Biodiversity Assessment - Pilbara
Pilbara
Introduction
Pilbara Craton has semi-desert-tropical climate. Active drainage by river systems such as Fortescue, De Grey and Ashburton. There are four subregions:
- Chichester. Undulating Archaen granite and basalt plains including significant areas of basaltic ranges. Plains support a shrub steppe characterised by Acacia pyrifolia over Triodia pungens hummock grasslands, while Eucalyptus leucophloeia tree steppes occur on ranges.
- Fortescue Plains. Alluvial plains and river frontages. Extensive salt marsh, mulga-bunch grass, and short grass communities on alluvial plains in the east. River Gum woodlands fringe the drainage lines. This is the northern limit of Mulga (Acacia aneura). An extensive calcrete aquifer (originating within a palaeo-drainage valley) feeds numerous permanent springs in the central Fortescue, supporting large permanent wetlands with extensive stands of river gum and cajuput woodlands.
- Hamersley. Mountainous area of Proterozoic sedimentary ranges and plateaux, dissected by gorges (basalt, shale and dolerite). Mulga low woodland over bunch grasses on fine textured soils in valley floors, and Eucalyptus leucophloeia over Triodia brizoides on skeletal soils of the ranges.
- Roebourne. Quaternary alluvial and older colluvial coastal and sub-coastal plains with a grass savanna of mixed bunch and hummock grasses, and dwarf shrub steppe of Acacia translucens or A. pyrifolia and A. inequilatera. Uplands are dominated by Triodia hummock grasslands. Ephemeral drainage lines support Eucalyptus woodlands. Samphire, Sporobulus and mangal occur on marine alluvial flats and river deltas. Resistant linear ranges of basalts occur across the coastal plains. Islands are Quaternary sand accumulations, basalt and/or limestone.
Overall Condition and Trend
Continental landscape stress classes range from 3 to 6 as assessed by the Landscape Health report (1 is most stressed, 6 is least stressed), but a combination of weed invasions, hot frequent bushfires, feral predators and grazing by exotic herbivores are causing a general loss of soil fertility and vegetation cover, and consequent loss of native species such as CWR mammals. Erosion from increased runoff velocities is occluding drainage lines.
Summary of conservation priorities
Need to improve conservation reserve system's CAR, and to control weeds and manage fire regimes both on and off reserves.
Natural values
Special Values comprise: Geological complexity of the Marble Bar - Nullagine mineral province. Persisting populations of threatened and endangered species (Dasycercus cristicauda, Lagorchestes conspicillatus, Macrotis lagotis, Rhinonicteris aurantius, Polytelis alexandrea). Arid zone populations of Trichosurus vulpecula arnhemensis, Macroderma gigas, Nyctophilus bifax dadelus. Physical features, endemic species and species-rich ecosystems associated with the Fortescue River, especially Millstream wetlands, Millstream aquifer, Fortescue Marsh and Chichester gorges. These are also refugia for various fire-sensitive plants. Species-rich, refugial ecosystems associated with gorges, waterfalls and mountain-tops of Hamersley Range with undescribed land snail, lizard and plant species. Endemic stygofaunal radiations in calcrete aquifers. Coastal islands act as refugia for vulnerable species now rare or extinct on the adjacent mainland (e.g. Pseudomys nanus, Ctenotus augusticeps), and breeding sites for turtles and sea-birds. Many sites significant to Aboriginal culture.Rock piles of Burrup Peninsula act as fire refuges.
Bioregional endemics include Ningaui timealeyi, an undescribed Planigale, Dasykaluta rosamondae, Pseudomys chapmani, Pseudantechinus roryi, Diplodactylus savagei, Diplodactylus wombeyi, Delma elegans, Delma pax, Ctenotus rubicundus, Egernia pilbaraensis, Lerista zietzi, Lerista flammicauda, Lerista neander, two or three undescribed taxa within Lerista muelleri, Notoscincus butleri, Varanus pilbaraensis, Acanthophis wellsi, Demansia rufescens, Ramphotyphlops pilbaraensis, Ramphotyphlops ganei, Stygofauna of calcrete aquifers.
