Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A study of the sustainability journey of Spier Holdings, a well known wine and leisure business in South Africa, offers a unique opportunity for interrogating corporate drivers for a lower carbon future. The business has established sustainability as a brand identity, declared carbon neutrality as a macro organisational goal in response to the global challenge of climate change, and sought scientifically and technologically appropriate ways of addressing this challenge. A preliminary analysis revealed various initiatives that are in place for measuring and reducing the business’ environmental impact, including carbon emissions. However, an in-depth study of the establishment’s environmental performance over two decades showed inconsistencies in year-on-year reporting, delays in shifting the supply chain, and gaps in implementation, particularly in the area of energy efficiency and adoption of renewable energy technology. Understanding and interrogating the business’ sustainability journey through a systems ecology and corporate citizenship framework proved inadequate. The case highlights that organizational goals for environmental performance areas, including the aim of carbon neutrality, and sustainability reporting are not sufficient catalysts for change. A complexity-based resilience approach allowed the business to be understood as an adaptive system. The sustainability story tracks different phases of a modified adaptive renewal cycle, which also determine the dominant management paradigms, strategic responses and forms of collaboration during each phase. Spier’s sustainability journey was found to be underpinned by a quest for corporate resilience which includes the resilience of the business (enterprise resilience) and of the social-ecological system within which it resides (SES resilience). The business responded to interdependent risks and uncertainties in its internal and external contexts, through investment strategies in key areas of corporate environmental performance. As a contribution to new knowledge, this thesis proposes an integrated corporate resilience framework for building enterprise resilience and ecological sustainability. This framework, and the accompanying mapping tool, reveals deep, ecological drivers for Spier’s environmental performance across corporate areas of lower carbon emissions, water sustainability, wastewater treatment, solid waste recycling and ecological custodianship. The framework is recommended for use by similar businesses, eager to configure their relationship with natural resources and ecosystem services, and by scholars, for investigating corporate performance towards environmental sustainability. / AFRIKAANSE OPSOMMING: ʼn Studie van die volhoubaarheidsonderneming van Spier Holdings, ʼn bekende wyn- en ontspanningsaak in Suid-Afrika, bied ʼn unieke geleentheid vir die ondersoek van korporatiewe aandrywers vir ʼn laer koolstoftoekoms. Die onderneming het volhoubaarheid as ʼn handelsmerkidentiteit gevestig, koolstof-neutraliteit as ʼn makro- organisatoriese doel verklaar in reaksie op die wêreldwye uitdaging van klimaatsverandering, en het wetenskaplik en tegnologies gepaste wyses gesoek om hierdie uitdaging die hoof te bied. ʼn Voorlopige analise het verskeie inisiatiewe wat gereed is vir meting en vermindering van die onderneming se omgewingsimpak aan die lig gebring, met inbegrip van koolstofvrystellings. ʼn Dieptestudie van die instelling se omgewingsprestasie oor twee dekades heen het egter inkonsekwenthede in jaar-tot-jaar-verslagdoening, vertragings in die verandering van die aanvoerketting, en gapings in implementering, in die besonder op die gebied van energiedoeltreffendheid en die ingebruikneming van hernubare energietegnologie getoon. Begrip en ondersoek van die onderneming se volhoubaarheidsonderneming aan die hand van ʼn raamwerk vir sisteemekologie en korporatiewe burgerskap het onvoldoende blyk te wees. Die geval beklemtoon dat organisatoriese doelstellings vir omgewingsprestasiegebiede, met inbegrip van die oogmerk van koolstofneutraliteit, en volhoubaarheidsverslagdoening nie voldoende katalisators vir verandering is nie. ʼn Kompleksiteitgebaseerde veerkragtigheidsbenadering het dit moontlik gemaak dat die onderneming as ʼn aanpassingstelsel beskou kan word. Die volhoubaarheidsverslag gaan verskillende fases van ʼn gewysigde aanpassings- hernuwingsiklus, wat ook die dominante bestuursparadigmas, strategiese reaksies en vorme van samewerking gedurende elke fase bepaal, na. Daar is bevind dat Spier se volhoubaarheidsonderneming onderstut word deur ʼn soeke na korporatiewe veerkragtigheid wat die veerkragtigheid van die