Botanic Gardens Trust, Sydney, Australia

Newnes Plateau Shrub Swamps

Vegetation and faunal interrelations with groundwater in montane peat swamps in the upper Blue Mountains

Doug Benson - Senior Ecologist and Lotte von Richter - Technical Officer, Evolutionary Ecology

Newnes Plateau Shrub Swamps are a series of low nutrient temperate montane peat swamps, at 1100 m elevation in the upper Blue Mountains, west of Sydney. They are listed as Endangered Ecological Communities under NSW and Commonwealth environmental protection legislation. 

Because of their unique flora we have been interested in the swamps for a number of years, and in 2012 we carried out transect-based vegetation studies in 10 of the main swamps. Analyses show a closely related group of swamps with expanses of permanently moist, gently sloping peatlands. Vegetation patterns are related to surface hydrology and subsurface topography, which determine local peat depth. While there is evidence that a group of the highest elevation swamps on the western side of the Plateau are more dependent on rainwater, the majority of swamps, particularly those in the Carne Creek catchment, and east and south of it, may be considered primarily groundwater dependent with a permanently high watertable maintained by groundwater aquifers.

Associated with these swamps are a number of threatened groundwater dependent biota which are restricted to these swamps (plants - Boronia deanei subsp. deanei and Dillwynia stipulifera; giant dragonfly - Petalura gigantea, Blue Mountains water skink - Eulamprus leuraensis). In collaboration with giant dragonfly expert Ian Baird of the University of Western Sydney, we explored the importance of groundwater dependence to the listed rare biota. This association of dependence leaves the entire swamp ecosystem highly susceptible to threats from any loss of groundwater, the major current one being the impact of damage to the confining aquicludes, aquitards, aquifers and peat substrates as a result of subsidence associated with longwall coalmining. Other impacts may also result from changes to hydrology such as damming, mine waste water discharge, increased moisture competition from pine plantations, recreational motorbike and 4WD vehicle tracks and climate change. We conclude that if these groundwater dependent ecosystems do not receive protection from activities such as longwall mining subsidence, significant ecological damage is unlikely to be avoided or able to be mitigated even where environmental protection legislation applies. 

 

 

 

 

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Doug Benson (left) and Ian Baird (right) record vegetation in Newnes Plateau shrub swamp on upper Marrangaroo Creek in February 2012.

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Cross-section of Gang Gang swamp compiled from transect points (x axis) at 5 m intervals, showing soil surface topography, peat depth (m), giant dragonfly (Petalura) habitat index (0-3, 3=best on left-hand scale) and Boronia deanei presence (1 on left-hand scale).