Beyond climate change, the acidification of the world's oceans is the "gorilla in the cupboard" which could lead to "a marine Armageddon", two science writers said yesterday.
Speaking at the Brisbane Writers Festival, Allana Mitchell and Dr Charlie Veron painted an apocalyptic vision of the fate of the oceans unless CO2 emissions are drastically cut.
Ms Mitchell, author of Seasick, said life on the planet's surface is dependent upon the oceans and human activity is changing their very chemistry.
"The ocean itself controls the carbon cycle, the oxygen cycle and the climate," Ms Mitchell said.
"The ocean contains the switch of life on the planet.
"If everything on land were to die tomorrow, the ocean wouldn't even notice, but if everything in the ocean were to die tomorrow, everything on land would also die," she said.
"We are actually changing the chemistry of the ocean.
"We've changed the temperature, we've changed the patterns of salinity, we've changed ice patterns, we've possibly changed the structure of the currents and taken out a lot of the biology of the ocean.
"And of course we've changed the pH (acidity)."
Dr Veron, former chief scientist with the Australian Institute of Marine Science, said acidification of the oceans will lead to mass extinctions once CO2 levels reach a tipping point and begin driving themselves.
He said the chemistry was simple: carbon dioxide is dissolved into water, creating very weak carbolic acid which attacks the carbonates that corals depend on.
"The corals can't develop properly," he said.
Some observers think 560ppm (parts per million) of Co2 is the "tipping point" at which a feedback mechanism kicks in, creating a self-fulfilling cycle driving itself towards mass extinctions.
"There's no doubt about this at all," he said. "By 2050 ocean acidification will have taken hold.
"By perhaps 2060 it will be uncontrollable by any means whatsoever because it will be driven by feedback reactions.
"It's a grim, grim business."
Dr Veron said he would take on the role of a "mini Al Gore", warning the public of the unrecognised dangers of ocean acidification and the destruction of the world's reefs.
"Mass extinctions are horrific beyond imagination," he said.
Ms Mitchell said we could face the fifth mass extinction on the planet, the last one being 65 million years ago.
AAP
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