Biodiversity
The use of invertebrates for biodiversity monitoring in Australian rangelands, with particular reference to ants
A review of research using invertebrates, particularly ants, as bio-indicators in Australian landscapes demonstrates that they can be powerful environmental monitoring tools because of their abundance, diversity and functional importance, their sensitivity to perturbation and the ease with which they can be sampled. Vertebrates, by contrast, are too mobile, generalised or uncommon to be effective indicator taxa. In particular, ants have proven to be effective biological indicators of mine site rehabilitation works. A case study of a pilot rangeland biodiversity monitoring program at Cobar NSW indicates that ant species abundance, diversity and distribution are highly responsive to rangeland management. Woodland and grassland ant communities indicate clear gradients in relation to rangeland condition. Despite the progress using ants as bio-indicators, there are a number of outstanding research and development priorities for using them in rangeland monitoring. These include documenting the extent to which ants reflect the response of invertebrates more generally, identifying the most appropriate sampling protocols to achieve reliable results, improving ant identification technologies, and simplifying the collection of ant data (A).
Biodiversity monitoring in the rangelands: a way forward, vol 1
A technical expert workshop held from 29 October to 1 November 2002 in Alice Springs NT aimed to identify knowledge gaps in the understanding of biodiversity monitoring in the Australian rangelands, to assess available tools and techniques for biodiversity monitoring and their applicability to rangeland conditions, to develop a manual of well-tested approaches to support planning of biodiversity monitoring programs, to develop a framework for monitoring change using expert knowledge to support adaptive management, and to develop a toolbox that has the capacity for measurable and meaningful benchmarking of the effectiveness of natural resource management (NRM) programs. Key initiatives arising from the workshop include a 'how to' manual describing the basic principles and delivery framework for biodiversity monitoring in the rangelands, and an e-network for planning biodiversity monitoring (A).
Monitoring rangeland biodiversity: plants as indicators
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).
Weeds and the monitoring of biodiversity in Australian rangelands
Weed invasion is widely recognised as a major threatening process for a wide range of ecosystems around the world. Australian rangelands already support a large number of alien plant species in a variety of growth forms, but in general their impact on biodiversity is poorly documented. Because weeds have the potential to alter any aspect of ecosystem structure and function there is real value in monitoring how biodiversity responds to weed invasions to enable the development appropriate weed management strategies. Monitoring the abundance, distribution and growth forms of weeds in rangelands is likely to be a useful indicator of rangeland condition. An overview of the nature of the current and future threat posed by invasive plant species in the rangelands considers how they affect rangelands systems, particularly the biodiversity that rangelands support and discusses the significance of invasive species for the monitoring of rangeland biodiversity (A).
Characterisation and assessment of rangeland resources
A project to characterise and assess rangeland resources conducted a biophysical and socioeconomic inventory of the Ord River catchment in the East Kimberley WA. The tools and capacity developed during the project provide a basis for implementing monitoring programs to assess future trends in rangeland resources. The socioeconomic profile can be used to assist in regional land use planning and management. An assessment of current biodiversity data serves as a precursor to a regional conservation plan and enables the identification of gaps to target future resource allocation. The project also developed a methodology for mapping land units that produces maps of high quality and resolution more cost effectively than traditional field-based methods. Interactive computer-based software, Vegmachine, was also developed to monitor rangeland condition using remote sensing. The results of the project provide a sound basis for an improved understanding of the East Kimberley?s rangeland resources, and the impact of intensified production (A).
Incorporating biodiversity monitoring into rangeland condition assessment.
Caption title. At head of title: Native vegetation. Principal investigator: Alaric Fisher. Host organisation: Tropical Savanna Management CRC. Duration of project: September 2001 to December 2003.
Building Grass Castles: Integrating Ecology and Management of Australia's Tropical Tallgrass Rangelands.
The tropical tallgrass rangelands of Australia are declining in condition in response to increased grazing pressure. However, large areas are still in good condition and many of the deteriorated areas are not yet irreversibly damaged. Increases in grazing pressure have been associated with the loss of perennial grasses, woody weed invasion, and increased run-off and soil loss in some areas. The population dynamics, diet selection patterns, defoliation responses of the perennial grasses and impacts of fire are outlined and ways this understanding can be incorporated into management are presented. The perennial grasses are sensitive to defoliation and can only be lightly utilised. Annual utilisation rates should not exceed 25% in areas of moderate and high fertility and this threshold'safe'level decreases to 15% on infertile soils in the monsoon zone of the north and north-west. Spelling pastures during the wet season, when they are particularly sensitive to defoliation, may enable utilisation during the rest of the year to be increased. Such a grazing regime allows fuel accumulation, increasing the opportunity for use of fire in managing exotic woody weeds and the treetshrub layer. Fire can also be used to improve animal distribution and reduce the formation of patches which are prone to soil degradation. Sown pastures and tree clearing can be used to increase carrying capacity and improve flexibility in the management of native pastures but careful consideration needs to be given to these improvements to prevent problems such as salinisation and unwanted spread of exotic pasture plants. One of the difficulties in developing recommendations relevant to management is that most of the ecological understanding is at the plant and plant community scale but most problems occur at the paddocWlandscape scale where our knowledge base is limited. Future work should focus at this large spatial scale so that ecological principles derived from a range of scales can be better integrated into guidelines more appropriate to extensive management of tropical tallgrass rangelands. Key words: grazing, population dynamics, defoliation, diet selection, fire, grass decline