Browsing by Author "Crespo, Olivier"
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- ItemOpen AccessA Global Systematic Review of Improving Crop Model Estimations by Assimilating Remote Sensing Data: Implications for Small-Scale Agricultural Systems(Multidisciplinary Digital Publishing Institute, 2023-08-17) Dlamini, Luleka; Crespo, Olivier; van Dam, Jos; Kooistra, LammertThere is a growing effort to use access to remote sensing data (RS) in conjunction with crop model simulation capability to improve the accuracy of crop growth and yield estimates. This is critical for sustainable agricultural management and food security, especially in farming communities with limited resources and data. Therefore, the objective of this study was to provide a systematic review of research on data assimilation and summarize how its application varies by country, crop, and farming systems. In addition, we highlight the implications of using process-based crop models (PBCMs) and data assimilation in small-scale farming systems. Using a strict search term, we searched the Scopus and Web of Science databases and found 497 potential publications. After screening for relevance using predefined inclusion and exclusion criteria, 123 publications were included in the final review. Our results show increasing global interest in RS data assimilation approaches; however, 81% of the studies were from countries with relatively high levels of agricultural production, technology, and innovation. There is increasing development of crop models, availability of RS data sources, and characterization of crop parameters assimilated into PBCMs. Most studies used recalibration or updating methods to mainly incorporate remotely sensed leaf area index from MODIS or Landsat into the WOrld FOod STudies (WOFOST) model to improve yield estimates for staple crops in large-scale and irrigated farming systems. However, these methods cannot compensate for the uncertainties in RS data and crop models. We concluded that further research on data assimilation using newly available high-resolution RS datasets, such as Sentinel-2, should be conducted to significantly improve simulations of rare crops and small-scale rainfed farming systems. This is critical for informing local crop management decisions to improve policy and food security assessments.
- ItemOpen AccessA Spatial Suitability Assessment of Maize and Tobacco in Response to Temperature and Rainfall Changes in Zimbabwe(2022) Nkoma, Tsungai; Crespo, OlivierClimate is changing, and this change poses threats to the agricultural sector. The impacts of climate are expected to become more extreme as the earth warms, and this change will affect climate suitability for different types of crops. The degree to which an increase in temperature patterns and rainfall variations will affect climate suitability for agricultural practices needs to be further understood. This can be achieved by performing a climate sensitivity analysis and contribute to informing adaptation policies and mitigation measures. This study aims to analyze the sensitivity of important crops in Zimbabwe, maize, and tobacco, in response to changes in temperature and rainfall patterns. This research paper used a sensitivity analysis of climate variables; rainfall, and temperature, using historical climate data derived from WorldClim for the period 1990-2018 to assess climate suitability. The historical climate data was used as the baseline to assess the sensitivity of maize and tobacco under a 2°C, 3°C, and 4°C temperature increase as well as a 5%, 15%, and 30% increase and decrease in annual average rainfall amount. The modified spatial climate data was computed in QGIS, and suitability was simulated using the Ecocrop model embedded in the DIVAGIS user platform. The results from this study indicated that in Zimbabwe, both crops are more sensitive to rainfall changes than to temperature changes (independently). A 5%, 15%, and 30% decline in the average rainfall will result in previously suitable areas becoming marginal, very marginal, and others unsuitable for both crops that are in agro-ecological regions I to III; i.e., provinces that include Mashonaland Central, Mashonaland West, Mashonaland East, Harare, and Manicaland. When crops are subjected to combined changes (temperature and rainfall), both crops become more sensitive. When exposed to high temperatures and low rainfall together, for instance, provinces such as Mashonaland Central, Mashonaland West, Mashonaland East, and Harare which are known as historically suitable areas for maize cultivation, will become marginal or very marginal. This change in suitability could have consequences not only on food security but also on people's livelihood and understanding the crops' sensitivity to climate changes helps support the well-being progress of the country.
- ItemOpen AccessAn integrated approach to climate vulnerability and adaptation assessment of smallholder production systems: evidence from horticultural production in Ghana(2020) Williams, Portia Adade; Crespo, Olivier; Abu, MumuniThe consequences of changing climate mainly impact negatively on agricultural production, particularly smallholder producers. Despite increased research on vulnerability and adaptation, African countries have still not realized their full potential in adapting to changing climate. Climate vulnerability assessments show limited use in guiding decision support for adopting proposed adaptation responses identified. This study examines climate vulnerability of smallholder producers and economically evaluates adaptation strategies identified. This is to enhance vulnerability assessment practice and provide support for decision-making on adoption to influence local level planning and actions on climate adaptation. The study further explores approaches to vulnerability assessment that link climate adaptation process. Smallholder horticultural production system in Ghana provided an appropriate case for this study. Mixed methods approach that combined field surveys, in-depth interviews, focus group discussions and field observations in two horticultural growing municipalities in Ghana (Keta and Nsawam) were adopted. Both qualitative and quantitative inputs for analysis were obtained. Specifically, a combination of theoretical insights from livelihood analysis (Livelihood Vulnerability Index) with an appraisal method (Cost Benefit Analysis) arising from an investment in adaptation options was used as the analytical framework for the study. Smallholder farmers in both case study sites showed different vulnerabilities based on their levels of exposure, sensitivity and adaptive capacity. Local knowledge, perceptions and effects of climatic trends (eg. increasing temperature and decreasing rainfall) on farmers' livelihoods resulted in identification of about twenty-four strategies practiced by farmers to manage changing climate. Costs and benefits analysis of the first five adaptation strategies indicated economic effectiveness both privately and publicly if adopted. However, in consideration of other factors like capital required, payback period for investments made and risks from implementation, two of the adaptation strategies particularly appeared as most suited choices while the role of targeted and dedicated external institutional, policy and stakeholders' support turned out to be paramount for successful adaptation. These observations have implications for the degree of influence vulnerability assessment has for local level planning and actions on climate adaptation. The study underscores vulnerability and adaptation should be considered synergistically. It therefore proposes a framing of vulnerability assessment to explicitly incorporate adaptation actions and their benefits to reduce vulnerability and provide better linkages to decision-making and policy relevance. Making decision support a major outcome from vulnerability assessment extends assessment outcomes from identification of vulnerable people/places to include identification and evaluation of adaptation responses, which facilitate the prioritization and selection of adaptation options for adoption. It concludes by highlighting pathways to reduce the vulnerability of farming communities such as exploring opportunities to expand a system's adaptive capacity through empowering farmers' socially and economically. Extra knowledge and policy interventions in vulnerability and adaptation discourse are further suggested to promote and encourage adaptation efforts.
