Jarrah Forest

The bioregion stands on the Yilgarn block inland plateau and includes wooded valleys such as those of Western Australia's Murray River and the Helena River. The Darling Scarp forms the western edge of the plateau, and the Swan Coastal Plain lies between the scarp and the coast. The scarp generally forms the western boundary of the bioregion, although it extends to the west coast at Cape Naturaliste. At the southern end of the plateau is the Whicher Range and inland is the lower Blackwood Plateau. The south eastern interior of the region includes the peaks of the Stirling Range, now preserved within Stirling Range National Park. Soils in the jarrah forest are infertile, especially for phosphorus, and are often salt-laden. The bioregion covers an area of . It is divided into two sub-regions: Northern Jarrah Forest comprising , and Southern Jarrah Forest comprising . The Swan Coastal Plain bioregion lies to the west below the scarp. The Warren bioregion, also known as the Jarrah-Karri forest and shrublands, is to the south. The Avon Wheatbelt bioregion, part of the Southwest Australia savanna ecoregion, is to the east. ==Climate==

The area has a warm Mediterranean climate, with more annual rainfallon the scarp than inland or to the north-east. == Flora ==

Jarrah Forest is unique in that it shares the co-dominate Corymbia species marri (Corymbia calophylla). Other eucalypts in these eastern areas include York gum (Eucalyptus loxophleba). Heath is a common understorey of the jarrah forest in the north and east. The smaller trees commonly found in Jarrah Forest include bull banksia (Banksia grandis), sheoak (Allocasuarina fraseriana), snottygobble (Persoonia longifolia) and woody pear (Xylomelum occidentale). Rare plants within Jarrah Forest include orchid species Drakaea confluens and Caladenia bryceana, and Baumea reed beds are unique to the forest and adjacent areas. == Fauna ==

browsing for nuts in a jarrah tree Jarrah Forest supports 29 mammal, 150 bird, and 45 reptile species. Mammals include the numbat (Myrmecobius fasciatus), Gilbert's potoroo (Potorous gilbertii), western quoll or chuditch (Dasyurus geoffroii), woylie (Bettongia penicillata), tammar wallaby (Notamacropus eugenii), western ringtail possum (Pseudocheirus occidentalis), common brushtail possum (Trichosurus vulpecula), quenda or western brown bandicoot (Isoodon fusciventer), and red-tailed phascogale (Phascogale calura). The chuditch, before the introduction of large mammalian pest species, was the largest carnivorous marsupial in south-west Western Australia, distributed across 70% of mainland Australia. It now inhabits only 2% and is listed as "vulnerable" under the Environmental Protection and Biodiversity Conservation Act of 1999. Other birds to inhabit Jarrah Forest include rare birds such as the forest red-tailed black cockatoo (Calyptorhynchus banksii naso), Muir's corella (Cacatua pastinator pastinator), black-throated whipbird (Psophodes nigrogularis), western bristlebird (Dasyornis longirostris), noisy scrub-bird (Atrichornis clamosus) and Baudin's black cockatoo (Calyptorhynchus baudinii). Reptiles inhabiting Jarrah Forest include legless lizards, dragon lizards, skinks, blind snakes, pythons and venomous snakes. Amphibians found in the northern sector of Jarrah Forest include the rare white-bellied frog (Geocrinia alba), yellow-bellied frog (Geocrinia vitellina) and sunset frog (Spicospina flammocaerulea). In particular, the insect group Apocrita, which includes wasps, bees, and ants, are a keystone group that, through predation and parasitism, keep other invertebrate populations controlled. The loss of Apocrita could be detrimental to the invertebrate community and to the jarrah forest ecosystem. Rare and endandered native bees include Leioproctus douglasiellus and Neopasiphae simplicior. == History ==

The first evidence of human habitation of the region was 50,000 years ago at Devil's Lair by ancestors of today's Aboriginal people. The Noongar are the Aboriginal inhabitants of the bioregion. The Noongar comprised 14 groups, which spoke distinct but mutually-intelligible languages. Aboriginal populations were generally denser on the coastal plain and along the coastal forest edge, and in the interior woodlands and shrublands, particularly near permanent streams and river estuaries. Population was sparse in the forested areas of the south. Logging was largely unregulated until the passing of the Forests Act 1918. == Environmental threats ==

