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The main challenges that are likely to face African populations will emanate from the effects of extreme events such as tropical storms, floods, landslides, wind, cold waves, droughts, and abnormal sea-level rises that are expected as a result of climate change. These events are likely to exacerbate management problems relating to pollution, sanitation, waste disposal, water supply, public health, infrastructure, and technologies of production (IPCC, 1996).
The pattern of distribution of human settlements often reflects the uneven
nature of resource endowments and availability between regions and within individual
communities. In Africa, as elsewhere, there are heavy concentrations of human
settlements within 100 km of coastal zones (Singh et al., 1999), in areas
of high economic potential, in river and lake basins, in close proximity to
major transportation routes, and in places that enjoy hospitable climatic regimes.
Changes in climate conditions would have severe impacts not only on the pattern
of distribution of human settlements but also on the quality of life in particular
areas.
The transport sector is based on long-term, immovable infrastructure such as
roads, rails, and water. Road networks have tended to link industrial centers
with major areas of agricultural activity; railways have been designed primarily
with a sea-route orientation to facilitate international shipments of primary
products. Climate change may lead to industrial relocation, resulting either
from sea-level rise in coastal-zone areas or from transitions in agroecological
zones. If sea-level rise occurs, the effect on the many harbors and ports around
the continent will be quite devastating economically for many coastal-zone countries.
Excessive precipitation, which may occur in some parts of Africa, is likely
to have serious negative effects on road networks and air transport.
More than one-quarter of the population of Africa resides within 100 km of a sea coast (Singh et al., 1999), rendering a significant number of people vulnerable to rises in sea level as a result of climate change. Modeling the effects of a 38-cm mean global sea-level rise in 2080, Nicholls et al. (1999) estimate that the average annual number of people in Africa impacted by flooding could increase from 1 million in 1990 to a worst case of 70 million in 2080. Jallow et al. (1999) estimate that the capital of The Gambia, Banjul, could disappear in 50-60 years through coastal erosion and sea-level rise, putting more than 42,000 people at risk. El Raey et al. (1999) discuss threats to coastal areas of Egypt from sea-level changes. East Africa coastal settlements also are at risk from sea-level rise (Magadza, 2000).
There are three response strategies to rising sea level and its physical impacts: retreat, adapt, or defend. Retreat can involve chaotic abandonment of property and cultural investments, or it can be an ordered, planned program that minimizes losses from rising sea level and maximizes the cost-effectiveness of the operation. The operation also seeks to leave surrendered areas as aesthetic looking as possible and to avoid abandoned structures that are an operational hazard to other social and economic activities.
The capacity of individual states to undertake coastal defense work may be limited. However, if such works are planned on a long-term time scale, it is possible to develop such defenses well before the crisis occurs and thus to spread the total capital costs over many years.
Because the problem of coastal management is regional, such a process would require:
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