The world's oceans are becoming acidic at a faster rate than at any time in the last 55m years, threatening disaster for marine life and food supplies across the globe, delegates at the UN climate conference in Copenhagen have been warned.
A report by more than 100 of Europe's leading marine scientists, released at the climate talks this morning, states that the seas are absorbing dangerous levels of carbon dioxide as a direct result of human activity. This is already affecting marine species, for example by interfering with whale navigation and depleting planktonic species at the base of the food chain.
Ocean acidification - the facts says that acidity in the seas has increased 30% since the start of the industrial revolution. Many of the effects of this acidification are already irreversible and are expected to accelerate, according to the scientists.
The study, which is a massive review of existing scientific studies, warns that if CO2 emissions continue unchecked many key parts of the marine environment - particularly coral reefs and the algae and plankton which are essential for fish such as herring and salmon - will be "severely affected" by 2050, leading to the extinction of some species.
Dr Helen Phillips, chief executive of Natural England, which co-sponsored the report, said: "The threat to the delicate balance of the marine environment cannot be overstated - this is a conservation challenge of unprecedented scale and highlights the urgent need for effective marine management and protection."
Although oceans have acidified naturally in the past, the current rate of acidification is so fast that it is becoming extremely difficult for species and habitats to adapt. "We're counting it in decades, and that's the real take-home message," said Dr John Baxter a senior scientist with Scottish Natural Heritage, and the report's co-author. "This is happening fast."
The report, published by the EU-funded European Project on Ocean Acidification, a consortium of 27 research institutes and environment agencies, states that the survival of a number of marine species is affected or threatened, in ways not recognised and understood until now. These species include:
• whales and dolphins, who will find it harder to navigate and communicate as the seas become "noisier". Sound travels further as acidity increases. Noise from drilling, naval sonar and boat engines is already travelling up to 10% further under water and could travel up to 70% further by 2050.
• brittle stars (Ophiothrix fragilis) produce fewer larvae because they need to expend more energy maintaining their skeletons in more acid seas. These larvae are a key food source for herring.
• tiny algae such as Calcidiscus leptoporus which form the basis of the marine food chain for fish such as salmon may be unable to survive.
• young clownfish will lose their ability to "smell" the anemone species that they shelter in. Experiments show that acidification interferes with the species' ability to detect the chemicals that give "olfactory cues".
The report predicts that the north Atlantic, north Pacific and Arctic seas - a crucial summer feeding ground for whales - will see the greatest degree of acidification. It says that levels of aragonite, the type of calcium carbonate which is essential for marine organisms to make their skeletons and shells, will fall worldwide. But because cold water absorbs CO2 more quickly, the study predicts that levels of aragonite will fall by 60% to 80% by 2095 across the northern hemisphere.
"The bottom line is the only way to slow this down or reverse it is aggressive and immediate cuts in CO2," said Baxter. "This is a very dangerous global experiment we're undertaking here."
Written for policy makers and political leaders, the document is being distributed worldwide, with 32,000 copies printed in five major languages including English, Chinese and Arabic. Every member of the US congress, now struggling to agree a binding policy on CO2 emissions, will be sent a copy.
Congressman Brian Baird, a Democrat representative from Washington state, who championed a bill in Congress promoting US research on ocean acidification, said these findings would help counter climate change sceptics, since acidification was easily and immediately measurable.
"The consequences of ocean acidification may be every bit as grave as the consequences of temperature increases," he said. "It's one thing to question a computer extrapolation, or say it snowed in Las Vegas last year, but to say basic chemistry doesn't apply is a real problem [for the sceptics]. I think the evidence is really quite striking."