Olivier Crespo

Computer-aided decision for human task allocation with mono- and multi-performance evaluation

An efficient Binary Search-based approach used to determine the sets of human resources allowing one to reach, for an enterprise process, a given performance level is presented. It is based on an enterprise process performance methodology integrating human skill influence. In a first step, this approach is compared with algorithms such as Hybrid Taboo-Descent, Simulated Annealing and Knapsack algorithms for different performance points of view (temporal, financial, quality oriented) on limited and large complexity examples. In a second step, this approach is generalized to integrate simultaneously several viewpoints.

Impacts of drought on grape yields in Western Cape, South Africa

Droughts remain a threat to grape yields in South Africa. Previous studies on the impacts of climate on grape yield in the country have focussed on the impact of rainfall and temperature separately; meanwhile, grape yields are affected by drought, which is a combination of rainfall and temperature influences. The present study investigates the impacts of drought on grape yields in the Western Cape (South Africa) at district and farm scales. The study used a new drought index that is based on simple water balance (Standardized Precipitation Evapotranspiration Index; hereafter, SPEI) to identify drought events and used a correlation analysis to identify the relationship between drought and grape yields. A crop simulation model (Agricultural Production Systems sIMulator, APSIM) was applied at the farm scale to investigate the role of irrigation in mitigating the impacts of drought on grape yield. The model gives a realistic simulation of grape yields. The Western Cape has experienced a series of severe droughts in the past few decades. The severe droughts occurred when a decrease in rainfall occurred simultaneously with an increase in temperature. El Niño Southern Oscillation (ENSO) appears to be an important driver of drought severity in the Western Cape, because most of the severe droughts occurred in El Niño years. At the district scale, the correlation between drought index and grape yield is weak (r≈−0.5), but at the farm scale, it is strong (r≈−0.9). This suggests that many farmers are able to mitigate the impacts of drought on grape yields through irrigation management. At the farm scale, where the impact of drought on grape yields is high, poor yield years coincide with moderate or severe drought periods. The APSIM simulation, which gives a realistic simulation of grape yields at the farm scale, suggests that grape yields become more sensitive to spring and summer droughts in the absence of irrigation. Results of this study may guide decision-making on how to reduce the impacts of drought on food security in South Africa.

Crop-Livestock Intensification in the Face of Climate Change: Exploring Opportunities to Reduce Risk and Increase Resilience in Southern Africa Using an Integrated Multi-Modeling Approach

The climate of Southern Africa is highly variable at most time-scales and follows a pronounced gradient with arid conditions in the west and humid conditions in the east. There is also a marked latitudinal rainfall distribution pattern, with the southern part having a low rainfall index and high variability and the northern part having higher annual rainfall and lower interannual variability (Kandji et al., 2006). Over the last 100 years, temperatures have increased by about 0.5◦C in the region and downward trends in rainfall have also occurred (Kandji et al., 2006; Morton, 2007). There has also been an increase in drought eventswith over 15 drought events reported in the region between 1988 and 1992. The frequency and intensity of El Nin˜o episodes have increased. Prior to the 1980s, strong El Nin˜o events occurred every 10–20 years; between 1980 and 2000, the region experienced five episodes with the 1982–1983 and 1997–1998 episodes being the most intense of the century (Reason and Jagadheesha, 2005; Rouault and Richard, 2005). These episodes have contributed to stagnant or decreasing agricultural production and worsening food insecurity in the region (Kandji et al., 2006). Unfavorable climatic conditions and projected climate change are among the major obstacles to achieving food security in the region and also have dire consequences for macro-economic performance.

Crop model usefulness in drylands of southern Africa: an application of DSSAT

Crop models are useful tools for simulating impacts of climate and agricultural practices on crops. Models have to demonstrate the ability to simulate actual crop growth response in particular environments before application. Data limitations in southern Africa frequently hinder adequate assessment of crop models before application. The DSSAT model was used to test the usefulness of crop models under data-limited dryland conditions of southern Africa by validation using data from experimental trial reports and district-wide crop yield estimates. Two crops each were selected in three locations to represent varying cropping and physical conditions in southern Africa, i.e. maize and sorghum (Mohales Hoek, Lesotho and Big Bend, Swaziland) and maize and groundnut (Lilongwe, Malawi). DSSAT performs well in simulating crop yields obtained from experimental trials. District-wide simulated mean crop yields were acceptable (relative difference ranged from −12.2% to +2.36%). However, the models capture of seasonal yield variation for some locations and crops was uncertain due to climate extremes. It was concluded that satisfactory crop model testing before application is possible and that DSSAT crop models are useful even under data-limited conditions.

Simulating the impact of climate change on maize production in Ethiopia, East Africa

BackgroundClimate change is expected to significantly 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.ResultsResults 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.ConclusionThe terrain and climate high variability of Ethiopia is emphasizing the extremely different 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.

Conservation Agriculture Among Farmers in Kalomo, Zambia: Potential for Productivity Under Climate Change

Conservation agriculture (CA) is a climate change adaptation measure being promoted for small-scale farmers in Zambia. CA is touted as a sustainable adaptation practice that can improve productivity in marginal farming areas. This chapter presents a study that analyzed CA practices in Kalomo District, Zambia, i.e., practices applied and associated challenges in management and implementation, from the perspective of agricultural extension workers and organizations promoting CA in the district. Results showed that farmers in Kalomo District do not apply all CA principles, owing to a number of limitations that range from governmental interventions, cultural beliefs, and poor access to extension services. These factors are likely to affect productivity and expose farmers to climate change and will need to be addressed.

Assessing Local Impacts of Climate Change on Crop Production in Southern Africa: Critiquing an Approach

Abstract This chapter details the common biophysical approach used to assess the impact of climate change on local crop production and critiques it to highlight usefulness and limitations in informing climate change response action. The chapter reviews various location-specific climate change impact studies in southern Africa and details their results in the context of the methodologies and tools applied. Ultimately lessons for improvements in future research are drawn. The chapter advocates future research efforts that will provide useful information for stakeholders in the agricultural sector to better respond to climate change as it affects vulnerable farmers, via improved local impact assessment and the incorporation of nonphysical local perspectives (i.e., going beyond biophysical impacts).