Great Barrier Reef

Definition

The world's largest coral reef system, lying in the Coral Sea off the north-eastern coast of Queensland, Australia, and a UNESCO World Heritage Site.

Key points

• The largest living structure on Earth and the largest coral reef system, stretching over about 2,300 km off the Queensland coast in the Coral Sea.
• A barrier reef: it lies offshore, separated from the mainland by a wide, deep lagoon, unlike a fringing reef (attached to the shore) or an atoll (a ring around a lagoon).
• Built by colonies of tiny coral polyps (with symbiotic zooxanthellae algae) that need warm (about 23 to 25° Celsius), shallow, clear, sunlit, salty water, so reefs are largely confined to roughly 30° north and south of the Equator.
• Declared a UNESCO World Heritage Site in 1981 for its extraordinary marine biodiversity.
• Under serious threat from coral bleaching (driven by warming seas linked to climate change), ocean acidification, cyclones, and pollution.

Why it matters for CAPF

Its status as the world's largest reef, the barrier-reef type, the Queensland-Australia location, the World Heritage listing, and the bleaching threat from climate change are recurring world-geography and environment facts.

Common confusion

A barrier reef (like the Great Barrier Reef, separated from shore by a lagoon) differs from a fringing reef (attached to shore) and an atoll (ring-shaped around a lagoon). Coral bleaching is the loss of the algae due to heat stress, not the death of the reef itself, though prolonged bleaching kills coral.

Parent note

important features of the world