Extent and rate of change in estuarine wetlands
More than 96% of the pre-European settlement extent of estuarine wetlands in Queensland remained in 2013. Changes in the extent of estuarine wetlands in Queensland have been monitored since 2001. The highest rate of estuarine wetland loss was recorded during the 2009-2013 period (0.03%) mostly in the North East Coast drainage division.
Of the two broad estuarine wetland types—mangroves and salt marsh/salt flats—the greatest ongoing losses have occurred in salt marsh/salt flats in the North East Coast Drainage division yet more than 95% remain intact.
At a statewide scale, about 96% of pre-clear extent of estuarine wetland remains. Estimated historical loss of estuarine wetlands is unevenly distributed across drainage divisions and catchments:
- 83% remaining in the North East Coast non-Great Barrier Reef (Non-GBR) division
- 92% remaining in the North East Coast Great Barrier Reef (GBR) division
- close to 100% remaining in the Gulf division.
Ongoing loss over 2001-2013 continued with the highest loss occurring in the 2009-2013 period of 326ha—a rate of 82ha/yr. This overall loss equated with 0.03% of 2013 extent. All but 30ha was lost within North East Coast GBR division.
- 297ha of salt marsh/salt flat was lost in 2009-2013 statewide. North East Coast-GBR division accounted for 269ha.
- Calliope catchment was predominantly affected due to expansion of port facilities at Gladstone
The estimated historic and current loss of estuarine wetlands has mainly occurred due to draining and bunding associated with conversion of estuarine plains to freshwater wetlands.
In addition to the drainage divisions, the ‘other’ category represented in the data includes islands within Queensland waters, as well as discrepancies in catchment coverages and coastline.
Historical loss of estuarine wetland extent in the Gulf drainage division has been minimal with close to 100% remaining.
Loss over the 2001-2005, 2005-2009 and 2009-2013 periods was not detectable.
North East Coast (GBR)
While 92% of pre-clear estuarine wetland remains within North East Coast Great Barrier Reef (GBR) drainage division, historical loss is unevenly distributed across catchments. Many catchments, particularly in the Cape York peninsula area, have close to 100% remaining whereas the Lower Burdekin, Boyne, Shoalwater and Barron catchments have less than 75%. Historical loss of estuarine wetland has been mostly salt flat/salt marsh (86% remaining): less than half remain in the Barron, Lower Burnett and Kolan catchments.
Loss of estuarine wetland over 2001-2013 period declined, or remained static at a low rate, for most catchments.
Declines in loss were recorded in the following catchments:
- Lower Burnett
Only Calliope catchment recorded an increase.
Loss during 2009-2013 was 294ha—a rate of 74ha/yr, which represents 0.07% of the 2013 extent. Of this, 260ha was salt marsh/salt flat wetlands in Calliope catchment.
Only two other catchments recorded losses of more than 2ha:
- Kolan, 4ha
- Styx, 3ha.
Loss of mangrove wetland over 2009-2013 period was 27ha, of which 24ha was in the Calliope catchment. The majority of catchments had no detectable change.
North East Coast (non-GBR)
Eighty-three per cent of pre-clear estuarine wetland remains for the North East Coast non-Great Barrier Reef (non-GBR) drainage division with historical loss unevenly distributed across catchments.
- Brisbane and Coomera and Nerang catchments have less than 75% remaining.
- South Pine River has only 50% remaining.
Ongoing loss over the 2001-2013 period was small. Losses of both mangrove and salt marsh/salt flat wetlands had generally decreased, with the exception of the South Pine River where loss of salt marsh/salt flat increased to 4ha (0.9% of 2013 extent) during 2009-2013 period.
Overall loss for the division was 6ha during the 2009-2013 period, a rate of 1.5ha/yr. This equates with 0.03% of 2013 extent.
Loss of mangrove wetland over 2001-2013 period decreased from 17ha (0.1% of 2013 extent) in 2001-2005 to 2ha (0.01% of 2013 extent) in 2009-2013.
- Only North Pine River catchment lost more than 1ha of mangrove wetland.
Loss of salt marsh/salt flat wetland over the 2001-2013 period decreased from 13ha (0.2% of 2013 extent) in 2001-2005 to 2ha (2005-2009) before increasing to 4ha (0.03% of 2013 extent) in 2009-2013.
- Only South Pine River catchment lost more than 1ha of salt marsh/salt flat wetlands.
Losses were primarily due to urban and industrial development.
Comparison between pre-clear (pre-European settlement extent) and remnant (current extent) estuarine wetland mapping. Data is based on the latest Queensland Wetland Mapping (version 4, 2013).