Adelaide and Mary River Floodplains (23430)
Australia, Australasia
Site overview
KBA status: confirmed
Global KBA criteria: A1a, A1c, B1, D1a
Year of last assessment: 2009
National site name: Adelaide and Mary River Floodplains
Central coordinates: Latitude: -12.4860, Longitude: 131.5068
System: freshwater, marine, terrestrial
Elevation (m): 0 to 10
Area of KBA (km2): 2585.92884
Protected area coverage (%): 31.79
KBA classification: Global
Legacy site: Yes
Site details
Site description: The IBA includes the whole floodplains of the Adelaide and Mary Rivers. The Adelaide floodplain extends from south of the Arnhem Highway to the river mouth (The Narrows), mangroves at the base of Cape Hotham peninsula (Wilshire Creek area) and includes Chambers Bay. The Mary River Floodplain extends east to Swim Thrings Creek floodplain and Point Stuart, where it abuts the Alligator Rivers IBA. Floodplain wetlands within the site include Lake Finniss, Melacca and Black Jungle Swamps, the artificial Fogg and Harrison Dams, and various billabongs and lagoons. The unusual morphology of the Mary River floodplain contributes to rapid overtopping of levees and inundation of huge seasonal wetlands, even in years of relatively low rainfalls. Chambers Bay is dominated by sand/mudflats with samphire and mangrove or sand-dune coastlines. The IBA includes waterbird colonies references W23, W25, W27 and W46 in Chatto (2000a). The mean annual rainfall at Middle Point Research Station is approximately 1380 mm, mostly falling in December-March.
Rationale for qualifying as KBA: This site qualifies as a Key Biodiversity Area of international significance that meets the thresholds for at least one criterion described in the Global Standard for the Identification of KBAs.
Additional biodiversity: The waterbird colony on the Adelaide River 15km from its mouth is the largest colony in the Top End, with an estimated 30,000 birds including at least 1500 Great Egret, 6000 Intermediate Egret, 4500 Little Egret, 9500 Cattle Egret (Chatto 2000a). A high count of 33,000-41,000 waterbirds was made at Finniss Lake Lagoon during surveys by Kingsford et al. (2008). Eighty-eight waterbird species recorded on the Directory of Important Wetlands in Australia website database. High counts of waders along Chambers Bay include 2300 Black-winged Stilt, 1960 near threatened Black-tailed Godwit, 1525 Terek Sandpiper, 1650 Grey Plover and 1500 Whimbrel (Chatto 2000b, 2003 and in litt. in Bamford et al. 2008). Coastal mudflats and nearby areas apparently support in the order of 10,000 shorebirds at times and thousands of Oriental Pratincole on the floodplain, before the Wet sets in, and up to 2000 Comb-crested Jacana have been counted at Fogg Dam (August 1983) (DEWHA 2008). Twice, single flocks of more than 2000 Black-tailed Godwit have been observed on swamps 20 km inland from the coast (Chatto 2003). Other species rarely recorded in the IBA include the near threatened Australian Bustard, the restricted-range Yellow-rumped Mannikin and the Australian Little Bittern. Non-bird biodiversity: A major breeding area for Saltwater Crocodile Crocodylus porosus.
Other site values: Woolner, Koolpinyah and Kerlin Stations, Annaburroo, Marrakai, Opium Creek, Melaleuca and Swim Creek pastoral leases. Protected Areas jointly managed by the NT government and the Limilngan-Wulna people. Traditional Ownership. Much of this IBA is on private or Traditionally Owned land.
Habitats
Land use: nature conservation and research | rangeland/pastureland
| IUCN Habitat | Coverage % | Habitat detail |
|---|---|---|
| Marine Intertidal | 5 | |
| Wetlands(Inland) | 90 | |
| Forest | 5 |
Threats
Summary of threats to biodiversity at KBA: Actions to mitigate the impact of rising sea-levels need to be considered: these floodplains have suffered more than anywhere in Australia from saltwater inundation. Invasion by alien plants and ungulates needs to be controlled.
| Threat level 1 | Threat level 2 | Threat level 3 | Timing |
|---|---|---|---|
| Invasive & other problematic species, genes & diseases | Invasive non-native/alien species/diseases | Named species | Ongoing |
| Natural system modifications | Fire & fire suppression | Increase in fire frequency/intensity | Ongoing |
| Climate change & severe weather | Storms & flooding | Only in the future |
Additional information
References: Bamford, M., Watkins, D., Bancroft, W., Tischler, G. and Wahl, J. (2008) Migratory Shorebirds of the East Asian - Australasian Flyway; Population Estimates and Internationally Important Sites. Canberra, Australia: Wetlands International - Oceania. Chatto, R. (2000a) Waterbird breeding colonies in the Top End of the Northern Territory. Technical Report 69, Parks and Wildlife Commission of the Northern Territory, Palmerston. Chatto, R. (2000b) A management strategy and protected areas system for coastal wildlife. (Documentation of selected sites in the Northern Territory of Australia which would qualify for nomination under the East Asian - Australasian Shorebird Site Network). Unpublished report, Parks and Wildlife Commission of the Northern Territory, Palmerston. Chatto, R. (2003) The distribution and status of shorebirds around the coast and coastal wetlands of the Northern Territory. Technical Report 73, Parks and Wildlife Commission of the Northern Territory, Palmerston. Chatto, R. (2006) The distribution and status of waterbirds around the coast and coastal wetlands of the Northern Territory. Technical Report 76, Parks and Wildlife Commission of the Northern Territory, Palmerston. DEWHA (2008) Directory of Important Wetlands in Australia. http://www.environment.gov.au/water/publications/environmental/wetlands/database/ accessed 2008. Harrison, L., McGuire, L., Ward, S. Fisher, A., Pavey, C., Fegan, M. and Lynch, B. (2009) An inventory of sites of international and national significance for biodiversity values in the Northern Territory. Department of Natural Resources, Environment, the Arts & Sport, Darwin, NT. Higgins, P.J. and Davies, S.J.J.F. (1996) Handbook of Australian, New Zealand and Antarctic Birds. Volume 3. Melbourne: OUP. Kingsford, R.T., Halse, S.A. and Porter, J.L. (2008) Aerial surveys of waterbirds - assessing wetland condition. Final report to the National Land & Water Resources Audit. University of New South Wales, Sydney. Jaensch, R. (1991) Lake Finnis: an internationally significant site for the Little Curlew. Stilt 25: 21. Smith, F.T.H. (1971) Little Whimbrel in N.T. The Bird Observer 471: 5-6. Ward, S. and Harrison, L. (2009) Recognising sites of conservation significance for biodiversity values in the Northern Territory. Department of Natural Resources, Environment, the Arts & Sport, Darwin, NT.