Queensland Holidays - Discover the Reef - Threats to the Reef

The greatest threats to the reef are caused by what humans do on land, and to a smaller extent are caused by natural phenomenon such as outbreaks of the Crown of Thorns Starfish.

Coral Bleaching
Widespread coral bleaching has been associated with the global warming caused by greenhouse gas erosion of the ozone. Sea temperature rises of as little as 1 degree can stress corals to expel the zooxanthellae unicellular algae within them that are responsible for coral’s spectacular colour and food source.

Crown of Thorns Starfish
The larvae of the reef’s most infamous marauder, the Crown of Thorns starfish, are known to multiply as a result of plankton blooms. This starfish is a voracious eater of tubular corals however it has been known to strip reefs of all corals when competition for food is increased due to its large numbers. Outbreaks of the starfish occur at semi-regular levels with the reef affected slowly returning to normal in the year between outbreaks.

Marine debris
Marine debris, especially plastic, glass, rubber and polystyrene litter, are tragic and preventable causes of death to marine animals such as turtles, whales and dugong. Littering within the Great Barrier Reef Marine Park Area and other Marine Parks attracts large fines.

Run-off
Run-off from agricultural fertilisers, pesticides, sewage, rubbish, heavy metals and oil spills also disrupts the gentle balance of reef ecosystems which grow best in waters with low concentrations of nitrogen and phosphorus.
Run-off sediment increases both water turbidity - limiting the amount of light that can get to deeper corals - and nutrient levels which can cause plankton and algal blooms.

Natural disasters
Natural disasters such as cyclones and flooding are lesser causes of localised reef destruction.