Western Mallee is an

Interim Biogeographic Regionalisation for Australia The Interim Biogeographic Regionalisation for Australia (IBRA) is a biogeographic regionalisation of Australia developed by the Australian government's Department of Sustainability, Environment, Water, Population, and Communities. It was devel ...

(IBRA) subregion in southern

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

. It is a sparsely populated subregion with an area of about 47,000 square kilometres, roughly centred on the town of Newdegate. Largely cleared for intensive agriculture, it still retains patches of native vegetation, but these are under environmental stress from threats such as rising

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

, and are poorly managed.

Geography

Western Mallee is roughly defined as the western half of the Mallee biogeographic region. It has an area of 47,636 square kilometres, which is only lightly populated. The main towns are Hyden, Gnowangerup and

Lake Grace A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

; lesser towns include

Kulin Kulin may refer to: Places *Kulin, Western Australia, a small town in Australia ** Shire of Kulin, a local government area *Kulin, Iran, a village near Tehran *Kulin, Lower Silesian Voivodeship, a village in south-west Poland *Kulin, Kuyavian-Pome ...

, Ongerup, Duggan, Newdegate,

Lake King Lake King is a town in the eastern Wheatbelt region of Western Australia, from Perth along State Route 40 between Kelmscott and Ravensthorpe. As of 2016, the town had a population of 95. The 2011 census recorded both the population of the tow ...

and Kondinin. The subregion contains a number of ecologically important freshwater wetlands, including the

Lake Bryde-East Lake Bryde Lake Bryde-East Lake Bryde is a DIWA-listed freshwater wetland system located in the Great Southern region of Western Australia. The system consists of two lakes: Lake Bryde, with an area of ; and East Lake Bryde, with an area of about . They ...

wetlands, a DIWA Wetland of National Significance and habitat for a critically endangered

threatened ecological community Threatened ecological community is a term used in Australia for ecosystems that are in danger of being lost due to some threatening process. Federally, threatened ecological communities are identified and protected under the ''Environment Protectio ...

of shrub lake beds; the

system of wetlands, also a DIWA Wetland of National Significance; and the Lake Cronin system.

Geology

Western Mallee is situated on south-eastern parts of the

Yilgarn Craton The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have be ...

. It has a gently undulating landscape, with somewhat more relief than eastern parts of the Mallee region. There are a variety of soils, including

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

s and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...

s over

kankar {{unreferenced, date=April 2008 Kankar or kunkur is a sedimentological term derived from Hindi, occasionally applied in India and the United States to detrital or residual rolled, often nodular calcium carbonate formed in soils of semi-arid reg ...

;

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

; lateritic pavements; and granite outcrops.

Gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

s also occur in the area. The subregion has occluded

drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditio ...

, with a number of lakes, both saline and fresh.

Climate

Western Mallee is semi-arid, with a warm, dry,

Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...

. It has seven to eight dry months, and a winter rainfall typically between 250 and 500 millimetres (10–19 in).

Vegetation

Only about 30% of the subregion retains its native vegetation. Within this area, most soil types carry mallee communities consisting primarily of ''

Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as euca ...

'' species. Sands and laterites support scrub-heath of

Myrtaceae Myrtaceae, the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All speci ...

and

Proteaceae The Proteaceae form a family of flowering plants predominantly distributed in the Southern Hemisphere. The family comprises 83 genera with about 1,660 known species. Together with the Platanaceae and Nelumbonaceae, they make up the order Pro ...

, and the finer-textured soils support ''Eucalyptus''

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

s; the latter have a particularly high diversity of flora, of which around 25% is rare. Granite outcrops also support a characteristic vegetation. There are also a number of vegetation communities of lesser extent, including some that are considered endangered or at risk. Most notable is the critically endangered community of ''Muehlenbeckia horrida'' subsp. ''abdita'' and ''

Tecticornia verrucosa ''Tecticornia verrrucosa'' is a species of plant that is succulent and halophyte (salt tolerant). This plant was a member of the Chenopodiaceae, which are now included in family Amaranthaceae. ''T. verrucosa'' was first described in 1972 by ...

'' that occurs on the lake beds of the

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

system. Gypsum dunes support a vulnerable ecological community of herblands and bunch grasslands, and an at-risk community of ''

'' aff. '' incrassata'' over low scrub; at least 80 plant species are likely to occur only on gypsum dunes, including several threatened species. Some plant communities of the Bremer Range are also considered vulnerable.

Flora and fauna

Information on Western Mallee's flora and fauna is scarce, as the area has not had a thorough biodiversity survey. What information is available has been gathered in the context of conservation assessment: The subregion contains many endemic plant species in the ''

'', ''

Acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus na ...

'',

such as ''

Grevillea ''Grevillea'', commonly known as spider flowers, is a genus of about 360 species of evergreen flowering plants in the family Proteaceae. Plants in the genus ''Grevillea'' are shrubs, rarely trees, with the leaves arranged alternately along the b ...

'', ''

Hakea ''Hakea'' ( ) is a genus of about 150 species of plants in the Family ''Proteaceae'', endemic to Australia. They are shrubs or small trees with leaves that are sometimes flat, otherwise circular in cross section in which case they are sometimes d ...

'' and ''

Banksia ''Banksia'' is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes, and fruiting "cones" and heads. ''Banksias'' range i ...

''; and various

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

. It contains numerous rare, endangered and priority flora. It also supports a number of rare or endangered fauna, including some that fall within the critical weight range for

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve sp ...

es. The

pig-footed bandicoot ''Chaeropus'', known as the pig-footed bandicoots, is a genus of small mammals that became extinct during the 20th century. They were unique marsupials, of the order Peramelemorphia (bandicoots and bilbies), with unusually thin legs, yet were abl ...

