History of crown-of-thorns outbreaks on the Great Barrier Reef

Interviews with Torres Strait trochus divers indicate that crown-of-thorns starfish outbreaks may have occurred in the early part of the nineteenth century. However, the first documented outbreak was recorded at Green Island in 1962.

There have been four major outbreaks on the Great Barrier Reef since the 1960s (in the 1960s, late 1970s, early 1990s and 2010) and the time between the start of each outbreak has been 15–17 years. The fourth and current outbreak began in 2010.

The Australian Institute of Marine Science estimates the Great Barrier Reef has lost approximately half of its coral cover since 1985. The research attributed the loss to three main factors in the following order: cyclones, crown-of-thorns starfish and coral bleaching.

It has also been estimated that if crown-of-thorns starfish predation had not occurred over the past 30 years, then instead of decline, there would have been a net increase in average coral cover.

Crown-of-thorns starfish outbreaks follow a pattern where they tend to spread north and south from the northern Cairns–Cooktown region, migrating south towards Innisfail between three and five years later, hitting the Townsville area five to eight years later, and reaching as far south as the Mackay region about 12 to 15 years after the start of the outbreak. There also appears to be a separate population near the Swains Reefs.

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