Location and Values: The Great Barrier Reef is located off the north-east coast of Australia and is the world’s most extensive coral reef system. Most of the reef lies within the world heritage area, making it by far the largest world heritage site globally – significantly larger than the whole of Italy (which, incidentally, had 54 world heritage sites within its 301,000 km2 area by 2018!). The Great Barrier Reef stretches for more than 2,000 km along the Queensland coast (corresponding with 14o of latitude), and includes some 2,500 individual reefs up to 250 km offshore. Biologically, the area is one of the richest and most complex ecosystems on earth, with a vast mosaic of reefs, islands and coral cays that have evolved over the millennia through four glacial-interglacial cycles. The structure and biological wealth of the present-day reef is the result of sea level changes that have periodically exposed, flooded and shaped the underwater world, which now supports an exceptionally rich marine fauna including a large number of endemic species. This is a place where exceptional natural phenomena occur, including the annual mass spawning of corals, migration of whales, communal nesting of turtles and seabirds, as well as spectacular aggregations of spawning fish.
Conservation Status and Threats. According to IUCN’s most recent Conservation Outlook Assessment (December 2020) the conservation status of the Great Barrier Reef is now considered ‘critical’, following a series of coral bleaching events in 2016, 2017 and 2020. The exceptional values which are recognized by the site’s inscription on the World Heritage List are now very seriously threatened by:
- Climate change. This is the single greatest threat to the site’s values, and the primary cause of recent bleaching events and death of corals over wide areas of the reef. Climate change has resulted in a decline in coral recruitment and reef building as well as observed declines in a range of other attributes including populations of loggerhead, hawksbill and northern green turtles, scalloped hammerhead sharks, seabirds and (possibly) some dolphin species.
- Catchment Water Run-off and Pollution. Forest clearance and poor agricultural practices in the mountain catchment areas of Queensland has resulted in excessive silt loads and pollution by agricultural effluents of the rivers that flow out along the coast next to the Great Barrier Reef. The degradation of waters from the catchment areas increases the turbidity of marine areas offshore and reduces the quality of the sea-water, affecting the survival and growth of corals in affected areas of the Great Barrier Reef.
- Coastal Infrastructure Development. Coastal infrastructure development including housing, roads, ports and mining activities is causing further run-off and pollution of the inshore waters, with sewage and other effluents that adversely affect the reef.
- Outbreaks of Crown-of-Thorns Starfish. This invasive species, which preys on many species of hard coral, can reach plague proportions and exacerbates the problems facing the Great Barrier Reef following bleaching events by further diminishing the viability of its corals.
- Over-fishing. Two thirds of the Great Barrier Reef is subject to commercial fishing, while a third is designated as no-take zones. Some species (such as scallop, snapper and pearl perch) are being over-fished, while gill-net fishing may result in the accidental capture of non-target species including those of conservation concern, such as dolphins, dugong, sawfish and sea snakes.
IUCN Conservation Outlook
UNEP-WCMC Site Description
Official UNESCO Site Details