- ItemOpen AccessAn investigation of the impacts of intra-seasonal rainfall variability on the maize growing season in Limpopo Province, South Africa from 1990-2014(University of Cape Town, 2020) Ramugondo, Ntanganedzeni; Crespo, Olivier; Pinto,IzidineRain fed maize is an important staple food crop for rural communities in Southern Africa as it plays a major role in ensuring food security and improving livelihoods. Rainfall consistency and intensity is an essential requirement for successful maize growing seasons. The variability of intra-seasonal rainfall characteristics such as onset, cessation and wet and dry spells threatens maize yields in Southern Africa. Previous studies have focused on the impacts of seasonal rainfall totals on maize yields. The aim of this study is to investigate the impacts of intra-seasonal rainfall variability on the maize growing season of Limpopo Province, South Africa from 1990 to 2014. A Self-Organizing Map (SOM) is used to identify and distinguish synoptic states and patterns that are conducive for growing maize in the province from those that are not. The SOM is trained using daily mean Geopotential height reanalysis data, composites for rainfall and moisture are then analysed to understand surface responses. CHIRPS daily rainfall data is used to analyse the variability of rainfall characteristics. The relationship between these rainfall characteristics and maize yield is evaluated to assess the impacts of variability on maize yields. The SOM shows that summer maize growing season is characterised by low pressure systems over the mainland which act as tropical sources of moisture and the formation of cloud-bands associated with Tropical Temperate Troughs. There is a trend in late rainfall onset and earlier cessation leading to a shift and shortening of the rainy season. The shifted and shortened rainy seasons are characterised by dry spells and high intensity rainfall events and are potentially more suitable for planting the shorter season maize cultivars. Regardless of these agrometeorological conditions being detrimental to yields, district level and provincially averaged maize yields show an overall increasing trend. This is a result of improved farming methods such as planting drought resistant short season yellow maize cultivars which can withstand dry spells.
- ItemOpen AccessAssessing climate change impacts and agronomic adaptation strategies for dryland crop production in southern Africa(2016) Zinyengere, Nkulumo; Hewitson, Bruce; Tadross, Mark; Crespo, OlivierDryland farmers in southern Africa operate under harsh conditions; infertile soils, erratic rainfall regimes, sub-optimal input levels etc. Crop yields have generally been low, negatively affecting food security and livelihoods. Climate change is anticipated to aggravate these already existing challenges. In the recent past, a wide range of studies has sought to understand how climate change will affect crop production. However, there are only few detailed localised studies that focus on understanding climate change impacts and adaptation under heterogeneous conditions that dryland farmers in southern Africa operate. This study sought to understand how climate change will affect food crop production in southern Africa's drylands and to provide insight on the potential of on-farm agronomic management strategies for adaptation. The study focused on three locations representing some of the agro-ecological conditions of southern Africa i.e. Big Bend in Swaziland (low altitude, hot and dry), Mohale's Hoek in Lesotho (high altitude, cool and wet and dry), and Lilongwe in Malawi (mid altitude, wet with moderate temperatures). The study was performed largely using a climate-crop model simulation approach supported by a review of similar approaches in the region, data collected from reported agricultural experimental trials, regional experts, downscaled climate projections (using up to 9 GCMs) and surveys.
