O objetivo da tese é analisar a relação entre modificações no padrão alimentar da população da cidade de São Paulo (demanda por alimentos) e padrão e intensidade da concorrência no setor alimentício (oferta de alimentos). Metodologia. Dados das Pesquisas de Orçamentos Familiares da Fundação Instituto de Pesquisas Econômicas da USP constituem a base analítica da evolução da demanda alimentar em São Paulo. O nexo causal entre demanda e oferta de alimentos é estabelecido pelo estudo do comportamento dinâmico da concorrência entre firmas do setor, número de produtos disponíveis, evolução dos preços e renda da população. O foco em laticínios deve-se à importância nutricional como fonte alimentar de cálcio. Resultados. A análise dos dados comprova a ocorrência de importantes mudanças no padrão alimentar paulistano, destacando-se elevação da disponibilidade de alimentos de alto teor protéico. A dinâmica da concorrência entre empresas de alimentos e a evolução dos preços dos laticínios denotam o emprego de estratégias de concorrência extra-preço, como diferenciação de produto, que influenciaram positivamente a demanda por laticínios. Conclusão. A adequação nutricional da dieta populacional é função direta da composição da demanda alimentar, variável altamente correlacionada a fatores econômicos, com destaque ao comportamento estratégico das firmas na determinação da estrutura de oferta alimentar. Os resultados demonstram a extensão da influência de estratégias de empresas alimentícias sobre o padrão de aquisição de alimentos pelo consumidor e, em conseqüência, o hábito alimentar da população. / The objective of the dissertation is to analyze the relation between modifications in dietary patterns of the population living in the city of São Paulo - Brazil (food demand) and pattern and intensity of the competition inside Brazilian food industrial sector (food supply). Methodology. Data from Families Budget Inquiry (POFs) of Foundation Institute of Economic Research from University of São Paulo (FIPE-USP) are the analytical base of food demand evolution in São Paulo. The causal nexus between food demand and supply is established through the study of dynamic behavior of variables as competition among food firms, number of food products available, evolution of food prices and population income. The focus on dairy products\' sector was performed because of its nutritional significance as food source of calcium. Results. Data analysis demonstrates occurrence of important changes in dietary patterns in São Paulo, emphasising the increase in high protein foods availability. The dynamics of food industrial sector competitive environment and the dairy prices evolution indicate the adoption of non-price competition strategies, such as product differentiation, which influenced positively dairy demand. Conclusion. Nutritional adequacy of the population\'s diet is a direct function of food demand composition, a variable highly correlated to economic factors, highlighting the role of firms strategic behavior in determining the food supply structure. Results show the extension of food firms strategies influence on consumers\' buying patterns and, therefore, on population\'s dietary habits.

O objetivo da tese é analisar a relação entre modificações no padrão alimentar da população da cidade de São Paulo (demanda por alimentos) e padrão e intensidade da concorrência no setor alimentício (oferta de alimentos). Metodologia. Dados das Pesquisas de Orçamentos Familiares da Fundação Instituto de Pesquisas Econômicas da USP constituem a base analítica da evolução da demanda alimentar em São Paulo. O nexo causal entre demanda e oferta de alimentos é estabelecido pelo estudo do comportamento dinâmico da concorrência entre firmas do setor, número de produtos disponíveis, evolução dos preços e renda da população. O foco em laticínios deve-se à importância nutricional como fonte alimentar de cálcio. Resultados. A análise dos dados comprova a ocorrência de importantes mudanças no padrão alimentar paulistano, destacando-se elevação da disponibilidade de alimentos de alto teor protéico. A dinâmica da concorrência entre empresas de alimentos e a evolução dos preços dos laticínios denotam o emprego de estratégias de concorrência extra-preço, como diferenciação de produto, que influenciaram positivamente a demanda por laticínios. Conclusão. A adequação nutricional da dieta populacional é função direta da composição da demanda alimentar, variável altamente correlacionada a fatores econômicos, com destaque ao comportamento estratégico das firmas na determinação da estrutura de oferta alimentar. Os resultados demonstram a extensão da influência de estratégias de empresas alimentícias