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The different methodological tools for ecological homologation are commonly based around the controversial inference of the species fundamental niche coming from its effective niche, this being considered the medium in which the species lives, bounded by the quantification of a set of environmental variables (parameters) that define it. The methodologies and models developed in this field are generally aimed at evaluating the suitability (homologation) of a species for a given site based on its "proximity" to the observed range of variation associated with its optimal ecological response (this usually means the center of gravity, the centroid of the point cloud, etc.). In contrast, little research has been directed towards developing methodologies which fix the reference at the limit values of the recorded variation range, and which define the conditions of ecological marginality.

At site-scale, conditions of species marginality with respect to the physical environment threaten its establishment, development and perpetuation and therefore its ecological stability. Based on the hypothesis that these conditions of marginality are focused on the edges of the parametric hypervolume that defines the fundamental niche of each species, a set of indicators has been designed to evaluate the degree of ecological marginality of a given site in terms of the specific species requirements. The application of the model to study episodes of vegetative decline in Aleppo pine stands has produced ecologically coherent results, showing a satisfactory capacity to identify the most important site aspects influencing the observed ecological behavior. It is therefore an easily implemented, transparent (white-box model) methodological tool providing a valuable means to explore the key characteristics of complex relationships between species and the physical environment in which they are found.