perturbation biotique

CONT: Although not universally accepted, the principle of setting physical boundaries first, followed by biological bounding, was stressed in many of the workshops. This initial focus on physical characteristics and processes of a system for establishing spatial boundaries was a reflection of the general agreement among workshop participants that environmental impacts should be traced from changes in physical structure or function through ecological linkages to the resulting biotic perturbations.
CONT: ... most predictions of biotic impacts are based on certain assumptions concerning physical changes; in effect, they are second-order predictions. Therefore, predicting even so-called direct impacts in biotic systems involves a much greater degree of uncertainty.