sobre o padrão de aquisição de alimentos pelo consumidor e, em conseqüência, o hábito alimentar da população. / The objective of the dissertation is to analyze the relation between modifications in dietary patterns of the population living in the city of São Paulo - Brazil (food demand) and pattern and intensity of the competition inside Brazilian food industrial sector (food supply). Methodology. Data from Families Budget Inquiry (POFs) of Foundation Institute of Economic Research from University of São Paulo (FIPE-USP) are the analytical base of food demand evolution in São Paulo. The causal nexus between food demand and supply is established through the study of dynamic behavior of variables as competition among food firms, number of food products available, evolution of food prices and population income. The focus on dairy products\' sector was performed because of its nutritional significance as food source of calcium. Results. Data analysis demonstrates occurrence of important changes in dietary patterns in São Paulo, emphasising the increase in high protein foods availability. The dynamics of food industrial sector competitive environment and the dairy prices evolution indicate the adoption of non-price competition strategies, such as product differentiation, which influenced positively dairy demand. Conclusion. Nutritional adequacy of the population\'s diet is a direct function of food demand composition, a variable highly correlated to economic factors, highlighting the role of firms strategic behavior in determining the food supply structure. Results show the extension of food firms strategies influence on consumers\' buying patterns and, therefore, on population\'s dietary habits.

The world is becoming more complex due to the increasing occurrence of social-ecological change. This is particularly evident in the developing world, especially on the African continent, where existing vulnerabilities (i.e. endemic poverty, weak governance, overpopulation and HIV/AIDS) are being exacerbated by the impact of climate change. Climate change poses a very real threat to millions of Africans, especially those who rely on the natural world for their livelihoods. The increasing variability of climate and rainfall patterns are said to have dire consequences on agricultural production which is the main livelihood activity of rural dwellers across the continent. The impacts of such change and variability include, changes in the frequency and intensity of droughts, flooding and heavy storms, leading to worsening soil conditions, desertification as well as disease and pest out-breaks which will likely result in reduced crop and livestock yields. A reduction in agricultural production will likely have a negative effect on the food security of millions of people. This study was conducted in the Eastern Cape of South Africa, in two rural villages, Fairbairn and Ntloko located in the former Ciskei homeland, with the purpose of exploring the nexus between climate change, cultivation and food security. This study combined social-ecological thinking with that of political ecology to create a robust lens, in which to analyse the complex interactions between humans and the environment. A mixed methods approach was used to gather the data which consisted of a household survey, using a structured questionnaire as well as semi-structured interviews with various respondents. Quantitative data were analysed using Excel and Statistica 13, whilst coding was used for qualitative data. The main aim of the study was to explore the extent and characteristics of cultivation in the two study sites, the role of household food production in food security as well as the challenges that local cultivator’s face with regards to climate change. In recent decades, there has been a decline in rural agricultural production with many fields that were previously cultivated, lying vacant and unused. However, as this study found, cultivation is still important as over 50% of sampled households cultivated a small area within the homestead. This was mainly done to supplement household food expenditure in order to save cash incomes. The results also found that although participants had perceived negative changes in climate and rainfall (amount, onset, duration), it was not considered the most important challenge for own production. Rather, lack of fencing and capital were seen as major hindrances to efficient own production. Understanding the complexity of own production and food security under a changing climate can help form better and more resilient policies and strategies for rural development, in addition to strengthening future livelihoods of rural people in an ever changing world.

