A disaster is said to occur when abnormal or infrequent hazardous events impact on vulnerable communities, causing substantial damage, disruption and casualties, and leaving the affected communities unable to function normally without external assistance. A disaster is therefore a severe disruption of the survival and livelihood systems of a society or community, resulting from their vulnerability to the impact of one or a combination of hazards, and involving loss of life and/or property on a scale which overwhelms the capacity of those affected to cope unaided (DfID 2000). Natural hazards may be hydrometeorological or geophysical and include floods, droughts, wild-fires, storms, cyclones, earthquakes, volcanic eruptions and landslides. Some of these hazards can lead to disasters. Disasters, whether natural, technological, biological or arising from internal conflicts within nations, are often shaped by anthropological factors.

Global warming
will lead to higher
estimated to
be between
0.2 and 0.5 °C
per decade for

Hulme and others 2001

Africa faces food insecurity that is a result of a combination of natural hazards and human factors (WFP 2006). Climate change and variability are being driven by various anthropological factors including increased demands for energy, and have impacts on environment and development, as well as land productivity. These impacts are discussed throughout Section 2: Environment State-and-Trends: 20-Year Retrospective and more specifically in Chapter 2: Atmosphere and Chapter 3: Land. Global warming will lead to higher temperatures estimated to be between 0.2 and 0.5 °C per decade for Africa (Hulme and others 2001). It is also likely that extreme events such as El Niño are being experienced more frequently, and have become more intense (IPCC 2001, Watson and others 1998), causing wide-ranging agricultural, hydrological, ecological, economic and health impacts (Adger and others 2002). Land degradation and vulnerability to erosion is directly linked to climatic factors. Extreme climatic events also lead to natural disasters like drought and floods which directly affect the health of the environment.

One effective response to address human vulnerability to environmental change is to strengthen mechanisms for early warning. Many actions can be taken to protect life and property if warning is received in time. While certain threats are inherently unpredictable, many of those arising from threats from environmental degradation and mismanagement, and from human activities, can now be anticipated with some precision. Early warning capacities are increasing steadily with technological advances in environmental observing, assessment and communications. Examples include the cyclone early warning systems that have been established in the Western Indian Ocean (WIO) islands.