Abstract for: Modeling household level food security with system dynamics: from crop decisions to food availability

Undernourishment is still a present problem in the world. Progress has been made in the fight against malnutrition over the last years, yet an unacceptable number of people still lack the food they need for an active and healthy life. Sub-Saharan Africa is still the region with the highest prevalence of undernourishment people. Within Sub-Saharan Africa, Zambia is one of the countries facing one of the highest prevalence of undernourishment levels. Many studies have been carried out to explain food security and its determinants. However, food security is not simply a function of production or supply, it involves several dimensions, as the agricultural system is complex. This research develops a system dynamics model-based approach to understand and assess the subsistence farming system, taking Zambia as a case study, a country facing a high prevalence of food insecurity. The study contains an assessment of factors affecting farmers' crop decisions and other important relationships within the subsistence farm management context. The system dynamics modeling approach provides valuable insights into the elements through which different conditions influence household food security. Food security, in subsistence farming, strongly relies on the decision of which crops to plant in a growing season. Assessing these decisions intends to improve our understanding of this process and thus support farmers in defining strategies to allocate resources more efficiently. Therefore, regarding the identification of factors influencing crop decisions, variables of three different types of resources were studied (human, natural, and financial). Variables such as labor availability, the age of the household’s head and gender, farmland size, wealth level, soil fertility, and district, were found to influence farmers’ crop decisions. Furthermore, farmland size and fertilizer were found to be key variables in the subsistence farming system, and are linked to several farm decisions. The system dynamics model is a complex structure containing different sectors characterizing each of the main dynamics of the subsistence farming system. Sectors represent crop decisions, yield and production, soil, sales decisions, income and expenditure, and food availability dynamics, representing the dynamics from the beginning (crop decisions) to the end (food availability). These dynamics are characterized by a set of indicators of the main variables of interest, considered as the key determinants of household food security. The evaluation of scenarios that express different household conditions, demonstrates that the size of the household and the gender of the households’ head are two factors that strongly influence household-level food security. The strategies of providing more access to fertilizer for female-headed viii households, and the implementation of conservation agriculture were tested as demonstrative intervention, and indicate that are possible strategies to increase food security. This study has taken an approach that offers an ample vision of a system, providing significantly more information than mere mathematical models that display only a specific subject of a complex system. It uses the System Dynamics methodology to assess food security supporting the understanding of events and causations, and allows the evaluation of policies and their long-term influence. It also identified the critical variables that affect the phenomenon of food insecurity and how they behavior over time. This thesis contributes to add a new perspective on decision-making and policy design. The results display the potential of this unique approach and structuring knowledge into a broader and dynamics context contested conventional suppositions. Keywords: food security; crop decisions; system dynamics; subsistence farming.