The impact of climate change and variability on tomato (Licopersicon esculentum) production in the Limpopo Province, South Africa

The Limpopo Province is a major tomato growing region in South Africa, producing 66% of the total annual tonnage of tomatoes. The Limpopo Province is particularly vulnerable to the impact of climate change, partly because it is exposed to extreme weather events. According to the Intergovernmental Panel on Climate Change (IPCC) Africa will be hit hardest by climate change as larger areas could be stricken by yield decreases of over 50% by the year 2020 because of an increasingly hotter and drier climate. This will threaten food security and the livelihoods of people in most parts of Africa. First and foremost in this research study, a detailed analysis of annual seasonal trends in minimum and maximum temperatures was investigated, as well as the diurnal temperature range over the Limpopo Province for the period 1950-1999. In particular, using daily data from 30 catchment areas, three temperature variables were calculated: the average, maximum and minimum temperature. The analysis demonstrated that there was an increase of 0.12°C every decade in the mean annual temperature for the 30 catchments over the 50-year period. Furthermore, the present study analysed the correlation of tomato records for the Limpopo Province with climatic variables in order to assess the climate change effects on tomato production and food security in South Africa. The trend analysis of tomato production in the Limpopo, tomato yield showed increased by a factor of 2 from 1971-2006. Thus the response of tomato production during that period of 35 years was more favourable. This shows that the largest values in tomato yield were in the last decades when temperatures were high. From our analysis, the trend of tomato production in the Limpopo, tomato yield increased by a factor of 2 during the period of 1971-2006 was not significant. In particular, during the spring, summer, autumn and winter seasons, tomato yield increased by a factor of 2 respectively. With the exception of February and June, most months registered positive trends in tomato production. The study reported in this thesis investigated the frequency of occurrence of heat waves (HWs) over Limpopo. The analysis of the occurrences of HWs over this region is important due to their impact on agricultural production as well as human health. Overall, our results indicate that during the period 1950-1999, the Limpopo Province experienced HW events. The results from the present study demonstrated that during the four seasons (spring, summer, autumn and winter) the HW trends were not monotonic over the five decades (1950-1999). Furthermore, the research reported in this thesis analysed the distribution of leafminer agromyzid pest over the Limpopo Province in a changing climate. The analysis of tomato pest distribution is vital because the leafminer agromyzid pest has a major impact on tomato production. In general, the aim of analysing the leafminer agromyzid pest was to determine how climate change influences the distribution of the leafminer agromyzid pest and hence impacts on tomato production in the Limpopo Province, South Africa. The present analysis illustrates that the leafminer agromyzid pest and climatic factors exhibit a non-linear relationship, which could be best described by a polynomial function of order two while in general, the influence of climate change on the spatial distribution of the leafminer agromyzid pest over the Limpopo Province is apparent.