You may have heard that Australia's famous Great Barrier Reef dies as warmer and acidic waters bleach the system's vibrant coral reefs. In fact, a heat wave in 2016 killed nearly a third of the system corals.
Now scientists in the journal Nature Geoscience have discovered that the reef has returned five times from extinction in the last year 30,000 years. However, the current pressures are probably much more intense than those in the past.
"I have great concerns about the ability of the reef in its present form to survive the pace of change caused by the many current burdens and such that are projected in the near future," said study author Jody Webster of the University of Sydney in a statement.
The international team looked beyond the boundaries of today's reef to find places where old coral could have grown. Then they drilled into the ocean floor and collected fossil corals and sediments for 30,000 years. These rock cores revealed the dramatic past of the coral.
Read more: Can the Great Barrier Reef survive after heatwave kills one third?
As the sea level rose and fell, coral reefs migrated. Low sea levels 30,000 and 22,000 years ago killed corals by exposure to air. The remaining reef shifted towards the sea and finally returned. [1