Résumé
In the debate about deforestation in the Brazilian Amazon Region, the cattle sector is pointed out as the major cause, and the access to the world market is perceived as a serious threat. However, the reality is far more complex as shown by the analysis of the commodity chains and the emerging land organization in several frontier areas. A multidisciplinary research team has developed an integrated approach in order to study those interactions, which in the Amazon are usually analysed separately. The livestock commodity chain can be divided into local, regional and "export" sub-chains. Each of these three activities owns a specific spatial influence, where it plays a particular role on the emerging land organization. In frontier areas, its action relies upon four successive and interdependent steps: cattle herd increase, emerging organization of the commodity chain, attraction of the frontier area and land organization. A spiral of events can make the frontier area occupation look like a steamroller, leaving behind a smooth space organised for one specific function: cattle and milk production. The understanding of this four-step trajectory might favour the identification of appropriate measures. The starting point is the production of reliable and up-to-date information. Beyond this information gathering, the measures should apply on two key processes in terms of spatial dynamics implication. First, the establishment of commodity chain regulations, to implement tools for municipal land management and to revitalize land use planning in the frontier areas. Secondly, land management particularly in critical municipalities, should rely on a participative implementation of spatially-explicit tools (GIS) with local administration and stakeholders. Finally, without measures for land use planning in frontier areas, the cattle commodity chain will often be the only emerging sector, which will organize the land in the most productive way, with the associated massive forest clearings.