It’s simple chemistry: Ocean acidification is bad news

Whenever we talk about climate change, it’s only natural to focus on what happens up in the atmosphere. But climate change has an evil twin: ocean acidification (also known as “the other CO₂ problem”).

By now you already know that when we burn things like coal and other fossil fuels, greenhouse gases like CO₂ get released into the atmosphere. But did you know that some of that CO₂ also gets absorbed by the oceans? And when that happens, it forms carbonic acid, making the oceans more acidic. Since oceans cover 70% of our little blue planet, that’s a LOT of surface area for them to come into contact with the atmosphere and for CO₂ to be transferred from air to water. In fact, the oceans absorb about 25% of the CO₂ we put into the atmosphere, or roughly 22 million tons per day (and have absorbed a full 50% of what we’ve emitted over the past 200 years).

Scientists used to think that the oceans were doing us a favour, climate wise, by taking in all that CO₂. Taking one for the team, if you will. The warming we’re experiencing now would have been that much worse had the oceans not absorbed so much of what we’ve emitted to date. Originally, scientists thought that the ocean could play this buffering role indefinitely and self-regulate. Sadly, the scientists were wrong; the natural regulating processes in the oceans can’t keep up with the amount of CO₂ being absorbed and their acidity is increasing. Today, the oceans are 30% more acidic than they were at the start of the Industrial Revolution. And if emissions keep on going at their current pace, scientists predict that the oceans could be 150% more acidic by the end of the century, with a pH level that hasn’t been seen since 20 million years ago.

So what happens when the oceans get more acidic? All sorts of bad things. Species like oysters, clams, corals, and sea urchins have a really tough time building their shells. For instance, mussels and oysters are expected to produce 25% and 10% less shell, respectively, by 2100. And tiny little pea-sized sea creatures called pteropods or “sea butterflies”—the inspiration for this mosaic—are already feeling the impacts. A lot of these species are at the bottom of the food chain, and when they’re threatened, the impacts ripple and cascade through the rest of the system, right up to us, with serious implications for the food security of millions of people.

And it’s not only shelled organisms that are feeling the impact of increasing ocean acidity; fish can also be affected. The excess acid in the ocean finds its way into their bloodstream, and they end up expending more of their energy to counter its effects and regulate the pH of their blood. That means fish have less energy to do other important things, like digesting food, fleeing from predators, hunting, and even reproducing. It can also mess with their behaviour, preventing them from hearing and avoiding predators, and actually making them bolder and more likely to venture away from shelter (thereby increasing their risk of predation), as well as compromising their ability to navigate. (And this, again, links directly to food security issues for a good chunk of the world’s population.)

If you want the 2-minute version of the story, I’d highly suggest watching this video, courtesy of Grist. And if you’ve got 20 minutes to spare, why not settle in and let Sigourney Weaver teach you about ocean acidification?

So, I think you probably understand by now that ocean acidification is a really big deal, which is why it was important for me to include a mosaic about it in this series. As I mentioned above, the images of the dissolving pteropod were by original inspiration—after having seen them, I just couldn’t shake them. To really get into the spirit of the issue, I decided that my mosaic should include shells that had been dissolved in acid, so I ran my own little homemade ocean acidification simulation. Do you remember making naked eggs as kids? You put an egg in vinegar (which is acidic) and its shell dissolves gradually over a few days, leaving only the membrane, or a naked egg. Fun times. Well, I figured I could use the same principle on some seashells that had been donated to me in recent years. And it worked like a charm. The shells bubbled and fizzed like crazy in the vinegar, and slowly but surely dissolved. The only thing I didn’t anticipate was just how much vinegar I would need: nearly 3L. I am so very very sick of the smell of vinegar at the moment. Some of the shells that I dissolved were quite beautiful in their original state, and someone on Facebook asked if it had been tough to sacrifice those to the vinegar. It had given me pause, to be sure, but I think it only serves to reinforce the message of the mosaic: ocean acidification will wreak havoc on those things we find most dear, beautiful, and life-sustaining.