Tuesday, February 10, 2015

Land reallocation in France: some nice maps

Some time ago, I blogged about one of my current projects on land reallocation in France. I have made some progress on this project in the meantime and I am going to report on it here.

I have worked with Elise Maigné, at Inra. Together, and with the help of Eric Cahuzac, we have been able to secure an access to the data on reparcelling events at the commune level. This data has generously been transmitted to us by Nadine Polombo, who has worked together with Marc-André Philippe to digitize the dataset originally in the hands of the French Ministry of Agriculture. Nadine believes that their dataset is the inly one that remains, since the Ministry of Agriculture has decided to destroy the original data and does not take care of reparcelling events any more. Since then, the data have been made accessible through the open data portal of the French government.

First thing is that there has been 22,374 reallocation events in France reported in this dataset. This is huge, since we have 36,681 communes in France. Some communes have actually undergone more than one reallocation event. There are 18,227 communes that have undergone at least one reallocation event. This means that 49.7% of all French communes have undergone at least one reallocation event.

The first issue with the dataset is that I miss some information: the opening date of the reallocation event is missing for 201 events, the closing date for 380 events and both dates are missing for 291 events. So I have 21,502 events with non missing information on the both opening and closing dates of the reallocation event.

Figure 1: Reallocation Events in France
The events with information on the opening date are presented in Figure 1. Reallocation events start with the end of WWII, with this first wave stopping around 1953. A second wave starts in the late 50s and peaks during the 60s. That is the main wave of land reallocation. Then several waves occur in the 70s, 80s and 90s.

Figure 2: First (1) vs Subsequent (2) Reallocation Events
Since some communes have undergone more than one reallocation event, it is interesting to plot the reallocation events depending on whether they are the first or not. This is done in Figure 2. The wave of the 90s seems to be mainly due to reallocation events occurring on communes that have already been reparcelled once. It is possible though that a different portion of the commune has been reparcelled in the two events.

What would be great now is to have an idea of the way reparcelling was rolled out over space and time. It would especially be nice to know which reparcelling events occurred in between 1955, 1970, 1979, 1988, 2000 and 2010, the dates at which agricultural censuses have been conducted in France. I would add 1963 and 1967 as two large surveys have been conducted at these dates. In order to do this, I have to use a GIS software. Since I use Stata to analyse this dataset, I'm going to use its GIS facilities (for the first time). The beautiful map presented on Figure 3 is the result of this exercise.

Figure 3: Map of the Reallocation Events in France
The first striking feature of this map is that land reallocation mainly occurred in the north of France and much less so in the South. One explanation could be that land in the north is much more fertile, but I do not think this exhausts all possible explanations. This will be the topic of subsequent investigation. The second striking feature is how much the timing of land reallocation is spatially autocorrelated. For example, the area around Paris (the Paris basin) seems to have been almost completely reparceled before 1955. The first wave of reparceling thus seems to have been mainly concentrated in this area. The outskirts of the basin are reached progressively during the 60s and 70s.

The second striking feature of this map is that it coincides very well with a rough map of the agricultural regions in France (see Figure 4).
Figure 4: Map of the Agricultural Regions in France
The cereal growing regions (yellow) seem to have reparcelled very early, while the areas in mixed cultures (light green) have reparcelled more slowly. Finally, forest regions or regions with open range cattle (dark green) have almost not reparcelled.

Obviously, this strong spatial autocorrelation is not good news for studying the causal effect of land reallocation on agricultural technology adoption. Indeed, what would have been great would have been that reparcelling occurs randomly across space, with communes within the Paris basin reparcelling early and others not so that comparing them captures the effect of reparcelling. Here, a raw comparison of reparcelling communes with non reparcelling ones would be biased by the soil qulaity and types of productions. One better comparison would condition on the agricultural zones: comparing communes within the Paris basin with early and late reallocation (if we can find any) is already better.  Actually, my idea is to try to use the finest possible grid size to compare close communes with different reparcelling date.

A last striking feature of the data is that sometimes communes undergoing reallocation seem to be aligned like on a line on the map. This is because land reallocation has occurred along a railroad track or a highway, when these infrastructures were built.


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