Will Coral Reefs be Gone by the End of the Century?

Quiet possibly. Ocean acidification caused by the same CO2 that causes global warming is causing them to die.

You might think you can take solace in the idea that coral reefs have been with us forever even when ocean chemistry changes, that there must be some way in which coral reefs survive through changing conditions, and that they may look different for a while but they can’t possibly entirely disappear. But the thing is, scientists have known for decades that coral reefs have in fact re-evolved numerous times from entirely different phylogenetic stock. This probably means that ocean acidification has happened before. So no, we are not going to get out of this easily.

You may take solace in the idea that if coral reefs have disappeared before that this is a natural process and they can disappear again and we can still drive around in our SUV’s and stuff. Wrong again. Those prior turnovers in reef history seem to have been associated with mass extinctions. So, no. we don’t get a pass on that one either.

Anyway, here’s what I want you to know. 1) There is a new book out by Peter Sale (author of Our Dying Planet: An Ecologist’s View of the Crisis We Face) talks about the Coral Reef problem and, more to the point, Shiril Kirshenbaum has a discussion of the problem and in this guest post.


If coral reefs interest you, you may be interested in this book on the history of the study of coral reefs by David Dobbs, and this conversation with Dobbs about his book.

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8 thoughts on “Will Coral Reefs be Gone by the End of the Century?

  1. Our Dying Planet costs $22.18 dollars for hard cover and $19.22 for Kindle edition. Slightly better is Reef Madness costing $17.65 hard cover, $14.39 Kindle.

    Amazon is really annoying me with this naked grab for profits at their customers expense. I’ll just ask the library to bring them in rather than buy them myself.

  2. You seem to be the right folks to ask… Since coral grows under water, how high were the sea levels in the past to allow the growth of the South Pacific islands. What % of the remaining ice sheets does that volume of water represent? Also how will that volume of fresh water affect the projections regarding acidification?

  3. There are no coral reefs of the kind that make islands on the ocean floor. All of them are on continental shelf.

    The islands that stick up out of the sea that are also coral stick up for a lot of different reasons including local uplift as well as older sea levels being higher ca 125,000 years ago, and that difference was several meters.

    Taller islands, and islands out in the ocean are almost all volcanic.

    That’s an interesting question about acidification. Part of the answer is this: The amount of carbon added to the atmosphere roughly correlates to sea level so if we had, say, 5 to 10 times the current amount of carbon we’d have about 120 meters of extra ocean. Say 5% of the ocean (that’s a very rough estimate) would be added with a 500% o 1000% increase in carbon.

    Those are very rough numbers, but it seems to me that the amount of carbon available to be absorbed in the sea is way more than needed in this scenario to saturate the marine environment and the amount of extra water is way less than needed to make a difference.

  4. To Greg, the truth is we haven’t had a 5-10% increase. We have have a 30% increase of CO2 concentration in the ocean. that is a huge increase. And that is only from the last 3 decades. Especially for animals (corals) that are incredibly delicate and need a maintained and constant water chemistry. This is very much a physics and chemistry question not a big picture question. If the CO2 increases by x amount the proton gradient will be infavor of the ocean not the coral. So the coral will start to dissolve (not only corals but shellfish too!) because they can not physically or chemically take calcium carbonate from the ocean. The ocean is taking the CaCO3 from the CORALS and Shellfish to buffer the acidification.

    So yes, the ocean is a big place. But is a very delicate one. And one that is rapidly changing. too fast for the organisms to respond.

  5. Sorry Greg, I did not realize that comment above was in response to the Fresh water comment. I now better understand what you were talking about! Though I would like to make a comment about melting iceshelfs. Corals need to stay at a certain depth (shallow for the most part) in order to live– there for rising oceans will actually still harm the reefs because the light penetration would not get down to the corals who need it.

  6. Sara, if sea levels rise slowly and the coral is not already killed off from acidification, they can rise with the ocean, depending on various conditions. The dynamics are interesting though; Imagine an area of the Caribbean with shallow seas around multiple island systems, then adding tens of meters slowly.

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