Plants and animals

by Tony Start, CALM WA

Regional overview

The Kimberley is an area of dramatic landscapes and a huge variety of habitats which support very diverse animal and plant communities. Quartzites, sandstones, limestones, lavas, granites and other rocks form high plateaux and rugged ranges. But once-mightier mountains have been eroded and transported by various processes to form sandplains, flood plains and vast tidal mud flats. Rock types determine both landforms and soils but water is a key factor in the process of their formation and in determining the distribution of fauna and flora within landscapes.

Most rain falls in humid, summer months. It is relatively high (more than 1200 mm) and predictable in the north west but meagre (less than 400 mm) and erratic towards the edge of the Great Sandy Desert. In the wet, torrents rush through usually dry gorges or down steep valleys. Some tumble straight into the sea but many feed into huge rivers that meander through flood plains made up of the alluvium they themselves deposited and they all recharge pools and aquifers that sustain life through the dry season.

The frill-necked lizard is found in the Kimberley and across northern Australia

Distribution of species

Sea and sandy deserts fringe the Kimberley savanna except to the east where it continues through to the Victoria River District. However, this is semi-arid country with a maximum rainfall approaching 800 mm near the coast. Many species of the Kimberley's more arid, central and southern savannas have continuous distributions into the Northern Territory and often into Queensland. Common examples are:

• Bauhinia (Bauhinia cunninghamii);
• Agile (Macropus agilis) and northern nail-tailed wallabies (Onychogalea unguifera);
• Red-collared lorikeets(Trichoglossus rubritorquis); and
• Frill-necked lizards (Chlamydosaurus kingii).

(To see a list of research findings on these species click on them.)

Further north, the Cambridge Gulf now separates the high-rainfall zones of the Top End and the north Kimberley. Most of the species endemic to the Kimberley are found in this area. However the occurrence of closely related species pairs and species with isolated populations in each region indicate past links with the plants and animals of the Top End.

Nevertheless, many more species of the far northern Northern Territory, which has a higher rainfall, are absent from the Kimberley than vice versa. These distribution patterns are illustrated with birds (see table) but other groups of animals, or plants could have been just as appropriate.

* Kimberley and Northern Territory. Many species extend further south in eastern Australia.