Jill Landsberg, Craig D. James, Stephen R. Morton, Trevor J. Hobbs, Jacqui Stol, Alex Drew and Helen Tongway
CSIRO Division of Wildlife and Ecology
Biodiversity Convention and Strategy Section of the Biodiversity Group, Environment Australia, January 1997
ISBN 0 6422 7010 4
The current state of knowledge of the native flora and fauna in semi-arid and arid Australia is not comprehensive: most of the species of invertebrates surveyed during this study and a few species of plants were new to science. Nonetheless the surveys have shown that these rangelands support a rich array of native flora and fauna, despite being managed primarily for pastoralism. There are no exotic bird, reptile or invertebrate species and exotic plant species are only a small component of floristic diversity. However, they appear to be favoured by the provision of water for livestock that has accompanied pastoral expansion. The surveys also show that many native species are disadvantaged by the provision of water. For the more diverse and abundant plant and animal groups, an average of 15-38% of the species at each of the localities surveyed showed trends of declining abundance with proximity to water. A small but significant number of plant species was found only at reference sites that were much further from water than most pastoral land.
The results from this study are not comprehensive, but they do show consistent trends across a whole range of species, locations, vegetation types and seasons. They indicate an urgent need for better conservation management, but a more regional perspective is needed before the results can be extended for use in bioregional planning. It is possible that some species identified as decreasers in this study may be more abundant or secure in parts of the landscape or regions that were not surveyed. In addition, the degree of regional threat to decreaser species depends on the regional pattern of pastoral management: fewer species may be at risk in regions which include many areas remote from water or where stocking rates have been traditionally light compared with more closely developed regions.
Previous prescriptions for grazing management that promoted large numbers of closely-spaced water points have resulted in a severe imbalance in water-access across much of the rangelands. Most of the pastoral rangelands are now accessible to water-dependent livestock and water-remote habitat suitable for grazing-sensitive biodiversity has been drastically reduced. Selective reduction in the number of water-sources offers strong prospects as a strategic tool for improving the status of rangeland biodiversity. It is not without costs, however, and it may not be effective in all circumstances. Costs include the direct cost of de-commissioning water points (capping free-flowing bores, relocating troughs, etc.) and the indirect costs associated with production foregone because of reduction in the area accessible to livestock. Effectiveness is likely to depend on the extent to which grazing is controlled by the distribution of water points. This control may be overridden in very small paddocks, or within very heterogeneous landscapes, or in regions where rabbit grazing is widespread and severe. It will also depend on the potential for recovery of landscapes which are released from the grazing pressures associated with artificial sources of water.
Australia is party to international conventions obliging us to strive to conserve our biodiversity; the primary instrument for this goal is the National Strategy for the Conservation of Australia's Biological Diversity (NSCABD). The Commonwealth Government's Natural Heritage Trust aims to provide a source of funds to assist in the protection of biodiversity, native vegetation and threatened species. Further, the declining status of rangeland biodiversity has been identified as a significant issue in the recently released Draft National Strategy for Rangeland Management (DNSRM), which recognises that endangered native species are disproportionately represented in the arid and semi-arid lands. The NSCABD raised concerns about the impacts on biological diversity of widespread provision of artesian water in naturally dry areas (2.5.1 b) and the DNSRM cited preliminary results from our studies on artificial waters as an issue of particular concern because the work implied potential ongoing declines in significant proportions of species. This final report confirms the preliminary results cited in the DNSRM and, to reflect that concern, the following recommendations are framed to refer to specific actions and objectives in the NSCABD and the DNSRM.
The NSCABD acknowledged a need to reduce negative impacts on biological diversity arising from the use of artesian waters (2.2.2 e and 2.5.3 d). Strategic closure of artificial waters is becoming recognised as an important component of management of arid and semi-arid nature reserves; e.g. it has been included in the recently completed plan of management for the arid Mallee Parks of Victoria. It is also recognised as a potential legislative tool for encouraging the retention of native vegetation in rangelands outside nature reserves (DNSRM 4.3.4). Implementing piped reticulation systems for water distribution is an important component of the South West Strategy, an integrated management program for rangelands in southwest Queensland. Schemes such as this also offer scope for working with land managers, for example, to deliberately space waters so as to leave some areas relatively untouched, as areas of high conservation value outside conservation reserves (DNSRM 4.3) if suitable incentive measures, such as those reviewed in "Reimbursing the Future" (Young et al. 1996), can be implemented.