- ItemOpen AccessAssessing the climatic suitability of Bambara groundnut as an underutilised crop to future climate projections in Sikasso and Ségou, Mali(2020) Ezekannagha, Ezinwanne; Crespo, OlivierThis study evaluates how future climatic projections will affect the suitability of bambara groundnut (Vigna subterranean(L) Verdc.), a type of underutilised crop in Sikasso and Ségou, southern Mali. This study was performed using a simulation approach, which considered the potential changes in suitability due to projected changes in two climate variables; temperature and precipitation. Monthly outputs of the two climate variables from 10 CORDEX bias-corrected regional projections under the Representative Concentration Pathway (RCP) 8.5 were applied. The suitability index range of bambara groundnut was projected, using the Ecocrop suitability model, considering three time periods: historical (1975-2005), near-term (2011-2040), and end of century (2070-2099). The results of this study showed that the model captured a long planting window for the crop in the regions across the time periods. With the projected increase in future climatic conditions, the suitability index range of bambara groundnut is projected to increase across the months suitable for planting the crop. Furthermore, Sikasso is projected to maintain a high suitability index in the near-term, and by the end of century, Ségou is expected to experience a potential increase in suitability index range and suitable areas, especially by the end of century. The results indicate that the CORDEX projections and suitability modelling technique applied in the study captured well the suitability of bambara groundnut in the regions which can help the farmers in making planting decisions. These results suggest an opportunity for optimal utilisation of the crop in the regions, as with a long planting window and expansion in suitable areas, farmers in the regions can plant multiple times and have more suitable areas to cultivate. This study contributes to improving the decision-making surrounding the promotion of underutilised crops as part of the strategy for climate-resilient agriculture and food security in Sikasso and Ségou.
- ItemOpen AccessAssessing the value of ecological intensification in improving smallholder farmers' food security and rural livelihoods in a changing climate(2019) Rusere, Farirai; Crespo, OlivierAttaining the twin goals of food security and environmental sustainability has spurred focus on two main models of production, sustainable and ecological intensification as means to produce more food per unit land area while simultaneously ensuring environmental sustainability. A better understanding of their suitability and applicability in diverse and heterogeneous biophysical and socio-economic situations of smallholder farmers is still largely needed in sub Saharan Africa (SSA). This study aimed to assess the value of ecological intensification of agriculture to improve food production systems and environmental sustainability in smallholder farming systems in the face of climate variability and change. This study uses two rural districts in South Africa namely Vhembe and Amathole from Limpopo and the Eastern Cape provinces respectively as a case study to explore how ecological intensification can help smallholder farmers. The study explored the fit and potential of ecological intensification in smallholder agricultural systems and steps to be taken to support its implementation and development. The study then uses the Design, Explain, Evaluate and Design (DEED) approach to develops pathways relying on ecological intensification technologies and suiting different farm types of smallholder agriculture. Two iterations of the DEED approach were performed that enabled characterisation of farmers and farming systems and farming systems analysis of challenges and constraints that helped to identify and link specific ecosystem services with suitable ecological intensification options. Furthermore, the study assesses the acceptance and use of ecological intensification options in the heterogeneous biophysical and socioeconomic context of smallholder farmers through the Unified Theory of Acceptance and Use of Technology (UTAUT) framework. Besides the productivity potential, the study sheds light on locally relevant knowledge that must be considered to enable acceptance and use of ecological intensification options. I finally explored the potential of ecological intensification to meet the goals of improving productivity and environmental sustainability concurrently through a biophysical modelling approach encompassing a farm typology, a crop model and a farm focussed greenhouse gas calculator. The results provide valuable insights into the ongoing debate on how to intensify smallholder cropping systems. More specifically, the results show that the integration of agroecological approaches in smallholder cropping systems has the potential to deliver ecological intensification in which productivity is improved and ecosystem services such as climate change regulation through reduction of GHG emissions from cropping systems are simultaneously increased to enhance environmental sustainability. Overall, the study articulates various pieces of evidence to show that ecological intensification is suitable, applicable and, can attain the twin objectives of improving food production systems concurrently ensuring environmental sustainability, in heterogeneous smallholder agricultural systems in SSA. This contribution raises the need for further attention to be given to smallholder agricultural intensification policies and research or to agricultural intensification to explicitly consider the heterogeneous biophysical and socioeconomic circumstances of smallholder farmers in SSA.
- ItemOpen AccessExploring adaptive policy management and evaluation for improved water resources management in the face of uncertainty and complexity in South Africa(2021) Ngcamphalala, Sandile; Crespo, Olivier; Louw, JohannEvidence-based water resources policy management is bedevilled by the challenge of uncertainty, with increased risk of policy failure and/or unintended or negative policy outcomes. Moreover, there is increased policy management complexity emerging from related systems' interdependencies particularly between the water resources policy management system with other environmental, economic, social and political systems. Such complexity imposes external interference with the performance dynamics of water resources policy management efforts. Consequently, water resources policy management strategies in furtherance of ‘water equity' as the ultimate goal of water resources management policy in South Africa, may be misplaced. As a result, the performance of water resources management policy is unlikely to follow a linear logic of change/impact. The adoption of adaptive policy management strategies to ensure policy flexibility and efficiency is warranted especially for policies managed in the face of deep uncertainty and complexity mainly driven by the interactions and interdependencies between numerous social, economic, environmental and political variables with risk for the emergence of more unpredictable policy outcomes. Successful adaptive policy management, however, must be guided through real-time credible and comprehensive evidence, which is complicated to generate in a context plagued with deep uncertainty and complexity. Using systems mapping as a systems' analysis tool, this study identified a comprehensive list of environmental, economic, social and political variables that interactively determine water resources policy management performance towards ‘water equity'. The different environmental, economic, social and political variables that interactively influence ‘Water Equity' results as identified in this study, help to determine key policy drivers and leverage points that can be monitored and evaluated in pursuit of credible and comprehensive water resources policy planning, implementing and performance evidence. The availability of credible and comprehensive evidence, however, does not imply automatic success of the adopted adaptive strategy. The study found that there are numerous other barriers on different aspects and levels of the policy that would have to be addressed to ensure the contextual success of adaptive and integrated water resources policy management in South Africa. These include, transformational changes in substantive water resources management policy design to ensure proactive intentionality to improve water resources policy management in the face of deep uncertainty; designing institutional policy governance structures that demonstrate clear appreciation of the heterogeneous water resources management needs across the country; and active commitment to fully and timely implementation policy decisions in a manner that ensures continuous learning, capitalises on policy performance opportunities, defends working policy strategies and facilitates real-time policy corrections.
