Intensified Control as New COTS Outbreak Hits Great Barrier Reef
An emerging outbreak of coral-eating crown-of-thorns starfish (COTS) has been identified on the Great Barrier Reef, prompting an intensified control program. This event marks the fifth recorded outbreak cycle in the northern Great Barrier Reef, while the fourth wave is still undergoing management.
The outbreak, described as potentially one of the most severe in 60 years, is concentrated in a 240-kilometer stretch between Cairns and Lizard Island, an area known for its coral diversity and tourism.
Outbreak Details and Historical Context
The Great Barrier Reef Marine Park Authority (GBRMPA) confirmed the current outbreak, noting that adult COTS densities are expected to increase substantially on reefs offshore from Cairns. Historically, the Great Barrier Reef has experienced four documented COTS outbreaks since the 1960s, with the most recent commencing in 2010 and still requiring ongoing management.
Studies suggest that cyclic outbreaks typically occur approximately every 17 years, indicating the current emergence is ahead of schedule. The northern region, specifically the Cairns to Cooktown area, has been identified as the initiation point for previous large-scale outbreak waves.
The Threat of Crown-of-Thorns Starfish
COTS are a native species to the Great Barrier Reef, but their uncontrolled proliferation can rapidly deplete coral.
Each adult starfish is capable of consuming approximately a dinner-plate's worth of coral every one to two days.
Long-term monitoring by the Australian Institute of Marine Science has identified COTS as a significant factor in coral loss. They are responsible for up to 40 percent of coral decline over four decades. A single mature female starfish can produce up to 200 million eggs annually, which can then spread through the marine park via ocean currents.
COTS are the world's second-largest starfish, capable of growing to nearly one meter in diameter, and possess venomous spines coated in a toxic slime. Natural predators include fish species such as emperor, snapper, coral trout, tuskfish, Maori wrasse, triggerfish, pufferfish, and the giant triton snail.
The precise causes of outbreaks are not fully understood but may involve factors such as:
- Excess nutrients from run-off
- Availability of live coral
- Ocean currents spreading larvae
- Reductions in natural predator populations
The COTS Control Program: A Coordinated Response
The Australian Government funds the COTS Control Program, which involves specialist dive teams working from dedicated vessels. The control method includes locating individual starfish, often by identifying scar trails, and injecting them with either cow bile or household vinegar. This work is described as slow and methodical. Areas between Irene Reef and Lizard Island, including Startle Reef, have been particularly impacted.
Currently, six dedicated vessels operate under the program across priority reefs, with teams of six to ten divers per vessel.
GBRMPA chief scientist Roger Beeden stated that operations would need to be doubled to effectively manage the emerging outbreak.
The program strategically repositions its fleet to suppress emerging outbreaks in the North while maintaining control efforts in the central and southern regions.
Since 2012, the program has protected over 830,000 hectares of coral reef habitat and removed almost 1.4 million starfish over 160,000 diver hours. Operating at an approximate cost of $175 per hectare, the program also employs approximately 140 people, including 14% Indigenous staff, and provides targeted training.
Dr. Beeden noted that the control program is considered the most effective human intervention for protecting the reef, as it allows for the suppression of outbreaks and the protection of coral across entire reefs and regions. He also indicated that coral restoration at the scale of the COTS control program is not currently feasible, with estimated costs of hundreds of billions of dollars using existing technologies.
Economic Stakes and Government Action
The COTS control program costs about $25 million annually. The tourism industry linked to the Great Barrier Reef contributes approximately $9 billion annually to the local economy and supports jobs in Far North Queensland. Protecting high-value tourism reefs off Cairns, which attract over one million visitors annually, is considered important for this industry.
Environment Minister Murray Watt announced an additional $1.4 million in funding for the program, recognizing its role in reef protection.
The COTS control program is a component of the Australian federal government's strategy to demonstrate active management of the Great Barrier Reef.
Australia is required to submit a State of Conservation report to UNESCO by February 1, ahead of a World Heritage Committee review later in the year. This report will detail progress on climate change, water quality, and reef management, including pest control programs.
Collaborative Efforts for Reef Protection
Sheridan Morris, managing director of the Reef and Rainforest Research Centre (RRRC), oversees two dedicated COTS Control Program vessels in the Cairns region. COTS crews and tourism operators are working to protect high-value tourism reefs.
The Reef Authority, through the Tourism Reef Protection Initiative (TRPI), funds tourism operators to monitor and cull COTS, contributing data to a unified management approach. Gareth Phillips, CEO of the Association of Marine Park Tourism Operators (AMPTO), highlighted the historical role of the reef tourism industry in reporting outbreaks and supporting early intervention efforts. The COTS control program has been cited as an example of collaboration among industry, science, and government.