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Biodiversity

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The Geographe Catchment resides within the Busselton-Augusta National Biodiversity Hotspot and South West WA International Biodiversity Hotspot. Biodiversity Hotspots being defined as areas with a high number of endemic species of flora and fauna which are also under immediate threat from impacts such as land clearing, development pressures, salinity and weeds and feral animals.

The South West Region has highly diverse flora with over 7000 plant species, of which nearly 80% occur only in the south west. The vegetation of the Swan Coastal Plain varies in its species composition and structure. Within the Geographe Catchment there are forests of marri (Corymbia calophylla) mixed with jarrah (Eucalyptus marginata) and blackbutt (Eucalyptus patens). Closer to rivers and streams flooded gum (E. rudis) occur with swamp paperbark (Melaleuca rhaphiophylla). Peppermint (Agonis flexuosa) woodland occurs closer to the coast forming important urban remnants for threatened fauna. Less than 35% of the pre-European vegetation remains in the catchment. Management of existing vegetation is therefore critical to enhancing the long-term survival of threatened flora, fauna and ecological communities and building resilience to increasing threats including climate change.

The Catchment is also home to a range of native fauna. Sixteen marsupial, ten mammal, seven introduced mammal and forty four reptile species have been identified in the region. The fauna of the area is under pressure from a range of threats including loss and fragmentation of habitat, decline of habitat quality through grazing and land degradation, introduction of domestic and feral animals and changes to fire regimes. As a result of these pressures population numbers of fauna species have reduced and several species have become extinct. Among those that have been afforded special protection status are: the Western Ringtail Possum, Quenda, Brush-tailed Phascogale, Chuditch, the Rakali or Water Rat, Baudin’s Black Cockatoo, Carnaby’s Black Cockatoo, and the Red-tailed Black Cockatoo.

Recovery Plans are in place for the Chuditch, Carnaby’s Black Cockatoo, and an Interim Recovery Plan is in place for Western Ringtail Possum. The Western Ringtail Possum is of particular significance in the catchment as the species is locally abundant in the Busselton to Dunsborough area and yet this represents one of the last remaining viable populations of the species. The possum’s primary habitat, the WA Peppermint Tree is under increasing threat from urban expansion.