A new study confirms that the threat from CO2 is exaggerated

A new study of the Great Barrier Reef will apparently confirm what I argued in The Rational Optimist that local pollution and over-fishing are a much greater threat to coral reefs than either climate change or changing alkalinity (sometimes wrongly called acidification).

The actual paper will appear in Current Biology, but this is from the press release from James Cook University (I hate it when scientists announce their results by press release before the journal article is available).

Update: here's the article in press, but behind a paywall.

Quoting one of the authors, Terry Hughes:

"This study has given us a more detailed understanding of the sorts of changes that could take place as the world's oceans gradually warm and acidify.

"And it has increased our optimism about the ability of coral reef systems to respond to the sorts of changes they are likely to experience under foreseeable climate change."

The good news from the research, says Professor Hughes, is that complete reef wipeouts appear unlikely due to temperature and pH alone.

"However, in many parts of the world, coral reefs are also threatened by much more local impacts, especially by pollution and over-fishing. We need to address all of the threats, including climate change, to give coral reefs a fighting chance for the future."

The press release gives more details of the study:

They identified and measured a total of 35,428 coral colonies on 33 reefs from north to south. Studying corals on both the crests and slopes of the reef, they found that as one species decreases in abundance, another tends to increase, and that species wax and wane largely independently of each other.

And:

"We chose the iconic Great Barrier Reef because water temperature varies by 8-9 degrees along its full length from summer to winter, and because there are wide local variations in pH. In other words, its natural gradients encompass the sorts of conditions that will apply several decades from now under business-as-usual greenhouse gas emissions.

This is a point that I have been emphasising recently: that natural variation in ocean pH is already greater than any future trend likely from carbon emissions.