How Resilient Are Coral Reefs?

On the Pacific coast of Panama, coral reefs exist in a fairly narrow band of tropics compressed between cold water currents that flow south along the California coast and north along the Peruvian coast. Not exactly the extensive coral reefs of the South Pacific, but still, they are there.

Sea surface temperatures in the tropical Pacific. That’s supposed to be Central America in the upper right, Indonesia in the lower left. Blue indicates cool water, red to yellow increasingly warm water. The ocean currents compress the tropics in the Eastern Pacific compared with the Western Pacific (

An elegant piece of research published last month in Science indicates that reefs may be resilient, able to cease growth during harsh times, and then regrow once conditions improve. The Pacific Panama reefs are about 7000 years old, but from 4000 years ago to about 1500 years ago, they quit growing. Then they started to grow again.

The 2500 years of no growth is correlated with a long period of intense El Nino and La Nina activity. If the greater stress of these events caused the reefs to stop growing, then the same should have occurred broadly around the tropical Pacific. This appears to be true.

How does a dormant or dying reef reef recover? In the case of the Panama reefs, it is very likely that as conditions improved, the reefs were recolonized from remnants of reefs that had survived in sites less affected by the stressful times.

Cauliflower coral, Pocillopora damicornis, dominates the coral community of the reefs off the west coast of Panama. According to cores made into several of the reefs, growth of this species ceased for 2500 years (

A reasonable conclusion is that if we now just stopped – and reversed – the increase in CO2 emissions that our current coral reefs could recover.

But that’s the kicker, isn’t it? CO2 emissions continue to rise every year, and we have no reason to think they will stabilize, let alone reverse, in any political future we can see.

Earlier this summer, 2000 coral reef biologists got together for one of their regular international meetings. They produced a Consensus Statement that they are all signing, and it is a clear, concise and grim summary of the predicament that coral reefs face as ocean temperatures rise, ocean acidification continues, and other stresses of over-fishing and pollution continue relentlessly. The only hope for coral reefs is for CO2 emissions to be reduced.

This is part of the statement (and here’s the full statement)
“CO2 emissions at the current rate will warm sea surface temperatures by at least 2-3°C, raise sea-level by as much as 1.7 meters, reduce ocean pH from 8.1 to less than 7.9, and increase storm frequency and/or intensity. This combined change in temperature and ocean chemistry has not occurred since the last reef crisis 55 million years ago.”

Coral reefs will not survive what we doing to the planet.
As I and many others have written before, that is beyond sad. We have evolved in a complex, beautiful and who knows how unique world, and we are wrecking it.

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