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If sea level rises, inundation could occur along more than 70% of the Nigerian coastline, placing land at risk many kilometers inland (Awosika et al., 1992). In Nigeria, inundation is the primary threat for at least 96% of the land at risk (Awosika et al., 1992; French et al., 1995). With a 1-m rise in sea level, up to 600 km2 of land would be at risk. This area includes parts of Lagos and other smaller towns along the coast. For the Mud Coast, a 1-m rise will place as much as 2,016 km2 of land at risk. Even with no acceleration in sea-level rise, current rates of land loss through edge erosion alone could cause losses of as much as 250 km2 by the year 2100. This land loss is equivalent to an average shoreline recession of 3 km. Erosion threatens a higher percentage of the land on the Strand Coast than in the delta (4.6-20.7% for the Strand Coast, versus 0.8-3.5% for the delta). Without consideration of oil wells in the Niger delta, the greatest value at risk is along the Barrier Coast-ranging from just over US$1.3 billion with a 0.2-m sea-level rise to almost US$14 billion with a 2-m rise. When the value of the oil fields is considered, the value at risk increases from US$81.4 million to almost US$2.2 billion with a 0.2-m rise and from US$6 billion to more than US$19 billion for a 2-m rise. On the Strand Coast, a 1-m rise will result in a value loss of more than US$18 billion; the largest contribution to this loss would come from the oil fields in the area.
In Nigeria, a potentially massive "environmental refugee" migration will occur. For a 1-m rise, more than 3 million people are at risk, based on the present population. The estimated number of people that would be displaced ranges from 740,000 for a 0.2-m rise to 3.7 million for a 1-m rise and 10 million for a 2-m rise (Awosika et al., 1992).
In Senegal, a 1-m rise in sea level could inundate and erode more than 6,000 km2 of land, most of which is wetlands (Dennis et al., 1995). In general, inundation is responsible for more than 95% of the land loss, independent of the scenario considered. Dennis et al. (1995) have shown that, under a 1-m scenario, buildings with a total market value of at least US$499-707 million would be at risk. On a national basis, tourist facilities represent 20-30% of the total value at risk under the 1-m scenario. Under the 1-m scenario, it is estimated that at least 110,000-180,000 people-or 1.4-2.3% of the 1990 population of Senegal-are at risk (Dennis et al., 1995). Nearly all of these people are located south of the Cape Verde peninsula; the bulk of the population at risk lives south of Rufisque.
In Cote d'Ivoire, a 1-m sea-level rise will lead to inundation of 1,800 km2 of lowland. The rate of shoreline retreat as a result of erosion is estimated to vary from 4.5 m to 7.4 m per annum (ICST, 1996). The most threatened infrastructures on the coastal zone are the Autonomous Port of Abidjan (Port Autonome d'Abidjan, PAA) and the port of San Pedro.
In The Gambia, inundation is projected to lead to a loss of 92 km2 of land for a 1-m sea-level rise. Shoreline retreat is projected to vary between 6.8 m in cliff areas to about 880 m for flatter and sandier areas (Jallow et al., 1996). If a 1-m sea-level rise were to occur as envisaged, without protective measures the whole capital city of Banjul would be lost in the next 50-60 years because a majority of the city is below 1 m. Preliminary analysis of data from the Gambian Department of Lands on the value of land and sample properties between Banjul and the Kololi Beach Hotel suggests that about 1,950 billion Dalasis (US$217 million) of property will be lost (Jallow et al., 1996). All of the structures located on land between Sarro and Banjul cemeteries and the whole of Banjul will be lost. (It was not possible to attach monetary value to this loss of public places.) According to Jallow et al. (1996), the entire population of Banjul (42,000 inhabitants) and people living in the eastern parts of Bakau and Cape St. Mary-as well as the swampy parts of Old Jeswang, Kanifing Industrial Estate, Eboe Town, Taldning Kunjang, Fagikunda, and Aruko-will be displaced.
Using sea-level rise scenarios of 0.5 and 1.0 m per century, Mwaipopo (1997) assessed the potential impacts of such a rise on the coastline of Tanzania. The results revealed that, with a 0.5-m and 1-m sea-level rise, about 2,090 km2 and 2,117 km2 of land would be inundated, respectively. With a 1-m sea-level rise, another 9 km2 of land would be eroded. Projected damage is expected to be about Tsh. (Tanzanian shillings) 50 billion for a 0.5-m rise and Tsh. 86 billion for 1-m rise.
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