Rippling with color and bursting with life, the Great Barrier Reef has been one of the most diverse places on the entire planet for 25 million years. Yet it now faces an uncertain future. Last year the reef experienced one of the worst bleaching events in recorded history, and quite worryingly, it seems that it is poised to go through round two.

The reef is now facing an unprecedented second bleaching event in two years. While it was thought that most of the reef would be able to survive last year’s event if given sufficient time to recover, it now seems that it’s getting no such breather.  

This new wave of bleaching comes hot on the heels of last year’s disastrous bleaching event, which saw a reported 22 percent of coral across the Great Barrier Reef die. The incredibly mild winter has not helped the situation. The surface water temperatures have not really dipped as was expected, meaning that the reef is already highly stressed as the second round of bleaching hits, increasing the risk that this current event will be catastrophic.

^{Bleaching is not only affecting the Great Barrier Reef, but coral all around the tropics, as seen here. © XL Catlin Seaview Survey}

What is also of concern this time round, however, is where the stark white coral has been spotted. Last year the worst-hit regions were in the far north of the reef, where water temperatures tend to be a little warmer anyway. The aerial surveys that have just been carried out, however, have found that the reef much further south, between Cairns and Townsville, is now feeling the heat.

This means that while last time round, the parts most heavily visited by tourists escaped much of the bleaching, this year is looking like those parts may well be hit. Last year it was revealed that the Australian government lobbied UNESCO to remove the reef from a report on World Heritage Sites at danger from climate change due to fears it may negatively impact tourism. Now, it seems, those very tourists could get to see the impact for themselves.

The scale of the bleaching will become more apparent as further surveys are done, and enough time has passed for the extent of coral mortality to be known. Just because the reef has been bleaching does not automatically mean that the coral will die – if the water temperatures dip for sufficiently long enough, the organisms can recapture the photosynthetic algae they eject. This means that it may be up to six months before we know the true impact on the reef this time round.