BONN, Germany Nearly 200 countries agreed on Friday to a moratorium on projects to fight climate change by adding nutrients to the seas to spur growth of carbon-absorbing algae.
The surprise deal followed 12 days of haggling at the U.N.'s Convention on Biological Diversity conference where Australia, Brazil and China had opposed until the last minute, halting the controversial plans for "ocean fertilization".
Opponents argue the little-tested process has unknown risks which could threaten marine life, for instance by making the oceans more acidic. Those in favor say it could be a new weapon to fight global warming.
German Environment Minister Sigmar Gabriel, hosting the talks, announced the accord on the final day of the conference at which some 5,000 delegates from 191 countries tried to agree on ways of protecting animal and plant life on earth.
"It's a very strange idea that technology can solve everything. It's very risky and shows what humans are ready to do. I'm glad we came to a de facto moratorium," he told reporters.
During the conference, delegates and environmentalists have consistently said that human activity and greenhouse gas emissions are causing the most serious spate of extinctions since the dinosaurs died out 65 million years ago.
Three species vanish every hour, they say.
This has major economic consequences and has heightened worries about a recent surge in world food prices due to booming demand as experts say wild stocks are vital to the long-term sustainability of crops.
Gabriel said the conference had succeeded in putting the issue of biodiversity on the political agenda. But activists said progress was too slow.
"The U.N. Biodiversity summit inches forward like a snail while animals and plants are being wiped out at great speed," said Martin Kaiser, head of Greenpeace's delegation in Bonn.
The moratorium on ocean fertilization was one of the few areas where action was taken.
Delegates adopted a document which said they would refer to the London Convention for guidance on fertilization issues.
The London Convention, which oversees dumping at sea, says its official advice is not to start ocean fertilization but wait until scientists come up with better research on its impact.
Several companies are working on the idea and the U.S.'s Climos is looking at adding iron filings into the ocean to spur algae growth. Other possibilities include adding large amounts of nitrogen, an ingredient in many land-based fertilizers.
One risk is that because carbon dioxide slightly acidifies water, animals including oysters, crabs and lobsters may have difficulty in forming their protective shells. That may make them vulnerable to predators and disrupt the sea food chain.
"There seems to have been a recognition about the risks of geo-engineering and that this could set a dangerous precedent. Some delegates were horrified when they found out about this," Pat Mooney of environmental group ETC Group told Reuters.
(Editing by Matthew Jones)