Statistical analyses
As a test of ELIA against biodiversity data components, we used
the observed abundance (i.e. total number of butterfly observations) and
species richness of butterflies and birds in the study transects. In
order to disentangle the direct and indirect effects on biodiversity of
energy storage and distribution, and of landscape composition and
configuration, Structural Equation Models (SEM) were built for each of
the studied biodiversity groups (butterflies, and breeding and wintering
birds). Specific SEM were performed for species richness and abundance
of all butterfly species clumped together and, in the case of birds,
separately for nesting and wintering species. SEM considered the direct
effects of the three ELIA components (E , I ,L ) and their indirect effects reflected in landscape composition
(Cm) and configuration (Cn). In order to reduce the number and the
redundancy of variables in the SEM, we performed a Principal Component
Analysis (PCA) on Cm and Cn variables (Table 1 ). Analyses were
performed using the SEM package in R (55 ).