Great Western Woodlands - Extraordinary biodiversity
The Great Western Woodlands is of global biological significance. 25% of all Australia’s plant species are found here and 20% of all Australia’s Eucalypt species! The region is home to many unique animals, many rare and threatened.
The diversity of the region has three key features.
First, there are extraordinarily high numbers of species. Second, the taxonomic composition and structure of ecological communities vary greatly over short distances across the landscape. Third, remarkable ecological processes allow such richness and biomass to persist under such semi-arid and infertile conditions.
The past few decades have seen the discovery, collection and description of many new taxa in south Western Australia, including the Great Western Woodlands, at a rate without parallel among the world’s temperate floras. Botanists are still regularly discovering species new to science.
It is estimated that 10–15% of Western Australia’s flowering plants remain unknown to science.
The high degree of local speciation in this region is eclipsed in temperate zones only by that of the Greater Cape flora of South Africa.
Our analysis shows that the Great Western Woodlands is one of the cornerstones to south-western Australia’s profound diversity of plants. The Western Australian Herbarium has records of 3314 flowering plant species from 119 families in the Great Western Woodlands and over 4200 different ‘taxa’ (which is a list that includes undescribed species as well as subspecies, hybrids, and varieties).
It is estimated that almost half of these species are endemic to south-western Australia. This is more than one-fifth of Australia’s estimated 15 000 flowering plant species, and more than twice the number of species than occur in the whole of the United Kingdom (1500 species).
Since the Great Western Woodlands are still largely intact, there are fewer rare, threatened or endangered species in this region than in more disturbed areas of the state, such as the Wheatbelt.
However, the Great Western Woodlands contains many species of plants that are threatened by past and present human activities.
A significant number of species are listed by the Western Australian Government as requiring special protection.
Forty-four plant species are listed as ‘declared rare flora’ by the state government because they are rare, in danger of extinction, or in need of special protection. An additional 422 species have been listed as ‘priority’ species because they are known to exist in few populations, or they are under threat, due either to small population size or to threats to the land they live on.
Small population sizes may occur because species have very restricted environmental tolerances, are adapted to very specific habitats, or have suffered a range decline due to some activity in the past.
The 464 declared rare flora and priority species are distributed across the Great Western Woodlands, although the western and southern boundaries appear to contain many more species per ‘half degree cell’ than recorded in other parts of the region. This could reflect sampling bias (since more sampling has been conducted in these cells), as well as the fact that this boundary abuts a landscape that has been heavily modified for agriculture.
The region has a diversity of different foraging, nesting or roosting habitat for an array of animals some rare and vulnerable.
Relatively few comprehensive surveys have yet been undertaken. The Western Australia Museum and Birds Australia Atlas database has recorded 49 species of mammals, 138 reptile species, 14 frog species and 215 species of bird in the region. In addition to the value of the region’s species richness in general, the number of different reptile species make the Great Western Woodlands exceptional among the world’s reptile communities.
Many of these animal species are known to be rare and vulnerable such as the Malleefowl, Red-tailed phascogale, Regent Parrot and White-striped Free-tail Bat.
On the WA government’s rare and endangered fauna list are 32 threatened vertebrate species that either exist, or are likely to exist, in the Great Western Woodlands.