About Great Western Woodlands
Natural values of the Great Western Woodlands
Equivalent to Africa’s Serengeti or South America’s Amazon, the Great Western Woodlands is an internationally significant area of great biological richness. The area covers almost 16 million hectares, (more than twice the area of Tasmania) and is a continuous band of vegetation spanning the edge of the Western Australian ‘Wheatbelt’ to the Mulga country in north - the inland deserts to the northeast and the Nullarbor plain to the east.
The Great Western Woodlands represents the largest remaining intact temperate Woodland on Earth and is extraordinarily biodiverse. It is an Arc for rare and threatened plants and animals, containing thousands of species found nowhere else on the planet. Amazingly, more than 20% of all Australia’s flora species and 25% of Australia’s eucalypt species are found in the Great Western Woodlands area. Dozens of rare and threatened animals such as the Chuditch, Malleefowl, Red-tailed Phascogale and White-Striped Freetail bat call this region home.
Unfortunately Australia has the highest rate of mammal extinctions in the world and, nationally, bird numbers are declining rapidly - especially woodland birds. That’s one reason why big intact regions like this one are so important.
An intact landscape
Large intact functioning ecosystems are vitally important for healthy environment and communities. The Great Western Woodlands is the largest remaining intact area of temperate woodland in the World!
Globally more than 30% of the Mediterranean biome has been modified for urban and agriculture development and less than 5% of the remaining habitats are protected. As a consequence, these areas consistently emerge as global priorities for biodiversity conservation.
In Australia over 35% of the Mediterranean habitat has been cleared for agriculture and urban development. Much of what remains is fragmented, and susceptible to overgrazing, salinisation and edge effects.
In WA over the last 180 years, more than 20 million hectares of bush (woodland and shrubland, as well as coastline communities including tuart forest) has been converted to agricultural or urban land. The western and southern boundary of the Great Western Woodlands is literally where the clearing has stopped.
Intact landscapes are important for healthy ecosystem function, a refuge for plants and animals and important for humans because of our reliance on healthy land for our survival.
In the Great Western Woodlands we have the opportunity to retain a functioning environment with most of its species still present, or able to be reintroduced.
An Ark for our wildlife
The Great Western Woodlands is an Ark for our wildlife providing a unique haven for a community of animal species that are now threatened elsewhere in Australia. This is because similar habitats in Western Australia and through much of southeastern Australia have been heavily fragmented and cleared.
The region has a diversity of different foraging, nesting or roosting habitats 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 general species richness, 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 Western Australian 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. These comprise 16 mammal, 8 bird and 8 reptile species.
In 2005 Wilderness Society, through a grant from the Wind Over Water foundation, conducted a vertebrate fauna survey of the Honman Ridge – Bremer Range, and found 19 species that were of conservation significance in that area alone.
Spectacular ancient landscapes
The Great Western Woodlands is an ancient landscape. It today stands largely as it has for millennia—a relatively flat landscape punctuated by breathtaking natural features. It is sitting on part of the Yilgarn Craton, one of the oldest landforms in the world. For more than 250 million years, the Great Western Woodlands landscape has seen no mountain building or glacial events, or been covered in oceans. This is an exceptionally long period of time for life to evolve.The landscape has a continuous biological heritage that has seen the development of the first flowering plants, the evolution of a complex mosaic of soil types, dinosaurs coming and going, and the appearance of humans.
There have also been large climatic changes. The landscape has slowly dried out in the past 20 million years, and in the past two million years there have been major fluctuations in rainfall. It is the interplay between the age and complexity of the soils, climate, isolation from eastern Australia and many other factors, which have provided the opportunity for a huge amount of speciation to occur. The complex array of vegetation, landforms and soil types results in many different types of habitat for wildlife.