Click here to link to a table of natural values within each subregion
Wetlands
Six wetlands of national importance are listed, including river courses, aquifer-fed springs, an inland salt marsh, natural springs and an artificial salt marsh. They act as refuges, support populations of endemic species, and are species-rich ecosystems. On average, their condition is fair (improvement requires significant management intervention) while trend is declining or static. TPs include grazing pressure, weed colonisation , changes to hydrology and water extraction for development.
Twelve wetlands of subregional significance have been identified, including riverine gorges, aquifer-fed springs, ephemeral swamps and lakes, claypans, river sections with permanent pools, and mangrove communities. Some are extensive. They act as refuges, support populations of endemic species, and are species-rich ecosystems. On average, their condition is fair (improvement requires significant management intervention) while trend is declining or static. Threatening processes include grazing pressure, weed colonisation , changes to hydrology and water extraction for development.
Nationally important wetlands
Map: IBRA map showing DIWA locations, towns, subregions, major roads and reserves and most common threatening processes.
Click here to link to a table of Australia's Important Wetlands (Directory of Important Wetlands of Australia): their type, condition, trend and threatening processes within each subregion.
Regionally important wetlands
Click here to link to a table of provisional identification of wetlands of regional significance: their type and special values within each subregion. The reliability of the overall subregional assessment is indicated.
Click here to link to a table of provisional identification of wetlands of regional significance: their condition, trend and threatening processes within each subregion.
Riparian Zones
Main river systems include the De Grey, Oakover, Turner, Fortescue, Robe, Cane and Ashburton. All arise in the region's uplands and are active systems. Their riparian zones are generally degraded to fair (significant management intervention required for recovery), and declining under trampling and grazing pressure from cattle and feral herbivores, colonisation by a variety of weeds such as Buffle Grass, mesquite and Parkinsonia, and fire.
Map: Riparian threatening processes.
Click here to link to a table of riparian zones: their average condition, trend and threatening processes for each subregion. The reliability of this overall assessment is indicated.
Ecosystems at risk
One Threatened Ecological Community has been declared Vulnerable by WA in the Pilbara, but 30 community-types are considered to be 'at risk', comprising:
- 14 fresh-water wetlands or wetland-types [3 swamps (NVIS 9), 7 spring communities (NVIS 8, 9, 15, 33, 36, 41), 1 rock pool community (NVIS 33), all major ephemeral watercourses (NVIS 4, 8), and 3 inland salt marshes (NVIS 39)],
- 4 lower slopes of ranges and valley floors with Mulga or Snakewood communities (NVIS 23, 24),
- 4 scree-slope and hilltop communities (NVIS 23, 32, 33 & 36),
- Coastal grassland and salt marshes throughout region (NVIS 31, 36),
- Mangrove communities throughout region (NVIS 40),
- 2 Stygofaunal communities near mines,
- Island communities in general (NVIS 23, 24, 33)
None are declared as threatened under State legislation, by they are considered to be vulnerable except for Mulga community (NVIS 24) which is probably endangered. Trend in the condition of these ecosystems is 'declining' on average, although 'lower slope mulga', 'fresh water swamps', 'mangroves', and 'island' communities are rapidly declining in some places.
All except islands are threatened by cattle, feral herbivores and fires. Feral mammals are ubiquitous on the Pilbara mainland, and also present on some islands. Wetlands and islands are being colonised by invasive weeds, such as buffle grass and kapok bush. Hydrological changes are also degrading mulga and mangrove communities
Map: IBRA map showing frequency of threatening processes for ecosystems.
Click here to link to a table of provisional list of threatened ecosystems in Australia: their broad vegetation type (National Vegetation Information System - Major Vegetation Subgroup), recommended status, current legislative protection as a threatened ecosystem, trend and bioregional distribution. These ecosystems are arranged in the bioregion of their principal occurrence. The reliability of the recommended status is indicated.
Click here to link to a table of provisional list of threatened ecosystems in each subregion: their threatening processes.
