Acid oceans 'the evil twin of global warming' could wipe out many marine species
The report, presented at the Copenhagen climate summit, said the acidity of the oceans has already risen 30 per cent since industrialisation began.
If levels continue to rise, acidity could increase by 120 per cent by 2060. This would make the seas more acidic than they have been for 21 million years, according to the IUCN report – which was part sponsored by Scottish Natural Heritage.
The acidity could put 70 per cent of cold water corals at risk by the end of the century.
The oceans act as a huge carbon sink, as is taken out of the atmosphere and dissolves in the seawater, where it forms carbonic acid.
As humans put increasing amounts of carbon into the atmosphere, the seas are becoming rapidly more acidic, damaging the ability of plankton, shellfish, molluscs and reef-building species to create skeletons or shells – with knock-on effects up the marine food chain.
"Ocean acidification can be best described as the evil twin of climate change," said Dan Laffoley, lead editor of the guide, and marine vice chairman of IUCN's World Commission on Protected Areas. As well as providing about half the Earth's natural resources, the oceans also produce half the oxygen we breathe.
Prof Laffoley warned that ocean acidification would affect seas and coastal areas all around the world. "No matter where you are, remember that every breath you take and every drop of water you drink connects you back to the ocean," he said.
Carl Gustaf Lundin, head of the IUCN Global Marine Programme, added: "The ocean is what makes Earth habitable and different from anywhere else we know in our solar system and beyond – now's the time to act to minimise the impacts on our life support system while we still have time."