The Porongurup Range is spectacular in the surrounding landscape, its massive granite domes rising dramatically from the plains. This rugged forest ‘island’ contrasts with the largely cleared surrounding countryside and agricultural land patterns. The Porongurup National Park encompasses the majority of the Porongurup Range. Birdwatchers, photographers, botanists and wildflower enthusiasts are attracted to the Porongurup National Park by the beauty and diversity of the landforms and wildlife. The proximity to urban centres in the southwest including Albany and Mt Barker also makes it a popular destination for visitors.
The Porongurup National Park is located in the Shire of Plantagenet, 35 kilometres north of Albany in the south of Western Australia. The Park covers an area of about 2,621 hectares although the range itself is 3,200 hectares in size. The granite domes of the Porongurup Range are clearly visible from the coast around 30 kilometres to the south, as well as further inland from the Stirling Range 25 kilometres to the north. The Porongurup Range is 12 kilometres long and three kilometres wide, with the highest point of 670m at Devil’s Slide. Other summits include Marmabup, Wall’s Summit and the Rock of Gibraltar at the western end of the range and Morgan’s View, Nancy Peak and Twin Peaks in the centre.
The Porongurup National Park lies within the traditional lands of the Minang group of the Nyungar people (Green 1984; South Australian Museum 2006). Although the importance of the Porongurups in Nyungar cosmology is documented (Colbung & Montrose 1994), neither the Porongurup National Park nor Stirling Range National Park has been subject to a systematic archaeological survey (CALM, 1999). However, accounts of Minang society (Hallam 1975; Meagher 1974; Anderson 1984) indicate such sites are likely to occur in the area.
The Porongurup National Park is the largest inland remnant between the coast and the Stirling Range and one of the largest granite massifs in Western Australia (Beard 1981). It is also among the oldest mountain ranges in the world. It owes its formation to the massive tectonic forces that have shaped the southern and western coasts of Australia. The range formed about 1,184 million years ago, the likely result of a collision between the Australian and Antarctic landmasses (Black et al 1992, Abbott 1980). It is representative of the Archaean plateau of Western Australia. The range consists of gneisses and granites formed of porphyritic biotite granite and adamellite. Over time the softer sediments surrounding the granite have eroded, forming the peaks, domes and ravines visible today. Outcropping granite rocks on the south coast of Western Australia are characterised generally by diverse and endemic plant species, and the diversity of microhabitats has enabled the persistence of species beyond their main range in the face of climatic fluctuations (Hopper et al. 1997).
At various times the Porongurup Range has been isolated as a true island, most recently during the Eocene period (55 million years ago) when the sea reached as far as the Stirling Range (Olver 1998). Evidence for this can be found in bands of laterite which are located throughout the south-west of Western Australia. Areas of deep sand similar to that found to the north and east of the range are also evident.
The Porongurup Range has a Mediterranean climate with cool to mild winters and warm, sunny summers (CALM 1999). Conditions become cooler and more humid higher up in the range. Typically, the northern slopes of the range receive 840mm of rainfall whereas the windward, southern slopes receive 900-1000mm (Olver 1998). Most rainfall is received between May and October although at times, occasional snow may fall on the taller peaks for short periods during winter and spring. Most drainage lines flow north or south, with Bolganup Creek and Cockatoo Creek the only significant creeks.
The Plantagenet Shire is among the most extensively cleared shires in South-Western Western Australia (Griffin 1995). Only two small areas of uncleared land abut the boundary of the Porongurup National Park. Wheat-growing, grazing, forestry and more recently vineyards have altered the appearance of the areas adjoining the park and have had an impact on the plants and animals that live there.
The Porongurup Range possesses a rich floral diversity. Researchers have identified 822 vascular plant taxa comprising 709 natives and 113 weeds (Keighery 1999). The majority of plant species can be found in the laterite soils of the lower slopes. The largest families are the Cyperaceae (31 natives, 2 exotics), Orchidaceae (57 natives, 1 exotic), Poaceae (17 natives, 17 exotics), Asteraceae (38 natives, 16 exotics), Epacridaceae (31 natives), Mimosaceae (21 natives), Myrtaceae (44 natives), Papilionaceae (47 natives, 11 exotics) and the Proteaceae (52 natives) (Keighery 1999). There are five species and five sub-species endemic to the Porongurup Range including the EPBC listed Villarsia calthifolia and Apium prostratum subsp. Porongurup Range (CALM 1999, Keighery 1999). Five species are confined to the boundary of the National Park – Brachysema subcordatum, Hibbertia bracteosa, Billardiera granulata, Apium prostratum ssp. nov and Villarsia calthifolia (Keighery 1989). In addition, at least 26 species occur at the inland margin of their ranges (CALM 1999).
The Porongurup Range has been recognised by Beard (1979) as a separate vegetation system from other vegetation systems in the south-west – the Porongurup System (CALM 1999). The system is characterised by bare massive domes surrounded by karri forest.