Click here to link to a table of provisional list of threatened ecosystems in each subregion: their recommended recovery actions
Species at risk
One reptile species is declared as Endangered, and 4 mammals, 4 reptiles and 2 plant as Vulnerable under WA state legislation. Under EPBC, six mammals are listed as Vulnerable (the listing for the Rhinonicteris aurantius only applies to its Pilbara populaton), one reptile is Endangered and five are Vulnerable (four marine turtles and a python), one bird is listed as Vulnerable (Alexander Parrot) and two plants are listed as Vulnerable. The vertebrates are declining (iii) or static (iv), the plants improving (v). Threatening processes in all cases include habitat changes associated with land-use (direct recreation/ hunting for turtles) and feral predators. Fire, grazing and invasive weeds are affecting the plants. Various other species are listed as priority taxa (P1 - P4) under State legislation, including 5 mammals, 4 reptiles (including Estuarine Crocodile), 5 birds (feral predators and fire) and 31 plants comprising trees, shrubs, grasses and herbs (weeds, grazing and fire).
Map: IBRA map showing frequency of threatening processes for species.
Click here to link to a table of species at risk in each subregion: their status, trend and subregional distribution. The reliability of the assessment of trend is indicated and whether recovery plans have been prepared.
Click here to link to a table of species at risk in each subregion: their threatening processes.
Click here to link to a table of species at risk in each subregion: their status recommended recovery actions.
Birds
Rich mineralisation, as found in the Pilbara, is not correlated with avifaunal diversity; for the most part the bioregion's birds are similar to those elsewhere in the semi-arid zone. A few limited range species occur in coastal mangroves and a Vulnerable subspecies of White-winged Fairy-wren occurs on Barrow Island. Other locally endemic subspecies do occur in the ranges on the mainland but they, are not currently considered to be of concern. A few rock doves occur in towns in an area otherwise lacking introduced birds. There are no major trends in guilds, apart from fewer mangrove birds being recorded during the second Atlas, which may be an artefact of sampling.
Status: Semi-arid avifauna, with local endemism at the subspecies level.
Rare and threatened: White-winged Fairy-wren on Barrow Island.
Increasers: None indicative of landscape health.
Indicators: Emu, Australian Bustard, Banded Lapwing, Black-tailed Treecreeper, Hooded Robin, Jacky Winter, Star Finch.
Trend: No major trends.
Scenario: Probably largely stable within large climate-driven fluctuations.
Actions: Ensure representative areas have an appropriate fire regime to maintain diversity.
Click hereto download a summary report including the physical characteristics of the bioregion, a species list, and summary statistics [Excel file]. The file may open on your screen. To save it to your system 'Save as' under the File menu.
Mammals
Number of species and status
There are 57 mammal species within this bioregion. (The maximum number of species recorded in a bioregion is 86 and the minimum is 25).
Click here to link to a table of number of species in each status class for this bioregion.
Click here to link to a list of mammal species and their status for this bioregion.
Critical weight range
The critical weight range (35 - 5500 g) of mammals is the size range of Australian mammals that have been most affected by environmental changes following European settlement. In this bioregion, the proportion of mammal fauna within the critical weight range is .474. (The maximum proportion of fauna within the critical weight range recorded in a bioregion is 0.632 and the minimum is 0.222).
Faunal Attrition Index
Faunal attrition is a measure of contraction or loss of species richness with a region. A high index value means many species have declined or are extinct in the bioregion. The index can be used to compare the status of mammal fauna to regional attributes such as changes since European settlement and average annual rainfall. The Faunal Attrition Index for mammals in this bioregion is .21. (The maximum faunal attrition index value recorded in a bioregion is 0.66 and the minimum is 0).
Click here to link to a table of Faunal Attrition Index for groups of mammals shows the contributions of each group to overall patterns of faunal decline.
Faunal Contraction Index
A range contraction index is a measure of the extent to which the range inhabited by a particular species has contracted. A high index value means that many of the species comprising the region's original mammal fauna have contracted from a high proportion of the regions they originally occurred in. The faunal contraction index for the mammal fauna in this bioregion is .24. (The maximum faunal contraction index value recorded in a bioregion is 0.51 and the minimum is 0.07).
Faunal Endemism Index
Endemic species are those restricted to certain regions. Regions containing endemic species are considered to have high biodiversity conservation values because opportunities to conserve those species do not exist elsewhere. A high index value means that the species comprising the original mammal fauna typically occurred in few bioregions. The faunal endemism index value for the mammal fauna in this bioregion is .66. (The maximum faunal endemism index value recorded in a bioregion is 0.79 and the minimum is 0.52).
