An aerial view of Abbot Point’s Terminal 1 with its coal stockpile
An aerial view of Abbot Point’s Terminal 1 with its coal stockpile Contributed

Long term dredging impacts remain unknown: report

A REPORT into the effects of dredging and dumping of sediment on the Great Barrier Reef has found "severe" impacts on local habitats but says the long-term impacts are still unknown.

A 19-member panel of experts compiled a dredge synthesis report, which was released on Wednesday.

The report said most current and proposed dredging activities were carried out within soft-sediment seafloor habitats.

While dredging and dumping had "severe" effects within the specific areas where it occurred, the report said the overall ecological impact on the reef was small.

"There is evidence of very low levels of mortality of marine turtles during dredging excavations," the report said.

"Although coral reef organisms are sensitive to dredging-related pressures, the exposure of coral reefs on the Great Barrier Reef to dredging pressures is generally low to medium, as the majority of dredging and disposal in the region takes place at some distance from coral reefs."

The report said available monitoring from recent dredging projects did not suggest there had been significant short-term coral mortality but sublethal effects were uncertain.

Project leader Dr Laurence McCook said there were challenges in assessing the effects.

"Understanding the significance of dredging impacts compared to other natural and human pressures remains difficult," Dr McCook said.

He said limited data made it difficult to compare sediment from dredging and the amount which flowed into the ocean from land.

"In many locations, the extent to which sediments are re-suspended and transported by waves and ocean currents or are stable in the long-term is also poorly understood," he said.

The report was a joint initiative from the Great Barrier Reef Marine Park Authority and Australian Institute of Marine Science.

One of the report's suggestions was for the marine park authority's dredge spoil disposal policy to take into account the declining condition of the reef's ecosystem, especially inshore areas.

It also said a better system was needed to predict long-term sediment dynamics and movements and better tools to assess stress in marine plants and animals from dredging and disposal.

Australian Greens Senator Larissa Waters said the report confirmed there were still gaps and uncertainty about the impacts of dredging. She said it should stop until long-term impacts were known.