Scientists Sound Alarm on Ocean Acidification

Sea snailAcidic waters may prevent coral reefs from surviving in most ocean regions by mid-century if current greenhouse gas emissions trends continue, an international panel of marine scientists said on Friday.

Oceans are absorbing larger amounts of carbon dioxide as more emissions accumulate in the atmosphere. As a result, seawater across the globe is slowly becoming more acidic, a process known as ocean acidification.

Greater acidity not only prevents reef-building corals from forming their carbonate exoskeletons, it also threatens the survival of other marine creatures that form their own shells, such as crabs, lobsters, and oysters.

Although the extent of ecosystem impacts remains unclear, the plight of these species affects the food supply for countless predators worldwide, including humans. The ripple effect throughout marine ecosystems could be disastrous, according to the Monaco Declaration [PDF], the science panel's joint statement.

The declaration represents 155 marine scientists from 26 countries who met at an ocean acidification conference [PDF] in October. Their statement urged governments to reduce greenhouse gas emissions and dedicate more resources to understanding acidification.

"The current increase in ocean acidity is a hundred times faster than any previous natural change that has occurred over the last many millions of years," the declaration said. "Policymakers need to realize that ocean acidification is not a peripheral issue. It is the other CO2 problem that must be grappled with alongside climate change."

Surface ocean acidity has increased 30 percent since the Industrial Revolution, the panel said. The level of acidity, measured in pH, currently appears modest - a 0.1 decrease of surface ocean pH worldwide, according to the Intergovernmental Panel on Climate Change (IPCC).

Yet some scientists may already be noticing the effects of acidification. Australian researchers reported last year that sea snails in the Southern Ocean are forming thinner shells in recent years. Similarly, researchers recorded more than 20 percent drops in the skeletal density of some Great Barrier Reef corals.

"By mid-century, ocean acidification may render most regions chemically inhospitable to coral reefs," the declaration said.

The IPCC predicts acidification could cause a 0.4 decrease in ocean surface pH by 2100. Based on current trends, acidification will likely be more severe at higher latitudes than near the equator.

"The chemistry is so fundamental, and changes [are] so rapid and severe that impacts on organisms appear unavoidable," said James Orr, chair of the October acidification symposium and an ocean climate modeler with the International Atomic Energy Agency's Marine Environmental Laboratory, in a press release [PDF]. "The questions are now: How bad will it be? And how soon will it happen?"

The declaration also notes that geo-engineering schemes - plans that would alter the environment intentionally in order to reduce the effects of climate change - are unlikely to address ocean acidification. In theory, an attemptĀ to deflect solar radiation would regulate the amount of sunlight that reaches Earth. But this would not reduce the amount of carbon dioxide in the atmosphere or oceans, scientists say.

Scientists have also discussed plans to spread greenhouse gas-absorbing algae throughout the ocean. But even if the algae reduced carbon dioxide in the air, the gases would then be stored under the sea.

"Mitigation strategies that aim to transfer CO2 to the ocean, for example by direct deep-sea disposal of CO2 or by fertilizing the ocean to stimulate biological productivity, would enhance ocean acidification in some areas while reducing it in others," the panel said.

The European Project on Ocean Acidification (EPOCA) was launched in June to organize research efforts across the European Union. In the United States, Congress is considering legislation that would develop a plan for ocean acidification research and monitoring.

Ben Block is a staff writer with the Worldwatch Institute. He can be reached at bblock@worldwatch.org.

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