Causality analysis and physio-economic impacts of climate change on maize production in South Africa.

Abstract

Agriculture, as part of the human ecological footprint on climate change, has become a serious concern because climate change has an impact on agriculture. For instance, when crop production is considered, climatic elements are influenced by greenhouse gas emissions that come from agricultural activities such as the application of synthetic fertilizers, herbicides and pesticides, as well as the use of heavy machinery in modern crop production. This study analyzed the possible causalities between climatic variables and maize production in South Africa using time series data for the period 1924 to 2016. The analysis was done using VAR Granger causality analysis to ascertain if there are feedback loops between climatic elements and maize production in South Africa. The results from the Granger analysis suggest a bidirectional causality that runs between maize production and temperature. Rainfall alone was found not to be significant in influencing maize production but a combination of both temperature and rainfall affects maize production in South Africa. The results from variance decomposition of the future forecasts suggest a relatively large magnitude of impact (13.37%) of temperature on maize production in the 3rd year of the forecast with the highest effect of 27.43% in the 15th year of forecast. The forecasted impact of rainfall on the other hand remained relatively low (below 10%) throughout the forecast period. Continued current production activities (use of synthetic fertilizers and agricultural chemicals, for example) will affect climatic variables both in the short term and in the long term, and the effects of these changes in climatic elements on maize production will be realized in the long term as revealed by the variance decomposition result. The study further investigated the impacts of global warming on maize production in South Africa using meta-analysis (for physical impacts) and the Ricardian analysis (for economic impacts). The meta-analysis made use of studies that investigated and reported percentage changes in maize yield owing to climate change in South Africa. The average estimated percentage change in maize yield was calculated from 34 studies using the bootstrapping sampling technique. Results from the meta-analysis suggest that maize yield will drop by more than 15% owing to temperature increase of about 20C to be realized between 2081 and 2100. The Ricardian analysis made use of time series data for the period 1987 to the end of 2018. The results from the Ricardian analysis also show that climate change is a significant threat to the South African maize industry, as it is estimated to lose an average of 38% of revenue owing to plus 20C warming. Given these outcomes, the study suggested the adoption of sustainable

farming activities such as minimum tillage, balanced fertilization and biochar amendments at a much faster rate in order to ensure a sustainable increase in maize production, while at the same time reducing the human ecological footprint on climate change. The study also recommends the recognition of the agricultural sector as one of the sectors that should be targeted by the carbon emission reduction systems.