Patagonia has been recently included as a “Centre of Plant Diversity ” (CPD Site A46) in a worldwide diversity conservation project under the auspices of the Museum of Natural History of the Smithsonian Institution (USA), IUCN and WWF (Smithsonian Institution, 1997).

Sheep grazing has been shown to reduce vascular plant diversity in several Patagonian ecosystems, both by promoting local extinction of preferred forage plants and by altering the relative abundance of species in the grazed plant communities (Schlichter et al., 1978; Perelman, León and Bussacca, 1997; Oliva et al., 1998; Cibils et al., 2000; Cesa and Paruelo, 2001). Soriano, Nogués Loza and Burkart (1995) assembled a list of 76 endangered species in Patagonia, of which a quarter are grasses, on the basis of the plant species replacement patterns under grazing described by several authors in Paruelo et al. (1993). Although the severity of extinction risk is not equal for all species listed by Soriano, Nogués Loza and Burkart (1995), this list would clearly be a good starting point to guide conservation efforts. Current efforts to prevent overgrazing may contribute to slowing down the rate of loss of endemic species, although these programmes do not address the biodiversity issue explicitly. Unfortunately there are few nature reserves in arid and semi -arid Patagonia, although many of the National Parks along the Patagonian Andes include areas of steppe-forest ecotone (Villamil, 1997). There are currently only two reserves well within arid and semi-arid Patagonia, which account for less than 0.1 percent of the region, namely Laguna Blanca National Park (about 110 km² in the province of Neuquen, created in 1940), and Bosques Petrificados Natural Monument (100 km² in the province of Santa Cruz) (Villamil, 1997).

Seed production

Although experimental sowing of native species has been successful in southern Patagonia, forage productivity of native plant species under cultivation was lower than that of introduced grasses and legumes (Mascó, 1995). Reseeding trials on degraded land were conducted in the sixties by an INTA-FAO Project (Molina Sanchez, 1968). Reseeding was biologically successful at many sites, but productivity under low moisture regimes was considered limiting for commercial application (Mascó and Montes, 1995), mostly because sheep production was the only activity considered in the economic analyses.

These results constrained local seed production to limited areas, namely: harvesting small stands of Elymus sabulosus and E. arenarius in western Santa Cruz and south-central Chubut to obtain seed for sand dune fixation; setting up two active gene banks in the region, which not only stored seed collections from natural stands, but also multiplied some material in experimental plots (Montes et al., 1996); and developing oil spill reclamation technology by scientists at INTA's Research Station in Trelew (Chubut), which included the setting up of a nursery to multiply native shrub germplasm such as Atriplex lampa to provide plantations at disturbed sites. There is currently no public or private funding for seed production of native species nor for rehabilitation of desertified areas with native plant species.

Recommendations and lessons learned

Most of the grazing management and ecology research in Patagonia has been conducted by INTA and institutions such as CONICET and the University of Buenos Aires. Beginning in the 1980s, pasture condition guides were proposed for evaluating different vegetation types. Initially, grazing treatments were recommended based on range management literature. The lack of understanding of soil-plant-animal relations thwarted further progress. Soil and vegetation responses to different grazing treatments were unknown. The nutritional and behavioural aspects of the grazing process were ignored. Realizing this, two long-term grazing trials were designed and conducted by INTA, one in SW Chubut (Siffredi et al., 1995) and one in southern Santa Cruz (Oliva et al., 1998).

Many rangeland evaluation techniques and recommended grazing strategies were thereafter based on the findings of INTA grazing trials. Short-grass biomass and key species height were used to assess carrying capacity and grazing intensity, respectively, in grass-dominated rangelands of Southern Patagonia (Borrelli and Oliva, 1999; Cibils, 1993). Pastoral Value (Daget and Poisonnet, 1971), a method based on step-point cover data, was proposed for shrubland steppes in northern Patagonia (Elizalde, Escobar and Nakamatsu, 1991; Ayesa and Becker, 1991)

In 1989, INTA and GTZ launched a joint project to control and prevent desertification in Patagonia, which was implemented during the 1990s. This project increased societal awareness regarding desertification problems, and 3 percent of all sheep farmers in the region adopted the techniques recommended. Since the early 1990s, interaction between farmers and range scientists has increased and has resulted in the application of grazing plans at an individual farm scale. This was possibly the birth of range management as a practical discipline in Patagonia. After more than two decades of research activities and one decade of practical experience, we have both recommendations and many new questions.

