Comparison of Australian Impacts with Southern and Eastern Africa

As Australia is a fairly prosperous “first world” country we are lucky to be able to withstand and survive El Niño and La Niña events without extreme loss of human life and loss of lifestyle.  Unfortunately other countries around the world are not so lucky.  The countries of southern and eastern Africa have very different climates, but most are situated in semi-arid regions where annual rainfall varies by 20-30 percent.  This variation can have devastating social and economic consequences.

In many of the areas agricultural production is mainly limited by the availability of soil moisture. Unfortunately heavy rains that occur due to La Nina events often do not significantly increase soil moisture because the soil does not absorb moisture quickly, and the rain tends to run off without entering into the soil.

During drought, reduced soil moisture results in a dramatic decline in vegetation cover and photosynthetic activity. This can be measured objectively on a broad geographic basis by recording changes in the absorption of different wavelengths of land areas passed over by above-ground light-sensing satellites. Figure 1 below show the dramatic decline in vegetation cover and photosynthetic activity in Southern Africa during a drought episode in March 2007 (a time when much of Eastern Australia was also in drought). The brown areas show reduced plant growth relative to the long term average (known technically as a negative ‘vegetation anomaly’) while the green areas show increased vegetation growth relative to the long term average (known as a positive ‘vegetation anomaly’). It can be seen in this image that while Namibia, Botswana, and much of South Africa were experiencing severe drought, Mozambique, Zimbabwe and Zambia were experiencing normal to above average vegetation growth. This reflects the regional variability that is characteristic of the impact of drought.

Figure 1:  A view of southern Africa showing the impact on vegetation growth caused by drought in March 2007. The  brown areas with negative ‘Vegetation Anomalies’ have reduced vegetation growth while green areas with positive ‘Vegetation Anomalies’ have enhanced growth. (Source: NASA, Earth Observatory, Natural Hazards)

During the year 1982-83, southern Africa experienced drought linked to the El Niño episode in much the same way that Australia did.  Agricultural production in Zimbabwe and Mozambique was reduced by the drought in 1982-83.  Although 1982 was a good year for Zimbabwe, there were heavy rains early in 1983 season, followed again by drought.  The harvest was down 65% on 1982; money was diverted from development projects into emergency drought relief funds.  The south and west of the country lost livestock as well as crops.  Transport and agro-industries were affected by the drop in production, and water was rationed.

Mozambique's 1982-83, drought was considered the worst in 50 years and led to many human and livestock deaths (although the exact figure varies due to poor record keeping). There was mass departure of refugees to neighbouring Zimbabwe which was also hard hit by drought.  In Botswana, key watering places dried up completely and the vitally important livestock population declined severely. As a result half the human population of Botswana had to be fed by emergency relief from overseas.  Normally one child in four in Botswana is considered at risk from malnutrition, but the figure increased during the drought to one in three.

One of the major problems in developing and third-world countries is that during drought years, which often coincide with El Niño years, the need for emergency food imports can dramatically reduce the already low foreign currency reserves.  Climate can then have indirect effects on development projects as governments have to cut back on expenditure to compensate for the foreign exchange loses.  This prolongs the effect of the drought year, affecting future crop yields in the years after El Niño.

However, on rare occasions, improvements in international market prices can sometimes offset the negative effects of drought related crop losses.  In 1984, in many parts of eastern Africa, the main wet season period from March to May received very low levels of rainfall which caused a severe drop in agricultural production (note that 1984 was not an El Niño year).  But, Kenyan tea and coffee export prices more than doubled as a result of this scarcity. This resulted in an increase in foreign exchange earnings for the region despite the drought.  This type of outcome should not be depended upon though, as it is NOT the norm when it comes to severe droughts and climatic events.

The graph below shows the rainfall index from 1960-1993.  The effects of the1982-83 El Niño episode is reflected in this graph as negative rainfall indexes which indicates a below average rainfall pattern.  This comparison perhaps suggests an association between the pattern of variability in the Southern Africa’s rainfall index and the variability in the SOI during the period 1960-1993. Looking at the years 1982-1983 specifically, the SOI plummeted at the same time that both Southern Africa and the main continent of Africa began to experience a period of severe rainfall shortages.  Fortunately southern Africa received some rain in 1984 but continental Africa did not have a chance to recover until the late 1980’s.

Figure 2:  A normalised rainfall graph of Southern Africa from 1960-1993 (Source: Food and Agricultural Organisation, Sustainable Development Department)