An eighty-mile beach, pristine reefs, and Australia’s oil field
I. Map boundaries: 10 to 20 degrees South; 112 to 120 degrees East
II. Countries (Provinces): Australia (Western Australia), Indonesia (East Nusa Tenggara [Southeast Islands]).
III. Overview
The Indian Ocean that dominates this map area marks the transition between the equatorial forests to the north and the desert to the south. Upper surface layers of the ocean are occupied by Indonesian throughflow waters, which are warm and of low salinity. These waters flow toward the poles because the lower density causes a difference in sea level height between the Pacific and Indian Oceans.
In between is the Rowley Shoals, a chain of three diverse coral reefs and islands preserved as marine protected areas. To the north of Rowley Shoals, marine canyons associated with upwellings enhance biological productivity and attract predatory fish, sharks, toothed whales, and dolphins. To the west of the Rowley Shoals is the Exmouth Plateau, a now-submerged leftover fragment from continental drift which is attached to western Australia. The plateau is 500 to 5,000 m in depth and is dotted with pinnacles. The extensive shallow continental shelf off of Western Australia shows enhanced fish diversity. Of the 500 fish species, 76 are endemic to Australia. Rowley Shelf is the location of Australia’s largest oil field, the North West Shelf Venture. A pipeline takes the oil to shore from the vicinity of Rankin Shoal.
The mouth of the DeGrey River extends into this map area. This isolated freshwater drainage harbors endemic fish species. To the east is Cape Keraudren and the beginning of Eighty-Mile Beach, an area of extensive tidal range and a wetland of international importance for shorebirds. The marshes of Eighty-Mile Beach contain freshwater springs, remnants of a wetter time in the geologic history of this area.
In the northeast edge of the map, Sumba is a non-volcanic island of low limestone hills and grasslands. Stone megaliths are present over much of the island, and endemic birds are found in remaining dry forest. The southwestern coast is known as a surfer’s paradise.
IV. Terrestrial Ecoregions
All are in the Australasia (AA) Biome
Tropical and Subtropical Dry Deciduous Forests
AA 203, Sumba Deciduous forests. This is mostly a grassland and savanna ecosystem; however, moist lowland evergreen forests are found in the southern coastal areas. An endemic sundew is found in the savannas, and the island has seven endemic birds. Found on Sumba Island in the East Southeast Islands Province, Indonesia.
Tropical and Subtropical Grasslands, Savannas, and Shrublands
AA706, Kimberly tropical savanna. This high-grass savanna has isolated trees and shrubs such as eucalyptus, kakadu plum and baobab; trees in coastal areas include 11 species of mangrove. The summer wet season is from October to March. Found in Western Australia adjacent to Eighty-Mile Beach.
Deserts and Xeric Shrublands
AA1307, Pilbara shrublands. Spinifex grass grows in clumps and rings, called hummocks. Occasional mulga trees dot the area. Found in Western Australia along the DeGrey River.
V. Freshwater Ecoregions of the World
Southern Asia Region
Tropical and Subtropical Coastal Rivers
748. Lesser Sunda Islands. Found on Sumba.
Xeric Freshwaters and Closed Basins
802. Pilbara. Found from the mouth of the DeGrey River west.
804. Paleo. Found to the east of the mouth of the DeGrey River. This area has isolated saline lakes but no permanent, fish-inhabited waterways.
VI. Marine Ecoregions of the World
Central Indo-Pacific Realm, Western Coral Triangle Province
132. Lesser Sunda. Found along coast of Sumba.
Central Indo-Pacific Realm, Northwest Australian Shelf Province
144. Exmouth to Broome. Found along the Rowley Shelf and Rowley Shoals of Western Australia.
VII. Ramsar Sites (Wetlands of International Importance)
Eighty-Mile Beach, Western Australia. This coastline is noted for large tidal mudflats and marshlands. Springs in the marshlands are a remnant of a paleoriver system that existed when the climate was wetter. The area harbors 300,000 migratory wading birds in the spring and is also an Important Bird Area for bar-tailed godwit and great knot. Flatback turtles use the beach for nesting. Terrestrial ecoregion AA706 and marine ecoregion 144.
