Bleaching blues with John Pickrell
News reports give the impression the entire Great Barrier Reef is dead or dying, but what’s the truth about damage to this national treasure?
RECENT CONVERSATIONS with friends made me realise that many people have been left confused about the bleaching events that have struck the Great Barrier Reef (GBR) two years in a row, causing more damage than any others since records began. While there is no doubt the impact is severe and widespread, there are also many regions that have escaped the bleaching, and, even within badly hit areas, the damage is patchy.
Most reef-forming corals are sedentary symbiotic animals that host algae that generate sugar and energy photo synthetic ally from sunlight. When reefs experience higher than expected water temperatures for long periods, the algae begin producing substances that irritate the corals, which expel them from their systems, breaking the relationship the corals need to survive. They therefore go white, appearing ‘bleached’. Small-scale bleaching is a natural process, but the massive events across the GBR we’ve begun seeing in the past two decades are likely to become so frequent that reefs can’t recover.We must tackle climate change swiftly, or we may have to accept the loss of reef systems all together.
The first recorded mass bleaching occurred in 1998 – then the planet’s warmest recorded year – causing the death of 16 per cent of the world’s reefs. Major bleaching events occurred again in 2002 and 2016.The latter bleaching was, at the time, the worst ever, and what is shocking is that this year it has been followed by a consecutive mass bleaching event when reefs have had no time to recover.
But is most of the reef dead and what does this mean for the future of its biodiversity and Australia’s tourism industry? While it’s true that only 7 per cent of reefs surveyed by air last year by the ARC Centre of Excellence for Coral Reef Studies at James Cook University (JCU) were completely free of any bleaching, it’s not accurate to say that 93 per cent of the reef is dying as some news reports then suggested.The aerial surveys looked at about a third of the 3000 reefs found across the GBR Marine Park.The surveys found that in the northern part, above Port Douglas, 81 per cent of reefs were severely bleached; in the central part, between Port Douglas and Mackay, the figure was 33 per cent; and in the southern area, below Mackay, just 1 per cent was severely bleached.The 2017 mass bleaching has impacted the central section more, perhaps simply because there were more corals left there – the data are still coming in.
In summary, as of mid-2017, much of the northern and mid-section of the GBR is very badly affected, while the southern parts have escaped the worst of it. And as of May, cooler waters have arrived from the south and the reef is starting to recover. There is no question that some areas are now coral graveyards, but the damage isn’t extensive and some types of rapidly growing corals are much more susceptible than others – but this also means they will recover quickly. Some corals may yet reabsorb algal symbionts and bounce back. While many fish and other animals, such as turtles, still remain, some of those that rely on branching corals severely affected by the recent bleaching events have perished. However, the patchiness of the damage – and the presence of the surviving fish species – means that many visitors to the reef can still have a great experience, particularly if they are visiting southern parts such as Lady Elliot and Heron islands.
With time, the GBR could regenerate, but at the moment it barely has a chance. What has happened in 2016–17 only underlines the reef ’s role as a ‘canary in the coalmine’ when it comes to climate change.The damage here has been so bad because reefs are more sensitive to temperature changes than other environments such as tropical rainforests.
The best thing you can do in the wake of this disaster is think of ways you can lighten your footprint on the environment and help hasten our transition away from fossil fuels towards renewable energy. Switch your electricity provider and plan to one that sources power from solar or wind, and vote for politicians who support swift actions on climate change.