There are four major plant communities in the Porongurup National Park – tall open forest (wet sclerophyll); open forest (dry sclerophyll); lithic complex (granite outcrops); and low open woodland. Karri forest dominates the tall open forest area, where the deep red soil known as karri loam and the high rainfall sustains the population (Beard 1981, NatureBase 2007). The karri forest is believed to have survived as a disjunct population in the Porongurup Range for over 5,000 years and is floristically different from the main areas of karri forest some 50 kilometres to the south-west (Barrett 1996, CALM 1999).
The open forest, located on the lower slopes in sandy, duplex or lateritic soils, is dominated by jarrah and marri trees. The main understorey species in this area includes wattle (Acacia leioderma), beard heath (Leucopogon revolutus) guinea flower(Hibbertia spp.)bitter pea (Bossiaea linophylla) and grass trees (Xanthorrhoea preissii)(Abbott 1982).At levels near 300m, where drainage is hindered, the open forest changes to open scrub dominated by banksias (Banksia littoralis), native myrtles (Agonis theiformis and Astartea fascicularis) and Kunzea recurva (Abbott 1982).
Along the rock rills and glades of the granite outcrops, scrublands, sedges and herbs dominate (Smith 1962). Most of the species endemic to the Porongurup Range are found in these areas. Granite outcrops in the South West Botanical Province, of which the Porongurup Range is the largest, support the highest levels of plant diversity, compared with any other granite outcrop in Western Australia (Hopper 1997).
A swamp dominated by Melaleuca preissiana is located on the western margin of the National Park and extends beyond the boundary. Minor communities including mallee heath, Eucalyptus tetragona and small areas of E. decipiens grow along Millinup Road. Higher up in the Porongurup Range regular cloud and fog cover provide an ideal environment for lichen, mosses and small flowering plants. Fifteen species of lichen and 300 species of fungi have been recorded in the Porongurup National Park (Herford 1996).
The varied topography of the Porongurup Range provides habitat for a wide variety of vertebrate species. The mammal species in the National Park include the western grey kangaroo (Macropus fuliginosus), brushtail possum (Trichosurus vulpecular), pygmy possum (Cercartetus concinnus), mardo (or yellow-footed antechinus – Antechinus flavipes leucogaster), mooti (or bush rat – Rattus fuscipes fuscipes), quenda (or southern brown bandicoot – Isoodon obesulus fusciventer) and honey possum (Tarsipes rostratus). The honey possum is the only representative of the family Tarsipedidae, and is found only in the coastal plain heaths of south-west Western Australia (Olver 1998, Herford 1996). Seventy-one bird species including the red-eared firetail (Emblema oculata) and Baudin’s black cockatoo (Calyptorhynchus baudinii) are also found in the park (Herford 1996). In addition, at least 17 reptile species are known to inhabit the park including King’s skink (Egernia kingii), the southern heath monitor (Varanus rosenbergi) and the marbled gecko (Phyllodactylus marmoratus) (Herford 1996). Several tree frog and southern frog species are also evident (Herford 1996).
A number of vertebrate species are listed under federal and state legislation as vulnerable or in need of special protection. The western ringtail possum (Pseudocheirus peregrinus occidentalis), crested shrike tit (Falcunculus frontatus whitei) and Baudin’s black cockatoo (Calyptorhynchus baudinii) are all recorded on the EPBC list of threatened flora and fauna species (EPBC Act 1999). Another listed species, the Noisy Scrub-bird was released into the Porongurup National Park in July and August 2006 as part of a translocation program.
The cool, wet mountain gullies of the Porongurup Range provide a refuge for a diversity of invertebrate species. A number of species have strong Gondwanan affinities, including the endemic trapdoor spider (Neohomogona bolganupensis), land snails (Bothriembryon spp.) and giant earthworm (Megacolex sp.) (Olver 1998, Herford 1996). Other species like the social crab spider (Diaea socialis) have outlying populations in the range (Olver 1998). Many of the relict species present in the Porongurup Range and in neighbouring Stirling Range are more closely related to invertebrate species found in mountainous areas of eastern Australia or on other Gondwanan continents than to the drier, low-lying areas surrounding the two ranges (Olver 1998). Other relict species found in the Porongurup Range include velvet worms (Oncophora), and an undescribed carnivorous snail (Paryphantidae sp). Land snails in particular, are an important indicator species of areas of moist refugia over long periods.
The Porongurup Range has the highest species richness and greatest abundance of spiders compared with other mountainous sites in south-west Western Australia. Twenty-seven species are found in the Porongurup Range compared with 26 from Bluff Knoll and 22 species from Mt Lindesay, both located in the Stirling Range National Park (Barrett 1996).
The spectacular seasonal wildflowers and the variety of outdoor activities draw thousands of tourists to the Porongurup National Park each year. Its conservation and management has strong support from among the local and wider community.