Rural areas are recognized as multifunctional spaces, where traditional agro-silvo-pastoral and other human activities (unrelated rural tourism, ecotourism, processing industries of agricultural and or extractive products, land maintenance, trade in local products, etc.) take place alongside each other. The integrated endogenous development model, established to mitigate the effects of human activity in protected areas, relies on the enhancement of specific resources of individual territories through the active participation of the community to promote local development. This model is intrinsically connected with the model of sustainable development, based on three cornerstones: environmental, social, and economic sustainability. The difficulty in achieving a reasonable balance among these values relates primarily to areas subject to protection (i.e., Parks and Natural Reserves). Ultimately, the environmental culture emphasizes the sustainability of natural resources, obviously in relation to these values and to the vulnerability of these areas. This paper outlines some relationships between environmental protection and the exercise of agricultural activities and other human activities in protected areas by using the theory of “rough sets”. The study aims to show that in the complex context of Etna Park (recognized World Heritage of Humanity by UNESCO in 2013), the model developed by the “rough sets” could provide useful guidance to policy makers to formulate local development strategies according to a model of the sustainable management of protected areas.