- ItemOpen AccessExploring the potential of using remote sensing data to model agricultural systems in data-limited areas(2020) Dlamini, Luleka; Crespo, OlivierCrop models (CMs) can be a key component in addressing issues of global food security as they can be used to monitor and improve crop production. Regardless of their wide utilization, the employment of these models, particularly in isolated and rural areas, is often limited by the lack of reliable input data. This data scarcity increases uncertainties in model outputs. Nevertheless, some of these uncertainties can be mitigated by integrating remotely sensed data into the CMs. As such, increasing efforts are being made globally to integrate remotely sensed data into CMs to improve their overall performance and use. However, very few such studies have been done in South Africa. Therefore, this research assesses how well a crop model assimilated with remotely sensed data compares with a model calibrated with actual ground data (Maize_control). Ultimately leading to improved local cropping systems knowledge and the capacity to use CMs. As such, the study calibrated the DSSAT-CERES-Maize model using two generic soils (i.e. heavy clay soil and medium sandy soil) which were selected based on literature, to measure soil moisture from 1985 to 2015 in Bloemfontein. Using the data assimilation approach, the model's soil parameters were then adjusted based on remotely sensed soil moisture (SM) observations. The observed improvement was mainly assessed through the lens of SM simulations from the original generic set up to the final remotely sensed informed soil profile set up. The study also gave some measure of comparison with Maize_control and finally explored the impacts of this specific SM improvement on evapotranspiration (ET) and maize yield. The result shows that when compared to the observed data, assimilating remotely sensed data with the model significantly improved the mean simulation of SM while maintaining the representation of its variability. The improved SM, as a result of assimilation of remotely sensed data, closely compares with the Maize_control in terms of mean but there was no improvement in terms of variability. Data assimilation also improved the mean and variability of ET simulation when compared that of Maize_control, but only with heavy clay soil. However, maize yield was not improved in comparison. This confirms that these outputs were influenced by other factors aside from SM or the soil profile parameters. It was concluded that remote sensing data can be used to bias correct model inputs, thus improve certain model outputs.
- ItemOpen AccessFuture crop suitability assessment and the integration of Orphan crops into Kenya's food systems(2021) Joshi, Namita; Crespo, OlivierClimate change is seen to be playing an increasingly key role in determining the level of food security within Kenya. In 2020, around 3.1 million people in the country faced acute food insecurity as a result of excessive rainfall, flooding and drought. There has also been a concentration of research on major crops, such as maize and common bean. This study, therefore, seeks to contribute to the research gap in future projections of crop suitability for major and minor crops in Kenya. Temperature and rainfall data, downloaded from CORDEX, from four statistically downscaled Global Climate Models (GCMs) under the Representative Concentration Pathways (RCP) 8.5 and 4.5 were used to run the Ecocrop model. The output was the suitability index spatially plotted over the country for maize, finger millet, common bean, broad bean and sweet potato, within three time periods: historical (1980-2009), near term (2010- 2039) and midcentury (2040-2060). To further understand the influence soil pH has on the climate suitability of these five crops, QGIS was used to overlap Ecocrop suitability outputs and Soilgrids soil pH rasters. CORDEX projections indicated a 2°C- 2.5°C and 1°C rise in temperature under RCP8.5 and 4.5 respectively, and rainy seasons becoming more intense and shorter. The suitability index of maize is projected to have a slight increase (20%) during the long rains, by the end of the century under RCP8.5. Along the RCP4.5 pathways, there is a greater increase in suitability for maize in counties along the coast and western Kenya. Results also project a significant suitability increase (50%) of the orphan crop- broad bean- during the dry season. The spatial distribution of suitability is widespread within many arid and semi-arid counties. This presents an opportunity to integrate legumes such as broad bean into the cropping system within a crop rotation with maize. This form of adaptation would help ease the pressure on the production of staple crops since suitability for maize and common bean is projected to decrease during the short rains. Soil pH results indicated the dominance climate has on determining overall suitability. For instance, pH suitability of finger millet was achieved in majority of the counties however, climate suitability does not favour the planting of this crop. For sweet potato, there is optimum pH and climate suitability, however, it is not greatly distributed around the country. Despite the low spatial distribution, these small areas of sweet potato production can also contribute to better food security in these counties.