Both the NSCABD and the DNSRM emphasise the importance of managing biodiversity on a bioregional basis to take account of regional differences in the natural and social environment, and many of their objectives are couched in bioregional terms (NSCABD 1.2; DNSRM 4.1, 4.2, 4.3). To help meet these objectives, it is important to assess the extent of regional variation in provision of water sources, so that regions that should receive priority attention can be identified. It is also important to undertake further research to extend our gradient survey results to regional scales, in order to clarify the regional conservation status of the decreaser species we identified.
The NSCABD and the DNSRM both identify a need for development and implementation of cost-effective methods for baseline audits and long-term monitoring of biodiversity (NSCABD 4.1; DNSRM 4.1, 4.5). This is particularly important for lesser known groups which are generally considered to include invertebrates, fungi and micro-organisms (NSCABD 1.6.1). Our work indicates there are also knowledge gaps in the inventory of understorey plants in the rangelands. In addition to traditional taxonomic approaches to inventory (NSCABD 4.1.5) there is also a recognised need for the development of biodiversity indicator groups (NSCABD 4.1.7 c) and biodiversity attributes (DNSRM 4.5.1) for assessing environmental disturbance.
Within this policy context, our research conclusions lead us to us to propose the following recommendations. Some actions stand out as providing at least partial answers to clear problems. Further research is also highly desirable, but the need for it should not be seen as a barrier to implementing actions. Instead, research-oriented recommendations should be seen as providing tools for implementing action-related recommendations.
- Implement (with appropriate safe guards) a staged program of strategic closure of artificial sources of water in conservation reserves in pastoral rangelands, in recognition of the small proportion of pastoral lands remaining outside the influence of water and the probable damage to biodiversity stemming from widespread provision of water.
- Promote adaptive management experiments by land managers outside conservation reserves in pastoral regions, to test selective water-closure as a tool for achieving balanced production and conservation goals.
- Determine economic and ecological costs and benefits of alternate scenarios for achieving regional conservation goals including:
- strategic water closures to provide different designs of unwatered areas
- control of grazing areas using other means (fencing, stock management)
- Using this knowledge, devise appropriate incentives for pastoralists to conserve biodiversity. Note that cost-effective monitoring of biodiversity (points 7-9) is necessary for assessment of progress toward its conservation.
- Undertake a detailed assessment of the spatial distribution of existing artificial waters in the major rangeland bioregions of Australia, to identify bioregions for priority attention.
- Undertake strategic surveys in representative bioregions to determine:
- what proportion of regional biodiversity can be identified as decreaser species, and to what extent this is influenced by variation in landscapes and management history;
- what proportion of the regional area provides suitable habitat for the persistence of decreaser species; and
- what landscapes and habitats within the region need particular conservation emphasis.
- In monitoring and surveying rangeland biodiversity use cost-effective methods that:
- target the plant groups and animal taxa identified in our study as rich in species, efficient to sample and representative of a wide range of habitats and niches;
- are conducted relative to "reference sites" representing as closely as possible the state of the environment before its management for pastoralism;
- contribute to the development and maintenance of archival collections of lesser known groups, particularly invertebrates, but also understorey plants.
- Undertake research to identify biodiversity attributes for incorporation in assessment and monitoring programs. Based on our results we recommend:
- that classification schemes be developed to group species into "indicator response types" based on biological attributes and response to disturbance. These schemes should complement taxonomic identification in ways that clearly relate to the mechanisms of species persistence and the attributes of species at most risk.
- Undertake research to determine relationships between biodiversity and landscape pattern, in order to identify broad-scale, landscape-based surrogates for monitoring biodiversity.