Large scale "geoengineering" solutions to climate change will not reverse rising acidity in the oceans which damages marine life, conservationists have warned.

The International Union for Conservation of Nature (IUCN) issued a call at the UN climate talks in Durban for countries to urgently address the issue of ocean acidification, caused by greater levels of carbon dioxide in the atmosphere.

The oceans absorb around a quarter of the carbon dioxide humans put into the atmosphere each year, the IUCN said, but the gas dissolving into the seas causes the water to become more acidic.

The IUCN said the acidity of the world's oceans had increased by 30% since the beginning of the Industrial Revolution, and could continue at an unprecedented rate in the coming decades.

But while ocean acidification has the same cause as climate change - increasing amounts of CO2 in the atmosphere - not all the solutions for global warming will help the situation faced by the seas, the International Ocean Acidification Reference User Group warned.

Efforts to reflect the sun's rays, through putting aerosols or even mirrors into the atmosphere, will not reduce levels of CO2 or protect the oceans.

Dr John Baxter, of Scottish Natural Heritage and deputy chairman of the Reference User Group which supports work in a number of regions and countries including the UK, said: "Geoengineering solutions, such as reflecting solar radiation, which are often suggested to deal with climate change, will not address the progressive acidification of the ocean.

"Both climate change and acidification need to be taken into account when designing solutions to these challenges."

And Professor Dan Laffoley, marine vice chairman of the IUCN's world commission on protected areas and chairman of the Reference User Group, said: "The increasing amounts of carbon dioxide that we emit into the atmosphere every day are changing our oceans, steadily increasing their acidity and dramatically affecting marine life. Only by reducing our CO2 emissions and enhancing the protection of oceans to strengthen their ability to recover, can we effectively address this issue."

He urged negotiators and ministers in Durban and at next summer's environmental summit in Rio de Janeiro to mark 20 years since the original Earth Summit in Brazil to acknowledge the problem and take appropriate action to tackle it.

Photo courtesy of the Kuwait Dive Team