**1. Introduction**

Increased greenhouse gas emission caused by human-induced activities such as the burning of fossil fuels and deforestation has accelerated the impacts of climate change in the 20th century. Recently, the intergovernmental panel on climate change report [1] indicated that natural and human systems have been significantly impacted by increased temperature, and increased frequencies of extreme weather events such as droughts and floods that are caused by changes in the climate system. The impacts of climate change on agriculture can no longer be ignored as agricultural production is largely dependent on the amount of water available and dry-land farmers who rely on rain-fed farming for their livelihood are particularly vulnerable [2]. Climate change impacts on agriculture resulting in the decline in crop yield may increase food insecurity globally [3,4]. This is largely because agricultural crops relevant to food security such as maize, wheat, and rice require significant amounts of water for production [5]. The amount of water required to produce 1 kg of these crops is estimated at 1.5 m3, 1.0 m3, and 2.5 m3 respectively [6]. It is therefore anticipated that areas with limited water availability due to climate change impacts will experience significant crop yield losses which would compromise food security in the long term.

Climate change impacts on agricultural production are increasingly becoming a major area of scientific interest [7]. Such impacts are significant in arid and semi-arid areas

**Citation:** Olabanji, M.F.; Ndarana, T.; Davis, N. Impact of Climate Change on Crop Production and Potential Adaptive Measures in the Olifants Catchment, South Africa. *Climate* **2021**, *9*, 6. https://doi.org/ 10.3390/cli9010006

Received: 20 October 2020 Accepted: 28 December 2020 Published: 31 December 2020

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which include a country like South Africa, a semi-arid country, with about two-thirds of its land area receiving a mean annual rainfall of less than 500 mm [8] during the summer months over the eastern parts of the country [8], where most of the agricultural activity takes place. The share of agriculture in the country's gross domestic product (GDP) is barely 4 percent [9]. However, despite this seemingly negligible contribution towards the country's economy, the agricultural sector accounts for almost 10 percent of the total employment in the country and about one-third of the country's total crop production is exported with considerable financial returns [10]. In addition, more than a million people in the country are indirectly dependent on the agricultural sector for their livelihood [11] and 94 percent of the agricultural products such as wheat, maize, and rice are consumed within the country [12]. The strategic importance of the agricultural sector in South Africa is therefore evident.

Increased rainfall variability and high temperatures are currently the key factors expected to have significant impacts on agricultural production in South Africa [8,13]. For instance, climate projection studies have illustrated that the frequency and intensity of droughts coupled with higher variability in rainfall will have negative implications on crop production [1]. A study undertaken by Erasmus et al. [14], projected a decline in precipitation in the Western Cape Province which they predicted would result in less water available for agriculture with related socio-economic impacts for farmers in the area. The anticipated increase in temperature of 1.2 ◦C in 2020, 2.4 ◦C in 2050, and 4.2 ◦C by the year 2080 and a projected rainfall decrease of about 5–10% in the next 50 years [8], thus presents a significant risk to South Africa's food security and socio-economic stability. Considering the socio-economic importance of agriculture and food security, it is therefore imperative to assess how future climate change will affect crop yield. Adaptation is an important factor that will minimize the severity of the impact of climate change on future crop production [15,16]. Potential adaptation strategies should thus be developed and consistently evaluated to effectively cope with climate risk.

Numerous studies have assessed the impact of climate change on crop production in South Africa [17–22], their findings indicate a decrease in crop yield as a result of a changing climate. Mayowa [23] examined the impact of climate variability on maize yield in South Africa using satellite-derived data and a neutral framework. The result of the study indicated that maize phenology could be impacted by climate variability, especially if the impacts are most severely experienced during the vegetative and reproductive period of plants. Studies by Gbetibouo and Hassan [24] and Deraasa et al. [25] used the Ricardian model to investigate the economic impact of climate change on major South African field crops and found that the production of field crops was more sensitive to changes in marginal temperature as compared to changes in precipitation. Results from their study implied that an increase in temperature somehow positively affected net revenue whereas the effect of precipitation decrease was negative. The study went further to highlight the importance of season and location in dealing with climate change, indicating that the spatial distribution of climate change impact and consequently the needed adaptation strategies vary across the different agro-ecological regions of South Africa.

Despite the fairly extensive research undertaken towards assessing the potential impacts of climate change on crop production in South Africa, to date, no study has evaluated the efficiency of adaptation strategies in order to provide farmers and decisionmakers with clear guidance on the best practices to be implemented. Further, many of the existing studies were either conducted at a national, regional, or provincial level which fails to capture climate change-related dynamics and its implications at a catchment level. It is important to understand how climate change affects crop production at a catchment scale since vulnerability and the intensity of climate change are location-specific and the formulation of adaptation strategies depends on the level of impacts. Specifically, the assessment of climate change and adaptive measures in terms of crop production have not been investigated in the Olifants catchment where crop yield could be more sensitive to climate change due to the vulnerability of the catchment to global change.

This study, therefore, aims to assess the potential impact of climate change on crop yield in the Olifants catchment using a high-resolution climate change model and it evaluates the efficiency of the adaptive strategies deployed by farmers to improve crop yield under current and future climate change scenarios for the catchment. The specific objectives of this study are: (1) to evaluate the impacts of climate change on the catchment reference evapotranspiration and crop water requirement; (2) to assess the influence of soil texture on crop yield under current climate condition; (3) to evaluate the impact of current and projected climate change on crop yield, and lastly, (4) to assess crop yield response to different adaptation measures in the context of changing climate.

The findings from this study are intended to provide relevant information on the expected changes in climate and its impact on crop yield at a catchment-scale as well as to guide policy-makers on the most suitable adaptation options to be implemented in order to improve future crop production and ensure food security.

The rest of the paper consists of Section 2 which details the material and methods used for analysis in the study, followed by a presentation of the results in Section 3. The discussion and concluding remarks are provided in Sections 4 and 5 of the paper.
