An acid test for policy

Coal-fired power station Ocean acidification is a mechanism through which emissions can impact humanity's food supply

There's more this week on the critical but in some ways under-covered issue of ocean acidification.

At root, it's simple chemistry. Carbon dioxide goes into the air from factory chimneys and hearths and car exhaust pipes, and some of it ends up dissolved in seawater, as carbonic acid.

As carbon dioxide in the atmosphere now tops 380 parts per million (ppm), whereas the past few million years have seen oscillations between about 180 and 280ppm, it's hardly a surprise that seawater is now more acid than during this recent period of Earth history.

It's been much higher in previous ages; but as always, it's not just the scale of the change that's important, but the speed.

A new study in Nature Climate Change journal [released to journalists but not apparently on the journal website as yet] has tried to measure the current rate of change against what happened in pre-industrial times.

It's reliant on computer models to provide historical estimates; but with that caveat, the numbers are startling, suggesting that the current rate of acidification is two orders of magnitude bigger than what happened at the end of the last Ice Age.

Can marine animals, plants and ecosystems live with that? If so, what will the oceans look like in the future? Will they still be able to provide us with the food we need?

Some experiments in the laboratory and in "natural laboratories", where CO2 seeps into the sea from the slopes of underwater volcanoes, suggest problems ahead.

For example, just last week an Australian research team found that moderately enhanced CO2 levels in seawater affect the brain chemistry of fish, changing operation of neurotransmitter chemicals that carry messages between neurons.

Coral and seagrass Observation of a natural CO2 seep near Papua New Guinea shows a healthy reef (l) away from the vent, but just seagrass (r) nearby - a picture of the seas in years to come?

Some readers may already have fingers poised ready to write comments along the lines of "it's not a rise in acidity, it's a fall in alkalinity - so don't call it acidification".

And you'd be right. At pH8.1 and falling, seawater is heading from the alkaline towards neutral.

But although that point is correct, it's also irrelevant. Organisms and ecosystems adapt to whatever acidity or alkalinity they find, and need time to do so; and in some cases, such as with animals that need to form shells, adaptation may be impossible.

Anyway, there's a wealth of evidence out there that ocean acidification is of concern - perhaps even more than the climatic effects of CO2 emissions - so I'm not going to provide a catalogue here.

If it is of concern, you might think there would be some kind of international agency or treaty or framework charged with tackling it.

If you think that, you'd be wrong.


Ocean pH levels (Image: BBC)
  • The oceans are thought to have absorbed about half of the extra CO2 put into the atmosphere in the industrial age
  • This has lowered its pH by 0.1
  • pH is the measure of acidity and alkalinity
  • The vast majority of liquids lie between pH 0 (very acidic) and pH 14 (very alkaline); 7 is neutral
  • Seawater is mildly alkaline with a "natural" pH of about 8.2
  • The IPCC forecasts that ocean pH will fall by "between 0.14 and 0.35 units over the 21st Century, adding to the present decrease of 0.1 units since pre-industrial times"

Acidification currently falls through the dividing lines that separate various UN institutions.

The climate change convention doesn't mention it, largely because it emerged as a potentially serious issue after the convention's establishment in 1992.

These days, acidification often crops up in speeches at the annual climate meetings, but rarely makes it into agreements.

Treaties on oceans, meanwhile, cover issues such as rights of access for shipping, fisheries, and pollution of the locally-acting kind.

And where should acidification fit, bearing in mind that the cause of the problem is so closely tied to the one supposedly being addressed in the climate convention whereas the impacts would be scattered around those relating to marine life, food and economic activity?

June's Rio+20 summit offers a way to put the issue on the tables of presidents and prime ministers; and it's a move being actively pursued.

Unesco's International Oceanographic Commission is one of the UN bodies keen to see acidification high up the Rio agenda; and this week, its executive secretary Wendy Watson-Wright explains why on the RTCC group's website.

As with climate impacts, there is an agenda concerned with dealing with the impacts of acidification, as well as the agenda concerned with reducing the trend itself.

A few years back, for example, scientists showed that keeping the fish population balanced and healthy on a reef offers some protection against impacts of rising water temperatures and acidity.

There's are ways to do this sort of thing through existing national and international mechanisms - provided the importance and the methods filter through.

Acidification is on the Rio agenda in the sense that the initial draft has a clause reading "We also propose to implement an international observing network for ocean acidification and to work collectively to prevent further ocean acidification".

Is that enough?

Richard Black Article written by Richard Black Richard Black Former environment correspondent

Farewell and thanks for reading

This is my last entry for this page - I'm leaving the BBC to work, initially, on ocean conservation issues.

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  • rate this

    Comment number 22.

    So stupid that it is funny.

    "Carbon dioxide in the ocean acts like alcohol on fish, leaving them less able to judge risks and prone to losing their senses."

    Seems talk of CO2 makes many people lose their senses.

  • rate this

    Comment number 21.

    Why are you still quoting that discredited Watts up website?!

  • rate this

    Comment number 20.

