Frammentazione ambientale, connettività, reti ecologiche

206 Reti ecologiche
blems, should be regarded as an original experiment from which ecology and landscape
planning can draw new knowledge.
Ecological levels and targets – Conservation strategies and ecological planning
will depend on the a priori selection of sensitive targets, such as species, communities,
ecosystems, or processes. Populations of individual species are easier, generally,
to investigate compared to higher ecological levels and may be considered
valid targets for evaluating the efficacy of corridors and ecological networks.
Structural level - The structural level is the basis for designing an ecological
network. Thematic maps and remote sensing allow us to analyze spatial structure
and patterns of the landscape mosaics, identifying sensitive ecosystems, areas of
anthropogenic fragmentation, gaps and corridors. The residual fragments can be categorized
in accordance to type, size, shape, quality, isolation, spatial articulation,
and functional relations to the matrix. The matrix itself can be analyzed on the basis
of type, origin, degree of anthropization, as well as of ecological and spatial variables.
Dynamic-functional level - The spatial pattern of the landscape may affect the
flows of energy and matter as well as the biological dynamics. From the structural
analysis, it is possible to point out some functional aspects: the landscape ecology
provides the tools for a first evaluation of cause-effect relations between structure
and function. However, the propedeutic structural analysis of the landscape may
not correlate to a definition of its connective functionality for sensitive species:
i.e., some species may be unable to disperse along apparently continuous areas for
a structural analysis (because of, for example, the edge effect).
Connectivity is a function both of a structural-cartographic component and of
an eco-ethological, species-specific one. The different function (connective, neutral,
or acting as a barrier) of the landscape elements for individual species will
then be bound to both components. Consequently, a functional ecological network
design must imply a species-specific approach of the structural patterns of
the landscape.
Some models have been proposed in order to take into account the ecological
role of landscape elements in sensitive species dynamics, evaluating, theoretically,
the relationships among patterns of distribution/abundance and patterns of landscape.
The functionality of the structural patterns may be analyzed considering their
role as habitat and/or corridors and of the minimal specific requirements for specific
viable (meta)populations.