This vast arid expanse extends into the heart of Western Australia. The mulga tree, a drought-adapted acacia, dominates here, and a variety of other plants grow in the understory. Annual rainfall is low here, and the infrequent summer monsoons rarely extend as far as the southern portions of this ecoregion. Mulga trees may reach up to 16 feet (5 m) high in areas with good rainfall and emu bushes and hop bushes grow alongside cassias in the understory. In drier areas, mulgas are accompanied by a grassy understory and this vegetation is known as Wanderrie country. Here, mulga trees grow in dense stands in places where rainfall drainage is concentrated.
The mulga tree possesses a number of adaptations that help it to thrive in this arid wilderness. These trees produce very long tap roots. Seedlings of only 3 to 4 inches (8-10 cm) in height can have tap roots that extend several 6 to 10 feet (a few2-3 meters) into the ground. They also have nitrogen-fixing bacteria on their roots that enable the trees to obtain nitrogen despite the low-nutrient soils in the region.
A wide variety of birds are found in this ecoregion, including flightless emus, bustards (bush turkeys), and a range of honeyeaters. Honeyeaters have unusual brush-tipped tongues that work much like a paintbrush, allowing them to empty a flower of its nectar in less than one second. The harsh, cackling scream of the blue-winged kookaburra rings out as small flocks of the striking Major Mitchell’s pink cockatoo fly overhead. Marsupials present in mulga shrubland include the bilby, a small bandicoot with rabbit-like ears, and the mole marsupial. The mole marsupial is an interesting example of convergent evolution--it has the same adaptations to a burrowing lifestyle as placental moles. Mole marsupials are blind, with enlarged forelimbs for digging and velvety fur that enables them to smoothly propel themselves through the soil. Red kangaroos, euros (shaggy wallaroos), brush-tailed opossums, and the endangered brush-tailed bettong can all be found in mulga scrubland. Reptiles found in this area include the thorny devil and the venemous mulga snake.
Cause for Concern
Grazing and mining are the main land uses in this ecoregion, but most of the land is uninhabited. In areas where grazingwith livestock occurs, mulgas may be overgrazed by livestock, especially by sheep.
For more information on this ecoregion, go to the World Wildlife Fund Scientific Report.All text by World Wildlife Fund © 2001