- ItemOpen AccessIntegration of seasonal forecast information and crop models to enhance decision making in small-scale farming systems of South AfricaMkuhlani, Siyabusa; Crespo, OlivierClimate variability threatens agricultural productivity and household food security, amongst small-scale farmers of South Africa. Managing climate variability is challenging due to the variation of climate parameters and the difficulty in making decisions under such conditions. Integrated seasonal forecast information and crop models have been used as a tool that enhances decision making in some countries. Utilization of such an approach in South Africa can enhance decision making in climate variability management. The study therefore sought to formulate a decision-making approach to enhance climate variability management in small-scale farming systems of South Africa through integrating seasonal forecast information and crop models. Current practices, challenges and opportunities for climate variability management by different small-scale farmer types were identified using focus group discussions and local agricultural extension officers. The Climate Forecast System version 2 (CFSv2) model-based forecasts were integrated with the Decision Support System for Agrotechnology Transfer (DSSAT) v4.7, a mechanistic crop model based on the Global Climate Model (GCM) approach. The GCM approach was the most appropriate technique for integrating seasonal forecast information and the crop model due to the compatibility in the forecast and crop model format. The decision-making process was formulated through assessing the simulation yield patterns under a range of farm management practices and seasonal forecasts for different cropping seasons, crops and farmer types for Limpopo and Eastern Cape, South Africa for 2017/18 season. The study assessed 48 different potential combinations of farm management practices: organic amendments, varieties, fertilizers and irrigation. Benefits of the decision formulation process and specific seasonal forecast-based recommendations were then assessed in the context of the performance of the practices under historical measured data for the conditions; 2011-2017, using percentile ranking. Assessing the yield response patterns under different farm management practices and seasonal forecasts (2017/2018), the study realized a range of decision scenarios. These are (1) low decision capacity and low climate sensitivity where there is low value for decision due to the homogeneous performance of the different management practices given climate forecasts. (2) high decision capacity and low climate sensitivity, where there is higher potential value for decision making as the different practices have uniform performance across climate forecasts. (3) High decision capacity and high climate sensitivity, where the good response to change in practices under changing climate forecasts. Confidence in the decision formulation process v was re-enforced as some of the decision scenarios were also realized under different conditions in the period; 2011-17. The scenario (2): High decision capacity and low climate sensitivity was predominant in locations with low forecast skill. In contrast the scenario (3): High decision capacity and high climate sensitivity was predominant in locations with high forecast skill. The decision formulation process allows for assessment of farm management practices in the seasonal forecast decision space. Although the case study realized some scenarios ahead of others, the process is robust and repeatable under any conditions. Although the process does not always offer recommendation with improved value for decision making, the value of recommendations is greater under decision scenarios with greater decision capacity. Such benefits are crop and location dependent. Improved seasonal forecasting skill increases reliability of the decision-making process, decision scenarios and associated recommendations. Such assertions need to be tested on the field scale to assess their practical feasibility.
- ItemOpen AccessInvestigating the impacts of climate services among commercial and smallholder farmers to improve the uptake of climate information(2023) Nyudwana, Sinazo; Crespo, OlivierClimate change has impacts on agricultural production through changes in precipitation, temperature, carbon dioxide fertilisation, surface water runoff, and climate variability. These changes affect the ability of a region's agricultural sector to sustain production. South Africa is particularly vulnerable because of poverty, food insecurity, and a low adaptive capacity. Therefore, there is a crucial need for adaptation in the agricultural sector, which requires sufficient climate information to achieve strong climate-resilient development. This research aims to assess how the uptake of climate information can be improved with climate services among commercial and smallholder farmers in South Africa. In this study, a total of 29 respondents were interviewed. These respondents consisted of a seasonal climate forecast provider, two agricultural advisors and 13 Western Cape and Eastern Cape farmers who were a representation of the two main farming systems in South Africa. The interview questions for the seasonal climate forecast provider and agricultural advisors obtained information on the rate of access to and use of climate services, as well as extension support and engagement. The farmer interview questions were designed to elicit farmers' perspective on climate risks, as well as access to and use of climate services, such as seasonal climate forecasts, in agricultural decision-making. According to the results of this study, farmer-researcher engagement and extension support is currently poor. This is demonstrated by the low response rate of 8% of commercial and smallholder farmers who reported using extension services, as well as a lack of awareness and understanding of seasonal climate forecasts. Furthermore, access to climate services and the use of seasonal climate forecasts differed among commercial and smallholder farmers, with 46% of commercial farmers with access but limited use due to lack of trust. In contrast, smallholder farmers had no access and usage due to a lack of awareness and understanding of seasonal climate forecasts. Additionally, the results revealed that both the commercial and smallholder farmers considered networks as an essential enabler to use seasonal climate forecasts. The networks mentioned were the local farmer groups and agricultural co-ops such as GrainSA and Overberg Agri. This research, therefore, recommends improving farmers' knowledge of seasonal climate forecasts through training and the development of accessible, context-specific climate services. Moreover, the dissemination and interpretation of seasonal climate forecasts by local agricultural advisors and extension officers is recommended. This will assist in the improved uptake of climate information and more active engagement among seasonal climate forecast producers, agricultural advisors, agricultural extension officers, and farmers. viii Keywords: Climate services; Seasonal climate forecasts; Commercial farmers; Smallholder farmers; South Africa
