La gestion des crises volcaniques constitue un sujet d'étude marginal, tous les domaines de recherche confondus. La complexité des phénomènes volcaniques (aléas multiples, incertitudes des prévisions), l'absence de cadre conceptuel et méthodologique établi pour l'étude des crises, les opportunités réduites de vivre des crises volcaniques, et la focalisation des chercheurs en sciences de la Terre sur l'aléa sont autant de raisons qui expliquent ce manque d'engagement. Cette thèse a pour objectif de combler partiellement ces lacunes en capitalisant des analyses sur les modes de gestion des crises. Elle propose ainsi des RETours d'Expérience sur la gestion de crises éruptives survenues en mai 2006 au Karthala (Grande Comore), et en avril 2007 au Piton de la Fournaise (La Réunion). S'y ajoute un RETEX sur la gestion des lahars consécutifs aux éruptions explosives de 2005 en Grande Comore. Ces cas d'étude reposent sur le vécu direct des crises analysées, puis sur un travail d'enquête auprès des autorités, scientifiques, médias et populations. Ils mettent entre autres en évidence un manque caractérisé de moyens, d'information et de formation de l'ensemble des acteurs sur les deux îles. Les causes profondes des facteurs de dysfonctionnement sont ensuite recherchées. L'analyse révèle le poids des composantes humaines, culturelles, politiques, socioéconomiques et territoriales dans les réponses apportées face aux crises. Enfin, cette thèse propose des outils et des approches pour améliorer la gestion des crises sur les deux îles. / Volcanic crisis management is a marginal study subject, whatever the research field. The complex nature of volcanic phenomena (multiple hazards, uncertainty of forecast), the lack of conceptual and methodological frameworks to study such crises, the reduced opportunities of experiencing volcanic crises, and the fact that Earth scientists focus on the hazard are all the reasons behind this lack of commitment. The objective of this thesis is to make up for some of these shortcomings by building up information on ways to manage crises. It provides post-crisis analysis about the management of the eruptive crisis of May 2006 at Karthala volcano (Grande Comore), and of April 2007 at the Piton de la Fournaise (La Reunion island). It also contains another analysis about the management of lahars subsequent to the explosive eruptions in 2005 in Grande Comore. These study case on personal experiences of analysed crises, then on investigations undertaken with local authorities, scientist, media and population. They highlight, amongst other things, a blatant lack of resources, information and training of all agents on both islands. The cause for such dysfunctioning factors are looked into. The analysis reveals the importance of human, cultural, political, socioeconomic, and territorial components in responding to crises. Finally, this thesis suggests tools and approaches to improve crisis management on both islands.

Tropical small-scale fisheries represent the main livelihood and protein source for a substantial portion of the global population. Growing pressures on marine resources, however, have left many fishing communities faced with declining catches and increased environmental degradation. Effective management strategies and governance institutions are thus critically important. Conventional top-down, exogenous approaches to fisheries management have been ineffective in more traditional and small-scale fisheries. Yet, there remains little understanding of the effectiveness of alternative approaches and few studies offer feasible solutions for managers in lesser developed nations. This case-study of artisanal fisheries in the Comoros examines how effective local fishing associations are at managing common fisheries resources, and provides some understanding of the underlying characteristics of effectiveness. To do so, qualitative methods were used to collect data on fishing practices, local knowledge and beliefs, governance structures, and livelihoods in male and female fisheries in five villages on Ngazidja island. The results of this study are organized into three papers. The first paper focuses on current fisheries trends on Ngazidja and the implications of the gradual shift from traditional to modern fishing practices. This paper contributes to the overall goal of this study as the modernization of the fishing sector may affect both the ecological sustainability of the fishery and the ability of local fishing associations to effectively govern fisheries. Results show that although the fishery sector is not undergoing a rapid modernization, loss in traditional practices, beliefs, and values are occurring and may be linked to corresponding declines in marine resources. Improved monitoring systems will help inform local governing institutions about the need to develop enhanced management practices. The second paper examines the effectiveness of community-based governance of artisanal fisheries and addresses the overarching goal of the study by improving understanding of the key elements of success of the community fishing associations. These fishing associations collectively design, monitor, and enforce local regulations. Decisions are based on local knowledge and experience, and management strategies are based on low-cost, practical solutions. Compliance with local regulations is high, primarily due to participatory decision-making, community-monitoring, and strong feelings of solidarity among fishers. The last paper looks at fisherwomen on Ngazidja and focuses specifically on documenting their fishing practices, livelihood contributions, and potential participation in fisheries management. This paper is critical to enhancing understanding of the impacts and potential of the fishery on Ngazidja as the sector has so far failed to take into account all marine harvesting activities, particularly those undertaken by women. Moreover, authorities have recently attempted to ban women from fishing as their practices are considered destructive to near-shore reefs and juvenile fish populations. Results from the study indicate that women’s fishing methods can be destructive and may have contributed to localized declines in intertidal marine resources and habitats. Yet, fisherwomen also provide substantial contributions to household livelihoods. Thus, banning the fishery altogether is not an acceptable solution. Instead, authorities should work to empower fisherwomen with the tools necessary to manage their fishery sustainably, which will eventually lead to improved conservation measures. Overall, this case-study provides a unique example of how collective governance of common-pool resources can be achieved within communities, and how feelings of empowerment and shared responsibility among users can lead to effective management practices. There are a number of clear lessons learned from the successes of this fishery that can be applied to other similar small-scale fisheries. Future research priorities should concentrate on assessing the ecological sustainability of current fishing and management practices, and paying particular attention to the recognition and inclusion of fisherwomen. Marine conservation and sustainable fisheries systems are only facilitated when all users are recognized and engaged in management and policy decisions. / Graduate