Most of Jarrah Forest has been cleared for agriculture, timber and mining, leading to the consequent degradation of flora and fauna species and ecosystems. Native flora also suffers from disease and exploitation of water sources for agriculture. Less anthropological threats include periodic wildfire, pathogens, variable climate and outbreaks of defoliating insects. Introduced species The significant population loss of fauna species in Jarrah Forest is attributed foxes and cats (Felis catus). Swarms of feral bees take over tree hollows, stealing the nesting sites of hollow-nesting birds. The range of the western quoll has dramatically reduced since European settlement. The loss of forest for agriculture and timber has resulted in diminishing population numbers of many fauna species. Spending a large portion of their lives in roosts, they are used as diurnal shelters, shelter during maternity, and shelter for bachelors, migrating and hibernation sites. Alcoa had handed back areas of its original bauxite mine in Jarrahdale in 2005 and 2007. The group's claim that Alcoa was clearing each year was denied by Alcoa, with Alcoa refuting the group's criticism. Along with concerns that Alcoa's operations could impact the drinking supply of Serpentine Dam, the Environmental Protection Authority (EPA) of Western Australia began looking into the company's operations and impacts after a referral from the West Australian Forest Alliance. In December 2023, Premier Roger Cook began stricter control over Alcoa's mining operations ahead of the EPA's decision. In 2024 the state government overturned environmental conditions on South32's Worsley Alumina expansion and approved the mine expansion on 20 December 2024. The project received federal approval in 2025. In 2025, the EPA opened a public environmental review for Alcoa's 2023–2027 mining management plan for the Darling Range and Alcoa's proposal to increase production at its Pinjarra refinery and transition mining at the existing Huntly Mine to the Myara North and Holyoake regions and re-enter the O'Neil region. The EPA received more than 59,000 public submissions related to the proposals. Following the closure of the public comment period, Alcoa withdrew exploration plans in parts of the Perth Hills. Disease Prevalent in the northern areas of Jarrah Forest, dieback disease, caused by the introduced soil-borne pathogen Phytophthora cinnamomi, is a serious threat to many plant species. The disease involves the formation of lesions (decaying tissue) starting in the roots and moving up the stem of a plant, and, in the case of many species, killing them. It negatively affects more than 22% of the plant species in the forest. P. cinnamomi has been found in suberized and partially suberized roots that are perennial and it is these roots that form the specialised feeder root system of the jarrah. The spread of dieback is exacerbated by altered drainage caused by mining and timber harvesting. The soil population of P. cinnamomi is generally highest during spring, the time of year when soil temperature and moisture levels are high. An increase in summer rainfall is likely to increase the harm that this pathogen causes in the northern and southern jarrah forests, with high mortality rates of jarrah expected. == Management ==

Forestcheck is a Department of Parks and Wildlife initiative that is responsible for monitoring biodiversity in the jarrah forests of south-west Western Australia. Monitoring total species richness, abundance and composition Forestcheck is designed to provide forest managers with accurate accounts of changes and trends in biodiversity associated with management activities. Shelterwood forest limits logging to a residual basal area of and gap release treatment to a residual basal area of The fungicide phosphite has been found to be effective treatment against P. cinnamomi, especially when applied before a plant is infected. The fungicide can be applied after infection, however the greater the time between infection and treatment, the less effective it will be. It is difficult to estimate the cost of plant disease in conservation areas; loss of conservation values cannot be given monetary value. However, the cost of controlling the disease can. It was estimated that the control of P. cinnamomi in 1989 cost the Western Australian Government at least , equivalent to in . Disease management plans focus on minimising the spread of the mould by restricting movement of propagules in soil and by translocating plant species from infected sites to healthy sites. Vertebrate fauna play a key role in jarrah forest ecosystem processes including pollination, grazing and predation. The chuditch, quenda and common brushtail possums are three such species considered essential in the development of a sustainable restored forest ecosystem. To prevent population numbers of these species and other vertebrates from further declining an aerial fox baiting program was introduced forest-wide. Management practices carried out to ensure the persistence of hollow-using species include protecting old growth jarrah forest and keeping extensive areas of forest reserved from logging. In the sections of jarrah forest are available to timber harvesting, science-based prescriptions have been implemented delegating those trees that are to be retained. ==Protected areas==

12.86% of the ecoregion is in protected areas. There are many small areas of parkland, and larger protected areas include the Dryandra Woodland and the Perup Forest Ecology Centre. The Walpole Wilderness Area, which was established in 2004, includes several national parks that cover a portion of the southern Jarrah Forest and the Jarrah-Karri forest and shrublands to the south. Lane Poole Reserve is the largest reserve in the Northern Jarrah Forest. There are few large and secure reserves such as national parks and nature reserves in the northern jarrah region where the best forest occurs. Much of this region is under long-term mining leases for bauxite owned by Alcoa and Worsley who have actively resisted attempts to allow the WA government to create substantial and secure reserves. Protected areas include: • Avon Valley National Park • Beelu National Park • Blackwood River National Park • Boyndaminup National Park • Bramley National Park • Dalgarup National Park • Dryandra Woodland National Park • Easter National Park • Gooseberry Hill National Park • Greater Kingston National Park • Greater Preston National Park • Greenmount National Park • Hassell National Park • Helena National Park • Hilliger National Park • John Forrest National Park • Kalamunda National Park • Korung National Park • Lake Muir National Park • Lake Muir Nature Reserve • Lane Poole Reserve • Lesmurdie Falls National Park • Midgegooroo National Park • Milyeannup National Park • Mount Frankland North National Park • Mount Lindesay National Park • Mount Roe National Park • Porongurup National Park • Serpentine National Park • Shannon National Park • Stirling Range National Park • Wandoo National Park • Walyunga National Park • Waychinicup National Park • Wellington National Park • Whicher National Park • Wiltshire-Butler National Park • Yelverton National Park == Benefits of protection ==

Unlogged buffers and old growth forest contain high densities of trees with appropriate hollows for roosting, where gap release and shelterwood areas do not. Within two to three years of the aerial baiting program mammal species numbers increased. Birds rapidly colonise and 95% of species found in old growth Jarrah Forest are now in rehabilitated forests ten years or older. The protection of old growth jarrah forest needs to continue, especially in the northern region and the best way to achieve this is to reclaim some of the mining lease areas granted to Alcoa and Worsley and create substantial reserves with A Class status. Additionally jarrah forest needs to be rehabilitated to promote further growth, decrease fragmentation and to maintain and improve flora and fauna biodiversity, a process that may take decades. == References ==