Geoscience Reference
In-Depth Information
2.3.3.2.
Step 2: to represent and to explore herds' movements and the changes in the
vegetation cover
In this example, the representation of the movement has served as a basis for the
construction of the “places of frequentation” as objects. In this sense, the operation
is reversed toward to the more common cases where objects are built before
considering their trajectories. In other words, focus goes classically from a static
point of view to a dynamic point of view. Here in contrast, it is the aggregation of a
series of movements that allow building fixed and static objects from the envelopes
containing the herd's movements during resting time. Regarding land use, the
context is rather classic, the scope of change having been built based on the
confrontation of land use at two dates.
Queries can be made from a database (DB), for example: what is the share of
pixels recorded as “in deterioration” in spatial portions identified as “staying places”
of herds? What is the proportion in the rest of the space? These same questions can
be derived from different geographical areas in order to compare them. They can
also be derived according to the species of the concerned animal. The same
questions may be addressed from a geographical information system (GIS), with a
proper visualization.
2.3.3.3.
Step 3: to analyze the relationship between the intensity of animal
frequentation and the change in vegetation cover
The initial question can also be addressed by a statistical approach. The purpose
is then a matter of formalizing the information in terms of statistical “individuals”
and “variables”. In this example, these “individuals” can be either spatial units such
as the identified places of frequentation, or pixels. According to the case, different
variables can be mobilized, on the one hand, to measure the intensity of the animal
frequentation, and on the other hand to evaluate the change in vegetation cover:
- variables characterizing the places of frequentation: the number of sojourns
and/or passages of animals herds, the share of different species in this number and
the share of space having recorded a degradation of the vegetation cover;
-variables characterizing the pixels: belonging or not to a “place of
frequentation”, having a degraded vegetation cover or not.
From the methodological point of view, we have to cross the places with regard
to the deterioration of their vegetation cover and to the intensity of their
frequentation and to look for the possible existence of a systematic relationship
between these two phenomena. In the first case, focus is restricted to the places of
frequentation, and a correlation analysis will allow measuring the intensity of the
relationship between the orders of magnitude characterizing, respectively, animal
