St Kilda township’s dead and dying trees another casualty of excess salt in soil and groundwater, report suggests

If the loss of mangroves and saltmarsh wasn’t bad enough for St Kilda residents, now a report has troubling news about more than 100 trees.

Almost half of the trees on public land in the township of St Kilda are dead or dying, a report to the state government has found, with excess salt most likely to blame.

While the report has not been made public, details of the planted tree health assessment appeared in the Energy and Mining Department’s latest update on the Dry Creek Salt Field and St Kilda mangroves.

Of the 273 trees assessed on public land within St Kilda, 27.5 per cent were “stressed” and 14.3 per cent were dead, mainly in the southern area closest to the affected area of mangroves.

That equates to 75 stressed and 39 dead trees.

“The preliminary report identifies elevated levels of salt within the soil as a likely contributing factor to poor planted tree health,” the department said.

“The underlying cause and timings of these elevated levels are matters that form part of the ongoing investigations, and further updates will be available in due course.”

A large area of mangroves and saltmarsh at St Kilda died last year after salt mining company Buckland Dry Creek pumped hypersaline water into a disused evaporation pond that cracked and leaked.

Later that year, residents noticed trees and other vegetation on both public and private land in the town looked sick, prompting Salisbury Council to set up a register of trees.

Kevin and Marilyn Collins with the large tree on their property that died in April, at the northern end of St Kilda. Picture: Tricia Watkinson

The latest update also stated the department and the council were “preparing to establish a groundwater monitoring network in the township … and determine if there is a risk to trees and infrastructure within the town from saline groundwater”. That could include groundwater flooding septic tanks or damaging concrete.

The update said the state government “continues to monitor activities and environmental conditions” in the area and promised to release further analysis of the extent of mangrove dieback using aerial imagery.

The company Buckland Dry Creek submitted its annual compliance report to the government on December 1. That report is being reviewed for compliance with mining regulations ahead of public release.

Local scientist Peri Coleman said the St Kilda & Surrounds Progress & Tourism Association have long been pushing for a groundwater monitoring network in the town.

“By watering our gardens madly we can try and hold the groundwater from the ponds away from our trees,” she said.

“The other thing is, as the groundwater comes up when they raise the levels of the ponds next to the town, if we've got a little flag on the top of the piezometer machine network, we would be able to see that pop up and anybody who’s at all concerned about their septic tank can go and get pumped out in advance, so that we have less flooded septic tanks.”