onderneming (ondernemingsveerkragtigheid) en van die sosiaal-ekologiese stelsel waarbinne dit gesetel is (SES-veerkragtigheid) insluit. Die onderneming het op onderling afhanklike risiko’s en onsekerhede in sy interne en eksterne samehange gereageer deur beleggingstrategieë in sleutelgebiede van korporatiewe omgewingsprestasie. As ʼn bydrae tot nuwe kennis, doen hierdie tesis ʼn geïntegreerde korporatiewe veerkragtigheidsraamwerk vir die opbou van ondernemingsveerkragtigheid en ekologiese volhoubaarheid aan die hand. Hierdie raamwerk, en die gepaardgaande beskrywingsinstrument, lê diep, ekologiese aandrywers vir Spier se omgewingsprestasie oor korporatiewe gebiede van laer koolstof-vrystellings, watervolhoubaarheid, die behandeling van afloopwater, herbenutting van vaste afval en ekologiese bewaring bloot. Die raamwerk word aanbeveel vir gebruik deur soortgelyke ondernemings wat graag aan hulle verhouding met natuurlike hulpbronne en ekostelseldienste vorm wil gee, en deur vakkundiges vir die ondersoek van korporatiewe prestasie met betrekking tot omgewings-volhoubaarheid.

<p>The present study is one of the first attempts to analyze the societal importance of seagrasses (marine flowering plants) from a Natural Resource Management perspective, using a social-ecological systems (SES) approach. The interdisciplinary study takes place in East Africa (Western Indian Ocean, WIO) and includes in-depth studies in Chwaka Bay, Zanzibar, Tanzania. Natural and social sciences methods were used. The results are presented in six articles, showing that seagrass ecosystems are rich in seagrass species (13) and form an important part of the SES within the tropical seascape of the WIO. Seagrasses provide livelihoods opportunities and basic animal protein, in from of seagrass associated fish e.g. Siganidae and Scaridae. Research, management and education initiatives are, however, nearly non-existent. In Chwaka Bay, the goods and ecosystem services associated with the meadows and also appreciated by locals were fishing and collection grounds as well as substrate for seaweed cultivation. Seagrasses are used as medicines and fertilizers and associated with different beliefs and values. Dema (basket trap) fishery showed clear links to seagrass beds and provided the highest gross income per capita of all economic activities. All showing that the meadows provide social-ecological resilience. Drag-net fishery seems to damage the meadows. Two ecological studies show that artisanal seaweed farming of red algae, mainly done by women and pictured as sustainable in the WIO, has a thinning effect on seagrass beds, reduces associated macrofauna, affects sediments, changes fish catch composition and reduces diversity. Furthermore, it has a negative effect on i.a. women’s health. The two last papers are institutional analyses of the human-seagrass relationship. A broad approach was used to analyze regulative, normative and cultural-cognitive institutions. Cooperation and conflict take place between different institutions, interacting with their slow or fast moving characteristics, and are thus fundamental in directing the system into sustainable/unsustainable paths. Ecological knowledge was heterogeneous and situated. Due to the abundance of resources and high internal control, the SES seems to be entangled in a rigidity trap with the risk of falling into a poverty trap. Regulations were found insufficient to understand SES dynamics. “Well” designed organizational structures for management were found insufficient for “good” institutional performance. The dynamics between individuals embedded in different social and cultural structures showed to be crucial. Bwana Dikos, monitoring officials, placed in villages or landing sites in Zanzibar experienced four dilemmas – kinship, loyalty, poverty and control – which decrease efficiency and affect resilience. Mismatches between institutions themselves, and between institutions and cognitive capacities were identified. Some important practical implications are the need to include seagrass meadows in management and educational plans, addressing a seascape perspective, livelihood diversification, subsistence value, impacts, social-ecological resilience, and a broad institutional approach.</p>