    #19. Right you are. "In a recent experiment in the Mediterranean, reported in Nature Climate Change, corals and mollusks were transplanted to lower pH sites, where they proved “able to calcify and grow at even faster than normal rates when exposed to the high [carbon-dioxide] levels projected for the next 300 years.” (same WUWT link)

  • rate this

    Comment number 19.

    How near is "away from the vent"? Unless a very long way, the fact that corals are flourishing would suggest that the somewhat elevated levels of CO2 sure to be found there are no problem for these organisms. In other words the article would disprove its intended point.

  • rate this

    Comment number 18.

    Wolfie Woods

    Some people are so dumb that think it's ok to say things like sceptics should be subject to state sponsored re-education, some even think that the Khmer Rouge provide a good model for controlling people for the sake of the planet. Now I wonder who uttered this garbage.

  • rate this

    Comment number 17.

    Richard, honestly, could you please provide your scientific credentials. I am under the impression that you have not a clue about science.
    Humans cannot "do" anything about pH of oceans, in the same way EU cannot legislate against the Sun spots.
    To BBC - please please find another person with a good scientific education to write quality pieces and not scaremongering - you owe it to the country.

  • rate this

    Comment number 16.


    "..basic school-boy science; carbonates react with acids to produce more CO2..."


    You should learn some then.

    Yes, a carbonate would react with say, nitric acid to become a nitrate of the metal and release CO2.

    It would "react" with carbonic acid to produce a, er, carbonate, and release carbon dioxide which in solution is er, carbonic acid.

  • rate this

    Comment number 15.

    "One spot in the ocean varied by an astonishing 1.4 pH units regularly. All our human emissions are projected by models to change the world’s oceans by about 0.3 pH units over the next 90 years, and that’s referred to as “catastrophic”"

  • rate this

    Comment number 14.

    "Scripps blockbuster: Ocean acidification happens all the time — naturally

    There goes another scare campaign."

  • rate this

    Comment number 13.

    #8 Eddy from Waring - limestone caves are formed when the insoluble limestone reacts with the dissolved CO2 to form soluble Calcium Bicarbonate.

    CaCO3 + CO2 + H2O → Ca(HCO3)2

    If you consider yourself past school-boy science, try this:

    That's 2005 - this story has been an established fact for quite a while.

  • rate this

    Comment number 12.

    @Eddy from Waring - basic school-boy science; carbonates react with acids to produce more CO2.

    The acidification of the oceans threatens not just corals, but anything with a carbonate structure, from algae all the way up to snails, starfish, crabs, lobsters and clams.

  • rate this

    Comment number 11.

    Hydrothermal activity, from volcanic vents support a rich eco-system converting dissolved carbonatious and esp. Sulphourous minerals into energy (no sunlight!) The limestone Karst regions inc. Yorkshire and Cheddar area are produced by weak Carbonic acid dissolving Calcium carbonate. Ref. Encyclopaedia Britannica

  • rate this

    Comment number 10.

    Human overpopulation is the cause of most of the planets woes,encouraged by the free market fundamentalists.As fish stocks fall and food prices go up will people see sense or is it another chance for more profit for the few at the expense of the many?

  • rate this

    Comment number 9.

    In any case, Calcium Carbonate, limestone, is slightly soluble even in pure water, so rain alone would eventually make caves in it.

  • rate this

    Comment number 8.

    "... Carbonic Acid has dissolved out the cave systems in the limestone areas of Yorkshire..."


    No it didn't. It was sulphuric and sulphurous acid from vulcanism, and nitric and nitrous acids from lightning dissolved in the rain that did that.

  • rate this

    Comment number 7.

    I'd say the death, or absence, of marine life around volcanic vents may be more likely conected to the presence of sulphur dioxide, hydrogen sulphide or carbon monoxide etc. rather than carbon dioxide, unless the levels of the latter were so high as simply to suffocate animal life.

  • rate this

    Comment number 6.

    Unfortunately most people are just too dumb it get it & politicians say what the dumb people want to hear that is why we need professional administrators & one world government, democracy is a big part of the problem.

  • rate this

    Comment number 5.

    Think of the Great Barrier Reef as the Amazon Jungle of the sea,Acidification is now destroying this vital habitat, Carbonic Acid has dissolved out the cave systems in the limestone areas of Yorkshire and Cheddar over millions of years, same Calcium Carbonate mineral (not a carbonate)

  • rate this

    Comment number 4.

    Those responsible have not yet cleaned up entire Gulf of Mexico.
    Those responsible have not yet cleaned up Nigerian Delta.
    There are those that would pipeline the Arctic!
    I could write about 1,000 more individual cases, but tell me: Does this look like govts care about pollution, acidity...or is it all greed & profit. There will be no change unless there is some kind of social awakening.

  • rate this

    Comment number 3.

    Hawaiian Islands will be one of the first to feel IMPACT. Eastern tropical Pacific should do better, because greater underlying natural variability of seawater acidity helps to mask changes. Caribbean & western Equatorial Pacific, both biodiversity hot spots, are vulnerable.
    So what?


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