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    We're Halfway to Turning Coral Reefs into Submarine "Gravel Parking Lots"

    Written by

    Mat McDermott


    Photo: NOAA/Flickr


    At the rate that carbon emissions are increasing, we could double today's 400 parts carbon dioxide per million–itself much higher than the 280 ppm at the start of the Industrial Revolution–by the end of the century. This would bring atmospheric CO2 concentrations into what Richard Norris from the Scripps Institution of Oceanography calls 'greenhouse world.' In a new paper in Science, Norris and colleagues give us a glimpse at what the world's oceans could look like in greenhouse world, using the past as reference.


    The last time the atmosphere had CO2 concentrations above 800 ppm was 50 million years ago. At the time the polar oceans were about 53°F, comparable to the water of the coast of present-day San Francisco, and the oceans in the tropics were hitting 95°F, comparable to a tepid bath. In these balmy oceans between 42 and 57 million years ago, the coral reefs all disappeared, Norris says, "Reefs were replaced by the 'gravel parking lots' of the greenhouse world"—that is by piles of single-celled organisms called foraminifera.


    Foraminifera photo: Wikipedia


    What's more, these hot hot hot oceans of the tropics and the sub-tropics had far fewer large animals than today's ocean ecosystem, because the food chain that supports such animals in cooler waters was broken apart. What small animals were there were insufficient to support large predatory animals, such as sharks, tuna, whales, seals, and seabirds. 


    If that's not dramatic enough for you, the scientists estimate that if carbon use continues on the trajectory its on now, the type of major ecological changes humans are bringing about on the planet will last for over 20,000 years. If we "abruptly" stop using fossil fuels, major ecological disruption will last for just a millennium. 


    The combined effect of changing temperatures, ocean acidification, rising sea levels, and changes in ocean productivity, will cause the marine environment to be "in a state of continuous change for 100,000 years." 


    If you can't find intrinsic worth in the colorful, awe-inspiring flora and fauna under the sea, how about some anthrocentric dread?: One of the most populated areas of the world coincides with the so-called Coral Triangle in Southeast Asia. Should the reefs in that region be wiped out, a distinct possibility by 2100 the way things are headed, food production in the region will decline 80 percent, putting the lives of 100 million people at risk.