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Ocean acidification could trigger economic devastation

Coral reefs, shellfish, and even top predators such as tuna could be devastated as human carbon-dioxide emissions continue to acidify the world’s oceans. These and other impacts of anthropogenic ocean acidification are laid out in a new expert assessment, released today.

Oceans act as a huge carbon sink, sucking up much of the CO2 released to the atmosphere. But taking up more carbon increases the acidity of the water, with wide-ranging effects on marine organisms.

The authors of the report, released today from the Third Symposium on the Ocean in a High-CO2 World, review the current science on the effects on marine organisms, and write that there is a “medium confidence” level that shellfish harvests will decline. There is also a medium confidence level that economic damage will result from impacts on coral reefs, with tourism, food and shoreline protection suffering. The size of this is unclear but one estimate is for $1 trillion in damage from coral loss alone.

Modelled global sea-surface pH.

Modelled global sea-surface pH.

Ocean Acidification Summary for Policymakers 2013

How larger species will fare as oceans acidify is less clear. The report gives only a “low confidence” rating to the idea that top predators and fin fish catches will be reduced. But any losses in this area could hit hard the 540 million people whose livelihoods depend on such fisheries.

Scientists also have a “very high confidence” that the ocean’s capacity to take up carbon decreases as waters acidify. So even larger cuts in human greenhouse gas emissions than currently envisaged may be needed to meet targets set to limit global warming as a result, the authors write.

The report is likely to be pored over by policymakers as it comes out ahead of the latest report from the IPCC’s working group II on the impacts of climate change, which is due next year. Although the new report was produced with a different methodology, it still represents one of the most comprehensive and up-to-date assessments of a major impact of CO2 emissions currently available.

Co-author Ulf Riebesell, an oceanographer at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, says more work is urgently needed to understand animals’ and plants’ abilities to adapt to a more acidic ocean, and to move researching the impact on single species to how ecosystems as a whole will fare. There is also a need to clarify on how these changes will affect the services that the oceans provide to humans — from food to protection from storms.

The report authors also say that the acidity of the oceans could increase by 170% by the end of the century, corresponding to a drop in surface ocean pH by 0.32. This occurs under a pessimistic scenario of high human emissions. Since the industrial revolution, surface ocean pH has dropped from 8.2 to 8.1. As pH is a logarithmic scale, the increase in acidity since the industrial revolution could reach around 170% under this scenario.

Under lower-emissions scenarios, this decrease would be around 0.07. But current emissions show no sign of dropping to those necessary to achieve such a goal, cautions Riebesell.

“If you look at current trajectories we’re no way below the [high emissions scenario],” Riebesell says. “Of course we hope the human race is smart enough to learn at some point and turn the wheel round.”

The report was sponsored by the International Geosphere-Biosphere Programme, UNESCO’s Intergovernmental Oceanographic Commission, and the Scientific Committee on Oceanic Research.


  1. Report this comment

    Peter Holland said:

    If the planet would indeed warm up (yes some areas do but others cool down, for instance there have been colder winters in Europe) the oceans would actually let go CO2. So the CO2 level in the oceans would drop.

    Nature adapts. It always has. In the past there have been much higher CO2 levels.
    CO2 is not toxic but good for plantlife (which converts it to oxygen).

  2. Report this comment

    David Bainbridge said:


    Your comments sound so reasonable. They also seem to say that something changes here, something compensates there and overall everything remains the same. What they actually do is totally confuse the issues. Acidification of oceans is not about temperature of oceans, it is about the amount of CO2 available to be absorbed into them.

    More importantly, there is no entity called “Nature”. There are just external conditions and they have changed dramatically over billions of years. “Nature” does not adapt, it changes. Species do not adapt to those changes, those changes adapt species by eliminating individuals who cannot survive in changed conditions. If all individuals are able to survive the changes, there is no change in the species. If no indiviuals are able to survive, the species becomes extinct. Evolution is what happens between those two extremes.

    Just over 2bn years ago this planet was uninhabitable. Perhaps the most momentous event in this planet’s history was the evolution at that time of cyanobacteria that used photosynthesis to extract the carbon they needed to multiply from CO2 in the atmosphere. Over the next 1.5bn years oxygen that photosynthesis released as a waste product made possible the world we now live in.

    Oxygen in the atmosphere precipitated mineral deposits and created carbonate rocks. The first complex multi-celled organisms evolved underwater, probably 700mya when there was 1% oxygen in the atmosphere. Some inherited photosynthesis and became the ancestors of plants, others used the oxygen they released and became the ancestors of animals and insects.

    Oxygen created the ozone layer that enabled organisms to move out of water onto land. The first were plants. Their photosynthesis increased oxygen in the atmosphere as high as 35% and CO2 from around 0.7% to a low of 0.02%. Oxygen plummetted to 10% when dinosaurs with bodies with low oxygen demand predominated. Mammals with high metabolism systems and oxygen hungry brains took over as oxygen climbed towards the present 21%.

    The carbon from cyanobacteria settled to form oil deposits. During the Carboniferous uninhibited plant growth sequestrated massive amounts of carbon in coal deposits. This has not been “Nature” adapting, it has been “Nature” being shaped by evolution of species, which are in turn evolved by changes in the conditions.

    Humans changed from simple, small hunter gatherer groups to more complex, larger agrarian societies over the last 10,000 years, a sweet spot, the longest period of relatively stable climate that our climate records have been able to identify.

    In recent centuries humans have developed industrial societies and a population explosion fueled by reversing hundreds of millions of years of carbon sequestration that were probably the major factor in creating the climate stability of the inter-glatial period that made possible the development of present complex human societies.

    So “Nature” is the result of complex interactions among many factors, important among which are the activities of species. Cyanobacteria started the process of carbon sequestration 2bn years ago that set the planet on the path towards our present state of “Nature”. On what grounds are you so confident that the reversal of that process by supposedly intelligent humans will not have equally profound effects on changing the state of “Nature”?

    Given that everything in present day complex human societies has developed in relatively stable climate conditions over the past 10,000 years, how confident are you that human societies will be able to survive if the actions of human societies tip climate back into the cycles of huge variances that have prevailed for most of the planet’s history?

    Increasing CO2 might benefit plants. The effects on humans and other animal species are unpredictable, but the signs are already showing. Studies of fish along the Australian coast have shown that species and their environments have been migrating south at an average of 7 kms pa over recent decades. Tropical fish species are now being sighted in the upper latitudes of the Southern Ocean. That has mainly been a temperature effect, what will be the consequences of increasing acidification on top of temperature increase?

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