VIII. Other points of interest
Bedout Island Nature Reserve, Western Australia. An Important Bird Area with the world’s largest population of brown booby and 19 percent of the world population of the lesser frigatebird. Terrestrial ecoregion AA1307 and marine ecoregion 144.
Cape Keraudren Reserve, Western Australia. Managed by the Shire of East Pilbara, this picturesque beach and white sand area is the western edge of the Eighty-Mile Beach Ramsar site. Terrestrial ecoregion 706 and marine ecoregion 144.
Glomar Shoals, Western Australia. This shallow area along the continental shelf (26 to 70 m) shows increased biological productivity. Marine ecoregion 144.
Mermaid Reef Marine National Nature Reserve. This flat reef is 500 to 800 m wide encircling a large lagoon up to 20 m deep. The area is completely submerged at high tide. Marine ecoregion 144.
North West Shelf Venture, Western Australia. Australia’s major offshore oil and gas producing area, producing 40 percent of Australia’s oil and gas. North Rankin A platform is the world’s largest gas-producing platform. Marine ecoregion 144.
North Turtle Island Nature Reserve, Western Australia. Terrestrial ecoregion AA1307 and marine ecoregion 144.
Rowley Shoals Marine Park, Western Australia. The park consists of Clerke and Imperieuse Reefs off Western Australia. For divers, the walls drop 230 m while the shallow lagoons have coral, fish and potato cod with no fear of people. Other notable sites are coral gardens, giant clams, and shellfish. The area has unique sponge assemblages and diverse shark fauna. Cunningham and Bedwell Islands are nesting areas for red-tailed tropicbirds, white-tailed tropicbirds, and little terns. Noted as the best shelf-edge ocean reef in Australia. Marine ecoregion 144.
IX. References
Abell, Robin and 27 others. 2008. Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation. BioScience 58:403-414.
Australian Department of Sustainability, Environment, Water, Population, and Communities. Mermaid Reef Marine National Nature Reserve. http://www.environment.gov.au/coasts/mpa/mermaid/index.html (Accessed 19 February 2011).
Australian Department of the Environment, Water, Heritage, and the Arts. 2008. The North-West Marine Bioregional Plan Bioregional Profile (www.environment.gov.au/coasts/mbp/publications/north-west/
BirdLife International. 2011. BirdLife’s Online World Bird Database. Accessed 19 February 2011 at http://www.birdlife.org/
Burbridge, Andrew A., Phillip J. Fuller, J.A.K. Lane, and Susan A. Moore. 1987. Counts of Nesting Boobies and Lesser Frigate-birds in Western Australia. Emu 87:128-129.
East Pilbara Shire. Cape Keraudren Reserve. http://www.eastpilbara.wa.gov.au/inter_site/php_scripts/see_ck.php (accessed February 19, 2011).
Heirtzler, James R. et al. 1973. Age of the Floor of the Eastern Indian Ocean. Science 180:952-954.
North West Shelf Venture. 2011. www.woodside.com.au/Our+Business/North+West+Shelf/ (accessed 19 February 2011).
Olson, David M., et al., 2001. Terrestrial Ecoregions of the World: A New Map of Life on Earth. BioScience 51:933-938.
Oppo, Delia W. and Yair Rosenthal. 2010. The Great Indo-Pacific Communicator. Science 328:1492-1493.
Ramsar Sites Information Service. http://ramsar.wetlands.org/ (Accessed 19 February 2011).
Spalding, Mark D. and 14 others. 2007. Marine Ecoregions of the World: A Bioregionalization of Coastal and Shelf Areas. Bioscience 57:573-583.
Western Australia Department of Environment and Conservation. Rowley Shoals Marine Park. http://www.marineparks.wa.gov.au/dive-in-to-marine-parks/index.html (accessed 19 February 2011).
Western Australia Department of Environment and Conservation. Park Finder. http://www.dec.wa.gov.au/component/option,com_hotproperty/Itemid,755/ (accessed 19 February 2011).
World Database of Protected Areas. http://www.protectedplanet.net/ (accessed 19 February 2011).