Small-scale fisheries employ many millions of people around the world, and are particularly important in developing countries, where the dependency on marine resources is high and livelihood diversification options are scarce. In many areas of the world however, small-scale fisheries are at risk which threatens the food security and wellbeing of coastal people. Small-scale fisheries management has in many cases been insufficient and new comprehensive approaches are recommended to achieve social-ecological sustainability in the long-term. The aim of this thesis is to analyze empirically how social-ecological elements of seagrass-associated small-scale fisheries in the Western Indian Ocean region can be addressed for a transformation from the current mostly degraded state to more sustainable social-ecological systems and secure future livelihoods. The main method used was semi-structured interviews with local fishers. The main findings show the crucial contributions seagrass-associated small-scale fisheries make to food security and income generation and highlight the need to acknowledge the social-ecological importance of seagrasses in the seascape (Paper I). A discrepancy between low societal gains of the fishing of sea urchin predator fish species and their crucial importance in the food web (in controlling sea urchin populations and the associated grazing pressure on seagrasses) was identified (Paper II). These results suggest catch-and-release practice of sea urchin predator fish species, which could contribute to more balanced predator – sea urchin – seagrass food webs in the long run. The use of illegal dragnets was identified as a major threat to local seagrass meadows (Paper IV). Institutional elements influencing the use of such destructive dragnet were identified to be normative, cultural-cognitive and economic, which constitutes an institutional misfit to the current emphasis on regulative elements in a hierarchical manner (Paper III). Concerning future co-management initiatives, gear restrictions and education were the favoured management measures among all fishers (Paper IV). A majority of fishers were willing to participate in monitoring and controls, and most fishers thought they themselves and their communities would benefit most from seagrass-specific management. These findings highlight the need for actions on multiple scales, being the local-, management-, policy- and governance levels. The suggested actions include: education and exchange of ecological and scientific knowledge, gear management including the cessation of dragnet fishing, strengthening of local institutions, an active participation of fishers in enforcement of existing rules and regulations and an introduction of adequate alternative livelihood options. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.</p>

O presente trabalho buscou reproduzir, a partir de simulação computacional utilizando modelagem baseada em agentes, a dinâmica do sistema sócio-ecológico que conecta comunidades quilombolas do Vale do Ribeira, São Paulo, ao palmito jussara (Euterpe edulis Martius), espécie considerada ameaçada de extinção e cuja exploração, atualmente, pode ser descrita como uma Tragédia dos Comuns. Com base na teoria acumulada de recursos comuns, em dados empíricos do sistema social quilombola e na dinâmica populacional do palmito, simulamos o impacto de duas políticas públicas distintas de gestão do recurso: a primeira é a proibição estatal de exploração do mesmo, que criminaliza os palmiteiros e não está surtindo os efeitos desejados de preservação; a segunda, projeta um cenário hipotético no qual o Estado flexibiliza as regras de exploração e permite que a comunidade gerencie o recurso. Ao comparar o estoque final de palmito jussara para diversos cenários, concluimos que existe um grande potencial para que a gestão comunitária do recurso traga benefícios econômicos às famílias quilombolas, ao mesmo tempo em que contribui para a preservação do mesmo na natureza. / This study intended to use agent-based modeling to reproduce the dynamics of the social-ecological system that connects the quilombola communities that live in the Ribeira Valley, São Paulo, to the palm tree Euterpe edulis Martius, an endangered species highly valued for its heart of palm, which has being heavily harvested and can be considered an example of a Tragedy of the Commons. Based on the theory on common-pool resources, empirical data regarding the quilombola social system and on the palm tree population dynamics, we simulate the impact of two different public policies towards the palm tree conservation: the first scenario is the current total-prohibition of extraction policy, which marginalize harvesters and is not working prom an environmental perspective; the second scenario simulates a hypothetical situation in which allows the community to explore and manage the resource. After comparing the final stock of Euterpe edulis for many conditions, we may conclude that there is a great possibility that community-level management is more able to bring economic benefits to the quilombola families, while also help to preserve the species.

