The impact of climate change on agricultural crop distribution in South Africa

A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science by Coursework and Research Report, University of the Witwatersrand, Johannesburg, March 2015.Climate change is considered a dominant factor that controls species distribution at a large spatial scale. Changes in climate conditions are expected to have a significant impact on the distribution of maize in South Africa in the coming years. Determining the potential changes in maize distributions is important, as it is a staple crop for the majority of South Africans and contributes significantly to the country’s economy. The specific objectives of the study were to 1) determine potential distribution of maize under current and predicted climate scenarios using Maxent, 2) determine how the environmental factors change between current and predicted climatic habitat distributions and their influence on maize distributions in South Africa, and 3) statistically compare present and future distributions of maize to see how current and predicted climate habitats differed. Distribution models for high and low maize producing areas were built in Maxent using Bioclim variables from Worldclim. Predicted changes in distributions were then projected using predicted 2050 climate. Two emissions scenarios, RCP2.6 (low emission) and RCP8.5 (high emission), from HadGEM2ES model were used to predict the climate suitability of maize. Model evaluations showed that models had adequate predictability for maize under different climate scenarios (AUC values ≥ 0.7). Precipitation of warmest quarter (Bio18), precipitation of wettest quarter (Bio16), annual precipitation (Bio12), and maximum temperature of warmest month (Bio5) variables contributed the most to model predictions. The models showed a decrease in suitable areas for maize growth in the Highveld region. Present range area for maize as climate changes from low (RCP2.6) and high (RCP8.5) emission scenarios showed a contraction. Predictive models suggest that the most affected areas under future scenarios is the western part of the Highveld region, which is currently characterized by relatively low mean annual precipitation. However, there was an increase in suitability in the Eastern Cape province. Statistical comparisons of current and predicted climatic niches for maize showed that there was little difference, this indicates that climate suitability of maize will not change significantly due to climate change, but that the geographic ranges where these climatic habitats are found will change dramatically. The capacity to develop strategies that will enable maize to adapt to climate change will be vital for South Africa’s agro-ecosystem and food security. The results from this study highlight the possible imposition of climate change on maize distribution and could be useful for future work to minimize the potential negative impacts of climate change on food production. Keywords: Climate change, food security, maize, Maxent, niche quantification, South Africa