Biodiversity publications archive

Refugia for biological diversity in arid and semi-arid Australia

Biodiversity Series, Paper No. 4
S.R. Morton, J. Short and R.D. Barker, with an Appendix by G.F. Griffin and G. Pearce
Biodiversity Unit
Department of the Environment, Sport and Territories, 1995

10. Refugia in Western Australia (continued)

10.29. Reference number WA29

Refuge area: Hamersley and Chichester Gorges and Ranges

Biogeographic region: Pilbara

Type of refuge: Gorges and Mountain ranges

Lat./Long. 21°10’ - 23°00’S / 116°10’ - 119°40’E

Quality of refuge: Extremely significant (8)

Area (km²): >10,000

Chief refuge value

Gorge pools are a significant, isolated area of habitat for endemic flora and fauna, which either do not occur elsewhere or are rare in the north-west of Western Australia, and the Ranges themselves appear to harbour a wide variety of organisms that are endemic to the area3, 6, 10, 11.

General description

The Hamersley and Chichester Ranges are spectacular rugged mountainous areas containing deep gorges and a series of ridges tending north-west to south-east. Many of the hills are over 1000 m and often rise 300 m above the colluvial fans and plains of the valleys. Streams funnel through the gorges and onto the plains beyond.

Millstream Pools (21° 35' S / 117° 05' E) include a 20 km length of the Fortescue River, which includes four permanent pools (Deep Reach Pool, Crossing Pool, Livistona Pool, and Palm Pool). The Pools are interconnected by a flowing channel. Water originates from surface inflow of the upper Fortescue River and from groundwater seepage from permanent springs. The uppermost pool (Deep Pool) is 50 ha in area and 20 m deep. The Pools lie in a broad shallow valley bounded by stony hills with typical arid vegetation (Triodia wiseana and T. pungens). Mudflats of the floodplain support river gum Eucalypus camaldulensis and cajeput Melaleuca leucadendron. Other trees include Sesbania formosa and the endemic, relict palm Livistona alfredii. Well-watered gorges of the Hamersley Range area are Kyalina Pool in the Hooley River, Wittenoom Gorge, Dales Gorge, and Hamersley Gorge. These support lush vegetation bounded by rocky gorge walls.

ANZECC-listed species

Pebble-mound mice Pseudomys chapmani (V), ghost bat Macroderma gigas (V), and black-footed rock-wallaby Petrogale lateralis (V)1, 9. Bilbies Macrotis lagotis and mulgara Dasycercus cristicauda occur along valley floors12.

Regional endemics

Within the gorges there are endemic insects, including dragonflies and damselflies3, and also plants such as the Millstream fan palm Livistona alfredii3.

In the range complex, numerous endemics occur. Among mammals: the red-eared Antechinus Dasykaluta rosamondae, Pilbara ningaui Ningaui timealeyi, and the pebble-mound mouse. Among reptiles, there is a suite of Pilbara endemics: the geckos Diplodactylus savagei, D. wombeyi, and Nephrurus wheeleri cinctus; the pygopodid Delma elegans; the agamid Diporiphora valens; the skinks Ctenotus nasutus, C. nigrilineatus, C. rubicundus, C. rutilans, C. grandis titan, Egernia pilbarensis, Lerista chalybura, L. concolor, L. flammicauda, L. neander, Morethia ruficauda exquisita and Notoscincus butleri; the goanna Varanus pilbarensis; the python Liasis olivaceus barroni; the elapid Demansia olivacea rufescens; and the blind snake Ramphotyphlops diversus ammodytes10, 11.

Relict species

Gorges in both areas have been described as “valuable refugia for plant species” (Brooker in Burbidge)7. The Millstream fan palm Livistona alfredii is a relict of a humid tropical paleoclimate3. Other relict plants include soft fern Ceratopteris thalictroides, and still pools contain Potamogeton javanicus; in damp mud the herbs Lobelia quadrangularis and Peplidium humifusum. Vegetation in narrow gorges at Hamersley Gorge, which are permanently shaded and permanently wet, includes two ferns Adiatum capillus-veneris and Pteris vittata and the trailing trigger plant Stylidium alsinoides1.

Other significant species

Among mammals, a major colony of the black flying fox Pteropus alecto occurs (rare beyond Kimberley)1; also P. scapulatus is present periodically3.

Many waterbird species are recorded at Millstream Pools3. There are 9 species of fish recorded, including Leiopotherapon apheneus (endemic?), L. unicolor, Fluvialosa erebi, Anguilla bicolor, Arius australis, Neosilurus glencoensis, Melanotaenia nigrans, Therapon unicolor, Therapon percoides, Therapon aheneus and Glossogobius giuris3. However, no fish are endemic to the Fortescue River.

Species of reptiles at Millstream dependent on water or moist environments are tortoise Chelodina steindachneri, the skink Lerista frosti, and the python Liasis olivaceus7.

Two relatively widespread species of frogs occur: Litoria rubella and Glauertia russelli7. The frog Pseudophryne douglasi is confined to permanent seeps or deep-shaded gorges in the Pilbara and North-west Cape11.

Key threats

Groundwater extraction (for water supply to Pilbara coastal towns); weeds (date palms, cotton palms, Parkinsonia, Ceratopteris and Nymphaea)3. Possibly excessive human disturbance.

Land tenure

Millstream-Chichester National Park, Karijini (Hamersley Range) National Park, Abydos-Woodstock Reserve; pastoral leases.

Key references

1. Dunlop and Sawle (1982)

2. Kitchener and Vicker (1981)

3. Jaensch and Lane (1993)

4. Muir (1983)

5. Storr (1984)

6. Kitchener and Caputi (1988)

7. Burbidge (1971b)

8. Kitchener (1980)

9. Kennedy (1992)

10. Johnstone (1983)

11. Cogger (1992)

12. How et al. (1991)