(''Chaeropus ecaudatus'') and crescent nailtail wallaby (''Onychogalea lunata'') previously occurred in the subregion, but both are now extinct. The

rufous hare-wallaby The rufous hare-wallaby (''Lagorchestes hirsutus''), also known as the mala, is a small macropod found in Australia. It was formerly widely distributed across the western half of the continent, but naturally occurring populations are now confine ...

(''Lagorchestes hirsutus'') is now extinct in the wild, and a further ten species of mammal are extinct in the subregion. The endangered

red-tailed phascogale The red-tailed phascogale (''Phascogale calura''), also known as the red-tailed wambenger, red-tailed mousesack or kenngoor, is a small carnivorous marsupial found in inland areas of south-western Western Australia, and has been reintroduced in ...

(''Phascogale calura'') still occurs in the region, as do the vulnerable black-flanked rock-wallaby (''Petrogale lateralis'') and heath rat (''Pseudomys shortridgei''), and the

western brush wallaby The western brush wallaby (''Notamacropus irma''), also known as the black-gloved wallaby, is a species of wallaby found in the southwestern coastal region of Western Australia. The wallaby's main threat is predation by the introduced red fox (' ...

(''Macropus irma'').

Land use

Western Mallee falls within what the Department of Agriculture and Food terms the "Intensive Land-use Zone" (ILZ), the area of Western Australia that has been largely cleared and developed for intensive agriculture such as cropping and livestock production. Within this zone, the vast majority of land has been cleared for agricultural purposes. In Western Mallee's case, only 31% of the area retains its native vegetation. Around 10% of the subregion is held within

nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...

s for conservation purposes, covering about 25% of the remaining vegetation. There is also a small amount of

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

mining, and a tourist industry centred on

Wave Rock Wave Rock ( nys, Katter Kich) is a natural rock formation that is shaped like a tall breaking Wind wave, ocean wave. The "wave" is about high and around long. It forms the north side of a solitary hill, which is known as "Hyden Rock". This ...

near Hyden. The subregion contains populations of ''

'' and ''

Melaleuca ''Melaleuca'' () is a genus of nearly 300 species of plants in the myrtle family, Myrtaceae, commonly known as paperbarks, honey-myrtles or tea-trees (although the last name is also applied to species of '' Leptospermum''). They range in size ...

'' species that produce commercial quantities of cineole oil, so in future the subregion is likely to support a plantation-based oil mallee industry, at least as a source of breeding material if not also land. The subregion's nature reserves are poorly managed. Little information is available for management purposes, as the subregion has not had a thorough biodiversity survey, vegetation mapping is available only at 1:250,000 scale, and there are virtually no historical records of fires or other significant events. Other than routine baiting of foxes in some reserves, there is little done to manage threats. The main threat, rising salinity, is completely unmanaged, despite having already caused widespread population declines and extinctions in lowland communities. The subregion was given a Continental Stress Class of 3 when measured against the criteria, but the authors of that assessment stated that it should more properly be rated at 2 or even 1, because of the poor connectivity of reserves within cleared areas.

Biogeography

Western Mallee was introduced in IBRA Version 6.1. Its region code is MAL2. It is one of two subregions of the Mallee region, the other being

Eastern Mallee Eastern Mallee is an Interim Biogeographic Regionalisation for Australia (IBRA) subregion in southern Western Australia. Geography Eastern Mallee is roughly defined as the eastern half of the Mallee biogeographic region. It has an area of aroun ...

.IBRA Version 6.1
data The Mallee,

Avon Wheatbelt The Avon Wheatbelt is a bioregion in Western Australia. It has an area of . It is considered part of the larger Southwest Australia savanna ecoregion. Geography The Avon Wheatbelt bioregion is mostly a gently undulating landscape with low reli ...

and

Geraldton Sandplains Geraldton (Wajarri: ''Jambinu'', Wilunyu: ''Jambinbirri'') is a coastal city in the Mid West region of the Australian state of Western Australia, north of the state capital, Perth. At June 2018, Geraldton had an urban population of 37,648. ...

regions together comprise

Hopper Hopper or hoppers may refer to: Places *Hopper, Illinois * Hopper, West Virginia * Hopper, a mountain and valley in the Hunza–Nagar District of Pakistan * Hopper (crater), a crater on Mercury People with the name * Hopper (surname) * Grace H ...

's Transitional Rainfall Zone of

Beard A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, usually pubescent or adult males are able to grow beards. Throughout the course of history, societal at ...

South West Botanical Province Southwest Australia is a biogeographic region in Western Australia. It includes the Mediterranean-climate area of southwestern Australia, which is home to a diverse and distinctive flora and fauna. The region is also known as the Southwest Aus ...

. Under the

World Wide Fund for Nature The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wor ...

's regionalisation of the world's terrestrial surface into "

ecoregions An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of l ...

", the Western Mallee subregion falls within the

Esperance Mallee Esperance mallee is an ecoregion on the South coast of Western Australia, south coast of Western Australia, a coastal strip where the predominant vegetation consists of short eucalyptus trees and shrubs. Location and description A part of t ...

ecoregion, one of 6 ecoregions comprising the

Southwest Australia Southwest Australia is a biogeographic region in Western Australia. It includes the Mediterranean-climate area of southwestern Australia, which is home to a diverse and distinctive flora and fauna. The region is also known as the Southwest Aus ...

ecozone.