9 September 2010

The Other CO2 Problem

Here's a sad story for you. One to leave you depressed, angry and feeling helpless. But anyone who loves the Maldives ought to read it. (Actually anyone who, anyone that, well, everyone actually).

I bought the August edition of Scientific American to read on the long journey, with stops, from Ireland to the Maldives. An article promised to give me more information on ocean acidification but the more I read, the lower I sank down in my seat. Yes, airplanes are one of the worst culprits of the great CO2 spike.

Ocean acidification is a result of too much carbon dioxide reacting with seawater to form carbonic acid. It has been dubbed "the other CO2 problem". As water becomes more acidic, corals and shelled animals have trouble building their skeletons and shells. Furthermore, the acidity interferes with basic bodily functions for all marine animals. By disrupting processes as fundamental as growth and reproduction, ocean acidification threatens the animals' health and even the survival of species.

The ocean interaction with CO2 mitigates some climate effects of the gas. The world's seas have absorbed roughly one third of all CO2 released by human activities. This 'sink' reduces global warming - but at the expense of acidifying the sea. Across the planet, there has been a 30% increase in acidification since the beginning of the industrial revolution. Marine life has not experienced such a rapid shift in millions of years. And paleontology studies show that comparable changes in the past were linked to widespread loss of sea life. It appears that massive volcanic eruptions and methane releases around 250 million years ago may have as much as doubled atmospheric CO2, leading to the largest mass extinction ever. More than 90% of all marine species vanished.

If we continue to emit greenhouse gases at current rates, scientists estimate that atmospheric CO2 will reach 500 parts per million (ppm) by 2050 and 800 ppm by 2100. That latter figure would constitute a 150% increase in acidity compared with pre-industrial times. In laboratory experiments just small changes in water pH has shown a range of effects at each stage of an animal's life, from sperm to adult, and across species from microbe to large fish.

Looking at the Maldives, tuna (and other fish we like to eat such as salmon and bass) is seriously threatened by the weak resistance to pH increases by copepod species, which support the prey that supports the tuna. A small increase in the water pH saw half the copepods in an experiment die within a week.

As for corals, increased CO2 levels narrow the temperature range in which colonies can survive. They become heat-stressed at lower temperatures than normal if exposed to higher CO2. This, with a general warming of the globe, would mean frequent bleaching events and widespread collapse.

Even if we manage to stabilise CO2 at 450 ppm by 2100, as some have suggested, it would spell doom for coral reefs and shell building animals. 350ppm seems like a rational target, I read. Ultimately, the solution to ocean acidification lies in a new energy economy. Only a dramatic reduction in fossil fuel use can prevent further CO2 emissions from contaminating the seas. An explicit plan to shift from finite, dangerous energy sources to renewable, clean energy sources offers us a more secure path forward. And it offers the planet, especially the oceans, a chance for a healthy future. So please get working on that solar-powered plane, guys, I feel baad.