Wild foods are an integral component of the household food basket, yet their quantified contribution to food security relative to other sources in the context of HIV/AIDS, climate change and variability remains underexplored. This study was carried out in Willowvale and Lesseyton which are rural communities in the Eastern Cape province of South Africa. Willowvale is a relatively remote, medium-rainfall coastal community, while Lesseyton is a peri-urban low rainfall inland community. Qualitative and quantitative methods were used to collect data from 78 HIV/AIDS afflicted households with 329 individuals and 87 non-afflicted households with 365 individuals in the two study sites. Households were visited quarterly over 12 months to assess food acquisition methods, dietary intake and quality, and levels of food security, and to determine strategies employed by households to cope with droughts. The wild foods investigated were wild meat, wild birds, wild fish, wild mushrooms, wild leafy vegetables and wild fruits. Diets were moderately well-balanced and limited in variety, with cereal items contributing 52 % to total calorie intake. Mid-upper arm circumference measurements showed that all respondents were adequately nourished. The bulk of the food consumed by households was purchased, with supplementation from own production, wild vegetables and wild fruits. In Willowvale, wild vegetables comprised 46 % of overall vegetable consumption for afflicted households and 32 % for non-afflicted households, while own fruit production comprised 100 % of fruit consumption. In Lesseyton, wild vegetables comprised only 6 % and 4 % of vegetable consumption for afflicted and non-afflicted households, while wild fruit comprised 63 % and 41 % for afflicted and non-afflicted households. More than 80 % of respondents from both afflicted and non-afflicted households had sufficient daily kilocalories, although the majority of afflicted households felt they were food insecure and sometimes collected wild foods as one of their multiple coping strategies. Hunting and gathering of wild foods was associated with site, household affliction status, gender, age and season. More than 80 % of respondents ate wild vegetables and said they were more drought tolerant than conventional vegetables, making them the most consumed wild food and approximately 16 % of respondents ate wild birds, making them the least consumed wild food. Approximately 14 % of respondents from afflicted households in Willowvale sold wild fish, whilst 34 % of respondents from afflicted households and 7 % from non-afflicted households sold wild fruits in Lesseyton. Strategies adopted by households to cope with droughts were different between the two study sites, and households in Willowvale used a wider range of strategies. Given the devastating effects of HIV/AIDS coupled with the drawbacks of climate change and variability on food security, wild foods represent a free and easy way for vulnerable households to obtain food.

How should the impact of HIV and AIDS on rural livelihoods be factored into efforts to monitor and stabilise household food security? With both HIV and AIDS and food security at the top of the global development agenda, this is a question posed by many scholars, practitioners, donor agencies and government departments. However, while there is an excess of discourse outlining the theoretical bases for how HIV and AIDS can, and is, radically transforming household food acquisition; there is a lack of empirical evidence from the South African context that demonstrates if, and how, HIV and AIDS changes household-level strategies of food acquisition and intake. This thesis explores the association of household-level mortality, chronic illness and additional child-dependent fostering with household experience of food security and food acquisition strategies, in three rural villages in the Eastern Cape and KwaZulu-Natal Provinces of South Africa. Qualitative and quantitative methods of data-collection were applied to 307 households in the three sites. For twelve months, both HIV and AIDS-afflicted and non-afflicted households were repeatedly visited at 3-month intervals, in order to be assessed for levels of food security, dietary intake and method of food procurement (purchased, cultivated, wild or donated). Overall, HIV and AIDS-afflicted households showed a significantly higher experience of food insecurity, probably attributable to shortages in food quantity. Dietary composition and overall diversity, however, was not significantly different. Although households with chronic illness and recent mortality showed a heightened investment in cultivation sources, the success of these strategies were to a great extent mediated by household income, and the level of medical treatment received by those who were chronically ill. Chronic illness was also associated with more donations, but these required considerable investments in social capital networks. Finally, use of wild leafy vegetables was not associated with household HIV and AIDS status, despite the financial, nutritional and labour-saving properties of these foods. Overall, the study suggests that there was little evidence of long-term planning and strategy in household food security responses. There was no evidence for shifts to labour-saving crops or foods and, in some instances, child labour was being used to ameliorate prime-adult labour deficits. Moreover, given that the vast majority (89.2%) of food groups were sourced through purchase, it is questionable whether investing in diverse food acquisition strategies would be advisable. Unless supported by medical treatment and steady earned household income, policies to promote intensified household agricultural subsistence production in the wake of HIV and AIDS are unlikely to provide households with anything more than short-term safety-nets, rather than long-term, sustainable food security solutions.