Great Barrier Reef

node · earth · Coral Sea, Queensland continental shelf

The largest coral reef system on Earth, running roughly 2,300 kilometres along the Queensland continental shelf and comprising on the order of three thousand individual reefs and several hundred islands. The Great Barrier Reef Marine Park, the management unit, covers about 344,400 square kilometres. It is not one reef but a shelf-edge system whose reefs sit at different distances from shore and behave differently: inshore reefs take the river runoff, mid-shelf reefs the crown-of-thorns outbreaks, outer reefs the open-ocean swell. Two features make it the most important reef in this Journey. It has been continuously surveyed since 1985 under a single monitoring programme, so its coral cover is one of the few long time series of reef condition anywhere. And it is the reef where recurrent mass bleaching was first documented at whole-system scale, in 2016 and again the following year, on a shelf where the previous assumption had been that the far northern reefs were remote enough to be safe.