New Endemism Index
Extant (still surviving) species that have undergone major range contractions can be considered 'new endemics'. Bioregions that contain new endemic species are often important refugia for threatened species. The new endemism index for the mammal fauna in this bioregion is .68. (The maximum new endemism index value recorded in a bioregion is 0.93 and the minimum is 0.5).
Click here to link to a list translocated species that has/have been successfully translocated into this bioregion.
Exotic Mammals
The number of introduced exotic mammal species that occur within this bioregion is 12. (The maximum number of introduced exotic mammal species in a bioregion is 16 and the minimum is 5).
Click here to link to a list of introduced exotic mammal species for this bioregion.
Extinct mammal species
The number of extinct mammal species that previously occurred within this bioregion is 11. (The maximum number of extinct mammal species in a bioregion is 29 and the minimum is 0).
Click here to link to a list of extinct mammal species for this bioregion.
Management responses
Reserve consolidation
There are two major National Parks: Karijini (in PIL 3) and Millstream-Chichester (in PIL 1 and PIL 2). The Mungaroona Ranges (PIL1) and many coastal islands (in PIL 4) are Nature Reserves. Meentheena (in PIL 1) and Cane River-Mount Minnie (in PIL 3) are Conservation Parks. Conservation lands are dominated by uplands and ranges country dominated by hummock grass communities on skeletal soils of uplands and on scree-slopes. Upper slope and mulga communities are also present. Networks of gorges, ephemeral watercourses with riparian woodland communities, freshwater springs and riverine communities are prominent features. A total of 1.7 million hectares (with examples of 42 of the region's 88 vegetation associations) is in this conservation estate, 8.7% of the region's area.
Forty-five vegetation associations are listed as having a high priority for reservation, they comprise various snakewood, cassia, acacia and eremophila shrublands, desert bloodwood or mallee/hummock grass, mulga/tussock grass, acacia and eucalyptus woodland, teatree, mangrove, grass plain, sedgeland, river gum, coolibah, samphire and pindan commuities. Various fresh-water swamps, claypans, inland salt marshes, mangrove stands and 'valley floor mulga woodlands' specifically identified among the thirty-four "at risk" communities identified earlier are also unreserved. Overall, riverine systems and wetlands have the highest priority. Priorities include some of the most productive parts of pastoral leases, others are coastal and island sites important for industrial development or prospective for minerals. Aboriginal lands may not be available for reservation.
Bioregional priority is Class 3 but should be class 2 because of its inherent bias. Subregional priority is PIL2 with only 0.8% in reserves. Next is PIL 1, with 3.9% in reserves but a further 2.7% of its area recently purchased by CALM. Reserve systems in PIL 1, PIL 2 and PIL 4 are highly biassed.
Invasive weeds, wildfires and eradication of feral mammals is an issue on all reserves, even those with resident staff; some reserves are seldom even visited by management staff, and access to Mungaroona Nature Reserve is difficult.
Click here to link to a table of comprehensiveness, adequacy and representativeness (CAR) of the National Reserve System in terms of ecosystems and area sampled and a ranking of reserve management. The bioregional priority for consolidating the National Reserve System is based on this CAR analysis and threat.
Table: Bioregional and subregional priorities and ecosystem priorities to consolidate the National Reserve System and associated ecosystem constraints.
There is no data available for this table within the bioregion.
Off-park conservation for species and ecosystem recovery
Recovery actions are identified for 1 bird, 8 mammals, 8 reptiles, 40 plants and 3 ecosystems:
- Habitat protection is required for five species of marine turtle (esp. nesting locations), dugong, Ctenotus angusticeps (a skink), estuarine crocodile, Lagorchestes conspicillatus, Macrotis lagotis and the tree Terminalia supranitifolia. Better fire control is needed for the land-dwelling species, and fox management for the mammals.
- The two bats (Macroderma gigas & Rhinonicteris aurantius) need protection and maintenance of old mine workings, mining industry code of practice, removal of barb-wire fences for Ghost Bats, surveys for natural roosts.