- ItemOpen AccessInvestigating weather information needs of smallholder farmers in the Eastern Cape province of South Africa(2023) Mantshiyose, Abenathi; Crespo, OlivierSouth Africa is continuously experiencing irregular weather and climate, which is attributed to climate change and the El Niño Southern Oscillation. These have resulted in temperature increases, irregular rainfall patterns, and increased frequency of extreme events. In South Africa, smallholder farmers are the most vulnerable to extreme weather events due to their limited capacity to adapt. Their vulnerability results from a series of factors constraining their ability to adapt, such as limited resources, knowledge, and skills. Furthermore, smallholder farmers are highly dependent on rainfed agriculture, making them more sensitive. The lack of weather information that is tailored for user needs or adapted well enough is also a concerning issue that exacerbates the living conditions of smallholder farmers. This makes it difficult for them to sustain their agricultural activities. Over the years, weather information has been recognized as having the potential to be useful in agriculture, especially in informing farming practices, planning, and reducing weather events impacts among smallholder farmers. However, access and use of weather information that applies to the context of smallholder farmers which is tailored to meet smallholder farmers needs, has been limited and has contributed to limited understanding and low use levels of weather information. This has increased the need to understand the weather information needs of smallholder farmers as this is important to ensure that farmers can effectively use and understand the information. In South Africa, limited studies have looked at the weather information needs of smallholder farmers. Hence, a shift of attention towards investigating the weather information needs of smallholder farmers has increasingly become necessary. The present study investigated how to better communicate the weather information needs of smallholder farmers in the Eastern Cape province of South Africa. A mixed-methods approach was used to collect and analyze the data. Interviews with open-ended and closed-ended questions were conducted with smallholder farmers and agricultural extension officers. Interviews were conducted to gain an insight on the baseline and characteristics of weather information farmers receive and their needs. The same was done with extension officers to get their insight on the needs of farmers and the needs of extension officers. 2 The findings of the study confirm that the current weather information system is inefficient as the information does not fully meet the needs of smallholder farmers. Most of the farmers expressed that they currently receive information on rainfall, temperature, and heavy rainfall but stated that they would like to receive information on drought as they are currently experiencing dry periods. The farmers mentioned that they receive weather information mostly from the television, radio, and a few from weather apps. Most of the farmers receive weather information in maps and audio, expressing that maps make it easy for them to visualize and understand the information. From the television, they receive the information in IsiXhosa and IsiZulu, and they mentioned that weather information in IsiXhosa is easy to understand as it is their local language. In weather apps, farmers mentioned that they receive weather information in English and expressed concerns about understanding weather information in English. As a result, most farmers preferred receiving weather information in IsiXhosa as they can understand the language. Additionally, farmers also expressed that they only receive weather information daily, and they stated that they would like to receive weather information daily, weekly, monthly, and seasonally to plan their farming activities and to know when to plant. Furthermore, most of the farmers expressed that they encounter some challenges with the information they receive. Some of the challenges included issues such as the inaccuracy of the information and scale issues. The farmers complained that the information they receive is not downscaled to their local scale, making it difficult for them to apply the information on their local scale decisions. Therefore, without significant improvement of the issues mentioned above and addressing the weather information needs of farmers, weather information use and understanding will remain low and will increase the vulnerability of smallholder farmers to extreme weather events. To prevent this, there is a growing need for weather information to meet the needs of smallholder farmers so that they can understand and use the information efficiently, especially in the face of increasing extreme weather events such as drought in South Africa.
- ItemOpen AccessModelling climate change impacts on maize and soybean yields in Central and Eastern Provinces of Zambia(2021) Chilambwe, Alice; Crespo, OlivierIt is widely recognised that the unfavourable impacts of climate change on agriculture production may add up significantly to the developmental challenges of ensuring food security and reducing poverty. In Zambia, climate change impact assessments on crops are mainly carried out using large spatial scale climate data, jeopardizing on local scale impacts and adaptation capability that reveal the range of agronomic conditions under which farmers in specific areas operate. Through two major maize and soybean producing provinces in Zambia, this study enhances the understanding of district production variations under location specific climate change. This study aims at providing a climate change impact assessment in the light of three Global Climate Models (GCMs), under two Representative Concentration Pathways (RCPs), and a crop simulation model Agrometshell (AMS). This allows for an exploration of crop production choices best suited at district scale, to feed into larger provincial and national future production programs. Two future climate periods were selected to cover both near (2020 – 2039) and long-term (2050 – 2069) climate. It was shown that the impacts of climate change on crops in Central and Eastern provinces will be beyond historical natural variation and will vary across districts and crops. Maize yields in majority of the districts will be impacted negatively whilst soybean yields will moderately benefit from future climate as five out of eleven districts studied are projected to have yield increases. These results suggest that climate change will increase the risk of food insecurity in the provinces studied and the country considering that maize is a central crop in overall agricultural crop production. Soybean which may offer an opportunity to balance with some maize loss could be accounted for in policy making to achieve future food security. This study improves knowledge and understanding of the impacts of climate change on district agricultural food production systems, and the need of good location specific knowledge to better address the challenge of climate change.
