Crown of thorns starfish (Acanthaster planci) feeds on porites coral head. Lizard Island, Great Barrier Reef, Australia © Lisa Bostrom Einarsson / WWF-Aus

Crown of thorns starfish (Acanthaster planci) feeds on porites coral head. Lizard Island, Great Barrier Reef, Australia © Lisa Bostrom Einarsson / WWF-Aus

Coral-eating starfish numbers could reach 60 million, GBR outbreak on track to be worst on record

10 Dec 2015

  • climate change
  • crown of thorns starfish
  • great barrier reef
  • marine species

A new publication commissioned by WWF-Australia says if the current outbreak of crown of thorns starfish (CoTS) follows previous patterns it will likely be the worst on record.

It’s estimated there are already between four and 12 million starfish on the Reef now. In The Starfish That Eat The Reef report Dr Glen Holmes calculates those numbers could reach 60 million over the next five years.

Studies have shown that one adult starfish can eat a dinner plate-sized patch of coral each day.



Dr Holmes also writes that the central and southern section of the Great Barrier Reef - “May well be reduced to coral cover levels well below an average of 10%”.

“It would be like a locust plague devastating vegetation,” Dr Holmes said.

Dr Holmes also, for the first time, estimated the area of coral previously destroyed by the starfish between 1985 and 2012. 

“The central and southern sections of the GBR lost over 60,000 hectares of live coral solely because of CoTS.

“To put that in perspective that’s the same as 60,000 football fields of coral eaten in less than 30 years,” said Dr Holmes. 

But The Starfish That Eat The Reef report, which explains the latest science on CoTS, is not all doom and gloom.

Scientists believe that CoTS can be controlled if chemical fertilisers flowing off the land into reef waters are reduced by up to 80% in the worst affected catchments.

Nitrogen pollution, the vast majority from agriculture, triggers algal blooms which feed juvenile CoTS allowing large numbers to survive – a major factor in outbreaks.

WWF Spokesperson Sean Hoobin said: “We can stop outbreaks before they begin. We just need to reduce polluted run-off from farms to remove the food source for crown of thorns starfish juveniles.

“Widespread uptake of precision farm practices can cut pollution and help give the Reef the clean water it needs to stop the CoTS outbreaks, and rebuild its coral gardens.

“Australian governments need to cap and reduce pollution to meet their pre-existing water quality targets by 2025, and provide the funding to help ensure we have clean water flowing off our farms,” he said.
WWF-Australia Media Contact:
Mark Symons, Senior Media Officer, 0400 985 571

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