10 Jan 2019


Sean Hoobin, Senior Manager of Freshwater Conservation at WWF-Australia shares why we need to start looking at the cause of crown of thorn starfish outbreaks.

Have you seen a crown of thorns starfish before?

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

As the name suggests, these starfish are prickly predators. There are millions upon millions of crown of thorns starfish in this current outbreak that are eating their way through coral on the Great Barrier Reef.

Eradicating them is hard work. Teams need to scour the Reef and individually inject each starfish with poison.

This is costly, time-consuming and doesn’t address the source of these mass outbreaks.

Culling can help protect select reefs but there is no way we can eradicate the millions of these starfish one-by-one to protect the entire Great Barrier Reef.

Right now, the Reef has its lowest levels of coral cover on record due to cyclones, water pollution, bleaching and starfish outbreaks.

To give our Reef the best chance of recovery, we need to take global action to address climate change, but also address local impacts like farm pollution which only Australians can do.

This is because run-off from farm fertilisers trigger outbreaks of these coral-eating starfish and cause them to multiply in plague-like proportions.

The starfish are natural predators of the coral on the Great Barrier Reef, but our unsustainable farming practices have upset the natural balance, with devastating consequences.

The Reef is already reeling from consecutive coral bleaching events in 2016 and 2017 and now crown of thorns starfish are feeding on the surviving, and potentially heat resilient coral.

It was shocking to see half the Reef bleach and die recently, but then to have starfish plagues eat surviving coral was heartbreaking.

Scientists are concerned the combined effects of coral bleaching and crown of thorns starfish outbreaks could leave the Great Barrier Reef unable to recover.

A new WWF-Australia report by Dr Udo Engelhardt* urges for a crackdown on the “excessive, and often illegal” use of industrial fertilisers that trigger outbreaks.

“When you have these two major impacts – crown of thorns starfish and coral bleaching – coincide in space and in time, this is the worst-case scenario. This is because you are losing those few corals that are showing signs of adaption to climate change,” says Dr Engelhardt.

“If you lose these due to starfish predation you’ve lost your insurance policy down the track. It is essential to manage these two threats concurrently, simultaneously.”

If we improve water quality, we have every chance of averting the next crown of thorns starfish outbreak. At the same time, giving the Reef the clean water it needs, means corals that have survived bleaching have every chance at regenerating.

There is hope. WWF-Australia is working with farmers through Project Pioneer and Project Catalyst to implement Reef-safe farming practices, to reduce pollution run-off and improve water quality. We're showing that good farming can be good for business and good for the reef. 

Together, we can protect the Reef from crown of thorns starfish and give it the best possible conditions to recover.

Read our report and watch the video below to learn more.

* Dr Udo Engelhardt, Director of Reefcare International Pty Ltd, is a senior researcher with 30 years’ experience in dealing with the crown of thorns phenomenon