Infoscience

Thesis

Dynamique du paysage rural de la partie nord-ouest de la Suisse: une analyse pour comprendre la variation des populations du lièvre brun (Lepus europaeus)

Since the 1950s, the population of the Brown hare (Lepus europaeus) has dramatically decreased in Switzerland as well as in other European countries. According to the Swiss Ornithological Institute of Sempach, this animal is an adequate indicator of the state of the landscape. Its decrease is probably due to intensification of agricultural practices, extension of urbanism and development of transport networks (Pfister et al., 2002). Today, the Brown hare is on the Swiss Red list of species that must be protected. This thesis presents an analysis of the landscape dynamics of the North-Western part of Switzerland, from the 1950s to the 1990s, through an historical analysis of the state of the landscape as it is perceived by the hare. In particular, we identify the factors of the landscape that are relevant for this animal, determine their trend of evolution, and finally postulate hypotheses for the evolution over the next years and their consequences for the hare populations. For each decade, 936 communes are described, using 40 variables related to agricultural practices, land-use, morphology, urbanisation, climate and geography. This database is called "Landscape". These data, mainly extracted from communal statistics, were found to be adequate to describe the evolution of the composition of the landscape at a large scale. We studied the content, the quality and the organisation of this database "Landscape" with the help of descriptive statistical methods (data distribution, histograms and boxplots at each decade, dynamics of the statistical characteristic values) and using principal components analysis (PCA). The latter reveals two groups of communes: urban (belonging to an agglomeration) and rural. On average, it also shows a very definite evolution of the urban character of both groups, from the 1950s to the 1990s. The three first components of the PCA explain only 45% of the variance. Therefore, we decided not to simplify the database by replacing our variables by these agglomerated variables, as the loss of information would be important. Among the 40 variables, 16 key-variables for the hare were identified. For this, an "Index of abundance of hares" was calculated for a sub-set of 125 communes, defined as the mean number of hares hunted per total communal area between 1980 and 1985. The link between this index and the 40 variables, describing the state of 125 communes in the 1980s, was analysed with the use of correlation, linear multiple regression, the method Pegase (a multivariate hierarchical divisive procedure, based on information theory (Phipps, 1981)), and additional information from the Swiss Ornithological Institute of Sempach. These methods were found to be complementary and their use enables us to take into account several perspectives. It would be interesting to go further by calculating this index for a larger number of communes in order to optimise the use of Pegase. The main trends of evolution of these key-variables, observed on the 936 communes, between the 1950s and the 1990s, are: 1. Decrease in the fraction of agricultural area; 2. Intensification of agricultural practices, increase in the mean ownership unit area (mean parcel size), changes of the type of agriculture; 3. Urbanisation and increased private car use; 4. Slight increase in rainfall. Two scenarios of evolution of the landscape for the next years are defined. Presuming that the identified trends will continue (Scenario A), the situation of the population of the hare will rapidly become critical: 1. The slow decrease in agricultural area will induce a pressure on the potential habitat of the hare; 2. The strong increase in areas of road/rail will reduce the habitat of the hare and most of all induce a fragmentation of the landscape, as well as barriers that are often impassable for the hare; 3. The extremely rapid increase in the number of cars will lead to an increase in road kill; 4. The increase in mechanisation in the agricultural practices, shown by the increase in the mean parcel size, the decrease in the working force and the slight increase in the number of tractors, are three reasons of important disturbance of the hare's habitat. In addition, the increasing rainfall, even if small, makes it probably more difficult for the animal, as it doesn't appreciate wet soils. On the other hand, in case the areas with corn stay relatively stable, and the grants for land improvement keep on decreasing, gradually "replaced" by grants encouraging extensive agricultural practices like direct grants for ecological compensation measure, the situation of the hare could stop getting worse. This scenario corresponds to a management of the territory that would not take into account new constraints and needs appearing with time. In order to take this into account, a second scenario (B) is defined, which is less extreme. It is based on trends for the future discussed by the Federal Agency for Agriculture, in the proposal for a modification of the law in the canton Vaud on country planning and buildings, and in the monitoring of Swiss statistics of the country. Both scenarios are rather pessimistic: for more than half of the key-variables integrated in both scenarios, the evolution probably leads to a negative situation for the hare. As this species is a good indicator of the quality of the landscape (Pfister et al., 2002), we recommend to take into account the needs for this species in the future management of the territory. According to our results, it would be important for the hare population to remain stable or even increase: 1. To encourage extensive agricultural practices; 2. To slow down, or better stop, the extension of urban areas and road/rail networks; 3. To reduce private car use. As these two last recommendations seem quite unrealisable in the near future, we propose to extend the network of favourable structures for the hare: hedges, fallow land and other areas close to natural state. At the same time, a plan of observation has to be developed, in order to control the results of these measures. These measures would enable sustainable growth of hare population, and, at the same time, sustainable management of resources and our patrimony.

    Thèse École polytechnique fédérale de Lausanne EPFL, n° 2558 (2002)
    Section de génie rural
    Faculté de l'environnement naturel, architectural et construit
    Institut des sciences et technologies de l'environnement
    Laboratoire de gestion des écosystèmes
    Jury: Hauke Harms, Hans Peter Pfister, Michel Phipps, Jean-Louis Scartezzini

    Public defense: 2002-5-15

    Reference

    Record created on 2005-03-16, modified on 2016-08-08

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