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The Effects of Artificial Sources of Water on Rangeland Biodiversity

Final report to the Biodiversity Convention and Strategy Section of the Biodiversity Group, Environment Australia

Jill Landsberg, Craig D. James, Stephen R. Morton, Trevor J. Hobbs, Jacqui Stol, Alex Drew and Helen Tongway
CSIRO Division of Wildlife and Ecology
January 1997

Published by Environment Australia and CSIRO
© Commonwealth of Australia, 1997
ISBN 0 642 27010 4

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"Once I was shown a little corner, a long way from the nearest water, which had managed to survive in something like its virgin state. It was a sight for sore eyes, and a very useful indication of the extent of the changes which had taken place since the white man settled the land. There was actually grass about, and the foliage of the shrubs grew down to the very ground; and I saw little bushes here which had practically vanished from the general landscape."

from Francis Ratcliffe "Flying Fox and Drifting Sand" Published in Australia by Halstead Press, Sydney (1951; pp 208-9). First published in England in 1938.

Contents

• Executive summary
• List of tables
• List of figures
• Introduction and methods
  • 1.1 Water, grazing and biodiversity in the rangelands
  • 1.2 Study design
  • 1.3 The gradients
    • 1.3.1 Locations
    • 1.3.2 Descriptions
      • 1.3.2.1 The NT mulga gradient
      • 1.3.2.2 The NSW mulga gradient
      • 1.3.2.3 The Qld mulga gradient
      • 1.3.2.4 The Qld gidgee/ chenopod gradient
      • 1.3.2.5 The WA chenopod/acacias gradient
      • 1.3.2.6 The SA chenopod/myall gradient
      • 1.3.2.7 The SA chenopod gradient
      • 1.3.2.8 The WA chenopod gradient
    • 1.3.3 Illustrations
    • 1.3.4 Potentially confounding influences
    • 1.3.5 Timing and seasonal conditions prior to surveys
  • 1.4 Survey methods
    • 1.4.1 Stratification of sampling at sites
    • 1.4.2 Assessment of flora
      • 1.4.2.1 Plant cover
      • 1.4.2.2 Species identification
      • 1.4.2.3 Plants growing in the understorey
      • 1.4.2.4 Plants growing in the overstorey
      • 1.4.2.5 Plants in the soil seedbank
      • 1.4.2.6 Overlap between plant groups
    • 1.4.3 Assessment of fauna
      • 1.4.3.1 Birds
      • 1.4.3.2 Reptiles and small mammals
      • 1.4.3.3 Invertebrates
  • 1.5 Statistical analysis
    • 1.5.1 Analysis of cover
    • 1.5.2 Analysis of species richness
    • 1.5.3 Analysis of species composition
      • 1.5.3.1 Species response groups in diverse, abundant groups and taxa
      • 1.5.3.2 Response types for individual species in less diverse or abundant taxa
    • 1.5.4 Analysis of species found at one site only
  
  
• 2 Diversity and abundance of flora and fauna
  • 2.1 Numbers of species and individuals
  • 2.2 Variation among gradients
    • 2.2.1 Effect of vegetation type and season
    • 2.2.2 Plant species represented in the seedbank compared with the field
    • 2.2.3 Exotic species
    • 2.2.4 New species and range extensions
      • 2.2.4.1 Plant species
      • 2.2.4.2 Invertebrate species
  • 2.3 Conclusions
    • 2.3.1 Richness and state of knowledge of biota
    • 2.3.2 Sampling efficiency
  
  
• 3 Analysis of biodiversity change along gradients
  • 3.1 Change in plant cover along gradients
  • 3.2 Change in species richness along gradients
  • 3.3 Change in species composition along gradients
    • 3.3.1 Species response groups in diverse, abundant groups and taxa
    • 3.3.2 Proportions of species in different response groups
    • 3.3.3 Contribution of exotics to response groups
    • 3.3.4 Effect of seasonal conditions on response groups
    • 3.3.5 Response types for individual species in less diverse or abundant taxa
    • 3.3.6 Species found only at reference sites
  • 3.4 Identities of species in different response groups
    • 3.4.1 Plants
    • 3.4.2 Birds
    • 3.4.3 Reptiles
    • 3.4.4 Ants
  • 3.5 Conclusions
    • 3.5.1 Nature and magnitude of biodiversity change
    • 3.5.2 Underlying cause
    • 3.5.3 Potential for seasonal recovery
    • 3.5.4 Relationships among measures of biodiversity
    • 3.5.5 Indicators of change
    • 3.5.6 Implications for regional conservation planning
  
