Valutazione del rischio ecologico nei siti di importanza comunitaria: il caso dei vegri (habitat natura 2000 6210) nel parco naturale regionale dei colli Euganei (Padova, nord Italia)

The paper deals with the development and first application of a GIS-based model of vulnerability for the conservation and enhancement of Natura 2000 habitat 6210 in sites of Community Importance. The general applied formula was (R=V x p x D), where R is risk, V is vulnerability, p is danger (exposure), D is the value of the biotic component. Presence and absence of orchids, whose important sites make the habitat 6210 a priority habitat, were sampled in 50-m side cells. The cells were used as map units for the calculation of the factors in the general formula. Human and natural threats were analyzed: the first being tourism and traffic, the second being abandonment and natural afforestation. The human danger was related to the road and paths networks length, the natural danger to the amount of woodland and scrub-land surface recognized through an unsupervised classification of aerial photos. Value and vulnerability related to the two threats were finally estimated for each orchid species and summed in every cell. After having applied the formula, several maps of natural and human induced risk were performed: they guided the decision-making process of several conservation projects performed by the local Natural Park Authority.