The Low Rainfall Zone is one of three biogeographic zones into which south west Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

 is divided, the others being the High Rainfall Zone

High Rainfall Zone

The High Rainfall Zone is one of three biogeographic zones into which south west Western Australia is divided, the others being the Transitional Rainfall Zone and the Low Rainfall Zone....

 and the Transitional Rainfall Zone

Transitional Rainfall Zone

The Transitional Rainfall Zone is one of three biogeographic zones into which south west Western Australia is divided, the others being the High Rainfall Zone and the Low Rainfall Zone...

. The LRZ is considered marginal to the south west, and extends throughout much of Australia.

The Zones were first defined by Stephen Hopper

Stephen Hopper

Stephen Donald Hopper is a Western Australian botanist, specialising in conservation biology and vascular plants. He has written eight books, and has over 200 publications to his name. He was Director of Kings Park in Perth for seven years, and CEO of the Botanic Gardens and Parks Authority for five...

in his 1979 paper Biogeographical aspects of speciation in the southwest Australian flora. Initially, they were defined in terms of rainfall, with the LRZ being that part of the South West with annual rainfall of less than 300 millimetres (12 in). As the LRZ was marginal to his study area, Hopper did not give a clear demarcation of the zone, merely stating that it