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Climatic variability and vulnerability to climate change

Climatic variability and associated floods and droughts result in increased risks of crop failure and therefore reduced food security, as well as higher incidences of malnutrition and disease. In Ethiopia, for example, the 1984 drought affected 8.7 million people, 1 million people died and millions more suffered from malnutrition and famine. This drought also caused the death of nearly 1.5 million livestock (FAO 2000). The 1991-92 drought in Southern Africa caused a 54 per cent reduction in cereal harvest and exposed more than 17 million people to the risk of starvation (Calliham, Eriksen and Herrick 1994). More than 100 000 people died in the Sahelian drought of the 1970s and 1980s (Wijkman and Timberlake 1984). Crop failure and livestock losses lead to increased dependence on imports and foreign aid, reducing economic performance and the ability to cope with future environmental disasters.

Climate variability in Africa

In the past 30 years, Africa has experienced at least one major drought episode in each decade. In Eastern Africa there were serious droughts in 1973-74, 1984-85, 1987, 1992-94 and in 1999-2000 (DMC 2000). The last Sahelian drought persisted for a decade, from 1972-73 to 1983-84. Severe droughts were recorded in Southern Africa in 1967 to 1973, 1982-83, 1986-87, 1991-92 and 1993-94 (Chenje and Johnson 1994).

The Western Indian Ocean islands are subject to tropical storms on average ten times a year during November to May. The El Niņo Southern Oscillation (ENSO), which affects much of Africa, has been associated with more frequent, persistent and intense warm phases over the past 30 years (IPCC 2001a). The 1997-98 ENSO event triggered higher sea surface temperatures in the southwest Indian Ocean, and flooding and landslides across most of Eastern Africa (Ogallo 2001).

In 1997 and 1998, parts of Eastern Africa suffered from high rainfall and flooding due to ENSO disturbances, and in 1999 and 2000 Southern Africa and the Western Indian Ocean islands experienced devastating cyclones and floods. Flood water is an ideal habitat for bacteria and mosquitoes. In Uganda, the ENSO-induced floods of 1997-98 caused more than 500 deaths from cholera, and a further 11 000 people were hospitalized (NEMA 1999).

The sea temperature rise of 1.0-1.5°C due to the ENSO disturbances is thought to have resulted in bleaching of up to 30 per cent of the coral in Comoros, 80 per cent in Seychelles (PRE/COI 1998), and 90 per cent in Kenya and Tanzania (Obura and others 2000).

Carbon dioxide emissions per capita: Africa (tonnes carbon per capita/year)

Africa contributes less than 3.5 per cent of global emissions of CO2; Northern and Southern Africa are responsible for more than 80 per cent of the region's emissions

Source: compiled from Marland, Boden and Andres 2001

The region's vulnerability to natural disasters is compounded by the anticipated impacts of global climate change. According to IPCC, Africa is the most vulnerable region in terms of predicted decreases in water and food security, because widespread poverty limits adaptive capacity (IPCC 1998). Changes in rainfall could also have serious consequences for those parts of Africa that depend on hydroelectricity.

The anticipated sea level rise resulting from global climate change may threaten many coastal settlements and islands including the Western Indian Ocean islands. The extent of sea level rise is still uncertain but the latest IPCC (2001a) estimates are in the range 10-94 cm by the year 2100. Even if anthropogenic greenhouse gas emissions were stabilized immediately, sea level would continue to rise for many years. IPCC also predicts that the intensity of cyclones, rain and wind will probably increase (IPCC 2001a), and the cyclone zone in the Western Indian Ocean could expand to include Seychelles (UNEP 1999).

Changes to rainfall and temperature patterns could also alter biodiversity, with many species not being able to adapt or migrate to more suitable areas. WWF forecasts that an anticipated 5 per cent decrease in rainfall in Southern Africa will affect grazing species such as hartebeest, wildebeest and zebra, threatening wildlife in the Kruger National Park, South Africa, the Okavango delta in Botswana and Hwange National Park in Zimbabwe. There are also fears that malaria could spread to new areas such as parts of eastern Namibia and northern South Africa (WWF 1996).

The region's ability to adapt to climate change will depend on several factors, including population growth and consumption patterns, which will affect demand for food and water, and the location of populations and infrastructure in relation to vulnerable coastal areas, which will determine economic losses due to sea level rise. Many countries will need to change their agricultural practices, particularly to reduce dependency on rainfed agriculture, and to avoid cultivation in marginal areas. Rural communities that currently depend on biomass for energy may be forced to seek alternative sources if climate change brings about changes to vegetation type and distribution.