East Trinity remediation a major success thanks to clever science

Scientists involved in an 18-year project to remediate acid sulphate soils at a north Queensland site have pulled off a major accomplishment, turning the once badly acidified land into a place where mangroves, native birds and other wildlife have now returned.

The 774-hectare site at East Trinity, located directly across Trinity Inlet, Cairns, was originally a natural estuarine floodplain, covered by mangroves and salt-marsh, but became an environmental disaster in the 1970s after being drained to create a sugarcane farm.

Queensland’s Department of Environment and Science (DES), along with Southern Cross University (SCU) and the Cooperative Research Centre for Contamination, Assessment and Remediation of the Environment (CRC CARE), conducted the remediation project, after the Queensland Government purchased the property in 2000 with the intention of protecting Trinity Inlet and the Great Barrier Reef.

Queensland Minister for Environment Leeanne Enoch said the processes used at East Trinity are now seen as a benchmark for rehabilitating acid sulphate soils.

“During the site’s transition to a sugarcane farm, a large 7km bund wall was constructed to prevent the natural flow of tide. Because of this, previously waterlogged soils were exposed to air, resulting in a chemical reaction where sulfuric acid was released at a level of acidity equivalent to battery acid,” Ms Enoch said.

“Acid water leaked from the soil into the waterways – along with large quantities of iron, aluminium and other metals – resulting in fish kills and the death of the mangrove forests. The sugarcane production also failed, and the soils and waters became severely degraded.

Speaker of the Queensland Parliament and Member for Mulgrave Curtis Pitt said when the government bought the property, original rehabilitation cost estimates started at $78 million, so scientists were tasked with delivering a low-cost solution.

“They chose to reintroduce the tide to the site, and also added lime to the tidal waters to further neutralise soil acidity. The program was a success, and now we see mangroves thriving once more, and the return of many species of fish and birds,” Mr Pitt said

“I have been strongly interested in the rehabilitation of the East Trinity site since I was first elected in 2009.

“What’s also rewarding is seeing this East Trinity research and field program leading to improvements in other acid sulphate soil-affected wetlands throughout south-east Queensland and reef catchments, and also being exported to other parts of the world.

“It’s become a real showcase for Queensland science, and I know the Department will continue to manage the East Trinity Environmental Reserve for long-term stability as the appointed trustee.”

Project leader for the East Trinity Remediation Project Professor Richard Bush said the project outcomes went well beyond the considerable scientific advancements.

“This initiative empowered the local community, brought all stakeholders together, nurtured a cohort of emerging international leaders in land management, and opened new opportunities for Traditional Owners. This is one of the most exciting projects I have been involved with,” Professor Bush said.

East Trinity is part of the traditional lands of the Mandingalbay Yidinji people, who run a cultural ecotourism business that welcomes visitors to East Trinity Environmental Reserve and adjacent Grey Peaks National Park.

Mandingalbay Yidinji Aboriginal Corporation Executive Director Dale Mundraby said the tours took in the remediated East Trinity site, showing tourists the transformation of the area and the role science has played in healing country.

“Our plan is to build eco-infrastructure on site at East Trinity, including a boat jetty, so we can extend our business to include guided walks of the area,” Mr Mundraby said.

“The eco-tours are really important, as they not only teach visitors about the cultural importance of the land to the Mandingalbay Yidinji people, but also produce an economic opportunity for the community, creating jobs and skills for local people.”

Further information:

• Mandingalbay Yidinji tours
• Mandingalbay Yidinji people
• CRC CARE Technical Report 41: Remediating and managing coastal acid sulphate soils using Lime Assisted Tidal Exchange (LATE) at East Trinity

Media contact: 0437 859 987