Logan River banks collapse as deadly fire ant crisis worsens

Logan River residents want the state to investigate possible links between deadly fire ants and accelerating river bank erosion as property owners live in fear of landslips.

A large fire ant nest near the Logan River. Picture: Stuart Webber

Logan River residents are urging the state government to investigate a rapid rise in erosion along the river banks and the possible links to deadly fire ant nests.

Landholders and Landcare volunteers say sections of the riverbank in suburbs including Buccan, Bethania, Beenleigh, Jimboomba and Cedar Grove are collapsing at an alarming rate, particularly after recent floods.

Some suspect the underground tunnelling of fire ants is making embankment soil soft and easily eroded by water, a claim yet to be backed by scientific evidence and denied by Logan River farmers.

Cedar Grove Landcare volunteer Rona Murtagh, who works on four properties along the river in Logan, said patrols in her area had found the ants’ nests had made the banks soft and easily washed away.

Landcare volunteer Rona Murtagh on the Logan River at Allenview where there is erosion along the river banks and an influx of fire ant nests. Picture: Invasive Species Council

“I’ve been here once a week for the past month and every time I return the soil is different,” Ms Murtagh said.

“The erosion was always there but never as bad as it is now, which is partly due to floods but the tops of the banks where the nests are, that’s where you really notice the damage.

“We need more free bait, we need more funding, we need more advertisement because we do not charge to do this.

“We need to do everything we can to stop them, for our community, our kids and for the river.”

The Invasive Species Council, a national environmental organisation, has taken up the call to government from residents, who live in fear of future erosion leading to the river bank collapsing.

It has asked the state to launch a formal investigation, warning that if the link between ants and erosion is proved, the cost and damage caused by the pest species has been severely underestimated.

Fire ant nest markers along the Logan River bank. Picture: Invasive Species Council

Invasive Species Council advocacy manager Reece Pianta said anecdotal reports from locals showed serious and rapid soil erosion in areas with high densities of fire ant nests.

He said the Invasive Species Council was unable to prove a direct causal link but was arguing that ignoring the possibility could mean missing a critical and costly consequence of the infestation.

“Landcare volunteers in Cedar Grove have noted erosion and riverbank collapse where fire ant infestation is high, which has serious implications for water quality and flood mitigation,” Mr Pianta said.

“It needs to be urgently investigated because if it is found true, Australian fire ants are likely causing more significant impacts than in other countries.

“It’s a national issue and should be a federal priority because Queensland cannot do this alone.”

He also said the ISC was prepared to connect researchers with international fire ant experts.

Fire ants are a notifiable invasive species in Queensland and pose significant threats to agriculture, ecosystems, and human health.

Nesting activity has been widely documented in open spaces, paddocks, urban blocks and disturbed lands, but rarely near flowing waterways.

Eagleby cane farmer Mick Herse, whose property backs on to the Logan River, said he had no doubt the erosion on his farm was the direct result of flood damage not fire ants.

Eagleby cane farmer Mick Herse, who is treating fire ants on his farm, says the river erosion is from flooding. Picture: Judith Kerr

“I’ve got two kilometres of river frontage and those ants mostly stay out of reach of the high tides but they do nest on the dry ground and on the edges of drains,” he said.

“The 2022 flood ripped through here and reshaped the banks and that’s what’s caused the erosion, not ants.”

Mr Herse said the government’s fire ant program had been effective and responsive, especially after Cyclone Alfred when the flood waters helped to spread the ants along the river.

“I can’t fault them,” he said.

“They dropped off pallets of bait this week and were meant to do aerial spraying next Monday, but that’s been delayed because of the rain,” he said.

He said hobby blocks of land along with residential acreage properties fronting the river were the real weak spots in the state’s containment strategy rather than commercial farms.

“It’s the five-acre blocks with a horse out the back and no one checking for nests that are the issue,” he said.

An Agriculture and Fisheries Department spokesman said they had received inquiries about the erosion claims and would consider further information.

Originally published as Logan River banks collapse as deadly fire ant crisis worsens