The size of the area impacted at the St Kilda salt fields and mangroves sites is less than first thought according to the latest scientific assessments revealed today.
Scientific monitoring also shows the site has stabilised with reduced salinity levels, resulting in an overall improvement to the site.
Independently peer-reviewed high-resolution imagery to map the area of impacted mangrove and samphire over time has been able to show that the total impacted area reported in January 2021 has been revised down from 45 hectares to 24 hectares. This includes nine hectares of mangrove dieback and 10 hectares of saltmarsh dieback.
The assessment has also shown that there has been no significant increase in dieback between December 2020 and July 2021, and that there is high confidence that no major areas of dead vegetation remain undetected.
Minister for Energy and Mining Dan van Holst Pellekaan welcomed the latest scientific assessment.
“The death of any mangroves is disappointing, so the State Government is relying on the very best scientific advice to manage this complex site,” Minister van Holst Pellekaan said.
“The new peer-reviewed vegetation mapping, updated hydrology and salinity data shows scientifically that the remedial actions taken have resulted in a welcome improvement to the overall health of the site.”
Minister for Environment and Water David Speirs said the State Government will continue to monitor the area.
“The St Kilda mangroves are of national significance as a sanctuary for migratory and resident shorebirds and the State Government is committed to protecting this important habitat,” Minister Speirs said.
“I was hugely concerned when I was first made aware of the issues at the site and we have been taking action to help restore the area ever since.
“The former salt fields are a complex site that need active management to protect the environment – and State Government is managing the site and delivering results, backed by the best science.”
In excess of 1GL of brine has now been pumped from the northern portion of the salt fields into the SA Water Bolivar outfall channel, where it is diluted with treated wastewater before being safely discharged into Gulf St Vincent.
The science is showing that salinity readings have dropped dramatically from 300 parts per thousand to 200 parts per thousand – just over 10 per cent above the historic average. Groundwater pressure has also reduced markedly, avoiding further impacts on the mangroves.
The scientific study compared the site to images from 1997, showing that much of the impacted area of saltmarsh adjacent to the evaporation ponds was generally degraded already.
Minister van Holst Pellekaan said the peer-reviewed analysis and recent recording debunks the alarmist claims of the Labor Party and some campaigners about the condition of the site.
“Just last week it was claimed the mangroves were an ‘unfolding disaster’, a ‘clear and present danger’ and hundreds of hectares ‘were holding on by its fingernails’, however, these views are in conflict with the clear scientific evidence,” Minister van Holst Pellekaan said.
“The science shows that that government action is improving the site. Our continued pumping efforts to reduce salinity in the ponds have resulted in a 33 per cent reduction.
“Specialists across government have confirmed that there is no indication at this stage that recent rain will cause any further impact to the mangrove area. While monitoring of salinity trends continues, it is expected that groundwater flows will continue to decline over time.
“Labor needs to stop ignoring the science and misleading the public; it’s everyone’s responsibility to call out and correct the reporting of uncorroborated, unscientific claims.”
Further detail on the peer-reviewed vegetation mapping, the reduction in salinity levels, and the groundwater analysis can be found at www.energymining.sa.gov.au/dry_creek_salt_field.
