Ocean Acidification: A Hidden Risk of Global Warming
I love swimming in the ocean, but I also know plenty of people who wouldn’t dream of it. There are too many unseen perils: the ominous tug of a current, razor-sharp oyster shells, sting rays buried in the sand and shadowy, slimy things brushing past. Even my fishermen friends, who depend on the ocean for their livelihoods, keep a respectful distance from the waves.
The ocean is awe-inspiring. We were born of it, and it gives us life by producing much of the oxygen we breathe and the water we drink. It is mysterious and vast. No wonder we speak of emptying oceans with teaspoons to describe impossible tasks.
Yet, unfathomably, we have accomplished the impossible. We have changed the basic chemistry of the oceans — drop by drop — in such a profound way that we may be destroying a web of life that we depend upon for our very existence. Those ocean creatures should be wary of us — not the other way around.
"Scientists are concerned that we are changing the ocean's chemistry so rapidly that we are outstripping the evolutionary pace of many organisms to adapt."
The change we've introduced is called ocean acidification.
The basic science is pretty straightforward: Since the industrial revolution, humans have been pumping ever increasing amounts of carbon dioxide into the air. Some of that CO2 is absorbed by the ocean, where it dissolves to form carbonic acid.
The ocean today absorbs nearly a third of the carbon dioxide we produce, probably mitigating the impact of climate change. But the ocean has absorbed so much CO2 that overall acidity levels are rising, and at a much faster rate than previously thought.
More acidic water makes it harder — and ultimately impossible — for some creatures like oysters, corals and mussels to form shells, which are made largely from the calcium carbonate, plain old chalk, that occurs naturally in seawater. That’s why acidification is sometimes referred to as "osteoporosis of the sea."
These tiny, lentil-sized pteropods are essential to the survival of creatures like the humpback whale. (Top photo: Limacina Helicina by Victoria Fabry.)
This process affects creatures up and down the food chain — from the tiny organisms that build the planet's coral reefs and the plankton drifting with the ocean currents, all the way to the whales that feed on the plankton.
Also affected are the lentil bean-sized pteropods, delicate, balletic creatures that nourish many of the fish we then consume. In other words, the ability of all ocean life to sustain itself is being compromised.
Scientists have been surprised at how sensitive plants and animals are to even small changes in CO2 levels. Some creatures have shown an ability to adapt to more acidic waters; lobsters, for instance, harden their shells in an initial response to acidity. But for many creatures, acid is deadly: Their shells disintegrate. And many scientists are concerned that we are changing the ocean's chemistry so rapidly that we are outstripping the capacity of many organisms to adapt.
Because the science is fairly new, we still do not fully understand the long-term effect of increasingly acidic oceans. The ocean is a complex, integrated, self-regulating system; how it will change is hard to predict.
As we conduct this uncontrolled experiment on two-thirds of the planet, scientists are racing to find ways to make the ocean more resilient. Doug Rader, EDF's chief ocean scientist, says: "Along with our partners from around the world — from Cuba to the EU, and beyond — EDF scientists are scrambling to understand why some reefs are more robust than others, why some fish populations bounce back, when others languish, and exactly what mix of strategies will suffice to maximize the resilience of the world's oceans.
"One thing is already clear," he adds. "Rebuilding ecosystem complexity, including restoring populations of large predators such as sharks, is central to the long-term survival of the seas."
The Obama administration signaled its commitment to acidification research when it appointed Jane Lubchenco to head the National Oceanic and Atmospheric Administration (NOAA). Lubchenco, a widely respected marine ecologist and former EDF Board member, has made clear, in Congressional testimony and elsewhere, the seriousness of this threat to the seas.
There is no controversy surrounding the science underlying the acidification of the ocean. There is no question about where the CO2 is coming from. There is no question about how the chemistry works. And there is only one known way to stop acidification: to reduce emissions of carbon dioxide. The more we reduce now, the less severe, and costly, the future consequences.
What can you do? Become an advocate for the oceans. Take care to minimize your carbon footprint—but keep in mind one of my favorite phrases: living sustainably is necessary, but not sufficient. It's equally important to demand comprehensive legislation that cuts carbon emissions.
And go ahead, take a swim. Bathe in those natal waters, and give thanks for the life they support. The ocean has the capacity to heal itself much faster than one teaspoon at a time. We need to give it that chance. We would be doing ourselves a big favor — giving our grandchildren a chance to inhabit a livable planet.
Editor's note, 2/12: The list of animals that will experience difficulty in forming shells has been updated.