Production function analysis of the sensitivity of maize production to climate change in South Africa

Abstract

Maize production accounts for about 40% of the entire area cultivated in South Africa and is highly sensitive to climate variability. Maize is thus conservatively a staple food for more than 70% of the South African population whilst the maize industry stimulates the economy directly by providing secondary industries with over a billion worth of business each year. This study used the production function approach to evaluate likely impacts of climate change on maize production in South Africa. Data for this study have been obtained from experimental research sites in the 19 main maize producing regions in South Africa. The estimated coefficients of the production function model were used to derive measures of elasticity and optimal climate damage points as well as to simulate partial and total impacts of changes in levels of climate variables on maize yield. The Inter-Governmental Panel on Climate Change (IPCC) benchmark predictions of global warming for Southern Africa indicates that with the doubling of carbon dioxide in the atmosphere, a hotter and drier climate for the western semi-arid regions of Southern Africa and a hotter and slightly wetter climate for the eastern sub-tropical regions of Southern Africa are anticipated. Results indicated that rainfall and net solar radiation diffused within the maize crop have a non-linear and significant impact on average maize yield. Solar radiation rather than temperature was included in the regression analysis as temperature measures did not perform well. The results illustrated that increasing rainfall levels in all three main growth stages (sowing to emergence, juvenile to tassel initiation, and tassel initiation to grain filling growth stages) would increase maize yields whilst increases in solar radiation particularly during tassel initiation to grain filling would decrease maize yield. These results suggest that farmers could adopt a number of adaptation options including manipulation of planting dates, introduction of heat tolerant maize varieties and other options to mitigate the negative impacts of highlighted increases in solar radiation levels. Results also showed that for the semi-dry regions of South Africa, early growth stages of the maize crop would be mostly affected by decreases in rainfall whilst for the wet eastern regions the forecasted drier conditions would affect mostly the late maize growth stages. To capture the cumulative impact of increasing solar radiation and rainfall amounts marginally across all growth stages, a climate simulation analysis whereby the two main IPCC warming scenarios predicted for the Southern Africa region were used. In the partial effects analysis rainfall and solar radiation changes were simulated separately for each growth stage at a time, whereas in the total effects analysis rainfall and solar radiation changes were simulated simultaneously across all growth stages. Results of these analyses suggest that the west semi-dry regions of South Africa might benefit from the forecasted decreases in both rainfall and solar radiation, especially if sensitivity of the maize crop during its second growth stage is mitigated through the introduction of irrigation. This study also illustrated that maize production in the wet east regions might benefit in all its three growth stages from the forecasted increases in rainfall and solar radiation, especially if sensitivity of the first growth stage is reduced through the possible shifting of planting dates to mitigate the effects of increased rainfall forecasted for this region. One should note however, that the maize crop has the ability to agronomically adapt easily to drier conditions. Other attributes which further assists the resistance of the maize crop to climate changes, include extensive conservation soil tillage farming practices which could be applied to optimise soil infiltration rates whilst minimising evaporation rates, thus reducing soil erosion. The above results highlight the need for investments in improving the adaptive capacity of farmers, especially small-scale farmers who are severely restricted by their heavy reliance on natural climate factors and at the same time lack complementary inputs and institutional support systems. The existence of institutional support systems may assist farmers in further understanding anticipated climate changes and available conservation agricultural practices e.g. cost effective irrigation control systems. Other adaptation options include improved capacity of all the stakeholders involved in maize production (farmers, processors, marketers, exporters etc.) to better the ability to cope with the adversities of climate change through the use of farm planning, available crop insurance systems with regards to floods and droughts, improved weather and climate monitoring and forecasting. At a regional scale, extensive agricultural planning and risk reduction programmes may assist with spreading losses over larger regional areas, which may serve to reduce overall risk to growers. One important limitation of this study was that the analyses focused on the experimental sites only and hence did not consider all maize production areas across the country (which includes sites under small-scale farming). Also, the model adopted for this study also did not include the effects of carbon dioxide fertilisation and price movements, which are crucial. In conclusion, then, there is an urgent need for the South African National Department of Agriculture to look at how maize farmers (and especially small-scale farmers) could be assisted in adapting their traditional cropping methods to the forecasted changes in climate, whilst taking into consideration all the options presented above.