The dugong has become functionally extinct in waters off China, a new study has found. 

Researchers from the Zoological Society of London and the Chinese Academy of Sciences said fishing, ship strikes and human-caused habitat loss had seen the number of dugongs in Chinese waters decrease rapidly since the 1970s. 

Let's take a look at why this is the case and how dugong habitats in Australia are tracking. 

Finding in China a 'wake up call' 

According to the report, it is the "first functional extinction of a large mammal in China's coastal waters". 

Dugongs have been classified as a national key protected animal since 1988 by China's Sate Council.

However, despite restoration and recovery efforts being a priority it "takes time that dugongs may no longer have," the report said.

For the study, scientists conducted interviews in 66 fishing communities across four Chinese provinces along the coastal region of the South China Sea.

Samuel Turvey, a co-author of the study, said the likely disappearance of dugongs in China was a devastating loss.

"Their absence will not only have a knock-on effect on ecosystem function, but also serves as a wake-up call," Professor Turvey said.

"[It is] a sobering reminder that extinctions can occur before effective conservation actions are developed."

Australia an 'important place' for dugongs 

Australia has been the most important place for dugongs for several thousands of years.

That's according James Cook University environmental scientist Helene Marsh.

She researches dugong population ecology and chairs the national Threatened Species Scientific Committee.

"In Australia, they have enormous cultural value to Indigenous people and they also have major biodiversity values because they're very strange animals," Professor Marsh said.

"They are the stuff of mermaid legend."

The finding in China did not surprise Professor Marsh.

She said in comparison to the rest of the world dugongs off Australia were fairing well.

"In northern Australia we have a very wide continental shelf which supports extensive seagrass beds and so we can support a lot more dugongs, because we have got the habitat, than anywhere else," she said.

Despite this, there are some areas of concern.

Extreme events destroying seagrass

According to the Australian Marine Conservation Society dugongs are dependant on shallow coastal waters and are vulnerable to rising sea levels.

Extreme weather events are putting pressure on seagrass, which is critical to the survival of dugongs.

"It is very concerning that we can get extreme weather events, some of which are likely to become more common with climate change, that destroy sea beds and then effect dugongs," Professor Marsh said.

This year's floods in Queensland destroyed large areas of seagrass in dugong habitats off Hervey Bay and Moreton Bay.

"The seagrass will probably come back, but it'll take a few years," she said. 

"The dugongs have to move or starve.

"This has happened before and then they stop breeding. Some of them move and some of them stay and starve, and then you get more stranded animals.

"There have been some more reports of strandings in that general region [south east Queensland] this year and green turtles were effected similarly.

"The numbers so far haven't been as serious as they were in 1992 and 1993, where I think the damage was more widespread." 

Torres Strait is Australia's 'dugong capital' 

Professor Marsh said there is dieback of deep water seagrass in the Torres Strait but the cause of it was not known.

"There's quite a bit of concern at the moment about the situation in Torres Strait," she said.

"If Australia is the dugong capital of the world then the Torres Strait is the dugong capital of Australia and then the most important place for dugongs in the whole world.

"I think we tend to think more about places closer to home than in the remote areas such as the Torres Strait, although there is some active work going on at the moment," Professor Marsh said.

ABC/ Reuters