Mangroves die-off in Queensland's Gulf Country and Limmen Bight 'may be due to warmer oceans'

Kristy Sexton-McGrath ABC 10 May 16;
* Australia is home to 7 per cent of the world's mangroves
* Mangroves take in 50 times more carbon than tropical forests by area and act like 'nature's kidney'
* Die-off coincides with a period of hot water in the southern Gulf, but more evidence needed

Warmer ocean temperatures could be the reason for huge areas of mangroves dying off in Queensland and the Northern Territory, researchers have said.

Experts have been focusing on hundreds of kilometres of mangroves along the coast of Karumba in Queensland's Gulf Country and at Limmen Bight in the Northern Territory that have turned a ghostly white.

"It appears to coincide with a period of hot water in the southern Gulf, but we need more evidence," Professor Norm Duke from Queensland's James Cook University said.

"I'm speaking ahead of the evidence so I have to be really cautious, but I do want to draw attention to this because we need more capability to respond and find out more about what's going on."

He raised serious concerns about the situation which he compared to coral bleaching happening on the Great Barrier Reef, which is the result of warmer ocean temperatures.

"We're talking about hundreds of kilometres of shoreline affected and an area of mangroves that would be a kilometre-wide in some places," he said.

"We don't have any firm data on the ground to confirm the full magnitude of what's going on.

"We're getting indications from what we can see on satellite imagery and also from people like fishermen, local residents, miners who are working in the area, that there's this massive incident of die-back of a large area along our shorelines.''

Mangroves act as 'nature's kidney'

Australia is home to 7 per cent of the world's mangroves.

They take in 50 times more carbon than tropical forests by area and act like "nature's kidney", Professor Duke said.

He said the die-off already appeared to be having an effect on fish stocks at Karumba - a small Gulf town that relies heavily on the industry.

"What we were told by one fishermen was that there is a reduction in catch, so there seems to be a correlation with what we might expect," he said.

"One of the values of these forests is to support local fisheries."

Aerial and underwater surveys of the Great Barrier Reef undertaken by James Cook University revealed 95 per cent of it had been bleached to some extent.