Table 1 Losses of Australian tidal marsh habitat by state according to available literature.

State/Territory	Area (km²)	Rate of loss (km² yr⁻¹)	Rate of loss ± SD (% total area yr⁻¹)	Time period	Causes of Loss	Method	Reference(s)
New South Wales	73⁶⁵	0.0931	0.01 ± 0.51%	1940s/1950s to 1990s	Incursion of terrestrial species, mangrove encroachment, reclamation.	Photogrammetric analysis of a subset of wetlands from nine estuaries within NSW	66
Queensland	5,322⁶⁷	1.3510	0.0184%	Pre-1750 to 2011	Agriculture, urban & industrial development	Aerial imagery and ground-truthing of QLD coast	68,69
South Australia	84⁶⁷	0.0824	4.4516%	1930s to 1970s & 1970s to 1990s	Mangrove encroachment, urban development	Photogrammetric analysis and ground-truthing for Gulf of St. Vincent, SA	70, 71, 72
Tasmania	37⁶⁷	0.0406	0.2963%	1952 to 2006	Expansion of Melaleuca ericifolia, land clearing, levees (approx. 90%).	Aerial photo interpretation and ground-truthing of Circular Head, Tasmania (representing 20% of Tasmanian tidal marsh area)	73
Victoria	279⁷⁴			Pre-1750 to 2008	Grazing, reclamation for agriculture, vehicle damage.	State-wide archival maps & field observations, aerial imagery & ground-truthing	74,75
Scenario I*		0.0423	0.0146% %
Scenario II*		0.3334	0.0914
Western Australia	2,965⁶⁷	13.54	18%	1999–2002	Cyclone	Aerial imagery & photography, field validation	76
Northern Territory	5,005⁶⁷	Unknown	Unknown	—	—	—	—

Literature that did not present values of the actual area lost was excluded from the summary. Total area lost per year in New South Wales is likely an underestimate, as this value is based on portions of selected estuaries only. There is no reliable information on tidal marsh loss for the Northern Territory. *Victoria state averages reflect two possible scenarios based on the ambiguity of tidal marsh in the Gippsland Lakes. “Scenario I: All ambiguous tidal marsh areas are natural. Scenario II: All the ambiguous tidal marsh areas are recent expansions, in which case they are counted as gains which offset other losses”⁷⁴. The rate of tidal marsh loss for Western Australia presented here is based on an episodic event, and is therefore likely to be an overestimate of typical annual loss rates.

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