Australia on Thursday said it was confident the Great Barrier Reef would avoid a World Heritage downgrade after a new report card showed pollutants entering the water had been significantly reduced.

UNESCO had warned that without action on water quality and rampant coastal development, the reef -- covering an area roughly the size of Japan -- would be declared "World Heritage in Danger".

Queensland state Environment Minister Andrew Powell said progress had been made as he released a government report card on action taken to improve water quality since 2009.

"I don't expect that will happen," he said of a potential UN downgrade.

"We are likely to be successful ... because the facts speak to that. The reef is now on the pathway to long-term improvement."

The report, which Powell will take to a UNESCO meeting in Doha later this month, shows reductions in key pollutants, including sediments and pesticide run-offs on the back of improved land management practices.

"Pesticide loads, we've reduced it by 28 percent across the whole reef catchment," Powell said.

"In terms of nitrogen -- that's what causes those crown-of-thorn starfish outbreaks -- we've reduced it by 16 percent overall."

But while improvements to water quality had been achieved, Powell conceded that the overall health of the reef still needed more work.

"The outlook in this report still suggests that it's poor and that is consistent with the fact we've had many decades now of natural disasters, but also agricultural practices and run-off," he said.

The report dealt only with water quality issues and not port developments linked to mining, which conservationists have warned could hasten the demise of the reef.

There has been particular concern about the government in December approving a massive coal port expansion in the region and allowing the dumping of millions of tonnes of dredge waste within the marine park waters.

WWF Australia chief executive Dermot O'Gorman said the report fell short of what was needed to save the reef.

"While the farming community has started to step up to the plate and address threats to the Great Barrier Reef, the resources industry are now set to undo that good work with destructive plans for dumping in the World Heritage area," he said.

The Australian Marine Conservation Society said while a reduction in sediment from farming was good news, dredging and dumping were ruining the reef.

"The mining industry, backed by the state government and the state-owned ports corporations, are treating the reef as a dumping ground," said spokeswoman Felicity Wishart.

Powell insisted to ABC radio that port development was not the main threat to the reef, one of the most biodiverse places on Earth.

"What I'm going there (Doha) to convince them of is that the real causes of concern for the reef are storms and cyclones, crown-of-thorns starfish, coral bleaching, and we're addressing those through the investment that we're putting into it," he said.

Earlier this year, the government said it was taking steps to bolster the reef's resilience to the threats of extreme weather events and climate change.

It is also working to reduce outbreaks of the predatory coral-feeding crown-of-thorns starfish.

On port development, it said no projects "have been approved outside the existing and long-established major port areas within or adjoining" the reef.