Mass coral die-offs at the Great Barrier Reef are a sign of far worse things to come

The Sea
The Sea

Just like doctors record a patient’s pulse to assess her health, scientists look at corals to check the health of the oceans. In the 2016 assessment, ocean doctors have only bad news to deliver.

The Great Barrier Reef, a UN heritage site and one of the wonders of the natural world, suffered one of its worst die-offs last year. It’s no coincidence that it happened during the hottest year on record. Our hunger for fossil fuels, which raises carbon-dioxide levels and heats up the planet, is slowly choking the life out of these exquisite creatures.

Corals are tiny polyps that live with colorful algae. Corals create protected calcium-carbonate homes for the algae, which in response provide oxygen to the polyps and clear away waste accumulated in their tiny homes.

Though they care not what happens to the world beyond, their loving relationship has a profound impact on the oceans. Corals occupy less than 1% of the oceans, but create an environment for more than 25% of all known marine fish species. One estimate suggests that the economic benefit of fisheries and tourism derived from coral reefs is more than $375 billion per year.

Sadly, however, corals are also highly sensitive to temperature changes. A change of merely 1-2°C (or 2-3°F) can cause corals to die en-masse, an event known as bleaching because all that’s left behind are their ghostly white, empty homes. (Ironically, this happens because heat causes algae to produce more oxygen, which above a certain threshold becomes toxic for the polyps.)

Between 1876 and 1979, only three bleaching events were recorded across the world. According to the latest study, published on March 15, three global bleaching events have occurred since 1998, scientists say. The 2016 event is by far the most widespread and damaging.

“We didn’t expect to see this level of destruction to the Great Barrier Reef for another 30 years,” Terry Hughes of James Cook University told the New York Times. “In the north… literally two-thirds of the reefs were dying and are now dead.”

Corals can recover from bleaching events, as new polyps occupy derelict homes. But the time between bleaching events is shortening, and that means many of the reefs will never recover. Scientists have found that when corals disappear, most fish around them do too. Those that remain become vulnerable to disease.

What’s worse is that coral die-offs often happen as other parts of the ecosystem collapse. In Australia, for instance, the Great Barrier Reef bleaching is happening at the same time as the degradation of forests, the dying off of certain frog species, the extinction of mammals, and the collapse of bird flocks.

In the end, you needn’t know any of these facts to be convinced to protect corals. The first time I saw corals in late 2014, I could only be forced away from the magnificent underwater world because my oxygen tank was running low. That I may never see such beauty again is not a thought I’d like to entertain.

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