- ItemOpen AccessPlant growth, stress tolerant traits and regulation of heat activated proteins in Aspalathus linearis (Burm. f.) R. Dahlgren exposed to elevated temperature and drought(2020) MacAlister, Dunja; Muasya, A Muthama; Crespo, Olivier; Chimphango, Samson B MClimate change is increasingly becoming a concern on plant growth, as seen in the increased number of warmer days and nights as well as an increased occurrence of heat waves, and drought periods globally. The Intergovernmental Panel on Climate Change has stated that global surface temperatures are constantly increasing and are likely to exceed 2 °C, compared to average temperatures in 1900, by the end of the 21st century. Changes in precipitation will also become more erratic, with high latitude and mid-latitude areas expected to have increases and decreases in rainfall respectively, while already dry areas will have increased frequencies of drought. Regions with Mediterranean climates, such as the Western Cape in South Africa, are particularly vulnerable to these climate impacts, with models and studies showing that there are already significant increases in temperatures, shifts in later winter rainfall and an increased severity of flooding. These climatic changes will impact both natural and agricultural plant species growth and distribution due to the changes in suitable growing conditions and regions. Plants are already exposed to a wide variety of environmental factors, each of which influences the growth, and deviations from the optimal conditions is considered abiotic stress and negatively affects plant growth. Plants in the field are rarely affected by only one stress as they are frequently exposed to a combination of abiotic stresses and with the changes in climate, plants will likely be experiencing abiotic stress such as heat and drought stress simultaneously. The aim of this thesis was to determine the effects of heat and drought on the plant growth and physiological performance of one of the most important indigenous commercial crops in South Africa, Aspalathus linearis (Burm.f.) R. Dahlgren, better known as rooibos tea, known for its many health benefits. This was achieved by focusing on three objectives: (1) determining the effects of temperature on plant growth and identifying the thermotolerant traits of the plants grown in the field along a temperature gradient, (2) determining the heat activated proteins and associated mechanisms for heat tolerance in field grown plants and (3) determining the physiological and morphological responses of A. linearis grown under two moisture regimes and later exposed to drought. The results for objective one are presented in chapter two, where a field study was conducted to observe the effects of temperature on the growth and stress tolerant traits of A. linearis grown at four farms sites in the Cederberg, South Africa along a temperature gradient. The four sites represent the rooibos farming area, from coolest to warmest respectively; Aurora (alt. 93 m), Citrusdal (alt. 588 m), Clanwilliam (alt. 312 m) and Uitsig (alt. 344 m). Aurora was also situated closest to the coastline, ∼18 km, compared to the other farms. The traits observed were changes in gas exchange, carbohydrate concentrations, phenolics and pigments, along with biomass, over a two-year period. Aspalathus linearis plants showed evidence of transpirational leaf cooling during summer and this, combined with lower chlorophyll and high phenolic content, could be considered acclimatized adaptive changes allowing the plants to mitigate the heating effects of elevated temperatures. Chapter three presented the results for objective two where the proteome of A. linearis was analysed from field plants along a temperature gradient. Protein samples were collected from the plants concurrently with the physiological samples for the previous chapter. These protein samples were quantified and then functionally annotated using the OrthoDB and UniProt databases. Overall, a total of 180 proteins were differentially expressed in the plants during exposure to high temperatures in the field. Of these 180 proteins, 113 were more upregulated in the cooler sites, Aurora and Citrusdal, and 67 proteins were more upregulated in the hotter sites, Clanwilliam and Uitsig thus indicating that with increasing temperatures there is a downregulation of proteins expressed during heat stress. From the 180 proteins, there were six main proteins involved in photosynthesis or light harvesting in A. linearis, with four of the six proteins upregulated in plants grown at Aurora, the cooler site, and in the hottest site, Uitsig. This agrees with results from chapter two, where plants from Aurora had superior photosynthetic rates compared to the other plants therefore allowing them to grow and produce better biomass. The hotter sites upregulated heat shock proteins more than the cooler sites, suggesting that their expression could be enhancing the thermotolerance of A. linearis plants through their chaperone activity where they protect other proteins against denaturation. There were also numerous proteins expressed in the plants which were related to oxidationreduction processes and antioxidants, most of which were expressed in the hottest site, Uitsig. One of the main concerns for plants during heat stress is the oxidative damage brought on by reactive oxygen species, and the expression of these proteins indicates that these proteins are contributing to the plants' thermotolerance through the production of antioxidant phenolic compounds as was seen in chapter two. In chapter four, a glasshouse study was conducted where plants were grown at two different moisture regimes (field capacities, FC) and then exposed to drought and both physiological and morphological parameters were measured. Morphological parameters measured included plant biomass, root/shoot ratios, total root length, average root diameter, total root surface area and specific root length. Physiological parameters measured were gas exchange, carbohydrate and phenolic concentrations, pigment concentrations, leaf relative water content and water potential. During drought, the gas exchange, relative water content and nonstructural carbohydrates in leaves were all reduced, while chlorophyll concentrations remained constant. Aspalathus linearis plants also had reduced stomatal conductance and transpiration, increased root/shoot ratios, root length and antioxidants such as polyphenol in leaves under drought conditions. Overall, changes in soil nutrients, including boron, available phosphorus, manganese and copper, and increasing temperatures had a negative impact on crop biomass, however, the phenolic content, which is a measure of tea quality, did not vary with sites. This suggests that farmers who are planning on shifting their rooibos farming further south of Cederberg, could still achieve good growth and high yields without compromising the quality of the tea. It was also seen that A. linearis plants upregulated heat shock proteins, along with proteins involved in antioxidant compounds particularly in the hotter sites thereby playing a critical role in their acquired heat-stress tolerance. Plants in the cooler sites upregulated proteins involved in photosynthesis and chlorophyll production, therefore allowing them to have higher photosynthetic activity and subsequently higher productivity. The up and down regulation was based on comparing the warmer sites (heat-stressed) to the cooler sites (control). The plants grown at lower FC and then droughted, exhibited drought tolerant mechanisms which included higher root/shoot ratios as well as thinner roots, both of which are effective for water and nutrient uptake. Overall, plants in the 30 % FC treatment recorded lower Pmax, gs and E after three days in the drought conditions while 70 % FC plants were only affected after five days. Furthermore, plants grown under low moisture (30 % FC) conditions produced 50 % lower biomass compared to plants grown under adequate moisture (70 % FC) conditions. This implies that low rainfall and the occurrences of dry spells and drought, associated with climate change are likely to reduce the production of A. linearis in the Cederberg area. The combination of both field work and glasshouse studies have provided insight into how these plants are affected by both heat and drought stress, as well as declining soil nutrients such as calcium, magnesium, manganese iron, copper and potassium. Aspalathus linearis is tolerant to high temperatures as well as dry conditions, however, more needs to be explored with regards to their thresholds particularly since climate change is likely to continue in the near future and eventually moving farming south will no longer be an option for farmers.