O deslocamento populacional forçado é um dos principais impactos de grandes projetos de infraestrutura, sendo grandes barragens um dos principais projetos responsáveis por esse tipo de movimento populacional. Estima-se que, até o final do século XX entre 40 e 80 milhões de pessoas haviam sido deslocadas por grandes barragens. O planejamento e a construção de empreendimentos hidrelétricos encontram-se em expansão tanto em nível mundial como especificamente no Brasil, país cujo investimento em geração hidrelétrica é estratégico e prioritário. Essa tendência sugere que o número de pessoas deslocadas por grandes barragens deva crescer nas próximas décadas, apresentando à sociedade os desafios intrínsecos do deslocamento populacional compulsório. Populações deslocadas por grandes barragens passam pelo estresse do deslocamento geográfico e pelos impactos ambientais decorrentes do próprio barramento, estresses que se sobrepõem no tempo e no espaço. Avaliar como esses estresses influenciam os modos de vida de comunidades deslocadas pode ajudar a entender os resultados do deslocamento compulsório e a desenhar medidas de gestão para o deslocamento. O objetivo geral desta pesquisa é compreender como os modos de vida de populações reassentadas em função da instalação de usinas são alterados em processos de deslocamento populacional, considerando as relações socioecológicas. Adotou-se como estudo de caso as usinas hidrelétricas do rio Madeira, Santo Antônio e Jirau. Foram levantados dados secundários e realizadas entrevistas em campo com reassentados e com autoridades, a partir das quais foram organizados dados quantitativos e qualitativos em uma abordagem metodológica mista. Como principais resultados, foi verificada a existência de cinco tendências de adaptação de modos de vida das pessoas deslocadas: (i) a valorização de atividades menos dependentes de ativos naturais em detrimento de atividades diretamente relacionadas a ecossistemas; (ii) a adoção de técnicas de controle de ecossistemas; (iii) a diminuição na diversidade do repertório de modos de vida; (iv) o direcionamento da produção para o mercado e (v) a inserção dos modos de vida em institucionalidades formais. Em conjunto, essas foram associadas a riscos como desarticulação social, aumento do risco à soberania alimentar, diminuição do acesso a recursos livres e diminuição do risco de perda de emprego. A partir desses resultados, recomenda-se medidas de gestão que considerem a interação socioecológica e a perspectiva de locais no processo de deslocamento populacional forçado. / Forced populational displacement is one of the major impacts of large infrastructure projects. Large dams are amongst the main projects that cause such displacement. It is estimated that by the end of the 20th century between 40 and 80 million people were displaced by large dams. The planning and construction of hydroelectric projects are expanding both globally and in Brazil, a country whose investment in hydroelectric generation is strategic and have being prioritized. Such trend suggests that the number of people displaced by large dams should grow in the next decades, making society face the inherent challenges of compulsory population displacement. People displaced by large dams go through the stress of geographic displacement and the stress of environmental impacts caused by the dam itself. These stresses overlap in time and space. Assessing how these stresses influence the livelihoods of displaced communities can help to understand the results of compulsory displacement and to design management measures for displacement. The goal of this research is to understand how the livelihoods of populations resettled due to the installation of hydropower plants are altered in processes of population displacement, considering socioecological relations. The hydroelectric plants of the Madeira river, Santo Antônio and Jirau, were adopted as a case study. Secondary data were collected, and field interviews were conducted with resettled people and with authorities. Quantitative and qualitative data were organized in a mixed methodological approach. As results, were identified five adaptive trends in the livelihoods of displaced people: (i) to value activities that are less dependent on natural assets at the expense of activities directly related to ecosystems; (ii) the adoption of techniques to control ecosystems; (iii) the decrease in the diversity of livelihoods repertoire; (iv) the orientation of production to cash crops to sell in the market and (v) the insertion of ways of life into formal institutions. Together, these trends were associated with risks such as social disarticulation, increased risk to food sovereignty, reduced access to common resources and reduced risk of joblessness. From these results, are recommended management measures that consider socioecological interaction and locals perspective in the process of forced displacement.

