Climate Variability and Maize Yield in South Africa

Wisdom Akpalu, Rashid M. Hassan, and Claudia Ringler


M aize is the primary food staple in southern Africa, and
50 percent of the total maize output in the area is produced
in South Africa, where maize constitutes approximately 70 percent
of grain production and covers 60 percent of the country’s
cropping area. Climate change could have a significant impact on
South African maize production. The scientific community has
established that the temperature in South Africa increased
significantly between 1960 and 2003 (by 0.13 degrees Celsius),
and further temperature increases and changes in the quantity and
pattern of rainfall are expected despite any attempts by the
international community to reduce greenhouse gas emissions.
Although the maize plant is quite hardy and adaptable to harsh
conditions, warmer temperatures and lower levels of precipitation
could have detrimental effects on yields, thereby increasing food
insecurity in the region.
This brief is based on a paper that uses household survey data
to explore the direct impact of climate variability, measured by
changes in temperature and precipitation, on maize yields in the
Limpopo Basin of South Africa.
Maize Production in South Africa
Sampled farms in the Limpopo Basin of South Africa produced
1,237 kilograms per hectare of maize using an average of 449 hours

of labor per hectare, 26 kilograms of seed per hectare, and
159 kilograms of fertilizer per hectare during the 2004/05 growing
season. A majority of the farms were rainfed; only 7 of the 25 farms
in the survey sample (28 percent) used supplementary irrigation
during the 2004/05 growing period (Table 1). Temperature and
precipitation data were obtained from weather services in South
Africa and were matched with farms within the neighborhood of
each climate station. The mean temperature for the months of the
2004/05 farming season was 21.4 degrees Celsius, and the mean
monthly precipitation was 71 millimeters (Table 1).
THE IMPACT OF CLIMATE VARI ABILIT Y
AND CHANGE ON MAIZE PRODU CTION
IN SOUTH AFRI CA
Under the study on which this brief is based, mathematical models
were applied to estimate the direct impact of climate variability on
maize yields. As was expected, an increase in production inputs—
including labor, seed, fertilizer, and irrigation—raises maize yields
substantially. Consistent with previous findings on the impact of
climate change and crops in South Africa, the results suggest that
a change in the amount of precipitation is the most important
driver of maize yields. A 10 percent reduction in mean precipitation
reduces the mean maize yield by approximately 4 percent.
Correspondingly, an increase in mean precipitation increases mean
maize yields; however, as rainfall continues to increase, the
additional gain in maize yield begins to diminish (Figure 1). Also
consistent with previous studies, the results suggest that changes
in temperature affect maize yields. As the mean temperature
increases from 21.4 to 21.6 degrees Celsius, the average maize
yield increases by 0.4 percent. However, like increased precipitation,
the gain in maize yields prompted by increased temperature
begins to diminish as temperature increases further.
Figures 1 and 2 show that an increase in either precipitation
or temperature from the 2004/05 mean values would increase
maize yields at a decreasing rate. The combined effect of changes
in temperature and rainfall on maize yields depends on the
magnitude and direction of each of the changes. As predicted by
climate models, the overall impact on yields of a marginal decrease
in mean precipitation simultaneous with a marginal increase in
mean temperature will be negative because the effect of reduced
precipitation on maize yields is stronger than the effect of
increased temperature. The figures also show that yields from

irrigated farms are higher than from non-irrigated farms, irrespective
of the temperature and level of precipitation.
Policy Impl ica tions
The scientific evidence shows that mean temperature in South
Africa has increased and is expected to increase further in the
future. At the same time, mean rainfall is expected to decrease by
5 to 10 percent, and rainfall variability is expected to increase over
the next 50 years. The results of this study indicate that such
effects would have a significant negative impact on maize yields
and consequently pose a serious threat to food security in South
Africa as well as other countries in the southern African region
that depend on maize imports from South Africa.
The results also suggest that one way to mitigate potential
yield loss due to climate change is to encourage irrigation. The
findings show that irrigated farms had higher maize yields than
did dryland farms; however, maize yields are determined more by
the level of precipitation than by the presence of irrigation,
indicating that irrigation practices partially mitigate the impact of
decreased precipitation on yields.
Additional observations and data on temperature and
precipitation at the farm level, rather than from nearby climate
stations, would increase the robustness of these results.
Nevertheless, while the study on which this brief is based could be
improved with better data, this research provides an important
starting point for further studies in South Africa and other
developing countries on the impact of climate variability and
climate change on crop yields and the resulting implications for
food security.
for further RE ADIN G
Akpalu, W., R. M. Hassan, and C. Ringler, Climate Variability and Maize
Yield in South Africa: Results from GME and MELE Methods, IFPRI
Discussion Paper No. 843 (Washington, DC, 2009).
W. Akpalu (akpaluw@farmingdale.edu) is an assistant professor at the State University of New York–Farmingdale. R. M. Hassan (rashid.hassan@up.ac.za) is the
director of the Center for Environmental Economics and Policy in Africa (CEEPA) at the University of Pretoria, South Africa. C. Ringler (c.ringler@cgiar.org) is a senior
research fellow in the Environment and Production Technology Division of the International Food Policy Research Institute.