Edges between agriculture and forest viewed as interfaces between social and ecological systems

Edges between forest and agricultural areas are very common in rural landscapes where temperate forests are fragmented. From an ecological point of view, edges are most often defined as the boundary between two distinct habitats. Therefore, they have common characteristics with habitats they separate. Conversely, they can be considered as special ecological environments with their own characteristics and species. The edges are also characterized by the flow of organisms, matter, energy and information through them. By analogy with membranes, the structure of the vegetation in edges are more or less permeable ensuring a filter function. Whenthe movements of organisms are parallel to the edge, they are recognized as a part of corridors. These interface effects, gradient and boundaries between spatial entities are important processes that were not as considered so far, as the effects of the surface, isolation or heterogeneity. However, forest and farm managers will need this information to adapt their managements in a context where the interactions between forests and agriculture will be more important, particularly through the valuation of ecosystem services, such as pollination and pest regulation. Moreover, changes in the landscape generally affect margins of habitats in the first place. These limits also often have a social significance that places them at the center of important management issues. From a socio-technical perspective, the edges turn out to be often used differently from the rest of the forest, including a higher frequency of cut. Interviews with managers show that their choices are the result of silvicultural decisions but also of the use of adjacent agricultural parcels for which edges can be an annoyance (for crops) or an asset (in the case of meadows for the shelter of animals). They are therefore important places of socialinteraction. Agricultural and forest environments can be seen as different ecological and social systems, characterized by a spatial structure of the biomass, a disturbance regime, management practices and different perceptions. In most cases, the edges also result from differential in the disturbance regime of vegetation, with a side with infrequent interventions, cuts in the forest, and on the other side more intensive and frequent interventions that hinder the development of trees for the benefit of crops. Theories of social and ecological systems and their dynamics, as panarchy, do not deal clearly with the phenomena that occur in the spatial limits of systems. At a finer spatial scale, edges may themselves be viewed as systems with their own characteristics, but the question of links with adjacent systems remains. The presentation describes these features of edges and the questions they pose, from practical examples drawn from several interdisciplinary works in landscape ecology, ethnology and geomatics. The possibilities of using the edges in an agro-ecological engineering of landscapes to enhance the ecosystem services they provide are exposed for discussion.