The clay pan basins and clay flats of south western Australia are collectively termed clay pans, and occur where clay soils form an impermeable layer close to the surface. Wetlands in clay pans rely on rainfall and surface runoff to fill and are probably not connected to groundwater. These wetlands contain a rich suite of geophytes and annual species that flower at different times as the clay pans dry towards summer. The clay pans are the most diverse of the Swan Coastal Plain wetlands and contain high numbers of local endemics. There are no specific suites of flora that characterise all the clay pans, but they share general characteristics of substrate, landform, hydrology and vegetation structure. They also all meet Keeley and Zedler’s (1998) definition of vernal pools; ‘precipitation-filled seasonal wetlands inundated during periods when temperature is sufficient for plant growth, followed by a brief waterlogged-terrestrial stage and culminating in extreme desiccating soil conditions of extended duration.’
The clay pans are comprised of reasonably productive agricultural soils and many were cleared and drained soon after European settlement. Other areas were mined for clay for brick and tile manufacture. Remnant vegetation in clay pans was largely on the Swan Coastal Plain close to metropolitan Perth including in some areas that have been cleared more recently for urban development.
Gibson et al. (1994) defined a series of floristic community types across the southern Swan Coastal Plain based on analysis of 509 quadrats. This included four units that occurred on clay substrates, and that varied in floristic composition due to a suite of factors including substrate and rainfall. These are:
Herb rich saline shrublands in clay pans (Swan Coastal Plain community type 7 as identified in Gibson et al. 1994 (SCP07))
Herb rich shrublands in clay pans (SCP08 – Swan Coastal Plain community type 8)
Dense shrublands on clay flats (SCP09 – Swan Coastal Plain Community type 9)
Shrublands on dry clay flats (SCP10a – Swan Coastal Plain Community type 10a)
All of these clay pan types were listed as threatened ecological communities (TECs) in Western Australia in the 1990s.
Data for the vegetation of the seasonal clay-based wetlands across the extent of south western Australia were analysed by Gibson et al. (2005) and vegetation units were identified based on floristic patterning. An additional clay pan type named ‘Clay pans with mid dense shrublands of Melaleuca lateritia over herbs’ was identified through the analysis, and was included on the Priority ecological community list for Western Australia in 2006. In 2012 the four clay pan types identified by Gibson et al. (1994) and the ‘Clay pans with mid dense shrublands of Melaleuca lateritia over herbs’ were listed as a critically endangered community under the EPBC Act, under the umbrella title ‘Clay pans of the Swan Coastal Plain ecological community’. This nationally listed ecological community is synonymous with (and has an identical footprint) to the five state listed clay pan communities.
There are 114 occurrences of the clay pan communities in 50 separate locations that occupy a total of about 909 ha. The communities are highly fragmented, with about 60% of occurrences under 10 ha in size. The clay pan communities occur in significant bushland including Ellenbrook, Forrestdale Lake, Moore River, Byrd Swamp, Austin Bay, Drummond and Kooljerrenup Nature Reserves; Wandoo National Park, the Greater Brixton Street Wetlands, Anstey-Keane damplands, Jandakot Regional Park, and Brickwood Reserve (See Appendix 1, 3).
A summary of total areas in land management categories for the clay pan types occurs in Table 1.
Table 1: Land management categories for clay pan communities
Conservation reserves (ha)
Other state, local government reserves (e.g. road, rail, recreation etc.) (ha)
C’mwealth lands (ha)
Private lands (ha)
Bush Forever (ha)
Clay pans with shrubs over herbs
Areas of the clay pans are listed as Wetlands of National Significance, including Brixton Street Wetlands, Ellen Brook swamp systems, and Forrestdale Lake Nature Reserve which is also a Ramsar site (Environment Australia, 2001). The threatened and priority flora that occur in the clay pan communities are listed in Table 2. Some of the clay pan sites were identified through surveys completed for Bush Forever, and some also occur in Bush Forever sites (Keighery et al. 2012; Government of Western Australia 2000; see Appendix 1). The aim of Bush Forever is to seek to protect listed sites through a specified planning process.
A suite of fauna depend on the vegetation and surface water habitat, and seasonal changes in the clay pans communities. Three species listed under the EPBC Act are dependent on clay pans and adjacent areas. These are the critically endangered western swamp tortoise (Pseudemydura umbrina), and two species of native bee; Leioproctus douglasiellus (endangered) and Neopasiphae simplicior (critically endangered).
Appendix 1 provides a summary of information about the occurrences including land tenure, extent, soils and condition.