CO2 Pollution Could Erase Coral Reefs

Coral reefs, nature’s most lively architecture, could come tumbling down and it could take millions of years for them to return, if carbon dioxide emissions aren’t cut quickly, scientists warned today.

The world’s oceans have absorbed 40 percent of the carbon dioxide emissions produced by humans in the industrial age, but that buffering is changing the chemistry of the oceans. Already, the acidity of ocean waters, which are generally basic, has shifted about 0.1 on the pH scale, or 10 percent, since pre-industrial times, and could get far more acidic by mid-century.

In a editorial in the journal Science, the researchers also noted that unlike CO2’s climate impacts, which vary between models to some extent, ocean acidification is based on basic chemistry and is nearly sure to occur if we continue burning fossil fuels, with disastrous consequences for some marine life.

“What we’re doing in the next decade could mean that for the next two million years, there are no coral reefs in the ocean,” said Ken Caldeira, a Stanford professor, and recent Wired profilee.

While most of the attention on the impacts of carbon dioxide emissions has focused on its ability to act as a greenhouse gas, that warms the earth’s climate, the changes CO2 emissions will bring to the world’s oceans are receiving increasing attention. The more CO2 in the atmosphere, the more of it that dissolves into surface ocean water. That small chemistry change could cause huge changes in marine biology.

Marine organisms, like coral, that build skeletons out of calcium could find themselves unable to do so. If current emissions trends continue over the next decade, the world’s marine creatures will be dealing with what’s essentially an alien ocean. The last time ocean conditions like those predicted for mid-century existed was long before humans walked the earth.

“I think in order to find something that is as extreme as what we continue to do this century, you have to go back to when the dinosaurs became extinct, 65 million years ago,” Caldeira said.

After the last acidification, it took two million years for coral reefs to recover. The Science paper called for lower CO2 emissions caps and for them to come quickly. Otherwise, he warned, the Great Barrier Reef and other structures like it will be destroyed and will take millions of years to return.

“Where a doubling of CO2 might seem like a realistic target from a climate perspective, but from an ocean chemistry perspective, it means changes that haven’t been seen in tens of millions of years.”

Unlike climate change, which Caldeira thinks could be partially counteracted through geoengineering, ocean acidification is a problem of a completely different scale. In the physics of climate change, he said, sulfur particles can have an outsized effect in counteracting the greenhouse effect induced by carbon dioxide. But ocean acidification, and the chemistry that underlies it, is fundamentally different.

“There’s no way around having a molecule-to-molecule response, so the scale of the solution ends up being the scale of the problem,” said Caldeira.

While some individual reefs could be preserved by various means, the broader problem appears difficult to geoengineer.

“At the scale of the whole ocean, I don’t think is anything simpler than transforming our entire energy system,” he concluded.

Alexis Madrigal, Wired News, 3 July 2008. Article.

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