books climate change conservation environment science

Seasick, by Alanna Mitchell

Seasick: The hidden ecological crisis of the global ocean is an eye-opening book. In a style that is part scientific enquiry, part travelogue, Alanna Mitchell visits a series of places where the ocean is changing, from Panama to Zanzibar. She explores the Great Barrier Reef, joins marine research expeditions, and takes a submarine to the deep sea on a search for sea sponges that can cure cancer. Two truths drive her investigation: 1) we don’t really know what we’re doing to the sea, and 2) we really ought to pay more attention, as “life on land is utterly dependent on the life and chemistry in the ocean.”

Some of the problems of the ocean are fairly well known. Rising sea levels are acknowledged, if not understood, and the media has covered the trash vortexes, dead zones and coral bleaching. Other problems are only just surfacing, such as the changing pH levels of the sea, something so new that only a handful of scientists are aware of it, let alone what it might mean. But climate change is changing the ocean, and since science in the oceans has always moved slower than science on the land, we hardly know about the effects of carbon emissions on the sea.

The atmosphere gets most of the attention when it comes to carbon emissions, but around a third of CO2 emissions are absorbed by the sea. In the atmosphere, CO2 lingers inert, but not in the sea. Here, carbon dioxide causes a chemical reaction, altering “the fundamental chemistry of the ocean.” Carbon dioxide dissolves in sea water, producing postively charged hydrogen ions which lower the pH levels – “the more carbon dioxide the ocean absorbs, the more acidic the ocean becomes.” The sea has already changed from 8.2 to 8.05, and so far nobody knows what this means, except that all lifeforms exist within a certain range and do not adapt to changes in acidity.

The biggest worry is what pH levels might do to the plankton. I didn’t know this, but plankton produce 50% of the earth’s oxygen – every other breath you take is thanks to microscopic sea creatures. Intriguing, and somewhat disconcerting given our cavalier attitude to the sea. Plankton is a vast carbon sink too, absorbing CO2 for photosynthesis, and carrying it to the seabed when it dies. There are global conventions to preserve the rainforests and the carbon sinks that they represent, but Mitchell meets marine biologists who were told as students that plankton were too insignificant to study. It all seems a little short sighted.

Which is Mitchell’s point, that humankind hasn’t realised how dependent we really are on the sea, for oxygen, for food, and for fresh water. (Every tear we ever shed ends up in the sea, Mitchell points out, through the magic of evaporation and rainfall.)

I plead guilty – this is one of those books where I felt I was really learning something new, making connections I’d never seen before, making up either for things I was never taught or things I’d forgotten at school. I’ve learned a whole lot of science, and have a new respect for the ocean. And I have a lot more to find out.


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