Something Missing

Something Missing

Have you ever walked down a familiar street and noticed that something has changed; that something is missing: a house, a tree, a bench? You try to picture what it is and how it looked before the change? But you just cannot quite catch the original picture. It seems blurred to memory.

The Great Barrier Reef could quite conceivably become one of those lost images, perhaps better documented than the house, tree or bench. It is becoming a victim to climate change and our failure to protect it against pollutants and run offs from agriculture, mining and associated industries.

In 1975 Gough Whitlam created the Great Barrier Reef Marine Park when it came under threat from mineral exploration and mining for cheap fertiliser for sugar cane plantations. Fast forward 50 years and Greg Hunt, environment minister, approved the Ardani Carmichael coal mine in 2015 despite acknowledging that climate change is the greatest threat to the reef. However, he considered, despite the evidence, that emissions arising from transport and other mining operations including burning coal from the mine was speculative and therefore that it was difficult to draw any firm conclusions about their effect on global temperature and climate change.

Increased sea temperature results in coral bleaching. Increased carbon emissions cause acidification of the ocean waters. Both these factors slow the growth of corals, weaken their skeletal structure and negatively affect the supporting ecosystem. Climate change is also responsible for increased severity and frequency of reef-smashing storms. These storms not only damage the reef but also are responsible for washing pollutants from the land into the ocean.

So what is involved in bleaching? Coral bleaching is the breakdown of the symbiotic relationship between the coral host and zooxanthellae, tiny marine algae that provide corals with 90% of the energy they need to grow and reproduce. Without zooxanthellae, the tissue of the coral animal becomes transparent. Once the coral bleaches it begins to starve. Coral reefs may take decades to recover.

Coral bleaching is not a new phenomenon. In the past, however, the period of time between bleaching events was longer. In this current bleaching event, thought to be one of the worst in recent history, some corals will recover when the ocean temperature falls to below 29.5 degrees Celsius. There is a possibility that some of the delicate corals, unable to recover, will be replaced by more robust corals. However, the problem is time and the conditions required for optimal recovery.

A recent study in Science (15 April 2016) suggests that in the past corals have been able to prepare themselves to tolerate gradual temperature rises. This slow rise in temperature and period of preparation reduced the severity of the bleaching thus increasing the likelihood of coral recovery and survival. When ocean temperatures rise rapidly and do not return to optimal temperature levels and remain at those higher than optimal levels for a period of time, the corals take longer to recover, regardless of storm damage to the reef itself. Because of rising ocean temperatures, bleaching events are likely to occur more frequently, without either the opportunity for a “practice run” or for full recovery. The result is likely to cost us one of our most unique and precious assets.

Will we in future only have a fleeting memory that something we once appreciated was there? Will we wonder about what is missing? And what else will go missing along with the coral? › What we do › Oceans

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