Australia’s 1,400-mile Great Barrier Reef—a wonder of the natural world—has had a tough go of it in the last decade. Pollution, rising ocean temperatures and recent bleaching events have altered—perhaps permanently—one of the most biodiverse marine ecosystems of earth. Now, environmentalists and reef advocates are up in arms over a recently approved plan that would allow 1 million tons of sludge to be dumped along parts of the reef over the next decade, with the operation beginning in March.

Ben Smee at The Guardian reports that the Great Barrier Reef Marine Park Authority recently approved the dumping of sludge, which will be produced by dredging to clear out and deepen the Port of Hay Point, home to one of the world’s largest coal loading facilities. Though Australia’s federal government banned dumping of sludge within the Great Barrier Reef’s boundaries in 2015, that only applied to new or capital projects and excluded sludge from maintenance projects, like removing sediment from shipping lanes, at the ports.

The announcement comes on the heels of major flooding in Queensland that washed a massive plume of pesticide-tainted sediment onto the reef, which could smother the delicate corals or lead to an algae bloom, reports Josh Robertson for the Australian Broadcasting Corporation. The reduced water quality along with the recent string of bleaching events has scientists worried that the already stressed reef could see more lasting damage.

Adding another one million tons of sediment to the reef, environmentalists argue, adds insult to injury, especially since sediment from erosion and agriculture are considered one of the major problems facing the reef. “The last thing the reef needs is more sludge dumped on it, after being slammed by the floods recently,” Australia Green Party senator Larissa Waters, who hopes to get the permit revoked, tells Smee. “One million tonnes of dumping dredged sludge into world heritage waters treats our reef like a rubbish tip.”

North Queensland Bulk Ports Corporation, which operates the port at Hay Point, argues in a statement that it developed its peer-reviewed plan along with the government of Queensland and has found the risks to the Great Barrier Reef are low. “Importantly, our assessment reports have found the risks to protected areas including the Great Barrier Reef Marine Park Authority and Great Barrier Reef Marine Park and sensitive habitats are predominantly low with some temporary, short-term impacts to benthic habitat possible.”

Simon Boxall from the National Oceanography Centre Southampton tells the BBC that the impact of the dumping will depend when and where the sludge, which is likely contaminated with heavy metals from the industrial port, is placed. If dredgers take it far enough offshore, away from the reef, the impact may be minimal. But dumping it close to shore could have big impacts, smothering marine life in shallow areas. “If they are dumping it over the coral reef itself, it will have quite a devastating effect. The sludge is basically blanketing over the coral,” he says.

If it’s dumped during the hot Australian summer, it could also lead to algae overgrowth, which could impact the coral.

“It's important they get it right,” Boxall says. “It’ll cost more money but that’s not the environment’s problem—that's the port authorities’ problem.”