Resource control in the western Pyrenees from 1800 to the present is addressed by reference to external factors: historical events; economic, technological and policy changes; and in the context of the “house system,” which functioned and continues to function as a control agent of environmental exploitation practices. The issue for the present is political, having to do with the conflict of legitimacy fed by the confusion that exists over the concept of the mountain: “free space” (high mountain zone) vs. “work space” (private mid-elevation mountain zone). The result is a multiplicity of actors and legitimacies. The saltus is a space charged with issues because it is in turn a mountain ecosystem and an agricultural ecosystem. Consequently there is but one space: the work space. The collective activation practices resulting from customary rights reflecting practices carried out in most cases over a very long time (Diego Moreno 1995) by households are the best at maintaining fragments of ancient prairies and forest coppices – reserves of potential biodiversity.