Ocean Acidification

As well as melting glaciers and rising sea levels, another significant problem associated with climate change is occurring invisibly to the human eye, and many scientists say that it needs to be urgently addressed.

In the 1980’s, an American marine scientist named Dr. Richard Feely began alerting the world that carbon dioxide emissions from human activities would be absorbed by the oceans acting as giant carbon sinks. This proposition has since been confirmed by experimental research, but the full extent of the consequent impacts still remains a large question mark.

 

A chemical reaction between CO₂ and seawater produces carbonic acid, a chemical that generally remains in the upper layer of the oceans. Before the industrial revolution, this oceanic acid content remained in a natural equilibrium with the natural CO₂ in the atmosphere, but the balance has now changed. Oceans are estimated to have absorbed about half of all human-generated CO₂, in the process slowing down climate change, but causing other serious problems. According to a report by the UK’s Royal Society in 2005, this acidification is irreversible within our lifetimes, and it will take thousands of years for the oceans to recover.

Coral reefs are major centres of biodiversity and have been referred to as ‘the rainforests of the oceans.’ In the journal Science in 2007, a team of {quotes}scientists estimated that within the next fifty years, the oceans could be too acid for coral to grow{/quotes}, and that by 2100 even existing reefs could be dying off. Australian reefs such as the Great Barrier Reef and those in the Caribbean could be at risk sooner than those in other parts of the world.

Similar threats are faced by a range of marine creatures, including shellfish, sea urchins, and starfish, which are finding it more difficult to form their shells. Off the US state of Washington mussels are in decline. Around Tatoosh Island, the ocean is becoming acid about ten times faster than expected, and about 10-20% of the mussels have already been replaced by acid-tolerant species of algae.

Phytoplankton are a type of plant plankton that inhabit tiny shells and release oxygen into the air. In the estimation of San Francisco State University biology professor Ed Carpenter, they are responsible for producing about a half of the world’s breathable oxygen. The Royal Society report warns that by 2100 some species of plankton will be unable to grow their shells. 

Meanwhile, Australian researchers believe that if carbon emissions follow future predictions, the Southern Ocean may become too acidic by 2030, affecting the pteropods that live there. (A pteropod is a type of marine mollusc.) Ben McNeil from the University of New South Wales Climate Change Research Centre believes that this tipping point will occur when CO₂ levels reach about 450 parts per million, a figure that it also the stabilisation target set by the Intergovernmental Panel on Climate Change (IPCC.)

As these small creatures form the base of the food chain, larger species such as fish, whales and dolphins are likely to be affected in due course. In human terms, this would translate into impacts on fishing industries and perhaps the loss of a noticeable chunk of the global food supply.

The only ways to halt this acidification process are for the world to decide on and adhere to cuts in carbon emissions, and ideally for us to remove some of the CO₂ that has already built up in the atmosphere.