La question de la migration des Grands Comoriens trouve sa justification dans la quête d'amasser de l'argent pour réaliser le grand mariage, étape nécessaire à la reconnaissance de l'individu dans la hiérarchie sociale. L'étude se propose de suivre l'itinéraire des premiers migrants Comoriens , les fameux navigateurs de la compagnie des Messageries Maritimes, depuis l'île de Madagascar dans les années quarante jusqu'en France, ensuite de voir leurs conditions d'installation dans la ville de Marseille avant de se pencher sur la contribution de la diaspora au développement économique et social de la Grande Comore. La présence des Grands Comoriens à Marseille depuis les années quarante s'est accrue au fil du temps. Ils sont devenus au bout de trois décennies la plus importante communauté noire africaine dans la cité phocéenne et marquent discrètement leur territoire de leur identité et particularismes. Très fortement liés à son île, la diaspora de la Grande Comore est devenue, grâce à l’apport matériel et financier qu’elle transfère, un acteur incontournable pour le développement de celle ci (25% du PIB, apport plus important que l’aide extérieur au développement). Mais le spectre d’une grave crise rode, car rien ne garantit que les nouvelles générations vont maintenir les transferts parce qu’elles sont préoccupées davantage par leur intégration dans la société française que par des considérations villageoises. / The issue of Grande Comore diaspora is closely linked to the need to raise money for the big wedding, necessary step for the recognition of the individual in his society. The research proposes to approach the topic by following the itinerary of the first comorian migrants, the famous navigators in the Messageries Maritimes company, from Madagascar to France in the forties, then show the conditions of installation in the city of Marseille, and then analyze their contribution to the economic and social development of their country of origin. The presence of Grand Comorians in Marseille which began in the late forties, has intensified over the years. They became, over three decades, the largest black african community in Marseille and are emerging slowly with their identity and particularisms. Strongly attached to their island , Grande Comore diaspora has become an indispensable actor thanks to the financial and material contribution it brings today for the development of the island(25% GDP, more important than foreign aid to development). But the specter of a deep crisis threatens the Comoros: nothing garantees the continuity of transfers by new generations more concerned with their integration in France and less affected by village solidarity.

La gestion des crises volcaniques constitue un sujet d'étude marginal, tous domaines de recherche confondus. La complexité des phénomènes volcaniques (aléas multiples, incertitude des prévisions), l'absence de cadre conceptuel et méthodologique établi pour l'étude des crises, les opportunités réduites de vivre des crises volcaniques, et la focalisation des chercheurs en sciences de la Terre sur l'aléa sont autant de raisons qui expliquent ce manque d'engagement. Cette thèse a pour objectif de combler partiellement ces lacunes en capitalisant des analyses sur les modes de gestion des crises. Elle propose ainsi des RETours d'EXpérience sur la gestion de crises éruptives survenues en mai 2006 au Karthala (Grande Comore), et en avril 2007 au Piton de la Fournaise (La Réunion). S'y ajoute un RETEX sur la gestion des lahars consécutifs aux éruptions explosives de 2005 en Grande Comore. Ces cas d'étude reposent sur le vécu direct des crises analysées, puis sur un travail d'enquête auprès des autorités, scientifiques, médias et populations. Ils mettent entre autres en évidence un manque caractérisé de moyens, d'information et de formation de l'ensemble des acteurs sur les deux îles. Les causes profondes des facteurs de dysfonctionnement sont ensuite recherchées. L'analyse révèle le poids des composantes humaines, culturelles, politiques, socioéconomiques et territoriales dans les réponses apportées face aux crises. Enfin, cette thèse propose des outils et des approches pour améliorer la gestion des crises sur les deux îles.

Cette thèse étudie du trafic des esclaves au départ de l’Afrique orientale (Mozambique) vers les Comores où des planteurs étrangers venaient les acheter comme engagés libres. Le sultanat de Saïd Ali né en 1883, a bénéficié de la protection de de la France en 1886. Malgré ce protectorat, l’esclavage n’est aboli qu’en 1904. Pour maintenir la main-d’œuvre coloniale, l’État protecteur a retardé cette abolition. Face aux hésitations, le sultanat est rattaché à Magascar en 1908, le sultan abdique en 1910, avant que la Grande Comore devienne colonie française en 1912. / This Thesis studies the slaves trade starting from East Africa to Comoros where foreign growers came to buy them as free Endentured servant. The Sultanat of Saïd Ali born in 1883 benefited of French protection in 1886. Even thought this protectorate, the slavery is abolished in 1904. To maintain the colonialworkforce, The Protecting State has delayed this abolition. In front of theses hesitations, the Sultan is attached to Madagascar in 1908, the sultan abdicated in 1910, before that the Great Comoro become a French colony in 1912.