  
• 4 Summary conclusions and recommendations
  • 4.1 Research conclusions
    • 4.1.1 A rich and diverse biota under threat
    • 4.1.2 The threat is probably very widespread
    • 4.1.3 Water is the underlying cause and the potential solution
  • 4.2 Policy context
    • 4.2.1 Potential for achieving conservation goals by controlling water
    • 4.2.2 Need for a regional perspective
    • 4.2.3 Need for cost-effective methods for survey and monitoring
  • 4.3 Recommendations
    • 4.3.1 Implement a program of strategic closure of waters
    • 4.3.2 Establish a regional perspective
    • 4.3.3 Develop cost-effective methods for survey and monitoring
  
  
• Acknowledgments
• Appendix 1 Provision of watering points in Australian rangelands: A literature review of effects on biota
  • Summary
  • Introduction
  • Distribution of artificial waters
    • Sources of artificial water
      • Unconfined aquifers
      • Artesian and sub-artesian aquifers
      • Stored surface run-off
    • Storage and supply of artificial water
      • Earth dams and open drainages
      • Troughs and controlled access
      • Wetlands
    • Density of artificial water
  • A brief history of pastoral expansion in Australia
    • Eastern Australia
    • South Australia
    • Western Australia
    • Northern Territory
  • Impacts of artificial water
    • Focus for grazing and trampling
      • Changes to vegetation cover and composition
      • Changes to vertebrate animals
      • Changes to above-ground invertebrates
      • Changes to below-ground invertebrates
      • Conclusions
    • Habitat for native flora and fauna
    • Maintenance of high abundance of kangaroos
    • Focus for drinking by other native animals
    • Focus for hunting/drinking by predators
      • Cats
      • Dingoes and foxes
    • Focus for foraging/drinking by feral animals
      • Camels
      • Horses and donkeys
      • Pigs
      • Goats
      • Rabbits
  • Concluding comments
  • Acknowledgments
  
  
• Appendix 2 Continental analysis of the distribution of water points in arid and semi-arid Australia
  • Introduction
  • Methods
    • Water Points
    • Piospheres
    • Vegetation
  • Results
  • Discussion
  • Acknowledgments
  
  
• Appendix 3 Correspondence graphs
• Appendix 4 Lists of species and response groups
  • A4.1 Plants
    • A4.1.1 Plants detected in the understorey
    • A4.1.2 Plants detected in the overstorey
    • A4.1.3 Plants detected in the seedbank
  • A4.2 Diverse and abundant animals
    • A4.2.1 Birds
    • A4.2.2 Reptiles
    • A4.2.3 Ants
  • A4.3 Animals in less diverse or abundant taxa
    • A4.3.1 Small mammals
    • A4.3.2 Springtails (Collembola)
    • A4.3.3 Beetles (Coleoptera)
    • A4.3.4 Grasshoppers and crickets (Orthoptera)
  
