Porongurup Range

If the Porongurup Range today resembles a granite island arising from the bed of land around it, it might be because that’s exactly what it once was. The Porongurup Range is granite, rocks that formed perhaps 1,150 million years ago far beneath the earth’s crust. Over time, the granite domes have emerged as the surrounding metamorphic rocks have been weathered down to their present height. About 55 million years ago, the sea level was much higher than at present, and the domes of the Porongurup would have formed islands as the sea lapped between it and the slopes of the Stirling Range to the north. Similar granite islands are still surrounded by the sea today and form islands lying off the coast from Albany, with the Porongurup Range representing their inland expression.

Covering only about 2000ha and reaching only 670m in height, the Porongurup Range punches well above its weight for beauty and diversity, and has been a popular place for holidays and recreation since the nineteenth century, with guesthouses established in the 1920s being well used and still in existence today. Most of the Range area is included in a National Park declared in 1925 and subsequently expanded slightly so that it now covers just over 2000ha. Before that, it had been covered by a pastoral lease and timber mills once operated in the area, too, so it is little surprise that controlling the introduced weeds in the Park is today a major conservation issue.

Nestled amongst vineyards on its northern slopes and plantations and farming land to its south, the Porongurup is only 20 km south of the Stirling Range National Park. The two Parks share some plants and animals, but the differences in the underlying geology and history make for some distinct differences too.

The Range includes karri forest, an outlier of a forest type now otherwise found mainly to the west of Albany within the higher rainfall zone (there is another small outlier just east of the Porongurups near ManyPeaks). The Porongurup outlier is thought to have been genetically isolated for around 5000 years and shows some signs of genetic divergence. Other vegetation types within the Range include Jarrah-Marri forest, woodlands on the foothills and the granite communities surrounding the domes themselves. It is within these granite communities that most of the ten species endemic to the Porongurup are found, including species like Mountain Villarsia (Ornduffia calthifolia). About 700 species of native plants are known from the National park area – and more than 100 weeds. A vigorous community effort, led by the Friends of the Porongurup Range and Oyster Harbour Catchment Group, tackled control of weeds over more than 1200ha of the Park following the 2007 wildfire and has improved the prospects for many of the native species to survive.

The cool moist habitats within the Range allow a great diversity of other organisms to thrive: more than 300 macrofungi and 15 lichen species are known and there are likely to be more; several Gondwana relictual invertebrates are also known, including the endemic spider Neohomogona bolganupensis, a Moggridgea spider that builds its nest on the bark of old, long unburnt Karri, and at least two other endemic spiders. The giant earthworm Megascolex sp, is also found here and as in the Stirling Range is dependent on niche environments – and probably refuge from fire.
Bigger fauna include the Western Ringtail Possum, Carnaby’s and Baudin’s Cockatoos and the Carpet Python. In such a small area of protected land and with the inherent risks of fires and other disturbances, management of the surrounding areas is critical to the survival of fauna populations. A local community group, the Friends of Twin Creeks, has secured a private reserve, Twin Creeks Reserve, as a node from which connectivity can be re-established between the Porongurup and the Stirling Range just 20km to the north. The Ranges Link (Stirling to Porongurup) is working on other restoration on private lands between the two parks, particularly on creeks and low lying land, to increase the areas of effective habitat available to species such as the Black-gloved Wallaby.