Bushwalking in the South west of Western Australia
torridonbooks.com.au Information for bushwalkers in Western Australia

Forest Diseases

Die-back disease is the most damaging of the many forest diseases that affect our forests. Itís caused by the pathogen Phytophthora cinnamomi infecting the root systems of native plants. The first sign of the disease is when many of the understorey plants start to die off; the Banksiaís are particularly susceptible to dieback. This is followed by the death of many of the larger trees. The Marri trees are die-back resistant, but Jarrah is most susceptible and a graveyard of dead Jarrah trees indicates the presence of die-back. Another dieback resistant plant is Parrot bush (Dryandra sessilis). This can take over the understorey in die-back affected areas, another strong indicator of the presence of the disease.

Warm wet weather enables the pathogen to produce large numbers of mobile spores on the roots of infected plants. These then swim through wet soil and infect neighbouring plants. Transport of soil by vehicles has spread the disease along many of the tracks and roads. Walkers need to be aware of the dangers of spreading die-back when walking through infected areas, in wet weather.

The South-west Forests

The South West of Western Australia once supported extensive forests of tall eucalypts and an under-storey of incredible biodiversity. Walking through the patchy and often threadbare remains of this forest we get an idea of what it would have been like, and some clues as to what happened to it. Many of the tracks that we follow are the remains of logging railways, constructed to haul the prized hardwood timber from the forest.

This map shows many of the forests and National parks of the south west.

The Jarrah-Marri Forest
The dry sclerophyll forest, mainly comprising of jarrah (Eucalyptus marginata) and marri (Corymbia Calophylla) trees, extends from Gingin, north of Perth, right down almost to the south coast. Its western boundary follows the Darling Scarp, the Whicher Range and the Leeuwin-Naturaliste ridge to the south coast. To the east the forest fades to Marri and Wandoo woodlands as the annual rainfall decreases.

Argyle forest, between Boyanup and Donnybrook, was extensively logged by the Bunnings company in the first half of the twentieth century. Logging ceased almost 70 years ago and much of the forest has grown back, though itís still badly degraded in places. This is state forest and not a National Park; four wheel drive tracks abound and trees are still being felled for firewood. However, some interesting bushwalks, following old logging tracks, are still possible.

Karri Forest
The magnificent Karri trees (Eucalyptus diversicolor) are found in the cooler and much higher rainfall areas of the southern forests, south of Nannup and Bridgetown, and along the inland regions of the south coast to Albany. Occurrences of Karri forest on the Leeuwin-Naturaliste ridge, south of Margaret River, and in the Porongurup Range, indicates that the karri forest once extended well beyond its present boundaries.

The Bibulmun Track crosses the Brockman Highway between Nannup and Bridgetown and enters the Karri forest. From here down to Pemberton it burrows through the dense forest. Much of it utilises the remains of an extensive network of old bush railways, constructed to haul the logs to the mills. Several day walks, through dense Karri forest, can be made from Donnelly River Village.

The walk along the Bibulmun track between Donnelly River village and Pemberton is also recommended. Itís a five day walk with four nights in the track huts. Youíll need to make some arrangements to have someone drop you off and pick you up at the start and finish of the walk.

Boranup Forest in the Leeuwin-Naturaliste National Park is easily accessible, just 20 kilometres south of Margaret River. A 15 kilometre circular walk through the forest is described here.

Tuart Forest
The tall Tuart trees (Eucalyptus gomphocephala) occupied the sandy coastal plains between the Darling Scarp and the Indian Ocean. Unfortunately, our sprawling coastal towns have all but eliminated the Tuart forest and all that remains are the small patches of woodland that extend no more than a kilometre or so from the roadsides.

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The Trees

Bullich (Eucalyptus megacarpa
Bullich (Eucalyptus megacarpa) in Argyle forest

Karri in the Porongurup Range
Karri trees in the Porongurup Range

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Last updated March 2010
© A T Morphet