In summer 2019, the Great Barrier Reef Marine Park Authority released its latest five-yearly report
on the condition of the world’s largest living structure. The warning was bleak; the future outlook for the reef has deteriorated from ‘poor’ to ‘very poor’ and points the finger at global climate change (alongside farming pollution, coastal development and illegal fishing) as the main threat.
Despite their tough exteriors, corals are fragile organisms which thrive in only very specific conditions. Sensitive to infinitesimal alterations in sea temperature, water quality, light levels and depth, they lack any buffers to weather the havoc wreaked by global climate change, coastal development, pollution and illegal fishing. Of these, global climate change is generally acknowledged by scientists and experts worldwide to be the main culprit for the dying reef.
In 2016 and 2017 the northern sections of the reef were devastated in mass bleaching episodes
(where the stressed corals eject the colourful algae that gives them their vibrancy), caused by ‘marine heat waves’ attributed to global warming. If the algae loss lasts too long, the corals risk becoming covered in seaweed – something that the more fragile soft corals can’t endure. Sea level rises – again attributed to global climate change – also continue to stress the reef.
Coral bleaching isn’t necessarily permanent, and the coral can recover if sea temperatures drop and the water is clean – as has been the case with a number of past El Niño events (a naturally occurring blast of warm water that appears every five years or so). However, the impacts have never been as hard-hitting or as long-lasting as recent bleaching events
. And if the coral dies, the tiny fish that shelter in it, and feed off it, will die, and the larger fish that depend on those smaller fish die, and so on, and so on. Cue complete ecosystem collapse.