In East Africa, fertility-climatic, agronomic, demographic-first defines the mountains' identity. This fertility has been acquired, built and maintained, while being part of a system of constraints which is specific to the mountainous environment. The concentration of people in these mountainous regions has often been related to logics of identity withdrawal, irredentism or territorial enclosure. Nevertheless, these mountains (e.g. Kilimanjaro, Mount Kenya, etc.) are far from "closed-into-themselves" areas; they have been placed at the heart of space that is integrated and open to world dynamics. Fertility and constraints take their particular meaning-or change them-within a larger context of structural evolution, which takes into account all geographical scales. Mobility of persons, circulation of goods, etc., have put the development of these altitudinal regions under systems of exchange and interaction with other areas, at short or long distances, from the peripheral lowlands to the worldwide market areas. For a long time, policies of development have been based on agrarian and naturalistic models, confining the mountain issue to the specific managerial constraints of these fragile environments, and emphasizing a too exclusive linkage between societies and territories at the local level. Over a given period, those models contributed to the valorization of the production potential of regions but, nowadays, they are not able to give tools to overcome the contradictions of sustainable development. The new forms of territorial competition at different geographical scales give the opportunity to redefine the architecture of relations which determine the originality and the competitiveness of those territories full of natural and human resources. There is the need to rethink the conditions of integration of those areas within a global space where essential resources (information, money, power) flow, in particular through urban expansion and the development of communication and marketing networks. Cities appear as essential constituents of mountain areas' dynamics. Urbanization strengthens the role of mountains as dynamic demographic poles and provides resources to rural areas like new additional jobs, services, information networks and projects. Conversely, in its relation to mountain areas, the city multiplies and exacerbates the competition for access to resources and thus creates a threat to mountain communities and ecosystems.