Predicting Potential Distribution of Orchis Galilaea in Lebanon Using GIS

Orchis galilaea is the only Lebanese orchid that is restricted geographically to Lebanon,
Palestine and Jordan. It is a terrestrial orchid that attracts its pollinator by sexual deception
while offering no reward. The full distribution of this orchid in Lebanon has not been
determined. This study is part of ongoing research into the population dynamics of the
orchid to form a management plan for its conservation. A Geographic Information System
(GIS) was used to identify the habitat characteristics of O. galilaea and map its
distribution in Lebanon by combining known locations with digital layers of
environmental variables, including topography, land cover, soil type, geology and
precipitation. Classes within each environmental parameter were defined and weighted
according to their frequency of occurrence at extant sites. A predictive GIS model was
developed by overlaying the five layers of the habitat characteristics. The predicted
distribution map of O. galilaea was then validated by confirming presence of the orchid
in the predicted locations and absence in the unsuitable areas through exploration field
trips. Eighty five locations were surveyed and seven previously unknown populations of
O. galilaea were discovered. These new O. galilaea locations were all correctly predicted
by the model as potential habitat. The accuracy of the model was confirmed as it was
significantly more likely to find the orchid in predicted suitable habitat compared with
unsuitable habitat. Combining ecological habitat characteristics using GIS proved to be a
useful tool to successfully predict the potential distribution of O. galilaea in Lebanon and
will assist in planning its conservation measures.