Coastal wetlands are a very important and often overlooked component of the Great Barrier Reef group of ecosystems. They act as natural filters for water, reducing erosion and nutrient run off, in addition to providing safe havens to numerous species of key reef fish and bird species during juvenile and adult life stages.
A large extent of the wetlands in the Great Barrier Reef catchment have been either drained or cleared, mainly to make way for farms and urban expansion. The Wet Tropics, Mackay-Whitsunday and Burnett-Mary regions have lost nearly half their total wetland area, while remaining wetlands are subject to various threats and disturbances, including invasive species such as feral pigs.
Feral pigs are a huge problem for wetlands because they dig up large areas of wetland soils, disrupting normal soil structure and plant communities, and kill native species such as turtles. Keeping pigs out of wetlands is a key objective for managers aiming to improve and protect Great Barrier Reef coastal wetlands.
A Tropical Water Quality Hub project is evaluating the effectiveness of different methods for repairing wetlands. One project site is looking at an 8 km fence installed to prevent pigs accessing a 56-hectare section of the Round Hill Reserve, in Eurimbula National Park south of Gladstone.
Project leader Dr Nathan Waltham from James Cook University is working with the Burnett Mary Regional Group (BMRG) and Queensland Parks and Wildlife Service (QPWS) to check water quality, soil dynamics, vegetation and animal species inside the protected area, compared to similar wetland areas nearby without pig fences.
“If we’re protecting wetlands from pigs using fences, the expectation is that there’ll be water quality improvements,” Dr Waltham said.
“There isn’t a lot of extant data on wild pig impacts on wetland quality, which is one of the knowledge gaps that we’re trying to plug with this project. We do have indications so far that the presence of feral pigs can affect oxygen availability and there are obvious changes to turbidity from them digging up soil and streambanks.”
Dr Waltham’s project includes evaluating other wetland remediation projects across the GBR catchment, including the removal of a bund wall at Mungalla Wetlands, a constructed wetland near Babinda, and invasive plant removals.
He said ‘each wetland was different’ and the project would be critical to helping environmental managers design wetland remediation projects on a case-by-case basis in the future.
“There’s a benefit-implication calculation for each wetland,” he said.
“It’s important to set up what goals you’re trying to achieve early in the project.”
A vital aspect of the project is the close cooperative relationship between researchers and landholders, especially Indigenous landholders in the case of the Mungalla Wetlands and Babinda constructed wetland project.
“There’s a lot of passion there, and has become an important two way sharing of knowledge and information,” Dr Waltham said.
“It’s their land and it’s in their interest to look after it, and wetlands are key to that.”
The project will continue for three years.