Adaptive management - the Santa Cruz example

The designing of a grazing plan with little research background and a lot of variation coming from weather, soils, vegetation and previous grazing management is highly problematic. Stuart-Hill (1989), working in South Africa, stated that it is almost impossible to define “proper” management in a one-step plan. He proposed adaptive management as the only way to deal with urgent decisions and limited knowledge rangelands. Our experience confirms his hypothesis: proper management is a process rather than a single decision.

In Santa Cruz, for instance, many farms began to apply adaptive management in the 1990s (Borrelli and Oliva, 1999) (Figure 4.6). Range evaluation methods were used to support stocking rate adjustments and other grazing allocation decisions. Annual monitoring of weather, vegetation and animal production variables at the level of individual paddocks provided feedback information that allowed the implementation of opportunistic grazing plans and corrections for possible errors in the initial stocking proposal. Farmer objectives and perceptions were very important in the planning process. Opportunistic grazing plans in southern Santa Cruz proved to be effective in terms of optimizing sheep production. Variable stocking rates were used to take advantage of favourable years and also to reduce the impact of periodic droughts, although it is not clear whether variable stocking rates were more beneficial to vegetation than moderate fixed stocking rates. Unfortunately, the vegetation attributes used as criteria for stocking rate adjustments (short-grass biomass and key species height) were inadequate for long-term monitoring.

The information collected on many sheep farms in southern Patagonia was used by INTA Santa Cruz to create a regional database. This proved to be a useful and simple tool to analyse the internal variation of carrying capacity estimations within each natural environment and grazing site. Many inferences made from small paddock grazing studies were confirmed at the commercial scale. This information on animal and vegetation responses to grazing management was important to calibrate stocking rate recommendations across range types in Santa Cruz (Kofalt and Borrelli, unpublished data).

Figure 4.6
Adaptive management for sustainable sheep production. (Based on Borrelli and Oliva, 1999)

The value of simple or flexible stocking strategies

Grazing management practices in Patagonia can be classified in terms of complexity (Table 4.4). The shift from a subjective, low-knowledge-level input, continuous stocking scheme (level 0), to an objectively-based, moderate and flexible continuous stocking strategy (level 1) promotes the greatest progress in grazing management (Borrelli and Oliva, 1999). Further increases in management complexity or sophistication can be expected to have less impact, at least in the drier and homogeneous environments of Patagonia. Level 1 recommended procedures have proved highly efficient in eliminating generalized continuous overgrazing (Borrelli and Oliva, 1999), identified as the most important cause of range degradation elsewhere (Heady and Child, 1994).

TABLE 4.4
Complexity levels of grazing management in Patagonia.

SOURCE: Golluscio et al., 1999, who adapted from a 1993 unpublished report.

Simple Level-2 rotational grazing systems (Table 4.4) were tested in southern Patagonia, but the advantage of changing from Level 1 was not evident (Borrelli, 1999). Only opportunistic rest of some paddocks and fencing of meadows proved to be worthwhile “sophistication” in grazing management. Intensive grazing of fenced meadows showed impressive results in terms of sheep production in NW Patagonia (Giraudo et al., 1996).

More specialized grazing systems (Level 3-type) are regarded as promising by researchers of the University of Buenos Aires on a large farm in NW Chubut, Argentina (Paruelo, Golluscio and Deregibus, 1992). The generalized adoption of these systems is limited by: scarce information regarding responses in other environments; the limited availability of paddocks for complex rotations; and the lack of managerial skills of most farmers. In the last decades there has been a debate in the range management literature about grazing systems (Kothmann, 1984) and the value of the optimal stocking rate concept (e.g. Ash and Stafford-Smith, 1996; Stafford-Smith, 1996). As an example,continuous moderate grazing has been shown as beneficial for combating undesirable shrub invasions (Westoby, Walker and Noy Meir, 1989). Many authors have considered that defoliation frequency was more important than defoliation intensity for proper grazing management, and proposed specialized grazing systems (Kothmann, 1984). Stafford-Smith (1996) pointed out that both temporal and spatial heterogeneity limit the possibility of controlling grazing intensity in continuous grazing treatments. However, for Patagonian conditions, these debates are stimulating but somewhat theoretical. Simple and flexible grazing strategies proved to be useful to optimize sheep production and to prevent rangeland deterioration for most situations. Severe restrictions limit the practical application of more complex grazing strategies.

Conflict between short- and long-term production

Many economic activities exhibit conflicts between short-term and long-term profitability when environmental impact is considered. Maximum short-term profits are attained by methods that may be harmful to natural resources, especially if hidden environmental costs are, as usual, not included in economic calculations. In this case, less profitable procedures in the short-term might be chosen for environmental protection, or environmental costs should be included in the economic analysis.