Les zones côtières à travers le monde sont soumises à de fortes pressions dues aux changements climatiques globaux, à la destruction d'habitats ou encore à la surexploitation des ressources marines. Ces différentes pressions peuvent induire des changements rapides d'état des écosystèmes caractérisés par de fortes modifications de la biodiversité, avec des écosystèmes entiers cessant de fonctionner dans leur forme courante. En conséquence, la pérennité des biens et des services écosystémiques produits par les zones côtières n'est plus assurée. Il en résulte des perturbations économiques et sociales évidentes pour les populations dont le mode de vie dépend de manière directe ou indirecte de la biodiversité côtière. Afin d'appréhender ces interactions homme-environnement, l'approche socio-écologique est de plus en plus utilisée pour illustrer le rôle de l'Homme sur la dynamique des écosystèmes marins côtiers ainsi que les bénéfices qu'il tire de ces derniers. Cette thèse a pour objectif principal d'explorer les concepts de l'approche socio-écologique appliquée à la gestion côtière. Ainsi, dans le premier chapitre de cette thèse nous résumons les spécificités, les défis et les enjeux de l'approche socio-écologique appliquée à la gestion côtière. Les chapitres 2, 3 et 4 s'intéressent à l'analyse du système socio-écologique et explorent des scénarios exploratoires d'évolution des principaux services écosystémiques du lagon de Moorea en Polynésie française. Enfin, nous discutons des avantages et des faiblesses de notre approche ainsi que des potentiels d'applicabilité en tant qu'outil de gestion des zones côtières. / Coastal areas around the world are under intense pressures from climate change, habitat destruction, and over-exploitation of marine resources. These different pressures can induce rapid changes in the state of ecosystems characterized by strong changes in biodiversity, with whole ecosystems ceasing to function in their current form. As a result, the sustainability of goods and services produced by coastal areas is no longer assured. This results in economic and social disruptions for populations whose livelihood depends directly or indirectly on coastal biodiversity. In order to understand these linked social and environmental interactions, the socio-ecological approach is increasingly used to illustrate the role of humans in the dynamics of coastal marine ecosystems and the benefits it derives from them. However, the majority of current research remains theoretical and few case studies applied to the management of coastal areas test this concept in a transdisciplinary approach. The main objective of this thesis is to fill this gap by exploring the concepts of the socio-ecological approach applied to coastal management. Thus, in the first chapter of this thesis, we summarize the challenges insights and perspectives of the socio-ecological approach applied to coastal management. Chapters 2, 3 and 4 focus on the analysis of the coral reef resource system and explore the social-ecological trade-offs revealed by a set of multiple driver’s scenarios in order to explore the potential evolution of the main ecosystem services of Moorea island lagoon in French Polynesia.