Lake Johnston is one of many massive natural Salt Lakes found in the Great Western Woodlands.The salt lakes are remnants of ancient drainage systems or rivers (Palaeochannels or Palaeodrainage systems) that originated in the late Cretaceous period about 65 million years ago. These drainage systems generally flowed north to south and eventually discharged into the ocean at the Great Australian Bight. As the land surrounding them eroded away, the drainage channels filled with sediments, resulting in the saline playas that we see today. The Palaeodrainage systems now terminate beneath the Nullarbor; none actually reach the ocean. The systems that underlay the salt lakes in the Great Western Woodlands are called the Cowan and Lefroy systems.
For a large part of the year the saline playas of the salt lakes have no surface water and often have a salt crust.
Even when dry, however, the lake playas support life, most of which is nocturnal. Iridescent Tiger Beetles and spiders roam the playa at night hunting insects, and Salt Lake Dragon lizards make hunting forays from their burrows on the shore.
Large numbers of aquatic fauna appear after heavy rains fill the lakes and wetlands. While the lake playas are dry, aquatic fauna is ‘resting’ in the form of cysts in the sediments. These cysts are activated by fresh water and hatch out into clam shrimp, fairy shrimp or brine shrimp larvae as well as the much smaller planktonic fauna such as Daphnia and copepods. Within a week or so of the lake filling, predatory insect larvae such as dragonflies, damselflies and various beetles hatch out—their parents having flown in from elsewhere—and hunt the crustaceans. The lake crustaceans complete their life cycles rapidly, since the lakes and wetlands often dry out or become too saline to support life within three weeks of filling. The fauna must therefore hatch, mature and produce eggs or cysts within that time.
In some years with good rain, the aquatic invertebrates reach such large numbers that wading birds such as avocets and stilts arrive en masse and breed on islands in the larger lakes. They have been known to produce two successive clutches of eggs if conditions are favourable and the (mainly) crustacean food source continues.
Under threat, but looking towards a bright future
The Great Western Woodland is under threat from significant increases in large, intense fires; climate change; fragmentation and loss of critical habitat; weeds and feral animals. The challenge now and in the coming decades is to maintain the natural values of the Great Western Woodlands, protect the ecological processes that sustain these values, and repair any environmental damage that has already occurred. If we fail in this challenge, then it is inevitable that much of this unique landscape will be lost.
We will also lose an opportunity to prevent the kinds of environmental problems now dominating most of southern Australia and its people—including species extinctions and land degradation.
Banded ironstone formations are iron rich knobs or ranges with flora and fauna quite different from the surrounding landscapes. There are very few of these features in the Great Western Woodlands and already some have been virtually removed by iron ore mining operations. The Helena and Aurora Range is currently under threat of mining and endemic plant species are at risk of extinction.
The challenges associated with climate change illustrate the importance of the Great Western Woodlands on a national and global scale. The Great Western Woodlands has massive carbon stores in its biomass, woody debris and soil. The estimated amount of carbon currently stored in the vegetation and soil is 950 million tonnes - equivalent to more than six times Australia’s greenhouse gas emissions for 2008. Poor land management, such as allowing the bushland to burn, can release this carbon as a greenhouse gas. Proper protection and management of the Woodlands can increase this stored carbon.
A rich mining heritage
The discovery of gold in the 1890’s saw a major influx of people into the region. This period known as the gold rush saw people travel from all over the world to try and make a fortune.
Within a decade, the region’s population had exploded to 50,000 people, the worlds longest water pipeline had been constructed, hundreds of mining companies had been floated on the London Stock exchange and many new towns had been built.
Today a total of 1,400 tonnes of gold has been extracted from the ‘greenstone’ ores, and nickel and other resources are also being extracted.
The Eastern Goldfields of WA is one of the richest mineral provinces in the World. Currently over 300 mines operate in the Great Western Woodlands and the industry is a major employer. There are more than 5000 existing mineral tenements in the Great Western Woodlands and almost 2,000 more pending. These tenements cover nearly 10 million of the 16 million hectares in the Great Western Woodlands.