London: A new study has revealed that the oceans are more acidic now than they have been for at least 300 million years, due to carbon dioxide emissions from burning fossil fuels.
And leading marine scientists have warned that a mass extinction of key species may already be almost inevitable as a result, the Guardian reported.
An international audit of the health of the oceans has found that overfishing and pollution are also contributing to the crisis, in a deadly combination of destructive forces that are imperilling marine life, on which billions of people depend for their nutrition and livelihood.
In the starkest warning yet of the threat to ocean health, the International Programme on the State of the Ocean (IPSO) said that this [acidification] is unprecedented in the Earth`s known history, and that we are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure.
They said that the next mass extinction may have already begun.
Coral is particularly at risk. Increased acidity dissolves the calcium carbonate skeletons that form the structure of reefs, and increasing temperatures lead to bleaching where the corals lose symbiotic algae they rely on.
The report said that world governments` current pledges to curb carbon emissions would not go far enough or fast enough to save many of the world`s reefs.
There is a time lag of several decades between the carbon being emitted and the effects on seas, meaning that further acidification and further warming of the oceans are inevitable, even if we drastically reduce emissions very quickly.
There is as yet little sign of that, with global greenhouse gas output still rising.
The findings are published in the State of the Oceans report.