O presente trabalho buscou reproduzir, a partir de simulação computacional utilizando modelagem baseada em agentes, a dinâmica do sistema sócio-ecológico que conecta comunidades quilombolas do Vale do Ribeira, São Paulo, ao palmito jussara (Euterpe edulis Martius), espécie considerada ameaçada de extinção e cuja exploração, atualmente, pode ser descrita como uma Tragédia dos Comuns. Com base na teoria acumulada de recursos comuns, em dados empíricos do sistema social quilombola e na dinâmica populacional do palmito, simulamos o impacto de duas políticas públicas distintas de gestão do recurso: a primeira é a proibição estatal de exploração do mesmo, que criminaliza os palmiteiros e não está surtindo os efeitos desejados de preservação; a segunda, projeta um cenário hipotético no qual o Estado flexibiliza as regras de exploração e permite que a comunidade gerencie o recurso. Ao comparar o estoque final de palmito jussara para diversos cenários, concluimos que existe um grande potencial para que a gestão comunitária do recurso traga benefícios econômicos às famílias quilombolas, ao mesmo tempo em que contribui para a preservação do mesmo na natureza. / This study intended to use agent-based modeling to reproduce the dynamics of the social-ecological system that connects the quilombola communities that live in the Ribeira Valley, São Paulo, to the palm tree Euterpe edulis Martius, an endangered species highly valued for its heart of palm, which has being heavily harvested and can be considered an example of a Tragedy of the Commons. Based on the theory on common-pool resources, empirical data regarding the quilombola social system and on the palm tree population dynamics, we simulate the impact of two different public policies towards the palm tree conservation: the first scenario is the current total-prohibition of extraction policy, which marginalize harvesters and is not working prom an environmental perspective; the second scenario simulates a hypothetical situation in which allows the community to explore and manage the resource. After comparing the final stock of Euterpe edulis for many conditions, we may conclude that there is a great possibility that community-level management is more able to bring economic benefits to the quilombola families, while also help to preserve the species.

Le changement climatique et les migrations humaines constituent deux problématiques majeures de notre époque. Et, partant du constat d’une connaissance fragmentée entre maximalistes et minimalistes, qui s’est traduite par une capacité limitée de la recherche scientifique à prendre en compte les interactions complexes entre le climat et les migrations humaines, cette thèse propose, à travers une approche renouvelée (celle de la vulnérabilité du système socio-écologique), une meilleure compréhension et explication des relations climat- migrations. Elle cherche à répondre à deux objectifs. D’une part, produire des connaissances nouvelles en nous appropriant de façon sélective et ordonnée les apports empiriques produits par les approches précédentes. Et, d’autre part, par une analyse instrumentée des interactions mises en évidence, générer des informations chiffrées pertinentes permettant un ciblage plus efficace des politiques. Cette thèse insiste en premier lieu sur une certaine difficulté à mettre en évidence une relation robuste entre changement climatique et migrations à l’échelle Sahélienne. Contrairement aux idées reçues sur l’image type du « migrant/réfugié climatique » sahélien véhiculée par les médias et reprise, sans un recul critique, dans la littérature grise et certaines études scientifiques, la région, souvent vue et analysée comme une entité relativement homogène, présente de fortes hétérogénéités spatiales physico-climatiques, outre celles socio-économiques. Et, ces dernières ne permettent pas une compréhension des migrations, une des expressions des transformations sociétales. Il convient de repenser la problématique sur des échelles plus homogènes (Sénégal des zones agro-écologiques et régions administratives)Nos résultats montrent un effet climatique accélérateur/amplificateur des migrations interrégionales sous-jacent aux conditions de vie des populations. Généralement, le climat ne suffit pas, à lui seul, à « produire » des migrations. Il transite par les variables socio-économiques (vulnérabilité initiale). Ce qui nous a amené à retenir l’appellation de «migrants éco-climatiques ». Ainsi, les politiques devraient aller à la fois vers : (i) des questions de développement en réduisant des vulnérabilités socio-économiques (pauvreté et inégalités) en agissant sur l’environnement d’action et les acteurs respectivement de manière cohérente et extensive ; mais, également, (ii) des questions d’économie du climat par la réduction de la vulnérabilité physico-climatique à travers des politiques d’atténuation et d’adaptation du milieu et des populations face au changement climatique. / Climate change and human migration are two major