  
• References

List of tables

Table 1.2.1  Target distances of sites from water.
Table 1.3.1.1   Actual distances (km) of sites from artificial sources of water.
Table 1.3.4.1  The main potentially confounding influences at each of the gradients
Table 1.3.5.1  Timing and seasonal conditions for the surveys of each gradient.
Table 2.1.1  Total numbers of species (both native and exotic) on each gradient, with the number of exotic species also shown in parentheses.
Table 2.1.2  Total numbers of individual seed bank plants and animals at each gradient.
Table 2.1.3  Numbers of individuals of non-target invertebrate groups (ie, groups not sorted to species-level) caught in small pit-traps.
Table 2.1.4  Numbers of individuals per gradient of invertebrate taxa caught in sweep nets.
Table 2.2.1.1  Seasonal variation in species numbers and abundance for selected plant groups and animal taxa at the four gradients dominated by acacia woodland.
Table 2.2.1.2  Variation with vegetation type in numbers of species of understorey plants and birds and numbers of individual birds, for the four gradients sampled after average seasons.
Table 2.2.2.1  Numbers of plant morphospecies detected in the seedbank and in the field.
Table 2.2.3.1  Contribution of exotic plant species to the total flora detected at the gradients.
Table 2.2.3.2  The exotic plant species detected along the gradients.
Table 3.1.1 Regression slopes for relationships between cover and distance from water.
Table 3.2.1  Numbers of species (native and exotic) of plants growing in the understorey at each site on each gradient.  The numbers of exotic species are also shown in parentheses.
Table 3.2.2  Numbers of species of plants growing in the overstorey at each site on each gradient.  (No exotic species were detected.)
Table 3.2.3  Numbers of species (native and exotic) of plants germinated from the soil seedbank at each site on each gradient.  The numbers of exotic species are also shown in parentheses.
Table 3.2.4  Numbers of species of birds at each site on each gradient.  (No exotic species were detected.)
Table 3.2.5  Numbers of species of small mammals (native and exotic) sampled at each site on each gradient.  The numbers of exotic species are also shown in parentheses.
Table 3.2.6  Numbers of species of reptiles at each site on each gradient.  (No exotic species were detected.)
Table 3.2.7  Numbers of species of ants (Hymenoptera: Formicidae) at each site on each gradient.  (No exotic species were detected.)
Table 3.2.8  Number of species of beetles (Coleoptera) at each site on each gradient.  (No exotic species were detected.)
Table 3.2.9   Numbers of species of springtails (Collembola) at each site on each gradient where species were identified.  (No exotic species were detected.)
Table 3.2.10  Number of species of grasshoppers and crickets (Orthoptera) at each site on each gradient where species were identified.  (No exotic species were detected.)
Table 3.2.11  Summary of regression coefficients (r² values) from regressions of species richness against distance from water point (in km).
Table 3.2.12  Summary of parameters for regressions where P-values <0.05 in Table 3.2.11.
Table 3.3.1.1  Species response groups for plants growing in the understorey
Table 3.3.1.2  Species response groups for plants growing in the overstorey
Table 3.3.1.3  Species response groups for plants in the soil seedbank
Table 3.3.1.4  Species response groups for birds
Table 3.3.1.5  Species response groups for reptiles
Table 3.3.1.6  Species response groups for ants.
Table 3.3.2.1  Proportion of species in response groups: plants growing in the understorey
Table 3.3.2.2  Proportion of species in response groups: plants growing in the overstorey
Table 3.3.2.3  Proportion of species in response groups: plants in the soil seedbank
Table 3.3.2.4  Proportion of species in response groups: birds
Table 3.3.2.5  Proportion of species in response groups: reptiles
Table 3.3.2.6  Proportion of species in response groups: ants
Table 3.3.3.1  Contribution of exotic species to response groups for plants in the understorey
Table 3.3.3.2  Contribution of exotic species to response groups for plants in the seedbank
Table 3.3.4.1  Proportions of species identified as decreasers in the plant groups and animal taxa that showed most evidence of seasonal variation.
Table 3.3.5.1  Small mammals:  Regressions for species with a total count of > 5 animals across a gradient.  (*=Exotic species.)
Table 3.3.5.2  Springtails (Collembola):  Regressions for species with a total count of > 5 animals across a gradient
Table 3.3.5.3  Beetles (Coleoptera):  Regressions for species with a total count of > 5 animals across a gradient
Table 3.3.5.4  Grasshoppers and crickets (Orthoptera):  Regressions for species with a total count of > 5 animals across a gradient
Table 3.3.6.1  Understorey plant species  found only at the reference sites.
Table 3.3.6.2  Overstorey plant species found only at the reference sites
Table 3.3.6.3  Plant species in the soil seedbank found only at the reference sites
Table 3.3.6.4  Bird species found only at the reference sites
Table 3.3.6.5  Reptile species found only at the reference sites
Table 3.3.6.6  Ant  species found only at the reference sites
Table 3.3.6.7  Plants growing in the understorey found only at one of sites 2, 4, 5 or 6
Table 3.3.6.8  Plants growing in the overstorey found only at one of sites 2, 4, 5 or 6
Table 3.3.6.9  Plants in the soil seedbank  found only at one of sites 2, 4, 5 or 6
Table 3.3.6.10  Bird species  found only at one of sites 2, 4, 5 or 6
Table 3.3.6.11  Reptile species  found only at one of sites 2, 4, 5 or 6
Table 3.3.6.12  Ant species  found only at one of sites 2, 4, 5 or 6
Table 3.3.6.13  Statistical analysis of differences among the  four equidistant sites in the number of species found only at one of them.
Table 3.4.1.1  Understorey plant species that were repeat decreasers
Table 3.4.1.2  Understorey plant species that were repeat increasers
Table 3.4.1.3  Understorey plant species that were mixed responders
Table 3.4.1.4  Seedbank plant species that were repeat decreasers
Table 3.4.1.5  Seedbank plant species that were repeat increasers
Table 3.4.2.1  Birds seen during the surveys that have been identified as having increased in range or abundance since European occupation of the arid zone.
Table 3.4.2.2  Birds seen during the surveys that have been identified as rare or threatened
Table 3.4.2.3  Proportions of increaser and decreaser bird species in guilds that predominantly forage at different levels.
Table  3.4.4.1  Species of ants that occurred on more than one gradient, their relative abundance, and response group if they were classified in the same response group when they occurred on more than gradient.
Table  3.4.4.2  Average percentages of species of ants in different functional groups and response groups across the four gradients in each major habitat type.
Table 3.5.1.1  Proportions of increaser and decreaser species per gradient, calculated for all species in the more diverse and abundant groups and taxa, and averaged across all gradients.
Table 3.5.1.2  Relative contributions of native and exotic plant species to the response groups in Table 3.5.1.1.  (There were no exotics among the animal species.)
Table A1.1  Recorded distances domestic stock move from permanent artificial water points in arid and semi-arid Australian rangelands.
Table A1.2  Changes in abundance and distribution of native species of birds in arid and semi-arid rangelands attributed to the effects of the provision of artificial water or pastoralism.
Table A2.1  Water points marked on a sample of 1: 250 000 map sheets covering rangeland areas.
Table A2.2.  Area of chenopod lands and the proportion of different vegetation categories that occur more than 10 km from a named water point.
Table A2.3.  Area of acacia lands and the proportion of different vegetation categories that occur more than 10 km from a named water point.

