for less inhabited conservation units, the arie's, or areas of ecological interest (areas de interesse ecológico), tend to be without human occupation, as small areas with extremely rare species of flora and fauna, and generally great biodiversity.

as the only stipulation of these protected areas is to have extraordinary species, the arie's can fall on both public and private land.

the arie's were established purely to protect and maintain the rare natural ecosystems and species that live within the areas, with conservational techniques, which includes the strict regulation of use of the areas, to make sure make sure that they fit within the objectives of the conservation.