Dear EarthTalk: I was horrified to read recently that our oceans are actually becoming acidic, that the continued burning of fossil fuels is changing the chemistry of our seas. What’s going on?
—Kim Richardson, San Diego, CA
It’s a known fact that our oceans are becoming more acidic as a result of the increasingly large load of human-generated carbon dioxide (CO2) entering our atmosphere. About 25 percent of all the CO2 we send skyward out of our tailpipes and smokestacks ends up in the world’s oceans, where it triggers chemical reactions in the water column that lead to increased acidification. Researchers estimate that the acidity of our seas has increased 29 percent since the dawn of the Industrial Revolution. If we do not slow down the pace of greenhouse gas emissions, our oceans could be two to three times as acidic in 2100 as they already are today, which could prove disastrous to marine ecosystems and the world’s food chain.
“When carbon dioxide is absorbed by seawater, chemical reactions occur that reduce seawater pH, carbonate ion concentration and saturation states of biologically important calcium carbonate minerals,” reports the National Oceanic and Atmospheric Administration (NOAA). These calcium carbonate minerals, typically abundant in areas where most marine life congregates, are the building blocks for the skeletons and shells of many marine organisms, from oysters to coral. “However, continued ocean acidification is causing many parts of the ocean to become undersaturated with these minerals, which is likely to affect the ability of some organisms to produce and maintain their shells,” adds NOAA. The process will not only wreak havoc on the shellfish we eat, but also on smaller marine organisms that are key components on the lower end of the marine food chain.
According to the Natural Resources Defense Council (NRDC), a leading green group, coral reefs around the world may face an even greater risk than shellfish because they require very high levels of carbonate to build their skeletons. “Acidity slows reef-building, which could lower the resiliency of corals and lead to their erosion and eventual extinction,” they write. This would be an unmitigated environmental disaster, given that an estimated one million marine species depend on healthy coral reefs for survival.
“Such losses would reverberate throughout the marine environment and have profound social impacts, as well—especially on the fishing and tourism industries,” NRDC reports. “The loss of coral reefs would also reduce the protection that they offer coastal communities against storms surges and hurricanes—which might become more severe with warmer air and sea surface temperatures due to global warming.”
Researchers are working on strategies to protect aquaculture farms from further losses due to acidic water, but any large-scale effort to address ocean acidification will require the slowing down or phasing out of fossil fuels. Powering our cars, heating our homes and running our machines and appliances all require burning fossil fuels which generate greenhouse gas emissions and in turn cause acidification. Cutting back on our consumption of oil, gas and coal and switching to renewable energy sources—solar, wind, biomass and others—will be a necessary part of the strategy to counteract ocean acidification.
We can all help by driving less and walking/biking more; upgrading our vehicles, light bulbs and appliances to more energy efficient versions; patronizing companies that work to reduce their carbon footprints; and pushing our state and federal governments to enact binding reductions in CO2 pollution.