The Great Barrier Reef is the world's largest coral reef system, composed of roughly 3,000 individual reefs and 900 islands that stretch for 2,600 kilometres (1,616 mi) and cover an area of approximately 344,400 km². The reef is located in the Coral Sea, off the coast of Queensland in northeast Australia. A large part of the reef is protected by the Great Barrier Reef Marine Park.
The Great Barrier Reef's environmental pressures include lowered water quality from runoff including suspended sediment, excess nutrients, pesticides, and fluctuations in salinity. The effects of climate change, including increased temperatures, storms and coral bleaching. Cyclic outbreaks of the crown-of-thorns starfish, overfishing which disrupts food chains, and shipping routes which can result in oil spills or improper ballast discharge also damage the reef.