List of figures

Figure 1.3.1.1  Location of the grazing gradients.
Figure 1.3.3.1  The NT mulga gradient showing sites 1 (upper), 4 (middle) and 6 (lower)
Figure 1.3.3.2  The NSW mulga gradient showing sites 1 (upper), 3 (middle) and 6 (lower)
Figure 1.3.3.3  The Qld mulga gradient showing sites 1 (upper), 4 (middle) and 6 (lower)
Figure 1.3.3.4  The Qld gidgee/ chenopod gradient showing sites 1 (upper), 4  and 6 (lower)
Figure 1.3.3.5  The WA chenopod/ acacias gradient showing sites 1 (upper), 4 and 6 (lower)
Figure 1.3.3.6  The SA chenopod/ myall gradient showing sites 1 (upper), 3  and 6 (lower)
Figure 1.3.3.7  The SA chenopod gradient showing sites 1 (upper), 4 (middle) and 6 (lower)
Figure 1.3.3.8  The WA chenopod gradient showing sites 1 (upper), 4 (middle) and 6 (lower)
Figure 1.4.1.1  Location of sites, landscape strata and sample replicates along a gradient.
Figure 3.1.1 Variation in the major categories of ground cover at the NT mulga gradient.
Figure 3.1.2 Variation in the major categories of ground cover at the NSW mulga gradient.
Figure 3.1.3 Variation in the major categories of ground cover at the QLD mulga gradient.
Figure 3.1.4 Variation in the major categories of ground cover at the QLD gidgee /chenopod gradient.
Figure 3.1.5 Variation in the major categories of ground cover at the WA chenopod /acacias gradient.
Figure 3.1.6 Variation in the major categories of ground cover at the SA chenopod /myall gradient.
Figure 3.1.7 Variation in the major categories of ground cover at the SA chenopod gradient.
Figure 3.1.8 Variation in the major categories of ground cover at the WA chenopod gradient
Figure 3.2.1  Graphs of polynomial regressions of species richness against distance from artificial water point for the four relationships with the highest r²-values
Figure 3.3.1.1  Relationships between abundance and distance from water for the grazing response groups identified by regression analysis of correspondence groups
Figure A1.1  Artesian and sub-artesian water basins in Australia
Figure A2.1.  Distribution of all water points named on the 1:250,000 and 1:100,000 topographic maps covering mainland Australia.

Authors:
Jill Landsberg¹, Craig D. James², Stephen R. Morton¹, Trevor J. Hobbs², Jacqui Stol¹, Alex Drew¹ and Helen Tongway¹
CSIRO Division of Wildlife and Ecology
¹ P.O. Box 84, Lyneham ACT 2602
² P.O. Box 2111, Alice Springs NT 0871.

Photograph credits:
Jill Landsberg and Craig James.

Information presented in this document may be copied for personal use or published for educational purposes, providing that any extracts are acknowledged.

The views expressed in this paper are those of the authors and do not necessarily represent the views of Environment Australia, CSIRO, or the Commonwealth of Australia.