- ItemOpen AccessSimulating the impact of climate change on maize production in Ethiopia, East Africa(Springer Berlin Heidelberg, 2018-02-13) Abera, Kidist; Crespo, Olivier; Seid, Jemal; Mequanent, FasilBackground: Climate change is expected to signifcantly impact agricultural production across Africa. While a number of studies assessed this impact in semi-arid southern Africa, or tropical West Africa, only a limited number took interest in the mountainous and climatically varying Ethiopia of eastern Africa. This study assesses the impact of climate change on maize production in three representative sites of maize growing areas in Ethiopia. The assessment relies on the DSSAT crop model simulation of maize under current climate and future projections (19 Global Climate Models and 2 Representative Concentration Pathways). The period 1980–2010 was used to represent the baseline climate, while future climate projections cover three periods; near term (2010–2039), mid-century (2040–2069) and end-of-century (2070–2099). Climate, soil and crop management data were collected for the study sites representing the maize growing areas in the country. Results: Results show that maize yields will decrease by up to 43 and 24% by the end of the century at Bako and Melkassa stations, respectively, while simulated maize yield in Hawassa show an increase of 51%. On the one hand, rainfall variability and rising temperatures are determining factors explaining yield decrease in Bako and Melkassa, while projected rainfall increase in Hawassa explain simulated yield increases. Conclusion: The terrain and climate high variability of Ethiopia is emphasizing the extremely diferent responses of current agricultural systems to climate change. Though adaptation approached can address some negative impacts, and in some case can take advantage of changes, this study reveals that dedicated local knowledge is necessary for national and regional decision makers to respond with local relevance to a global exposure, in order to face food security challenges.
- ItemOpen AccessSpatio-temporal effects of projected climate on future crop suitability over West Africa(2020) Egbebiyi, Temitope Samuel; Crespo, Olivier; Lennard, ChrisFuture climate is projected to deviate from present-day by unprecedented measure, hereafter climate departure, with direct consequences on food security. West Africa, one of the hotspots for climate departure globally, has suffered significantly from climate change impacts via extreme events with large impacts on food production. A better understanding of the impact of climate departure on crop growth suitability and planting season is still unknown and is highly needed in West Africa, owing to its high vulnerability and low adaptive capacity. This thesis developed a methodology aimed at defining the cropping system to investigate the projected timing of climate departures from historical variability and their impact on crop growth suitability over West Africa. For the study we used 4 statistically downscaled Global Climate Models, GCMs at station level for the period 1951- 2100 under RCP8.5 across the three AgroEcological Zones (AEZs) of West Africa for eight crops, cassava, maize, mango, orange, pearl millet, plantain, pineapple and tomato. Climate variables minimum mean monthly temperature and total monthly precipitation were used as input crop suitability model, Ecocrop to develop a new approach to define and characterise cropping systems departure from their normal regime, called crop-climate departure (CCD), to better understand the timing of future changes in crop suitability. Also, the concept of CCD was defined, tested and applied in West Africa for five different crops types, using 10 GCMs downscaled by regional climate model, RCA4 as input into crop suitability model Ecocrop. The downscaled GCMs were also employed to examine the impact at the different global warming levels, 1.5, 2.0 and 3.0oC on crop suitability over West Africa. Using the GCMs at station level, we develop the concept of crop-climate used in characterizing the suitability of different crop across the three AEZs of West Africa. The result highlights the constraint, a reduction in suitable area, of growing cassava and pineapple only in the Guinea zone by mid and end of century. In contrast, there is an observed and projected opportunity, increase in suitable areas, of growing maize in southern Sahel by the end of the century while mango remains suitable across the three West African AEZs. The application applying the concept crop-climate departure on different crop types showed in decrease suitable areas for most crops by the end of century with horticultural, cassava and cereals respectively are the crops mostly affected. The changes in crop-climate relationship suggests a future constraint in crop suitability could be detrimental to future food security over West Africa. Finally, our findings from the impact of different global warming levels, 1.5. 2.0 and 3.0oC highlights the potential of sustained suitability for all the crops and improved food security under 1.5oC global warming for all the six crops but a contrast under 3oC over West Africa except for cowpea and groundnut. Our findings for cowpea and groundnut showed an increase suitable area into the southern Sahel with increasing global warming level. The study holds great value at regional scale where improved preparedness and regional cohesion could make the difference in making decision for a food secure Africa. Further studies to explore associated short and long-term adaptation options to changes in crop-climate relationship are recommended.