Geoscience Reference
In-Depth Information
outlined above and imposes itself as spatial
and
dynamic. It contains a dozen
interrelated modules, respectively dedicated to demographics (including the
processes of moving in together, divorcing and moving out of young people),
education, employment and migrations. This last module has three phases and a
submodel of choices has been developed for each of them:
- the decision of the individual to migrate;
- the choice of a new labor market;
- the choice, within the corresponding region, of a cell of residential localization.
Once the model is elaborated, it can be used to estimate all the phenomena
associated with the actions introduced in the model. It has been used notably to
explore the consequences of different policies in the area of immigration with
regards to the 22nd Century, showing that a difference of 20,000 people in the
annual flow of immigration is reflected, within a century, by a decrease of the
Swedish population of several millions (Figure 4.6). Alfredsson [ALF 02] focusing
on the links between the behavior of households in terms of heating and
transportation means, used this same model to show that even scenarios introducing
significant changes of behavior at the individuals level, result in a low impact in
terms of CO
2
emissions, due to the importance of the forces of inertia. In this last
example, the consequences in which the author is interested in, belong to the scope
of the global level, but the changes whose effects are to be studied, unlike the
previous examples, belong to the scope of the individual level.
Similar principles have been mobilized in the MICDYN model which has been
applied to explore different scenarios on the distribution of the population in the
Languedoc region. The model was used to better understand the process leading
either to an urban concentration or to an urban sprawl around the largest cities, or to
a diffusion of urban growth on the whole of the territory [ASC 00, HOL 07b]. The
originality of this model lies in the fact that while the dynamics is based on
individual choices, the interactions between different spatial dimensions have been
taken into account. In particular, entities referring to the mesogeographical level
have been introduced. These are the municipalities, which appear as interacting with
the individual choices: on the one hand, an evaluation of the social composition of
the municipality is made to construct an indicator of attractiveness differentiated
according to the social category of the individual concerned; on the other hand, a
strong population growth of a municipality is accompanied by a growth in induced
employment related to services. Finally, the growth is distributed over the
neighboring municipalities when the density exceeds a critical threshold.
