Clay pan wetlands were once widespread across the Swan Coastal Plain but it is estimated that more than 90 per cent of them have been cleared. Many were cleared, filled or drained for agriculture, or for housing due to their location close to the coast.

The clay pan communities are a series of wetlands found on clay soils that rely on winter rainfall to fill, and then dry to hard water-resistant clay pans in summer. The wetlands are characterised by the flowering of different groups of plant species as the wetlands dry.

The clay pan wetlands are the most species rich of the Swan Coastal Plain seasonal wetlands. Due to the amount lost however, the plant communities of these wetlands are amongst the most threatened in Western Australia.

There are four main distinct threatened clay pan communities recognised to date on the Swan Coastal Plain. Each vary in plant composition due to differences in soil type and where they sit in the landscape which influences the depth and the amount of time the community is flooded by water. The herb rich saline shrublands have heavy clay soils and hold water generally from winter to mid-summer. The herb rich shrublands in clay pans occur in low lying flat areas with a clay layer allowing for seasonal flooding. The dense shrublands on clay flats occur very low in the landscape and as such hold water for a very long time. The shrublands on dry clay flats are the most rapidly drying of the communities.

THREATS

The clay pan communities of the Swan Coastal Plain are threatened by a number of different factors, mainly because they occur in the most densely populated parts of coastal Western Australia and on some of the most productive agricultural soils in that landscape. Changes to the natural water flows through housing development, vegetation clearing and drought are a significant threat, with many of the plant species relying on the filling and gradual drying of the wetlands at the appropriate times of the year to survive.

Other threats include rising saline groundwater, invasion from weeds, too frequent fires, feral animals, illegal recreational activities, rubbish dumping and Phytophthora dieback. Many of the wetlands occur as very small isolated patches and as such the threats above can have severe consequences over a very short period of time.

“Photographing the clay pan communities in spring is essential in order to capture the many varieties of wildflower in full bloom. Growing out from a clay base, it was remarkable the way all the different colours mingled together – reds, pinks, purples, whites. It was easy to forget that in a few weeks this vibrant landscape would disappear, leaving only the sun-cracked surface of the clay bed.”
Tim Swallow – Photographer