Jarrah Forest is an interim Australian bioregion and ecoregion located in the south west of Western Australia.IBRA Version 6.1 data The name of the bioregion refers to the region's dominant plant community, jarrah forest – a tall open and open forest in which jarrah (Eucalyptus marginata) is the dominant overstorey species.Koch, J. M., & Samsa, G. P. (2007). Restoring Jarrah forest trees after bauxite mining in Western Australia. Restoration Ecology, 15(s4), S17-S25.
Jarrah Forest is recognised globally as a significant hotspot of plant biodiversity and endemism, and is also managed for land uses such as water, timber and mineral production, recreation, and conservation.McCaw, W. L., Robinson, R. M., & Williams, M. R. (2011). Integrated biodiversity monitoring for the jarrah (Eucalyptus marginata) forest in south-west Western Australia: the Forestcheck project. Australian Forestry, 74(4), 240-253.Rix, M. G., Edwards, D. L., Byrne, M., Harvey, M. S., Joseph, L., & Roberts, J. D. (2015). Biogeography and speciation of terrestrial fauna in the south‐western Australian biodiversity hotspot. Biological Reviews, 90(3), 762-793.Whitford, K. R. (2002). Hollows in jarrah (Eucalyptus marginata) and marri (Corymbiacalophylla) trees: I. Hollow sizes, tree attributes and ages. Forest Ecology and Management, 160(1), 201-214.
Location and description 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). Marri, formerly formally known as Eucalyptus calophylla, is a prevalent canopy species and the jarrah forest is commonly called jarrah-marri forest. Other eucalypts are present but in much less abundance. The Southern Jarrah Forest contains extensive areas of wetland vegetation in the south-east, dominated by paperbarks including the swamp paperbark (Melaleuca rhaphiophylla), and other eucalypts such as the swamp yate (Eucalyptus occidentalis) and the Albany blackbutt (Eucalyptus staeri).
The eastern forest is largely wandoo woodland, dominated by the canopy species wandoo (Eucalyptus wandoo), and, on breakaways, powderbark (also known as powderbark wandoo) (Eucalyptus accedens). Other eucalypts in these eastern areas include York gum (Eucalyptus loxophleba). The upland areas are particularly rich in plant life, while the drier inland plateau is less so. The wetter valleys with fertile soils contain flooded gum (Eucalyptus rudis), bullich (Eucalyptus megacarpa) and blackbutt (Eucalyptus patens). 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).Koch, J. M. (2007). Restoring a jarrah forest understorey vegetation after bauxite mining in Western Australia. Restoration Ecology, 15(s4), S26-S39. 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
Jarrah Forest supports 29 mammal, 150 bird, and 45 reptile species.Nichols, O. G., & Nichols, F. M. (2003). Long‐Term Trends in Faunal Recolonization After Bauxite Mining in the Jarrah Forest of Southwestern Australia. Restoration Ecology, 11(3), 261-272. 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). Most of these were once widespread vertebrate species but are now limited to the fragmented portions of Jarrah Forest.Nichols, O. G., & Grant, C. D. (2007). Vertebrate fauna recolonisation of restored bauxite mines—key findings from almost 30 years of monitoring and research. Restoration Ecology, 15(s4), S116-S126.
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.Morris, K., Johnson, B., Orell, P., Gaikhorst, G., Wayne, A., & Moro, D. (2003). Recovery of the threatened chuditch (Dasyurus geoffroii): a case study. Predators with Pouches: The Biology of Carnivorous Marsupials. CSIRO Publishing, Melbourne, 435-451. It now inhabits only 2% and is listed as "vulnerable" under the Environmental Protection and Biodiversity Conservation Act of 1999. For species such as the brushtail possum, population decline has not been extensive as they will colonise older restored minesites.
Carnaby's black cockatoo (Zenda latirostris) is endemic to south-west Western Australia and is listed as endangered under the EPBC of 1999.Environmental Protection and Biodiversity Conservation Act 1999 (Cth) (Austl.). 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).Abbott, I. (1998). Conservation of the forest red-tailed black cockatoo, a hollow-dependent species, in the eucalypt forests of Western Australia. Forest Ecology and Management, 109(1), 175-185.
Reptiles inhabiting Jarrah Forest include legless lizards, dragon lizards, skinks, blind snakes, pythons and venomous snakes. The western bearded dragon (Pogona minor) was found in restored forest rather than old growth forest.Craig, M. D., Stokes, V. L., Hardy, G. E., & Hobbs, R. J. (2015). Edge effects across boundaries between natural and restored jarrah (Eucalyptus marginata) forests in south‐western Australia. Austral Ecology, 40(2), 186-197.
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). Endemic frogs inhabit the southern sector of Jarrah Forest such as the small western froglet (Crinia subinsignifera) and the western marsh frog (Heleioporus barycragus).
Diverse invertebrate fauna communities are also present within Jarrah Forest. Many of these invertebrate species are responsible for nutrient recycling, an essential element of Western Australia's biodiversity.Grant, C. D., Ward, S. C., & Morley, S. C. (2007). Return of ecosystem function to restored bauxite mines in Western Australia. Restoration Ecology, 15(s4), S94-S103.Heath, M., Ladd, P., & Davis, J. (2007). The effect of prescribed burning on the leaf litter invertebrates of the jarrah forest, with special reference to Apocrita (Insecta: Hymenoptera).Majer, J. D., Brennan, K. E., & Moir, M. L. (2007). Invertebrates and the restoration of a forest ecosystem: 30 years of research following bauxite mining in Western Australia. Restoration Ecology, 15(s4), S104-S115. 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."Hassell, Cleve W., and Dodson, John R. (2003). "The fire history of south-west Western Australia prior to European settlement in 1826-1829". in Fire in ecosystems of south-west Western Australia:Impacts and management. Ian Abbott and Neil Burrows, eds. Backhuys Publishers, 2003, pp. 71–85.
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.
The Aboriginal inhabitants deliberately set fires to manage the land and vegetation. Evidence from lake and estuarine sediments and firsthand accounts suggest that fire intervals in well-settled areas were frequent – from one to ten years – compared to unoccupied forests and offshore islands, where fire intervals were 30 to 100 or more years. Frequent burning reduced woody cover and encouraged the growth of low shrubs, herbs, and grasses, fostering open woodlands, shrublands, and savannas and limiting areas of dense forest and thicket.
Settlement of the region by Europeans began in the 19th century. Forests were logged for timber, and areas cleared for agriculture and pasture. The Noongar were dispossessed from much of the land, and the fire regime changed from one of deliberately-set low-intensity fires to one of general fire suppression, with accidental or lightning-set fires which are less frequent but often more intense.
Jarrah (Eucalyptus marginata) is considered one of the best general purpose hardwoods in the world. The British started logging the jarrah forest in the 1840s to produce timber for use in construction, transport and power, and to protect water supplies.Abbott, I., Mellican, A., Craig, M. D., Williams, M., Liddelow, G., & Wheeler, I. (2003). Short-term logging and burning impacts on species richness, abundance and community structure of birds in open eucalypt forest in Western Australia. Wildlife Research, 30(4), 321-329. Logging was largely unregulated until the passing of the Forests Act 1918. The following 50 years saw forest management expand to include water quality and yield, soil management, rehabilitation of mined forest, recreation and nature conservation. Jarrah was harvested for woodchips as well as high quality furniture and flooring until the Government of Western Australia responded to decades of campaigning by placing a ban on native forest logging in 2024.
Environmental threats