Without considering the impact extreme weather events have on plant growth and yields, we may be over-estimating future food supply, putting nations at risk of food insecurity.

The continuous supply of services provided by agricultural systems is increasingly threatened by climate change in association with an estimated increase in the frequency of extreme weather events such as droughts, heat waves or heavy precipitation events. Thus Improving the accuracy of prediction of crop and pasture yields is essential for planning for future food security and identifying mitigation and adoption measures for global warming and extreme weather events. Such information is essential for national food security and contingency planning for extreme events. A recent modelling experiment by researchers at the University of Pretoria shows that models that ignore the effect of extreme weather events in predicting crop yield could lead to over-predictions and over-confidence in the potential yield of crops.

The main effect of weather on crop performance is already captured by existing models. However, the effect of extreme events (cold temperature, high temperature or water deficit) on leaf growth and/or biomass production, pollination, flowering, and seed set are not accounted in existing modelling solutions. An EU-funded Modextreme consortium where Dr Eyob H. Tesfamariam, PhD candidate Mr Robert Mangani, and Dr Abubeker Hassen are partners have developed modified modelling solution which consider extreme events. The team has been characterising these events and predict these to enable preparedness. The model shows that in Gauteng province, predicted maize yields in the near future (2021 – 2040) and far future (2041 – 2060) may be up to one quarter lower than current estimations done by existing modelling solutions. Although Gauteng contributes a relatively small proportion of maize to the overall national supply of this staple food, the impact could be far more catastrophic in the major maize producing areas.

Dr Abubeker Hassen and Dr Eyob Tesfamariam have also been conducting research on the effect of drought on grassland productivity, rain use efficiency and forage quality. The effect of climate change and extreme events needs to be quantified at different levels by taking into consideration their impact on farm input supplies, animal production, farm logistics and farm export.  Data from the rain manipulation experiment showed that a 60% reduction in rainfall has resulted in significant change in species composition and up to 50% decrease in forage biomass. In terms of utilisation a defoliation interval of 60 days generally has resulted in better rain use efficiency compared to 45 days interval. .

Their results provide deeper understanding of the behaviour of plants under drought conditions and has led to the identification of species that are more drought tolerant under natural environments. Their research also provides insight into the potential changes in the nutrient composition and nutritive value of grasses under drought conditions. This is not only of importance to livestock production but offers insight into the possible behaviour of forage and food crops should climate change lead to increasing bouts of drought.

Stakeholders participating in a workshop to review their findings expressed appreciation of the thorough and innovative work, calling for greater engagement with representatives from various government departments. The participants expressed appreciation for the insights shared, saying such knowledge is needed to guide and direct current policy drafting processes for climate change.

For more information on this research, please contact Dr Hassen ([email protected]) and Dr Eyob Tesfamariam ([email protected]).