Southwest Australia savanna
Kalbarri National Park, Western Australia Photograph by Mike Fields
The Southwest Australia savanna is an ecoregion in the southwestern portion of Australia, which comprises approximately 65,200 square miles of land area. This is an arid region, a considerable portion of which has been converted to wheat cultivation. The Southwest Australia savanna is considered to lie within the Mediterranean Forests, Woodlands & Shrub biome. Austral summer temperatures often exceed 40 degrees Celsius.
There are 458 vertebrates recorded in the ecoregion, including seven endemic species. There are also 21 threatened vertebrate taxa present, six of which are mammals.
Location and general description
The Southwest Australia savanna ecoregion occurs in the southwestern portion of Australia.
It cover approximately 65,200 square miles of land area.
This arid ecoregion is a transition zone between the high flora endemism mediterranean climate influence of the southwest corner and the interior semi-arid sandplains at the north.
Much of the land area has been converted to agriculture, chiefly planted to wheat.
Southwest Australia savanna ecoregion (in yellow). Source: WWF & Peter Saundry
Biodiversity features
Brush-tailed phascogale. Source: Friedrich Specht (1927) The primeval habitat of this ecoregion was comprised of savanna interspersed with eucalyptus woodland, mallee woodlands, shrublands and heath habitats. However, in the arable south of the ecoregion, extensive agricultural conversion to wheat farming has been carried out in the last two hundred years. Much of the original savanna is extant within the north of the Southwest Australia savanna, where acacia dominates, rather than eucalyptus. Flora of the ecoregion include many species of woody and herbaceous taxa. The scented Acacia rostellifera. is an example common tree taxon. The best-preserved area of pristine natural environment manifests at the multi-coloured sandstone gorges of Kalbarri National Park along the Murchison River.
Endemic reptiles in the ecoregion are: Allen's ctenotus (Ctenotus alleni), Christina's lerista (Lerista christinae), Lerista eupoda and the Yuna broad-blazed slider (L. yuna). Endemic amphibians in the ecoregion are represented by the dumpy frog (Arenophryne rotunda), which is a fossorial anuran that burrows in moist sand to achieve hydration.
Purple-crowned lorikeet (Glossopsitta porphyrocephala), Australia. Source: John Milbank
Threatened mammals in the ecoregion are: the Endangered banded hare-wallaby (Lagostrophus fasciatus), the Near Threatened black-footed rock wallaby (Petrogale lateralis), the Near Threatened brush-tailed phascogale (Phascogale tapoatafa), the Near Threatened red-tailed phascogale (Phascogale calura), the Endangered numbat (Myrmecobius fasciatus) and the Near Threatened western quoll (Dasyurus geoffroii).
Special status birds here are the Near Threatened Australian bustard (Ardeotis australis), the Near Threatened black-tailed godwit (Limosa limosa), the Near Threatened blue-billed duck (Oxyura australis), the Near Threatened bush thick-knee (Burhinus grallarius), the Vulnerable fairy tern (Sterna nereis), the Vulnerable fat eastern curlew (Numenius madagascariensis), the Vulnerable great knot (Calidris tenuirostris), the Vulnerable malleefowl (Leipoa ocellata) and the Endangered slender-billed black cockatoo (Calyptorhyncus latirostris), the Endangered white-tailed black cockatoo (Calyptorhyncus baudinii) and the Near Threatened star finch (Neochmia ruficauda).
Special status amphibians in the Southwest Australia savanna are the Near Threatened Main's ground froglet (Geocrinia lutea). Special status reptiles in the Southwest Australia savanna are: the Near Threatened Bardick snake (Echiopsis curta), the Vulnerable Shark Bay ctenotus (Ctenotus zastictus) and the Endangered woma (Aspidites ramsayi).
Kilbarri National Park
Source: Protected Planet One of the major protected areas of the ecoregion is the Kilbarri National Park. This coastal preserve is noted for the diversity of herbaceous plant species.
There are 21 endemic taxa on the coastal cliff tops and gorge locale chiefly within the Kilbarri. One such noted taxon is the Kalbarri catspaw, a small flowering plant that is typically observed on newly burned ground. Several orchid species occur only within the Kilbarri and its environs, including the Kalbarri spider orchid and the Murchison hammer orchid.
The small-petalled Beyeria, earlier deemed to be extinct, was re-discovered in the National Park in 1994. The population inside the park is one of only three known populations.
Current status
The Southwest Australia savanna is classified with a conservation status of Critical/Endangered by the World Wildlife Fund; furthermore this ecoregion is designated as a G200 area, meaning it is among the highest priority worldwide for conservation. The Southwest Australia savanna is given the World Wildlife Fund ecoregion designation AA1209.
Types and severity of threats
Chief threats are a continuation of agricultural land conversion and the introduction of alien species of flora.
Justification of ecoregion delineation
The Southwest Australia Savanna ecoregion comprises three IBRA’s (acryonym for Interim Biogeographic Regionalisation for Australia): Geraldton Sandplains, Avon Wheatbelt, and Yalgoo (Thackway and Cresswell. 1995). Vegetation includes savanna woodland, mallee scrub and heath. This region is a transitional zone between the coastal mediterranean climate and the central arid regions. A portion falls within the Southwest Botanical Province Centre of Plant Diversity (Beard 1995), and the southern portion of this ecoregion falls within the Southwest Australia Endemic Bird Area (Stattersfield et al. 1998).
References and notes
- J.S.Beard. 1995. Southwest Botanical Province. Pages 484 – 489 in S. D. Davis, V. H. Heywood and A. C. Hamilton. editors. Centres of Plant Diversity. Volume 2. Asia, Australasia, and the Pacific. WWF/IUCN, IUCN Publications Unit, Cambridge, UK.Stattersfield,
- A.J & M.J.Crosby, A.J.Long, and D.C Wedge. 1998. Endemic Bird Areas of the World. Priorities for biodiversity conservation. BirdLife Conservation Series No. 7. BirdLife International, Cambridge, United Kingdom.
- Australia Department of Environment and Conservation. 2010. Annual Report. Department of Environment and Conservation: 2009-2010. ISSN1835-114X
- C.Michael Hogan, J.-M.Hero & J.D.Roberts. 2012. Arenophryne rotunda. ed. M.S.Koo. Amphibiaweb
- R.Thackway and I.D.Cresswell. editors. 1995. An Interim Biogeographic Regionalisation for Australia: a framework for establishing the national system of reserves, Version 4.0. Australian Nature Conservation Agency, Canberra.
- Western Australia. Department of Environment and Conservation. 2007. Shark Bay terrestrial reserves and proposed reserve additions: draft management plan 2007 Department of Environment and Conservation; Conservation Commission of Western Australia. Bentley, W.A.: Dept. of Environment and Conservation. section Bioregions
- Portions of the Justification for ecoregion delineation were prepared by Angas Hopkins of the World Wildlife Fund
