Last Friday the Australian Institute of Marine Sciences (AIMS) organised The Silent Climate Change Issue, a forum where some of the world’s leading scientists in the field discussed Ocean Acidification. Acidification threatens the livelihoods of tens of millions of people, some of the greatest biodiversity on Earth and perhaps Australia’s most precious asset. It’s a global problem for which Australia clearly has a special responsibility.

Ocean acidification is intimately related to global warming in cause and cure, but there are crucial differences that mean we can’t afford to drop it in that basket; so public awareness is important. 150 people turned up, but as far as I could tell I was the only journalist, and as close as they got to a politician, which has to be considered a bad start.

What is acidification? When carbon dioxide dissolves in water it produces a slight acid. A third of the billions of tonnes of CO2 we are dumping in the atmosphere each year is being absorbed by the oceans, affecting their chemistry.

The oceans are not turning to acid, and probably never will. They’re actually slightly alkaline, and all the carbon dioxide we are adding is bringing them closer to neutrality.

Obviously the oceans are big. If the extra CO2 was evenly distributed the effect would be almost imperceptible. However, the oceans mix slowly, so the top 200m are storing most of the carbon dioxide and seeing most of the chemical change.

A pH of seven is neutral. In 1960 the oceanic surface average pH was below 8.2. It’s now near 8.0, with slight variations by region.

The figures don’t sound terrifying, but the consequences are. Marine creatures rely on the alkaline nature of the oceans to form calcium carbonate skeletons, which together form coral reefs. For at least 800,000 years, and probably much longer, the marine environment has been in the 8.2-8.3 range. As carbon dioxide levels build up sea creatures are losing their ability to form these skeletons.

Tens, perhaps hundreds, of millions of people depend on coral ecosystems for their protein. The Great Barrier Reef alone is worth $5 billion a year in tourism and fishing.

Reefs won’t crumble to dust, unless the oceans get more acidic than anyone expects, but new corals will cease to replace those that die. One scientist at the forum presented evidence that calcification rates had fallen by 0.8% a year over the last two decades.

Ocean acidification strips away some of the complexity of the global warming debate. The problem is pretty much all about carbon dioxide. The lesser greenhouse gasses aren’t relevant.

On the other hand, many of the harebrained “geoengineering” solutions offered to allow us to keep polluting with impunity won’t help. The proposal to pump billions of tonnes of sulphur dioxide into the atmosphere to cool the planet, will make things much worse.

The science is also simpler. Most of us have to take it on trust that CO2 is a warming gas but you can demonstrate the basic science of acidification of with some seawater, a candle, jar and strip of litmus paper.

When an audience member asked about solutions the panel was unambiguous: we have to cut carbon emissions. There was a bit of discussion about why further research is still needed. Not all corals are affected equally and we need to know which species will go first and how acidification interacts with the numerous other anthropogenic threats to reefs.

No one, however, wanted to cloud the key message: if we keep building coal fired power stations, driving gas guzzling cars and building freeways rather than train lines we need to get used to the idea we won’t have a reef to swim on and wonder at, our greatest resource for pharmaceuticals will be gone, and millions of starving Indonesians are going to be looking for new homes awfully soon.

Stephen Luntz attended The Silent Climate Change Issue as a guest of AIMS. He is a staff writer for Australasian Science and an active member of the Australian Greens.

Peter Fray

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