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The PAYSAGRI model: from agricultural plot to landscape

Depigny S., Poix C., Chevillot B.. 2005. In : Conference on Multi-agent modelling for environmental management, Bourg Saint Maurice - Les Arcs, France, 21-25 mars 2005. Bourg-Saint-Maurice : s.n., 2 p.. Colloque CABM-HEMA-SMAGET 2005, 2005-03-21/2005-03-25, Bourg-Saint-Maurice (France).

Nowadays, social reorganization of rural territories is topical issue. More and more people, who don't belong to agricultural corporations, live on these territories. This phenomenon creates some disagreements. On the one hand, new residents think that landscape is only their living environment. According to them, landscape must be suitable for hobbies. New residents wish this landscape not to evolve. On the other hand, farmers don't understand these new expectations, which sometimes contradictory their activity. This situation results from a lack of knowledge about the processes of landscape evolution. For agronomist point of view, these processes are deeply linked to agricultural system changes. One cannot see landscape just as a picture of a territory, but more as the result of economic activities. The main objective of our model is to clarify and to explain relationships between public policies, agricultural system changes and landscape changes. Two stages are necessary for this modelling. Firstly, we must understand how public policies are applied and how these policies change strategies of agricultural systems. Secondly, we try to assess landscape evolutions, which are due to the reorganization of agricultural systems. Our modelling is based on medium altitude areas where the main part of land is managed by agricultural systems. The Paysagri model is based on three concepts: The landscape is the measured variable. Considering geoagronomy, landscape can be seen as a puzzle made of many pieces. According to this point of view, each piece is both a component and a consequence of a sociological and economical system. In our model, landscape is a puzzle made of all agricultural plots of the studied territory. The plot is the elementary object in the model. That's why it is assumed homogeneous; i.e. the model doesn't handle phenomena that occur inside the plot. We keep the only information that is essential for the farmer's decisions. Texture and age characterize a plot. The textures are ¿ natural meadow ¿, ¿ artificial meadow ¿, ¿ crop ¿ or ¿ unused ¿. The transition for one texture to another is the result of agricultural practices on the plot during a year. The agricultural practices are the factors that modify the texture of the plots. In the present version of our model, we only implemented the dairy farming functioning. This choice is due to the fact that dairy farming is the most important activity of the studied areas (north of the Massif central). The model is based on the point of view of the breeder. The herd and its feeding are of great importance to the farmer's decision process. We modelled two kinds of farming activities: the usual ones and exceptional ones. The usual ones are fodder production and herd grazing. To do that, the breeder must carefully choose the plots for each activity, according to production capacities of each plot. The second ones correspond to the agricultural system adaptations. The breeder can give up some plots, for example because of their lack of production capacities. He can also use new plots that he recently inserted in the agricultural system or that were unused for some time. These exceptional practices are essential in the Paysagri model. They represent the most important variations of area used by the agricultural systems. In our model, a special attribute named ¿landscape perception¿ is associated with each breeder. That's why the breeder has a key role in his agricultural system changes. The ¿landscape perception¿ attribute guides the farmer's choice concerning the exceptional practices. This attribute is an original point of our model, because technical and economical facets of the farmers are not only aspects taken into account. The breeder's feeling about his occupation, his living environment, his way of life... are numerous elements considered in the model. Public policies are the first cause of agricultural system changes. They influence the breeder's strategy and the i...

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