This seems not to be the case for Patagonian sheep farming systems. While overgrazed farms are likely to produce not only more but also finer wool, nutritional restrictions will decrease lambing rates and survival of adult sheep, promoting decreases in overall meat sales. If overgrazing occurs in the most arid biomes, reproduction and survival is depressed beyond the equilibrium point of the flock and sheep population numbers decline (Golluscio et al., 1999). A properly managed sheep farm sells 24 to 44 percent of the herd annually (depending on the natural environment), whereas sales from overgrazed farms range from zero to 15 percent (Borrelli et al., 1997). Consequently, sound management pays off in the short term, even using conventional economic analysis. This becomes more evident for mixed lamb and fine-crossbred-wool production systems, but is also valid for fine-wool production systems.

The role of Decision Support Systems

The availability of computers broadens the possibilities for environmental assessment and management by range technicians. The joint INTA-GTZ project, mentioned above, introduced satellite imagery processing facilities and skills in Patagonia. The use of Landsat TM images was adopted as a cost- and time-efficient service to help make accurate inventories for rangeland surveys. In some areas, carrying capacity could be estimated directly from Landsat TM Images (Oliva et al., 1996). In others, image processing provided accurate range site maps and useful information to guide field sampling. Geographical Information System (GIS) technology was used in 1994 to combine satellite information with other data sources, such as soil maps, climatic data, property boundaries and other significant variables. For vast and isolated regions such as Patagonia, where farms cover big areas that are often hard to access with vehicles and where there are few trained people to conduct range evaluations, this technology multiplies human power and reduces operation costs.

Decision Support Systems (DSS) are clearly a new dimension for range management. Adaptive management information at the individual farm level could be loaded into a GIS database. Modelling would provide integration of different sources of information, to assist range managers and scientists to predict probable outcomes of specific problems at farm and regional scales, such as: flock allocation, mixed grazing, native flora and fauna conservation, spatial heterogeneity of grazing, long-term vegetation changes, economic evaluation of grazing strategies, and many other parameters (Bosch et al., 1996). Feedback information from associated farmers would be used to improve the power of predictive models. The development of DSS should increase the accuracy and soundness of grazing management strategies and also allow for further reduction in the labour and time costs associated with range evaluation and management.

Priorities for development programmes and research

Development programme priorities for Argentinian Patagonia over the next five years, as set out by INTA (Carlos Paz, pers. comm.) involve developing or adapting technology for: sustainable sheep farming systems (including the development of eco-certification protocols); management and reclamation of degraded grazing land, in particular areas that have been severely disturbed by mining or oil extraction; regional GIS to develop DSS; genetic improvement of ultra-fine Merino sheep and Angora goats (including the use of biotechnology); and improvement of wildlife use (guanacos and rheas).

Sustainable sheep farming priorities include both the development of ultra-fine Merino wool production systems, especially in the provinces of Chubut, Río Negro and Neuquén, and the improvement of meat production systems on sheep farms of the grass -steppe biozone, either along the Andes foothills or on the Magellanic steppes in southern Santa Cruz and northern Tierra del Fuego. The latter include the development of quality protocols. Rangeland management and reclamation priorities include the development of routines for long-term monitoring of pasture vegetation, the improvement of technology to reclaim old mining and oil field areas, areas severely overgrazed by sheep (with particular emphasis on riparian meadow ecosystems), and the development of GIS to run DSS at both regional and single-farm scales (INTA-CRPS, 2001b; INTA-CRPN, 2001). Besides these main lines of development, agrotourism programmes will also continue to be developed, especially in areas with outstanding scenic values and adequate infrastructure support.

Research priorities are obviously related (but not limited) to development priorities for the region mentioned above. The main priorities as stated by the Secretaría para la Tecnología, la Ciencia y la Innovación Productiva (National Science and Technology Department) (one of the few local science and technology funding agencies) for the next five years are (SETCIP, 2000): impact of climate change at regional scales; study of ozone-layer dynamics and the consequences of increased ultraviolet radiation levels; catchment conservation and management for improved soil and water quality; evaluation and preservation of biodiversity; improvement of ecological risk assessment, including the development of monitoring systems; studies regarding appropriate use by tourism of natural reserve areas; improvement of sustainable sheep and goat production, including the development of quality protocols; production of organic foods; and study of rural and urban labour conditions.

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