Key Threats: Australia

Threats to Biodiversity

• Perth is one of the fastest growing urban areas in Australia. The increase in human population is causing extensive water use and putting pressure on remaining native vegetation in the Swan Coastal Plain of Southwest Australia (Hobbs 1998).

• Woodland, shrubland and mallee (a multi-stemmed Eucalyptus) in Southwest Australia have undergone large-scale clearing for wheat cultivation. This has increased the number of rare and endangered plants, and left only 44% of original fauna intact (Hobbs, 1998, Rijavec et al. 2002; Hopper et al. 1996; Saunders 1993; Garkaklis et al. 2003)
• Remaining native vegetation in Southwest Australia has been estimated at 2-3%. These fragments are rarely viable since they are generally unfenced, which makes them susceptible to overgrazing and experience modified microclimates along their boundaries (Hobbs, 1998).

• A richness of endemic plants often occurs on unique soil types containing iron ore or nickel. As a result, these areas tend to suffer adverse effects from mining. The related infrastructure of roads can also spread invasive plants and pathogens (Coates and Atkins 2001).

• The soil in riparian areas, floodplains, wetlands and valley floors are becoming more salty (a process called salinization) because farmers have replaced deep-rooted native plants with shallow-rooted crops. This causes more rainfall to accumulate as groundwater which mobilizes stores of salt within the earth. Salinization in the Southwestern wheatbelt threatens 470 plants and 400 animals (Cramer and Hobbs 2002, ANZECC 2001; Hopper and Gioia 2004; Kieghery et al. 2004).

• Forests and heathlands in Southwest Australia are affected by the “dieback” pathogen Phytophtora cinnamoni, which is spread by the movement of moist soil (on hiking boots, for example) between infected and uninfected areas. Known as the “biological bulldozer,” it has caused entire ecological communities to collapse, with 6,000 plants estimated as susceptible (CALM 2004; Coates and Atkins 2001).
• Remaining native vegetation is seriously impacted by invasive alien plants that either arrived with European settlers, were introduced as grazing species, or escaped from ornamental plantings. Estimates suggest four plant species have become extinct and 57 are under threat from invasive plants (Leigh and Briggs 1992).
• Introduced animals such as cats and the European red fox prey on native mammals, ground nesting birds, lizards and insects.

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