Ecosystem services in a mountain grassland socio-ecological system
The ecosystem service (ES) concept is increasingly used in different scientific disciplines and is spreading into policy and business circles to draw attention to the benefits that people receive from biodiversity and ecosystems. Nevertheless, while the number of case studies considering various dimensions of the interactions between ecosystems and land use via ES has been steadily increasing, integrated research addressing interrelationships between biodiversity, ES and land use has remained mostly theoretical. This thesis aims through a socio-ecological approach to understand: (1) Which ES are potentially delivered given ecological dynamics, (2) how these ES are perceived by stakeholders in terms of value and knowledge, (3) how human management affects ES delivery, and (4) how ES are taken into account in land management decisions, thereby considering feedbacks from ecosystem to the land use system through ES. To address these questions, an interdisciplinary study was conducted on Villar d'Arène (French Alps) a municipality where the subalpine landscape is shaped by extensive mountain livestock farming. Statistical modelling and geographical information systems where combined to analyse the determinants of the spatial distribution of biodiversity and ES within the landscape using ecological (including plant functional traits), biophysical and land-use data. The following ES were mapped: agronomic value, aesthetic value, water quality, carbon storage, soil fertility, soil moisture, conservation of plant diversity and pollination. These allowed us to quantify trade-offs and synergies in the current landscape and to identify key management types supporting multifunctionality. The dynamics of ES was projected under four different scenarios integrating climatic, socio-economic and land-use changes, which were developed using a participative approach with regional experts and local farmers. Analyses of projected scenario impacts showed that ES synergies and trade-offs evolve differently when considering direct effects of climate on ecosystems, and/or their indirect effects through farmers adaptive responses. Interviews with local stakeholders (experts from nature conservation and agricultural extension, farmers and inhabitants) of mountain grasslands showed that the ES concept is still relatively unknown in explicit terms. Nevertheless after defining ES to interviewees, they expressed a variety of relevant interests and knowledge. Although all stakeholders valued a common set of ecosystem services (agronomic value, aesthetic value, water quality, and conservation of plant diversity), we identified negative and positive representations of the effects of grassland management on ecosystem services, depending on stakeholders perceptions of the relationships between soil fertility and biodiversity, and biodiversity and the other services. Finally, a role-playing game explored how ES cognition mediated environmental feedbacks on farmers' behaviours. Results emphasized the influence of other factors such as socio-economic or climatic context, topographic constraints, social value of farming or farmer individual and household characteristics, on the link between ES and land-management decisions. This case study demonstrates the interest of an integrated approach decomposing the feedback loop from ecosystems to land use when studying ES for scientific or policy purposes.