issues of our time. Starting from the observation of a dichotomous knowledge between maximalists and minimalists, which results in a limited capacity of scientific research to take into account the dynamic and complex interactions between climate and human migrations, this thesis proposes a better understanding and explanation of the climate-migration relations through a renewed and integrative approach (the vulnerability of the socio-ecological system). It aims to fulfill two objectives. On the one hand, to produce new knowledges those take into accounts socio-ecological interactions and feedbacks at different spatial and temporal scales and, on the other hand, to propose a quantified instrumentation of these social-ecological interactions and feedback. This contribution could serve as a starting point for a decision-making tool to evolve towards more targeted and effective policies.This thesis emphasizes a certain difficulty in highlighting a robust relationship between climate change and migration in the Sahel region. This latter, often seen as a relatively homogeneous entity, presents complex socio-economic and physical-climatic spatial heterogeneities that do not allow a stronger understanding of migratory movements which are in change since the 1970s. For this purpose, a reduced complexity model, based both on a partitioning of the study area (Senegal) and a partitioning of data (agro-ecological zones and regions of Senegal), is mobilized as a framework for the analysis of social-ecological migrations in terms of vulnerability induced by climate change. Thus, the innovative heuristic framework built (knowledge model with a sequencing of variables) has made it possible to instrument the climate-migration relationships within Senegal.Our results show an accelerating/amplifying climatic effect of interregional migrations underlying the living conditions of populations. In general, climate alone is not sufficient to "produce" migration. The climatic effects channel through the socio-economic variables (initial vulnerability). Under these results, we retained in fine the name of "eco-climatic migrants". Thus, policies relating to eco-climatic migration in this western part of the Sahel should move towards both: (i) development issues by reducing socio-economic vulnerabilities (poverty and inequality) by acting on the environment and the populations consistently and extensively respectively; and (ii) climate economics issues by reducing the physical-climatic vulnerability through appropriate mitigating and adapting policies to face climate change.

Les récifs coralliens hébergent la plus grande biodiversité sur Terre et fournissent la nourriture, le revenu économique, la protection côtière et les valeurs culturelles pour des millions de personnes. L'accessibilité des écosystèmes via les réseaux routiers est un déterminant majeur de leurs conditions, les écosystèmes les plus accessibles étant les plus menacées. Longtemps, l’estimation de l'accessibilité par l’Homme s’est limitée à l'utilisation de la distance linéaire qui ignore l’irrégularité des côtes maritimes et les réseaux routiers, facteurs influençant le temps nécessaire pour atteindre les lieux de pêche. Cette thèse présente un double enjeu : (i) développer des indices d'accessibilité intégrant l’hétérogénéité du milieu marin pour quantifier les impacts humains sur les récifs ; (ii) évaluer l'importance de ces nouveaux indices, en interaction avec les mesures de protection, pour expliquer les variations de la biomasse de poissons. Dans un premier temps, j’ai caractérisé la proximité des hommes aux récifs, en tenant compte des surfaces rencontrées (routes, chemin, eau) qui influencent le temps de trajet jusqu’aux récifs. Le temps de trajet a permis de calculer un indice de gravité, défini comme la population humaine divisée par le temps de trajet au carré, pour évaluer le niveau de pression humaine de n'importe quel récif au monde. J'ai trouvé que le temps de trajet et la gravité sont des déterminants majeurs de la biomasse de poissons à l’échelle globale. Dans un second temps, trois applications utilisant ces nouveaux indices ont permis de montrer que (i) la gravité permet de révéler l’efficacité des actions de conservation : les réserves placées là où les impacts humains sont modérés à forts fournissent des gains de conservation élevés pour la biomasse de poissons, mais elles sont peu susceptibles de protéger les prédateurs supérieurs, qui sont uniquement présent dans les réserves soumises à de faibles impacts humains ; (ii) en utilisant un cas d'étude réalisé dans le Nord-Ouest de Madagascar, j'ai illustré comment la proximité du marché peut affecter les communautés de pêcheurs et, finalement, engendrer des changements dans l'exploitation des ressources marines ; (iii) j’ai développé une nouvelle approche, le Community-Wide Scan (CWS), pour identifier les espèces de poissons qui contribuent de manière significative à la biomasse et à la couverture corallienne des récifs