Brad Plumer writes: The world’s oceans are turning acidic at what’s likely the fastest pace in 300 million years. Scientists tend to think this is a troubling development. But just how worried should we be, exactly?

It’s a question marine experts have been racing to get a handle on in recent years. Here’s what they do know: As humans keep burning fossil fuels, the oceans are absorbing more and more carbon-dioxide. That staves off (some) global warming, but it also makes the seas more acidic — acidity levels have risen 30 percent since the Industrial Revolution.

There’s reason for alarm here: Studies have found that acidifying seawater can chew away at coral reefs and kill oysters by making it harder to form protective shells. The process can also interfere with the food supply for key species like Alaska’s salmon.

But it’s not fully clear what this all adds up to. What happens if the oceans keep acidifying and water temperatures keep rising as a result of global warming? Are those stresses going to wipe out coral reefs and fisheries around the globe, costing us trillions (as one paper suggested)? Or is there a chance that some ecosystems might remain surprisingly resilient?

That’s one of the big outstanding questions on climate change. “We understand the physics of simple things like how oceans become acidic,” said Richard Norris, a paleobiologist at Scripps Institution of Oceanography, UC San Diego. “But when it comes to how ecosystems might react, that’s big and complex and messy, with all these interactions going on, both physiological and how organisms interact with each other.” [Continue reading…]