· Sweet Waters in a Salty Land
· Special Features
· Did You Know?
· Wild Side
· Cause for Concern
· Looking Ahead

Global 200 Snapshot

The Southwest Australia Rivers and Streams ecoregion has been relatively isolated, so many species have evolved in this ecoregion and nowhere else on Earth.  

Sweet Waters in a Salty Land

After Antarctica, Australia has the fewest rivers and the least run-off of any continent. Although southwestern Australia is not considered arid, only 36 inches (90 cm) of rain fall each year in this area. There are several rivers in this ecoregion: the Swan, Murray, Blackwood, Warren, and Frankland, as well as many inland lakes. Some of the lakes and rivers in this ecoregion are dry for part of the year.

Special Features

Because the short coastal rivers found in this ecoregion are in a relatively dry area, there is less species diversity here than in eastern Australia, where rivers are longer and have been more permanent, thus providing more varied and stable habitat for species to live. However, because these rivers have been isolated for so long, many of the species that have evolved here are endemic. The pools and marshes that form among granite outcrops come and go with the seasons and support unusual species of plants and insects that have adapted to the changing availability of water.

The salamaderfish lives in temporary pools in southwestern Australia. Where does the fish go when the pools dry up? It burrows underground until it reaches damp sand. This fish is able to breath by absorbing oxygen through its moist skin, like the lungless salamanders of North America do. Salamanderfish have been found as deep as 2 feet (60 cm) below ground! And when the pools fill again with water, the fish emerge from underground.

Wild Side

There are many endemic species living here: Nine of 14 fish species are endemic, as are 12 of 19 fairy shrimp species. Among this ecoregion’s distinctive species is the salamanderfish, the only species in the family Lepidogalaxiidae. The salamanderfish may be related to galaxiids, of which there are three endemic species in this ecoregion as well: western minnow, black-stripe minnow and western mud minnow. Other endemics are freshwater cobbler, western pygmy perch, long-headed goby, and King River perchlet. In addition, the anadromous pouched lamprey inhabits this ecoregion.

Cause for Concern

A number of introduced species, including rainbow trout and brown trout, have proliferated in streams and rivers of the region. With the exception of one endemic species, all of the introduced species are far larger than the native freshwater animals found here. Habitat loss, particularly of important seasonal pools, alteration of the natural flow of water, and negative impacts from agricultural practices, including the loss of streamside trees and other vegetation, all pose threats to the native plants and animals. In addition, the waterlogging of lands next to irrigated agricultural areas has led to the layering of salts in the soil that were blown in with ocean spray from the sea over millions of years. Thus, rivers and streams in this region, as well as groundwater sources, are becoming highly saline.

Looking Ahead

Check back soon for more about the conservation of this ecoregion.