Under Threat

The unique and diverse ecosystems of the Southwest Australia Ecoregion are impacted by a number of threats that are particularly destructive within this region.

Threat Snapshot

Changes to and destruction of habitat
• Human Incursions and Competition for Resources
    - Land clearing for urbanisation
    - Fragmentation
    - Agricultural impacts
    - Mining and quarrying
    - Unsustainable recreation
• Impacts of introduced plants and animals
• Impacts of problem native species

Changes to Processes
• Changes in local and regional climate
• Drought (extended)
• Erosion, sedimentation, acid sulphate soils and Salinity
• Increased flooding episodes
• Changes to fire mosaics and regimes
• Changes to processes such as hydrology, pollination and nutrient cycles

Pollution

• Herbicides, pesticides, insecticides;
• Waste products
• Chemical and oil spills


Key underlying causes for biodiversity loss are based on the alteration and destruction of habitat; and the decline of our natural resources is based on over extraction and exploitation. For example it has been estimated that 93% of the original vegetation in the Wheatbelt (1) and 80% of the Swan Coastal Plain has been completely cleared (2). The Swan Coastal Plain, the most populated region in Western Australia, is experiencing significant pressure from urban development and growth. It is estimated that around 70 – 80% of the original wetlands on the plain have been cleared, drained or filled since European settlement, although with continued wetland losses this figure is likely to be much higher (3). The ecological function of many remaining wetlands has been so significantly altered that they now bear little resemblance to their original state (4).
 

Perth is one of the world’s most naturally diverse cities however clearing is occurring at an alarming rate – well over a football field a day (5). It is also believed that broad-scale clearing in the Southwest Australia Ecoregion may be responsible for reduced rainfall in cleared areas (due to a change in the land's surface and a reduced ability to form moisture-carrying clouds) (6). The sandplain heathlands near Perth have almost entirely been converted as the urban centre expands. Urban expansion reaches as far east as the Darling Scarp and has spread in a north-south direction as well (7).

Introduced plants and animals impact the Southwest Australia Ecoregion in a variety of ways including:

• Predation/herbivory by introduced species such as stock, rabbits foxes, cats, dogs and insects;
• Invasion of environmental weeds; and
• Diseases such as Phytophthora Dieback

Environmental weeds cause serious economic loss for agriculture and reduce the biodiversity of bushland (8). There are approximately 1,009 recorded weed species in the Southwest Australia Ecoregion (9).

Phytophthora Dieback is caused by the water mould Phytophthora cinnamomi. The disease was first noticed in the jarrah forests in 1940 but not identified until 1965 by which time thousands of hectares of forest had been destroyed (10). Phytophthora dieback has spread to other habitats throughout the Southwest Ecoregion including kwongan shrublands and the iconic Stirling Range National Park.  Over 40% of native plant species in the Southwest Australia Ecoregion are susceptible to this pathogen where it is causing catastrophic impacts on the biodiversity of the region (reference Dieback Working Group “Managing Phytophthora Dieback in Bushland edition 4 2008”.

Certain native species can also cause problems to sensitive ecosystems. For example agricultural use has allowed galahs (Cacatua roseicapella) to invade from arid regions, but galahs ringbark trees and may be contributing to woodland decline (11).

Although native plants are highly adapted to fire, the alteration or intensification of burning regimes can dramatically change the composition and condition of the natural vegetation (12). Fires pose a different threat on the coastal plain than they do in forests; on the coastal plain they are commonly the agent for woodland invasion by weeds (13).

Today, most usable private land in the region is farmed, although it requires the application of phosphate, as well as zinc, copper, cobalt, and molybdenum (14). The agricultural Wheatbelt zone is the most highly cleared area in WA due to past land clearing. Some local government areas have less that 5% of original native vegetation remaining (15).

Large-scale mining for bauxite is increasingly a threat to Southwest Australia's ecosystems; the region is one of the largest producers of alumina in the world. Open-pit mining destroys habitats and pollutes waterways (16).

Ecoregion conservation addresses overarching threats including those:

• Operating over multiple areas;
• Operating across boundaries; and
• Within and outside an ecoregion (17)

References

  1. World Wildlife Fund -  Southwest Australia savanna (AA1209) Wild World
  2. Beard, J. S. 1995. South-west Botanical Province. Pages 484 – 489 in S. D. Davis, V. H. Heywood and A. C. Hamilton. editors. Centres of Plant Diversity. Volume 2. Asia, Australasia, and the Pacific. WWF/IUCN, IUCN Publications Unit, Cambridge, UK
  3. .State of the Environment Report 2007 (http://www.soe.wa.gov.au/report/inland-waters/loss-or-degradation-of-wetlands.html)
  4. State of the Environment Report 2007 (http://www.soe.wa.gov.au/report/inland-waters/loss-or-degradation-of-wetlands.html)
  5. State of the Environment Report 2007 (http://www.soe.wa.gov.au/report/biodiversity/loss-or-degradation-of-native-vegetation.html)
  6. State of the Environment Report 2007 (http://www.soe.wa.gov.au/report/biodiversity/loss-or-degradation-of-native-vegetation.html)
  7. White, M. E. 1994. After the Greening: the browning of Australia. Kangaroo Press, Kenthurst, New South Wales, Australia
  8. http://florabase.calm.wa.gov.au/weeds/ Compiled by Alex Chapman; last updated on 24 July 2009
  9. http://florabase.calm.wa.gov.au/search/advanced?alien=y&current=y&southwst=*&type=sum
  10.  Conservation International -  http://www.biodiversityhotspots.org/xp/hotspots/australia/Pages/conservation.aspx#indepth
  11. World Wildlife Fund - Southwest Australia woodlands (AA1210) Wild World
  12. Conservation International -  http://www.biodiversityhotspots.org/xp/hotspots/australia/Pages/conservation.aspx#indepth
  13. Hopper, S. D., M. S. Harvey, J. A. Chappill, A. R. Main, and B. Y. Main. 1996. The western Australian biota as Gondwanan heritage – a review. Pages 1-46 in S. D. Hopper, J. A. Chappill, M. S. Harvey, and A. S. George, editors. Gondwanan
    Heritage: past, present, and future of the western Australian biota. Surrey Beatty & Sons, Chipping Norton, Australia
  14. Conservation International -  http://www.biodiversityhotspots.org/xp/hotspots/australia/Pages/conservation.aspx#indepth
  15. State of the Environment Report 2007 (http://www.soe.wa.gov.au/report/biodiversity/loss-or-degradation-of-native-vegetation.html)
  16. Conservation International -  http://www.biodiversityhotspots.org/xp/hotspots/australia/Pages/conservation.aspx#indepth
  17. Presentation by Richard McLellan
  • _q2y8526
  • _q2y8575
  • Final_rubbish_dumping_at_clementi_road_reserve__c__julia_cullity
  • Final_salinity__c__ray_mcknight_006

The Southwest Australia Ecoregion Initiative is a consortium project - find out more about how we're achieving conservation through collaboration.

learn more

A large number of agencies, organisations, individuals and community groups are conducting a wide variety of projects aimed at conserving the rich biodiversity of the SouthWest Australia Ecoregion...

learn more