de l’Indopacifique, celles-ci pouvant constituer des espèces cibles à protéger. Dans le contexte de changements globaux et de perte de biodiversité, la mesure d’accessibilité constitue un outil puissant et permet de relancer le défi de gestion durable et efficace des socio-écosystèmes coralliens. / Coral reefs have the greatest biodiversity of any ecosystem on the planet and support ecosystem goods and services to million people who depend directly on them for food, economic income, coastal protection and cultural values. Ecosystem accessibility, through road networks, is the main driver of their conditions, with the most accessible ecosystems being most at risk of resource depletion. To date, measuring accessibility to humans was strictly limited to examining the linear distance which ignores ragged coastlines and road networks that can affect the time required to reach fishing grounds. This thesis presents a double challenge: (i) developing new metrics of accessibility that account for seascape heterogeneity to better assess human impacts on coral reefs; (ii) evaluating the importance of coral reef accessibility, in interactions with their management, to explain variations of fish biomass. First, I developed novel metrics of reef proximity to human populations and markets based on the friction distance which is related to transport surfaces (paved road, dirt road, water) influencing the effective reach of human settlements. Travel time was used to build the gravity index, defined as human population divided by the squared travel time, to assess the level of human pressure on any reef of the world. I found that both travel time and gravity are strong predictors of fish biomass globally. Second, three applications using these new metrics highlighted that (i) gravity identified critical ecological trade-offs in conservation since reserves placed with moderate-to-high impacts may provide substantial conservation gains for fish biomass while reserve locations with low human impacts were more likely to support higher-order predation, (ii) using a study case in Northwest Madagascar, I illustrated how market proximity can affect fishermen communities and, ultimately, trigger changes in marine resources exploitation, and (iii) I implemented a new Community-Wide Scan (CWS) approach to identify fish species that significantly contribute to the biomass and coral cover on Indo-Pacific reefs and which provided tractable conservation targets. Within the context of global changes and biodiversity loss, the thesis challenges the sustainable and efficient management of coral reef socio-ecological systems with accessibility being the cornerstone.

The prevalence of childhood overweight and obesity is increasing at an alarming rate in the United States. Currently more than 1 in 3 children aged 2-19 are overweight or obese. This is of major concern because childhood overweight and obesity leads to chronic conditions such as type II diabetes and tracks into adulthood, where more severe adverse health outcomes arise. In this study I used the premise of the social ecological model (SEM) to analyze the common levels that a child is exposed to daily; the intrapersonal level, the interpersonal level, the school level, and the community level to better understand what risk factors are significantly associated with child weight status. Data came from the 2012 National Survey of Children's Health (NSCH) (n=41,361). Frequencies and confidence intervals were used to describe risk factors at each level. Bivariate analyses were conducted between each risk factor and the outcome variable. Using all risk factors that were significantly associated with overweight and obesity in the bivariate analyses, multinomial logistic regressions were performed for each SEM level. The 4 SEM levels were then analyzed together using stagewise multinomial logistic regression. A significance level cutoff of 0.05 was applied to all analyses. Thirty-three percent of participants were overweight or obese. Child sex, race, age, child physical activity participation, mother’s education and health, the child’s family structure, the child’s participation in extracurricular activities, frequency of family meals at home, safety and engagement in school, the number of amenities and the safety and support within their communities were found to be significantly associated with child weight status. The odds ratios of the covariates in the final stagewise model were similar to those in each individual model. Understanding both the risk factors associated with child overweight and obesity in each individual level and in the complete socio-ecological perspective is important when working toward more effective policy and program creation and the reduction of childhood obesity. Recognizing that all levels of a child's SEM influence his or her likelihood of being overweight or obese can lead to more effective strategies that tackle multiple SEM levels collectively instead of each level independently.