Carbon emissions lead to dangerous changes in oceans

The rise in carbon dioxide (CO2) emissions is driving fundamental and dangerous changes in the chemistry and ecosystems of the world's oceans, warn international marine scientists. More than 30% of the CO2 released from burning fossil fuels, cement production, deforestation and other human activities goes straight into the oceans, turning them gradually more acidic. "Ocean conditions are already more extreme than those experienced by marine organisms and ecosystems for millions of years," the researchers said. "This emphasises the urgent need to adopt policies that drastically reduce CO2 emissions." Ocean acidification, which the researchers call the "evil twin of global warming", is caused when the CO2 emitted by human activity, mainly burning fossil fuels, dissolves into the oceans.

It is happening independently of, but in combination with, global warming. "Evidence gathered by scientists around the world... suggests that ocean acidification could represent an equal - or perhaps even greater threat - to the biology of our planet than global warming," says study co-author, Ove Hoegh-Guldberg. "The resulting acidification will impact many forms of sea life, especially organisms whose shells or skeletons are made from calcium carbonate, like corals and shellfish," adds Hoegh-Guldberg, professor at the Australian Research Council Centre of Excellence for Coral Reef Studies. "These changes are taking place at rates as much as 100 times faster than they ever have over the last tens of millions of years," Hoegh-Guldberg says.

The scientists say there is now persuasive evidence that mass extinctions in past Earth history, like the "Great Dying" of 251 million years ago and another wipeout 55 million years ago, were accompanied by ocean acidification, which may have delivered the deathblow to many species. "These past periods can serve as great lessons of what we can expect in the future, if we continue to push the acidity the ocean even further," said lead author, Carles Pelejero, from the Marine Science Institute of CSIC in Barcelona, Spain, according to a release of the ARC Centre. "This will create conditions not seen on Earth for at least 40 million years," he said.

These findings were published in the latest issue of Trends in Ecology and Evolution.