A major UN conference on climate change opened in Nairobi Monday with appeals from environmentalists and officials from around the world for urgent action to stem the advance of global warming and the threat it poses to billions of lives on the planet.

"Climate change is rapidly emerging as one of the most serious threats that humanity has ever faced," Kenyan Vice President Moody Awori said at the opening session of the two-week Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC), reports AFP.

It is the first time that such a conference has been held in Africa, the continent identified in a report released Sunday by the UN as the most at-risk from the impact of global warming. Not only are its coastlines threatened with flooding, but some 800 million people are facing the increasing occurrence of droughts and famines, while up to one quarter of species' habitats could be lost due to unpredictable weather patterns, floods and droughts.

The report also warned that unless steps are taken to help African countries, some 480 million people on the continent may face water security issues by 2025.

"There is a great task ahead of us," he told delegates to the conference which expects to bring together some 6,000 experts, officials and lobbyists from across 189 nations.

"Climate change threatens catastrophic impacts that will transform the world we live in," European Union delegation chief Stavros Dimas said in a statement on Monday, echoed by others.

"The worst impacts of climate change can be prevented only if governments act now," said Steve Sawyer of the environmental watchdog Greenpeace.

"Future generations will not forgive us if we delay," he said. "The legal, moral and political obligations of the rich are clear: they must dramatically reduce their emissions."

The Nairobi meeting has brought together environmental experts and officials to devise a strategy to follow the UN Kyoto Protocol on greenhouse gas emissions when it expires in 2012. The conference will also seek to convince some of the world's top polluters who remain outside the treaty to do more to stop climate change.

As the conference got underway, environmental groups issued a string of bleak assessments about the global dangers posed by climate change, particularly on developing nations, many of them in Africa.

Activists will put pressure on those countries whose leaders have signed the protocol but whose parliaments have failed to ratify it, they said.

These include the United States, the world's biggest single polluter, and Australia, the biggest polluter on a per capita basis and a major supplier of fossil fuels such as coal which cause global warming.

The protocol is an annex to a 1992 treaty on climate change, which has been hamstrung by the uncontrolled release of ozone-depleting gases, especially from developing nations like India and China, AFP reported.
Experts have warned that the treaty in its present form will not even dent the greenhouse gas problem.

The summit will also address ways in which rapidly industrialising countries such as India, China and Brazil can minimise the environmental damage of their economic progress.

Despite being the second world polluter, China is still exempt from targeted emission slashes owing to its developing country status.

The Stern report released last week warned governments that it would be more costly for them in the long run if they did not take action on climate change now.

The Nairobi conference is also due to address the proposed creation of an Adaptation Fund to help poor nations make the necessary changes to cope with climate change.