Great Barrier Reef Has Gone Through 5 'Death Events' Over The Past 30,000 Years: Study

The Great Barrier Reef has survived five death events in 30,000 years, but research says modern times may be pushing it past its breaking point.

Changing sea levels and drops in water quality have caused the reef to fight for its life five times through thousands and thousands of years, but it turns out, the reef is incredibly tough and adept at recovery.

In a study published in the journal Nature Geoscience, an international team of researchers reconstructed the reef's evolution going back 30 millennia.

Led by Jody Webster, associate professor from the University of Sydney, the group went back to study a period preceding the Last Glacial Maximum around 20,000 years in the past. At that time, the sea was 118 meters lower than current levels.

Causes, Survival Of Events

Two of what the scientists dubbed death events happened 30,000 and 22,000 years ago and were caused by subaerial exposure, which is when the reef becomes exposed to air. The reef responded by moving back toward the sea.

Two more death events occurred at the deglaciation period 17,000 and 13,000 years ago, this time brought about by the sea levels rising rapidly. The reef then moved toward the land to survive.

Finally, the last known death event was 10,000 years in the past, just before the development of modern corals that now make up the Great Barrier Reef. The cause of this event is observed to be a high increase in sediment and lower water quality coupled with a general sea level rise.

Key to the reef's survival is their ability to migrate laterally, so they can adjust and keep pace with the moving shoreline. The continuity of the reef habitats is also significant, the researchers suggest.

In The Future, Survival Is Not Guaranteed

Although the study shows that the Great Barrier Reef can show great resilience, Webster says it would be very difficult for the reef to survive its current stressors, especially since the rise in the sea's surface temperature is occurring much faster than ever. He also says that since the European settlement in the region, there has been a surge of sediment flux in the waters.

Other factors that also contribute to the Great Barrier Reef's perilous survival include the sharp decline in the coral coverage and widespread coral bleaching.

Studies have shown that a huge chunk of Australia's gem is destroyed — and even with the reef's penchant for survival, scientists are not confident it can recover.

"I have grave concerns about the ability of the reef in its current form to survive the pace of change caused by the many current stresses and those projected into the near future," Webster admits.

It's crucial for humankind to take a look at modern practices to see industries can reduce their impact on the already-depleted reef. The reef is discovered to be sensitive to sediment fluxes, Webster points out.

"In the current period, we need to understand how practices from primary industry are affecting sediment input and water quality on the reef," he explains.