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Executive Summary
Several climate regimes characterize the African continent; the wet tropical,
dry tropical, and alternating wet and dry climates are the most common. Many
countries on the continent are prone to recurrent droughts; some drought episodes,
particularly in southeast Africa, are associated with El Niņo-Southern Oscillation
(ENSO) phenomena. Deterioration in terms of trade, inappropriate policies, high
population growth rates, and lack of significant investment-coupled with a highly
variable climate-have made it difficult for several countries to develop patterns
of livelihood that would reduce pressure on the natural resource base. Under
the assumption that access to adequate financing is not provided, Africa is
the continent most vulnerable to the impacts of projected changes because widespread
poverty limits adaptation capabilities.
Ecosystems: In Africa today, tropical forests and rangelands are under
threat from population pressures and systems of land use. Generally apparent
effects of these threats include loss of biodiversity, rapid deterioration in
land cover, and depletion of water availability through destruction of catchments
and aquifers. Changes in climate will interact with these underlying changes
in the environment, adding further stresses to a deteriorating situation. A
sustained increase in mean ambient temperatures beyond 1°C would cause significant
changes in forest and rangeland cover; species distribution, composition, and
migration patterns; and biome distribution. Many organisms in the deserts already
are near their tolerance limits, and some may not be able to adapt further under
hotter conditions. Arid to semi-arid subregions and the grassland areas of eastern
and southern Africa, as well as areas currently under threat from land degradation
and desertification, are particularly vulnerable. Were rainfall to increase
as projected by some general circulation models (GCMs) in the highlands of east
Africa and equatorial central Africa, marginal lands would become more productive
than they are now. These effects are likely to be negated, however, by population
pressure on marginal forests and rangelands. Adaptive options include control
of deforestation, improved rangeland management, expansion of protected areas,
and sustainable management of forests.
Hydrology and Water Resources: Of the 19 countries around the world
currently classified as water-stressed, more are in Africa than in any other
region-and this number is likely to increase, independent of climate change,
as a result of increases in demand resulting from population growth, degradation
of watersheds caused by land-use change, and siltation of river basins. A reduction
in precipitation projected by some GCMs for the Sahel and southern Africa-if
accompanied by high interannual variability-could be detrimental to the hydrological
balance of the continent and disrupt various water-dependent socioeconomic activities.
Variable climatic conditions may render the management of water resources more
difficult both within and between countries. A drop in water level in dams and
rivers could adversely affect the quality of water by increasing the concentrations
of sewage waste and industrial effluents, thereby increasing the potential for
the outbreak of diseases and reducing the quality and quantity of fresh water
available for domestic use. Adaptation options include water harvesting, management
of water outflow from dams, and more efficient water usage.
Agriculture and Food Security: Except in the oil-exporting countries,
agriculture is the economic mainstay in most African countries, contributing
20-30% of gross domestic product (GDP) in sub-Saharan Africa and 55% of the
total value of African exports. In most African countries, farming depends entirely
on the quality of the rainy season-a situation that makes Africa particularly
vulnerable to climate change. Increased droughts could seriously impact the
availability of food, as in the Horn of Africa and southern Africa during the
1980s and 1990s. A rise in mean winter temperatures also would be detrimental
to the production of winter wheat and fruits that need the winter chill. However,
in subtropical Africa, warmer winters would reduce the incidence of damaging
frosts, making it possible to grow horticultural produce susceptible to frosts
at higher elevations than is possible at present. Productivity of freshwater
fisheries may increase, although the mix of fish species could be altered. Changes
in ocean dynamics could lead to changes in the migratory patterns of fish and
possibly to reduced fish landings, especially in coastal artisinal fisheries.
Coastal Systems: Several African coastal zones-many of which already
are under stress from population pressure and conflicting uses-would be adversely
affected by sea-level rise associated with climate change. The coastal nations
of west and central Africa (e.g., Senegal, The Gambia, Sierra Leone, Nigeria,
Cameroon, Gabon, Angola) have low-lying lagoonal coasts that are susceptible
to erosion and hence are threatened by sea-level rise, particularly because
most of the countries in this area have major and rapidly expanding cities on
the coast. The west coast often is buffeted by storm surges and currently is
at risk from erosion, inundation, and extreme storm events. The coastal zone
of east Africa also will be affected, although this area experiences calm conditions
through much of the year. However, sea-level rise and climatic variation may
reduce the buffer effect of coral and patch reefs along the east coast, increasing
the potential for erosion. A number of studies indicate that a sizable proportion
of the northern part of the Nile delta will be lost through a combination of
inundation and erosion, with consequent loss of agricultural land and urban
areas. Adaptation measures in African coastal zones are available but would
be very costly, as a percentage of GDP, for many countries. These measures could
include erection of sea walls and relocation of vulnerable human settlements
and other socioeconomic facilities.
Human Settlement, Industry, and Transportation: The main challenges
likely to face African populations will emanate from extreme climate events
such as floods (and resulting landslides in some areas), strong winds, droughts,
and tidal waves. Individuals living in marginal areas may be forced to migrate
to urban areas (where infrastructure already is approaching its limits as a
result of population pressure) if the marginal lands become less productive
under new climate conditions. Climate change could worsen current trends in
depletion of biomass energy resources. Reduced stream flows would cause reductions
in hydropower production, leading to negative effects on industrial productivity
and costly relocation of some industrial plants. Management of pollution, sanitation,
waste disposal, water supply, and public health, as well as provision of adequate
infrastructure in urban areas, could become more difficult and costly under
changed climate conditions.
Human Health: Africa is expected to be at risk primarily from increased
incidences of vector-borne diseases and reduced nutritional status. A warmer
environment could open up new areas for malaria; altered temperature and rainfall
patterns also could increase the incidence of yellow fever, dengue fever, onchocerciasis,
and trypanosomiasis. Increased morbidity and mortality in subregions where vector-borne
diseases increase following climatic changes would have far-reaching economic
consequences. In view of the poor economic status of most African nations, global
efforts will be necessary to tackle the potential health effects.
Tourism and Wildlife: Tourism-one of Africa's fastest-growing industries-is
based on wildlife, nature reserves, coastal resorts, and an abundant water supply
for recreation. Projected droughts and/or reduction in precipitation in the
Sahel and eastern and southern Africa would devastate wildlife and reduce the
attractiveness of some nature reserves, thereby reducing income from current
vast investments in tourism.
Conclusions: The African continent is particularly vulnerable to the
impacts of climate change because of factors such as widespread poverty, recurrent
droughts, inequitable land distribution, and overdependence on rain-fed agriculture.
Although adaptation options, including traditional coping strategies, theoretically
are available, in practice the human, infrastructural, and economic response
capacity to effect timely response actions may well be beyond the economic means
of some countries.
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