Corals from tropical oceans are to be placed in deep freeze at a British zoo to preserve them for posterity as they face destruction from rising greenhouse gas levels.

The Zoological Society of London (ZSL) is planning the first global “coral cryobank”, where hundreds of samples from each species would be stored in liquid nitrogen.

The decision follows research showing that most coral reefs will be largely dead by 2040, wiped out by a combination of rising temperatures and increasing acidity in oceans. They include Australia’s 1,600-mile Great Barrier Reef, most Caribbean reefs and those in the “coral triangle” which spans Indonesia, the Philippines, Malaysia, Papua New Guinea, and East Timor.

“Carbon dioxide emissions are rising fast and are already above the safe level for corals,” said Dr Alex Rogers, head of marine biodiversity at the ZSL.

“Some reefs are already beginning to fail and many will die within a few decades. We need a plan B, and freezing them is the best option.”

Whipsnade zoo in Bedfordshire has been earmarked for the new coral bank.

The desperate nature of the plan reflects the despair among scientists about rising CO2 levels, which have a dual effect on coral reefs.

At the heart of the problem is the 35 billion tons of CO2 generated annually by human activities — a level that is rising by 2%-3% each year.

In the atmosphere, CO2 traps solar energy and increases air and sea temperatures to a point that kills coral.

Half the emissions of CO2 also dissolve into the sea, raising acidity until it dissolves the calcium carbonate mineral from which reefs are built.

Coral reefs around the world are already showing the impacts. This year the Australian Institute of Marine Science found growth rates of corals on the Great Barrier Reef had fallen by 14% since 1990.

Another study, led by Dr Charlie Veron, a former chief scientist at the institute, warned that CO2 levels were already so high that corals were doomed.

“Atmospheric CO2 concentrations of 350 parts per million represented a threshold for the world’s reefs,” said Veron. “Beyond that, damaging heating becomes too frequent and the ecosystem starts to decline. We are already at 387ppm and reefs are beginning to fail.”

Today 120 legislators from 16 countries will attend talks in Copenhagen organised by Globe, a high-level inter- governmental organisation, to discuss the threat to coral reefs and how to preserve samples for the distant future.

The idea of setting up a coral bank arose from the success of projects such as the Svalbard Global Seed Vault which preserves thousands of plant seeds from around the world in a cooled cavern on the Norwegian island of Spitsbergen.

It follows a breakthrough in regenerating coral from frozen samples. Craig Downs, of the Haereticus Environmental Laboratory, developed the technique and is now working with the ZSL. “We can take 1mm-2mm biopsies from coral, freeze them at -200C and thaw them out to regenerate back into a polyp,” he said. “We are proposing to do this for every species of coral on the planet.”

There are about 1,800 known tropical corals and another 3,350 cold-water species. Downs proposes keeping 1,000 samples of each in a small warehouse.

The Smithsonian Institution in Washington is discussing setting up a similar facility to mitigate against failure.

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