Sometimes the scale of a problem defies attempts to precisely define its reality and impact. Global warming is one such problem. Acidification of the oceans is another. These both represent tangible changes, one to the earth’s atmosphere; the other to the seas. Scientists have for years taken measurements, made comparisons, and generally (as in a consensus) agree that there are changes occurring – rising temperatures in one case, and increased acidity (lowering pH) in the other. They both share (at least one) cause – increase in greenhouse gasses, especially carbon-dioxide. CO2 reacts with the water of the oceans to form carbonic acid, the main cause for the decrease in pH (that is, somewhat counter intuitively more acid).

However, global warming is a cause célèbre – famous or infamous as the case may be. Acidification of the oceans is one of the ‘problems’ that seemingly few people have encountered except on perhaps a random television program, or read about in a magazine. In some respects, the changing pH of the oceans is just as ‘big’ an event as global climate change. Unfortunately, while global climate change has proven difficult enough to quantify and predict, ocean acidification is very difficult to quantify and especially to demonstrate (or predict) what the effects will be.

A very good (and relatively short) article in The Economist, The other carbon-dioxide problem outlines some of the difficulties of getting a handle on the acidification problem.

There are some areas where acidification has demonstrable effects – with coral reefs in particular. Nevertheless, in most cases (including the corals) acidification is part of the vast oceanic ecosystems, where adaptation to change and adversity is part of the normal process of nature. What might be destructive of one thing (say coral) could be the boon for another species. As the article describes it…

If some creatures can tolerate lower pHs and others cannot, you might expect things to average out: the tolerant and adaptable prosper, the more pernickety perish. For the “primary producers” in the ocean—the mostly single-celled creatures that photosynthesise—this will probably be the case. But changes in the relative prevalence of different photosynthesisers could still matter. The ecology of the oceans is all about who eats what, and small changes in the population of certain creatures near the bottom of the web could have large effects on larger ones that eat them. Some creatures may be double-whammied by having less of what they like to eat and by the pH itself, amplifying the disruption. And adaptation is not without costs: dealing with lower pH may divert a creature’s resources from other ends.

[Source: The Economist]

In short, ocean acidification, like global climate change, covers a vast amount of territory both literally and in terms of natural systems. There are so many factors at play, not the least of which is the intervention of humankind, that it is extremely difficult to be ‘definitive’ about the problem. Which is why, on a case by case basis, results from ocean acidification research should be taken with a grain of (sea) salt; while at the same time realizing that the cumulative research can provide proof of unmistakable trends.