A new report by a conservation group warns that food and water supplies in Africa could be put at risk if global warming continues at the current rate.

The World Wide Fund for Nature, WWF, says climate change could spell disaster for millions: changes in the amount and distribution of rainfall would affect crops and animals alike.

As an example of the impact of climate change, WWF says that the ice-cap on Mount Kilimanjaro has shrunk by more than 80% since 1900.

The WWF calls for the implementation of limits or reductions in greenhouse gas emissions, which contribute to global warming, that were adopted at the Kyoto international climate conference in 1997.

The global implementation of the Kyoto protocol on gas emissions has been effectively blocked by the decision of United States President, George Bush, to reject mandatory controls on gas emissions in March 2001.

The United States is the world largest producer of greenhouse gas emissions.

US key

Reduced rainfall in the semi-arid Sahel region south of the Sahara desert is another example of the effects of pollution and climate change on Africa in the WWF report.

"If carbon pollution is left unchecked, climate change will have a pervasive effect on life in Africa.

"It will threaten the people, animals and natural resources that make Africa unique," according to the report's author, Dr Paul Desanker, Co-Director of the Centre for African Development Solutions in Johannesburg.

He says the coming World Development Summit in Johannesburg must decide to implement the convention on pollution and gas emissions agreed at Kyoto five years ago.

The United States is key to achieving this, he told BBC News Online.

As the largest producer of carbon pollution and greenhouse gas emissions, the United States can make or break international attempts to limit pollution.

"If the US doesn't come aboard to limit gas emissions, this will be a complete waste of time," according to Dr Desanker.

He says that action on emissions by the European Union and other industrialised countries will have no significant effect if the United States is not persuaded to back the Kyoto convention.

Coral reefs

The WWF report also calls for action to support sustainable land use in Africa and the development of "clean and affordable" energy sources in Africa by 2010.

Dr Desanker says Africa should be helped to develop energy provision that does not rely mainly on burning fossil fuels such as coal, which increase carbon pollution.

The Fund's report also warns that climate change is leading to "widespread loss of human life and livestock".

It also says that East Africa's coral reefs are in danger of disappearing. Over 50% of the area's reefs have died as a result of "bleaching" through pollution.

The loss of reefs will affect fisheries, food security, marine biodiversity and tourism income.

Further climate change will also threaten vulnerable animal and plant species in Africa and threaten migration routes for animals and birds within Africa and between Africa and other continents.