'The coastline [as it is now] will be completely changed by the end of this century because the sea level is rising along the coast at around two centimetres every year,' said Stefan Cramer, Nigeria director of Heinrich Boll Stiftung, a German environmental NGO.
Even where urban areas appear unscathed, sea level rise will still challenge towns and cities by threatening the underground water supplies from which millions of people across the region draw their water.
'[Increasing salinity] will make the ground water undrinkable and unsuitable for agricultural purposes. The result will be food and water insecurity,' agreed George Awudi, Ghana Programme Coordinator for the environmental lobby group Friends of the Earth.
The effects of sea-level rise will be most “dramatic” in Nigeria's economic capital Lagos which is just five metres above sea level, with some parts of the city lying below sea-level, Cramer said.
The flooding is likely be most severe in Lagos because of its position at the southern end of the Gulf of Guinea where stronger tropical storms from the South Atlantic create storm surges up to three metres high, Cramer said. He estimates that most of the 15 million inhabitants of Lagos will be displaced and Nigeria’s southern Delta region where oil installations are located will also be swamped.
Other major urban centres in West Africa which experts have identified as at risk of flooding are Banjul in The Gambia, Bissau in Guinea Bissau, and Nouakchott in Mauritania. All three capitals are at or close to sea level.
Environmentalists blame the gradual melting of the 3,000 metre-thick Greenland ice cap in the A rctic as being responsible for the coastal erosion along the Coast of Guinea. Greenland is three times the size of Nigeria and its emptying into the Atlantic causes a rise in the sea-level.
'It is all due to climate change - the greenhouse gas emissions result in global warming and subsequent melting of the Greenland ice cap,' Cramer said.
Compounding the situation in West Africa, in August 2007 a tropical storm 5,000 kilometres off the coast caused a shift in the strong currents that run near the Nigerian coast and destroyed a protective sand bar.
Environmental experts have different solutions to the problem.
'I think the best way out for the moment is devising simpler and more cost effective solutions such as how to preserve towns and villages under threat and preventing sea water intrusion', the director of the UN Framework Convention on Climate Change (UNFCCC) Yvo de Boer said.
'The sensible option is moving to higher ground which is a tough option especially for Nigeria as it means giving up its economic centres in Lagos and its oil installations in the Delta', Cramer said.
But Awudi at Friends of the Earth described relocation as an 'unthinkable option” due to its economic, social and cultural implications.
'Every solution to a problem must focus on the major cause of that problem and in this case greenhouse gas emissions by industrialised countries which are responsible for sea-level rise must be effectively tackled,' Awudi said.
'The industrialised countries should take proactive steps in curtailing their emissions responsible for climate change which will have a positive impact on sea-level rise,' he said.
However according to Cramer even if the industrialised countries do stop their greenhouse gas emissions, the trend of rising sea levels would continue unchanged for another 50 to 100 years.
The experts all made their comments on the sidelines of a UNFCCC working meeting in the Ghana capital Accra where representatives of 150 countries have gathered to continue preparatory negotiations for a landmark climate change conference due to be held in Copenhagen in December 2009 where a successor to the Kyoto Treaty is to be signed.