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The "Global warming scenario" is an hypothesis derived from theoretical models, it points out to conclusions that have not yet been proven. There are numerous inconsistencies between the predictions made and the observed climatic facts, thus invalidating the global thermal curve in term of climatic significance. For one case, the study of the North Atlantic aerological unit shows that climatic change is not global, but regional: indeed, the Western side is cooling while the Northeast's is warming. One of the reason is that the 1970's brought a fundamental climatic turn not "seen" by the models, with a gradual increase of violent perturbations and of the irregularity of the weather pattern (rapid mode of the general circulation)

This study seeks to explain the mechanisms presiding at the ligneous cover mutations in Northern Cameroon. A rather harsh climate and difficult economic conditions endow the tress with a special place into the survival process. Standing, they maintain and protect the soils, out down, they provide goods of great value (wood products, wood fuel, etc.). Therefore, the ligneous cover mutations result from a fragile equation between the imperious need to profit and the will to preserve in the long run the earth resources. The equilibrium totally depends on a combination of highly interactive elements such as agriculture and wood fuel exploitation, soil and subsoil quality, climate, demographic evolution, as well as on economic, psychological, sociological and cultural reasons. All these lead to a complex and perpetually changing System whose understanding is essential to explain ligneous cover mutations. Its study leads to the relativization of the causal relationships between the population high densities and the clearing phenomenon, butalso reveals the importance of both the agricultural techniques (in constant evolution) and the living conditions in regard to the ligneous cover mutations. On a more general level, since all the elements taking part in the process don't have on a temporal basis the same effect on the tree-system, any prediction on the future of the ligneous cover mutations is uncertain.

According to the «Ivorian Survey on Urbanization and Migrations», between 1988 and 1993 out-migration from cities to villages was responsible for a lost in the urban population. What could be more surprising in a country known otherwise for its extraordinary rapid urban growth? As this paper demonstrates, this phenomenon does not result from bad measurements, but from ancient migratory flow which, until today, has been concealed by « rural exodus » and urban growth obsessions. Available data indeed show that since the beginning ofthe sixties this flow has regularly grown, until it became predominant in the urban-rural exchanges in 1983-1984. In fact, the economic recession, whose traces were already perceptible at the beginning of the eighties, has created a new deal, adding to classical return migrants (heirs, retirees, widows, etc.) new types of urban-rural migrants: the jobless from the modem economic sectors, youths excluded from school and unable to find a job in the cities, children fostered in villages so as to reduce the cost of living in urban settings, etc.). Urban-rural migrants do not constitute an homogenous social category, even if it is dominated by youths (in 1993, three quarters of them are under 30 years old). Corning from cities, they meet with difficulties in integrating to the villages, nevertheless, from an economic and spatial point of view they contribute to the transformation of rural areas. Urban out-migration brings up socio-spatial recompositions at the local and the national scales.

This paper seeks to evaluate the relevance of the notions of order and disorder in the understanding of the power relationships underlying the development of Argentina's suburbs (urban peripheries). It focuses on the links between spatial order and disorder, on one hand, and social order and disorder, on the other. By looking into the example of Alto Comedo - a city of 60 000 built from scratch in less than ten years and located in the suburbs of San Salvador de Jujuy, in the North-west of the country - we observed that the urban space reflects several types of orders: colonial, military, religious, informal economic, repressive, festive, etc. All of them are affected by a set of disorders: legal, political, urban, social, etc. The actors involved in the reproduction of spatial segregation are thus clearly identified. The social order imposed by the upper classes perpetuates its domination upon the geographical space ofthe cities, and thereby on the disadvantaged social groups, which are rejected to the suburbs.