News•September 24, 2012

Ocean Acidification Threatens Food Security, Report

Pakistan, Thailand, the Philippines, Iran, and China are among the top 50 nations whose food security may be threatened by the effects that the rise of manmade carbon-dioxide (CO2) gas emissions are already starting to have on fish and shellfish, according to a new report by Oceana, an international ocean conservation organization.

Coral reef ecosystems are especially susceptible to damage from the increasing acidity of ocean waters. Click on the image to see a larger version.
Credit: NOAA Photo Library.

While global warming is expected to affect the food supply of many nations by increasing drought, heat waves and torrential downpours, this report focuses on countries that depend heavily on the oceans for sustenance.

“Fish and seafood are an important source of protein for a billion of the poorest people on Earth,” said Matthew Huelsenbeck, a marine scientist with Oceana, “and about three billion people get 15 percent or more of their annual protein from the sea.”

In order to assess which countries are at greatest risk, Huelsenbeck and his colleagues looked at two entirely different effects of CO2 on the oceans: the warming caused when carbon dioxide traps extra heat from the Sun, and the rise in the acidity of seawater as it absorbs some human CO2 emissions to form carbonic acid.

Increased acidity makes it harder for shell-forming organisms, such as clams, oysters, and corals, to build their shells. That in turn affects people who depend on these sea creatures for food, or who eat the fish that depend on coral reefs for their habitat.

Rising temperatures, meanwhile, have forced some fish to migrate away from their normal territory. “Some fish just don’t like it too hot,” Huelsenbeck said. A recent NOAA study, for example, found that Atlantic cod populations in the Gulf of Maine are shifting northeastward in response to rising ocean temperatures. In fact, the waters off the coast of New England were the warmest on record this year. Fish migration may not be a big problem for countries with modern fishing fleets, such as the U.S., but poorer nations with more local fishing fleets can’t simply follow their food supplies as they swim away.

The disparity in resources between rich and poor countries, combined with projections of population growth through 2050 and the percentage of the population that’s undernourished, were the main factors that went into the national rankings, under the heading: “Lack of Adaptive Capacity.” Another main factor was “Exposure,” meaning the vulnerability of nearby seafood supplies to both warming and acidification. The final factor in the rankings was “Dependence” — the degree to which each country relies on protein from the sea in its mix of food sources.

CO2 from the atmosphere gets absorbed by the oceans, and chemical reactions take place that break it down into carbonic acid, which harms marine life. Click on the image for a larger version.
Credit: NOAA.

Put all of these factors together, and the most endangered country in terms of marine food security turns out be the Maldives, the low-lying island nation in the Indian Ocean that’s already under imminent threat from rising seas. Pakistan, at number eight on the list, is the worst-off of major countries, followed at number 10 by Thailand. Iran occupies the 27th spot, the Phillipines are ranked 34th, followed by China at number 35. Peru and South Africa also are ranked among the top 50 countries lacking adaptive capacity.

While it’s possible to deal with some aspects of climate change through adaptation — building sea walls to keep out the rising ocean, for example, or irrigating crops affected by drought — there’s really no way to de-acidify the ocean once it’s undergone that chemical change.

Even the wildly ambitious geoengineering schemes that propose to cool off the planet by reflecting extra sunlight back into space would do nothing to keep seawater from growing progressively more acidic. “Reducing emissions,” Huelsenbeck said, “is the only way to prevent it.”

The report urges governments to “establish energy plans that chart a course for shifting away from fossil fuels and toward clean energy production” and to end fossil-fuel subsidies — but environmentalists have been saying pretty much the same thing for years, with little effect.

The authors also urge a reduction in overfishing and other destructive fishing practices. They call for the establishment of marine protected areas where fishing is banned entirely and pollution is cut back dramatically, to give marine populations at least a fighting chance of staying somewhat healthy. And they urge fisheries managers to take climate change and ocean acidification into account when putting together fishing regulations and policies.

These suggestions are ambitious as well, but they may be a more realistic bet — for the moment, at least — for keeping the nations at greatest risk from losing some of their crucial supply of nourishment from the sea.