- Petrogale lateralis and Petrogale rothschildi need to be translocated to Pilbara islands, then fox control.
- Broad-scale surveys to clarify the distribution and status of stygofaunas are required, followed by habitat protection as required in regions where research shows that mine dewatering may affect their persistence.
- Weed (Buffle Grass) control is urgently needed on coastal islands. Its interaction with indigenous fauna is unknown, but it eliminates native flora.
- Wetlands of lower De Grey River require protection from weeds, stock and feral herbivores, including pigs. Fencing is required if lands remain under cattle production.
- Surveys to clarify distributions, status and TPs are neded for Falco peregrinus, Sminthopsis longicaudata, Ramphotyphlops gaini and 38 plant species (including herbs, shrubs, grasses, trees and sedges).
Significant off-park conservation activities are needed in PIL2 particularly habitat protection through agreements, while significant biodiversity gains can be made from translocations (in PIL4), and from fire control, habitat protection and feral mammal control (mangroves, lower riparian fencing and fox eradication in PIL3 and PIL4. Weed control is urgent, especially on the islands.
Integrated NRM
Existing actions:
- Threat Abatement Plans on pastoral lands for vegetation (incuding fire), for fox and feral herbivore control, and for de-commissioning and revegetating mine-sites.
- Industry codes of practice with capacity building through Land Conservation District Councils and Chamber of Minerals and Energy in liaison with landholders.
- Environmental management systems, ecological sustainable product marketing
Opportunities
- Legislated 'duty of care' for pastoral leases, aboriginal lands and mining areas.
- Joint or compatible management of pastoral lands owned by mining companies
- Institutional reform e.g. rural reconstruction, industry reconstruction, new joint management arrangements and excision of high quality conservation lands when leases/tenements are renewed.
- State and local government planning for CAR reserve system, and National Action Plan for Water Quality and Salinity.
Constraints
- Lack of funding to acquire high value lands held under pastoral lease on open market, and to adequately manage our existing estate for control of fire, weeds and feral herbivores even on major National Parks,
- Need more cooperation by Pastoral Lands Board in re-structuring un-viable leases after reserve areas are excised.
- Need to increase awareness of conservation values through education of various industry (mining, pastoral) and the public in general.
- 'Conservation Through Reserves' is limited by extensiveness of mining leases, tenements and associated infrastructure, resulting in unnecessary alienation of high quality conservation areas (eg Legendre Island).
Region-wide priority is to integrate conservation into pastoral production/development systems.
Map: IBRA map showing frequency of recovery actions (species).
Map: IBRA map showing frequency of recovery actions (ecosystems).
Map: IBRA map showing existing projects part of NRM.
Click here to link to a table of contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: existing measures and effectiveness.
Click here to link to a table of contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: feasible opportunities and comments.
Further Information & Gaps
Data gaps and research priorities
- No environmental geology / regolith mapping at better than 1:250 000.
- No quantitative (quadrat-based) regional survey of flora or fauna, so regional flora and fauna is poorly known. Only small, local areas have been examined in detail by biologists, usually for industrial development.
- There are few detailed data on ecological requirements and life histories of virtually all invertebrate species, plants, persisting CWR mammals, uncommon vertebrate and plant species, and ecologically dominant plant species (eg hummock grasses). There are few data to provide a regional context on population-trends for even ecologically significant species such as native rodents, dasyurids, spinifex reptile communities, termites, ants, weeds such as buffel grass, kapok bush and ruby dock.
- No quantitative data on the impact of weed colonisation, fire in hummock grasslands, exotic herbivores on aquatic and terrestrial communities and long term effect of mining on stygofaunas.
References
Environment Australia 2000. Revision of the Interim Biogeographic Regionalisation of Australia (IBRA) and the Development of Version 5.1. - Summary Report. Department of Environment and Heritage, Canberra.
A complete list of references is available by clicking here.
Further information
View the Landscape Health in Australia report.
View the Terrestrial Biodiversity Assessment 2002 report.
Download the Terrestrial Biodiversity Assessment 2002 Database - Biodiversity Audit Data Entry System (BADES), and specifications
Click here to link to a table of some major data gaps in each subregion in terms of protecting biodiversity.
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