Is the Great Barrier Reef dead?
No. It’s not. We just had a massive bleaching event, but we know from past research that corals are able to recover from the brink of death.
So bleached corals aren’t dead corals?
That’s right. There’s lots of confusion about what bleaching means.
Coral is an animal, and the animal exists in symbiosis with photosynthetic algae. The algae provides food for the coral in exchange for a great home. But when the water gets too warm, the algae become chemically destructive to the coral.
When that happens, the coral convulses and spits out puffs of algae to protect itself. That removes all the color from the coral tissue which is transparent, allowing you to see right through to the underlying skeleton. So you are not necessarily seeing dead coral, you’re really just seeing clear coral without its algae.
But bleaching is still bad, right?
Bleaching events are worrisome because if the coral misses this key food source from the algae for too long it will literally starve to death. But, if the water temperature comes back down, it will welcome the algae back. The key is that the water temperature change has to be relatively quick.
Has the Great Barrier Reef been through anything like this before?
It has had very severe bleaching events associated with large El Ninos like we had last year, but the problem is we are seeing baseline ocean temperatures getting warmer every year. When you pile a strong El Nino on top of this ever warming trend, you get more extreme and more prolonged bleaching episodes.
What was striking about this year was the extent of the damage. It was staggering. By important metrics the ’97-’98 El Nino was bigger, but the damage from this last one was far more extensive.
So how can you remain hopeful about the fate of Great Barrier Reef and other reefs in the Pacific?
I work on a research site in the Christmas Islands that is literally smack in the middle of the Pacific Ocean, and which was
much more devastated than the Great Barrier Reef. It was worse off than any reef in the world with up to 85% mortality. But even in the face of that whole-scale destruction, we saw individual corals that were still alive, looking like nothing had happened.
I cling to that. I know from my own site that there is a lot more resilience baked into the system then we can hope to understand right now and that out of the rubble will come a reef that may not look exactly like it looked before, but may be better adapted for future temperature change.