Enquiries, telephone 06-2500717 or 2500713
Biodiversity Group, Environment Australia

Cover design: CSIRO Division of Wildlife and Ecology
Printed by: Panther Publishing and Printing, Canberra

Executive summary

Artificial waters are a potential threat to the persistence of many components of native biological diversity in arid and semi-arid Australia. Supplies of water have proliferated in the rangelands since settlement for pastoral purposes. Today, few areas of pastoral rangeland are further than 10 km from an artificial source of water. This widespread provision of water allows large grazing animals - principally sheep and cattle but also kangaroos and feral livestock - to graze virtually all of this rangeland. Our study aimed to determine the effects of the provision of artificial waters and of the grazing it allows, on the native plants and animals inhabiting two of the major biomes of inland Australia.

Methods

The study was based on field surveys which sampled biodiversity along gradients in grazing intensity extending out from artificial water sources. Each gradient continued to a reference site remote from all waters, where grazing by stock was minimal. Five further sites were sampled along each gradient, at locations progressively closer to the artificial water. Four such gradients were surveyed in chenopod shrublands and four in acacia woodlands at widely separated localities across the pastoral rangelands of central and southern Australia. At each of the six sites along each gradient systematic samples or counts were collected of understorey plants, overstorey plants, plants in the soil seedbank, birds, reptiles, small mammals, ants, beetles, springtails, grasshoppers and crickets.

Results

The gradients were particularly rich in plant species, a quarter to a half of which were detected only in the soil seedbank and would not have been apparent from once-only field surveys. The most species-rich animal taxa were ants and birds. Most of the invertebrate species collected were new to science. Several new plant species were also identified. Exotic species were generally a minor component of the gradients' diversity, except at the chenopod gradients, where 3-11% of plant species were exotic.

The gradients showed little evidence of severe degradation: plant cover at sites very close to water was little different from cover at water-remote sites. A pilot study of landscape function conducted at two of the gradients found indications of early stages of degradation: landscape patches close to water showed more evidence of tree die-back and may have lost some of their ability to capture, store and utilise water and nutrients.

There were major changes in the composition of biodiversity at different distances from water. The results show that some species in most groups of plants and animals increased in abundance at sites closer to water ("increasers"), but that some decreased at such sites ("decreasers").

• On average, between 15% and 38% of species in different taxonomic groups appeared to be decreasers;
• between 10% and 33% appeared to be increasers; and
• the remaining species did not exhibit any demonstrable response to the artificial water.

Nearly all decreaser species were natives. A small but significant number of the decreaser plant species at each gradient was found only at the gradient's reference site, where grazing intensity was minimal. This is of particular concern because of the extreme reduction that has occurred in the area of pastoral rangeland this far from water. Increaser species included natives and exotics. Buffel grass, Cenchrus ciliaris, was a particularly prominent exotic increaser at one gradient. No exotic bird species were detected, but many of the increasers were species whose ranges have expanded since water has been provided.

Some species of plants and animals were much more abundant in better seasons, but decreaser trends did not abate. For understorey plants at woodland gradients decreaser trends appeared more pronounced in better seasons. At the two woodland gradients surveyed after better seasons, much higher proportions of decreaser plant species were found than at two similar gradients surveyed after drier seasons. The persistence of plant species in the seed bank indicates their potential for seasonal recovery but in this group, too, there were significant proportions of decreaser species.

It is likely that most species of plants and animals show these responses because of the direct and indirect effects of the grazing which radiates out from sources of water. Some species of birds may also be directly advantaged by the availability of drinking water. Regardless of mechanisms, the ultimate cause of the changes detected in most taxonomic groups is likely to be the provision of artificial sources of drinking water.

Given how widespread artificial waters have become throughout the chenopod and acacia rangelands, the results suggest that some 15-38% of species are at risk of declining substantially throughout these lands. Although similar proportions of species are favoured by the provision of water and grazing, and from 36-75% seem unaffected by it, the challenge is to develop strategies that will provide for the persistence of the vulnerable decreaser species.

As a consequence of these results, and in the context of Australia's national commitments to conserve biodiversity, the report makes the following recommendations: Recommendations

Implement a program of strategic closure of waters

1. 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.
2. 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.
3. 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)
4. 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.

Establish a regional perspective

5. 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.
6. 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.

Develop cost-effective methods for survey and monitoring

7. 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.
8. 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.
9. Undertake research to determine relationships between biodiversity and landscape pattern, in order to identify broad-scale, landscape-based surrogates for monitoring biodiversity.

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