Rangelands Condition

Historically, there has been no widely used or accepted system for assessing the condition of rangelands in northern Australia. Consequently, there is a generally poor understanding of vegetation change and its consequences for long-term productivity and stability in the northern Australia pastoral industry. The state and transition approach to understanding vegetation dynamics has recently been put to use in the northern rangelands as a communication tool and for identifying gaps in knowledge in research. State and transition models are also being used in an integral computer-based system to assess the spatial variability in the condition of grazing lands and then to evaluate the implications (environmental and economic) of the outcomes of alternative management scenarios. If state and transition models are to used more effectively in the management of extensive grazing lands, the question of paddock heterogeneity and uneven grazing distribution needs to be addressed.

The potential cattle carrying capacity of Kimberley rangelands has been reduced from an estimated potential of around 1 million cattle units by as much as 30 to 40% as a result of declining range condition. However, while cattle numbers were undoubtedly excessive in some areas, the area of severely degraded and eroded rangeland in the region is relatively small. While some pasture types are defined as being in poor range condition, others pasture types remain in close to pristine condition. An analogous situation exists in parts of the Northern Territory, particularly the Victoria River District. Uneven cattle grazing patterns are commonly associated with reduced carrying capacity. Some preferred pasture types are constantly overgrazed, other pasture types are only lightly used. Concentrations of feral animals exacerbate the problems associated with this preference for one community or species over another. Therefore the impact of this localised degradation is often a symptom of more fundamental problems associated with uneven grazing patterns. Yet, since localised areas of degradation occur within larger good condition areas its impact is wider, and severely reduces the ability to graze the total area. Moreover, isolation of degraded areas merely moves the problem to another locality, as the fundamental problem of spatially uneven grazing pressure remains unresolved. Under extensive grazing systems, stocking large paddocks at the carrying capacity is only the most preferred pasture type, foregoing the carrying capacity of the often much larger but less preferred types avoids the problem. This strategy has a high opportunity cost in a large proportion of seasons. Another alternative is to fence along pasture type boundaries, and so permitting each pasture type to be stocked at its own capacity. But, both initial capital expenditure on fencing and on-going maintenance are expensive. Since the gross value of per unit area of the rangeland is low, neither of these options is readily adopted by land managers. Concurrently, in terms of its future potential productivity, the rehabilitation of very poor condition or degraded rangeland is often uneconomic. This encourages prevention of degradation rather than rehabilitation. A preferred option to addressing this problem, and one that may be more commercially acceptable to managers, would be modify the cattle grazing distribution to the extent possible by low cost means, and so making forage use more uniform across the landscape, while concurrently monitoring the grazing impact on the more preferred pasture types to ensure that they are not being overused. By partially mitigating the effects of spatially uneven grazing pressure and strategically spelling areas based on identified soil and vegetation indicators, a more uniform and sustainable grazing pattern would exist, permitting more profitable and sustainable production. Moreover, a more uniform cattle grazing pattern could improve cattle diet, and hence cattle performance. Therefore, the long-term economic sustainability of the extensive cattle industry could be improved through the better management of the rangeland resource.

Plants are relatively sensitive to many of the pressures acting on rangeland biodiversity and also relatively amenable to measurement. Metrics based on plants therefore have considerable potential as highly efficient indicators of rangeland biodiversity condition and should be included in biodiversity monitoring frameworks. A hierarchical approach that incorporates low intensity, broad-scale monitoring to provide context and high intensity local-scale monitoring to provide an understanding of processes is recommended. Seven of the eleven core set of indicators recommended by the National Land and Water Resources Audit (NLWRA) rely on plant-based metrics. These are: progress towards an adequate and representative reserve system, extent of clearing, cover of native perennial ground layer vegetation, the distribution and abundance of exotic plant species, the distribution and abundance of fire sensitive species, and the distribution and abundance of grazing-sensitive species. Case studies of thecurrent state of knowledge about the seven indicators in the Gascoyne-Murchison Strategy area and Cape York Peninsula showed it would be possible to monitor most of them at the regional scale. However, current monitoring programs fail to achieve that. The case studies also identified two possible additions to the set of indicators: explicit indicators of grazing pressure and fire regimes and explicit inclusion of minimally disturbed reference areas to provide a standard against which to assess the biotic integrity of areas under pressure (A).

Regional inventory and condition surveys in the rangelands of Western Australia aim to provide comprehensive description and mapping of the biophysical resources of the region together with an evaluation of the condition of the soils and vegetation. The reports contain information which can be used to plan sustainable land management at the subcatchment, lease or paddock scale and survey inventory enables location of land types of particular land use or conservation value.