Résumé
Agroforestry systems provide ecosystem services, on which adaptation to climate change could increasingly rely. In Mesoamerica, under a tropical wet climate, coffee-based agroforestry can maintain supporting and regulating services such as drought resistance, soil formation and flood regulation, that help facing extreme rainfall events. However, under conditions of global market fluctuations and weak policy support, coffee-based tropical agroforestry systems (AFS) are abandoned or imperiled by the extension of pasture and sugarcane areas. These land use changes also threaten biodiversity in biological corridors (BC) where protected areas are connected by AFS, as in the Costa Rican Central Volcanic ? Talamanca BC. In its Balalaica subcorridor delimited by two rivers and crossed by a mountainous spine, local stakeholders and a pluridisciplinary research team aim at understanding the dynamics of land use change affecting AFS and the mechanisms at work. On the basis of the Resilience Assessment guide with emphasis on existing knowledge, either local or scientific, an historical profile and two threshold cascades were built in a two-step process: initial results obtained out of available literature, were then revised during working sessions with stakeholders and academic experts. Three scales were considered: the focal system Balalaica; its farms at the smaller scale; Costa Rica at the larger one. The historical profile was constructed over a century, and specified for the last 30 years. It illustrates the combined effects that recurrent coffee crises and new national regulations have had at the farm level, where the creation and the bankruptcies of agricultural transformation units was determinant. Successive development phases could be identified that characterize the Balalaica subcorridor within the national context and correspond to different phases of several adaptive cycles. The threshold cascades propose a conceptual model on how ecological or economic disturbances at the national scale affect the profitability of coffee plantation in the subcorridor, which lowers the economic importance of coffee for households and the cultural identity felt towards it, leading to land use changes and their ecological consequences, mainly soil degradation with pasture and connectivity loss with sugarcane. Bound this way, each phenomenon gets more irreversible. Reconsidering the concept of adaptive cycle allows to complete the analysis of coffee agroforestery resilience and to question the transformability of this type of socio-ecological system at the farm and plot scale. Fluctuations in coffee and sugarcane areas are interpreted as resulting from two connected adaptive cycles; a same plot moving from one cycle to the other and back after some years. Such type of land use change has recently became a more irreversible conversion to sugarcane, and we found that alternative practices in coffee plantations interact with this transformation. Doing so, we identified four alternative adaptation trajectories of coffee farms to exogenous disturbances. This analysis highlights a possible progressive adaptation of coffee systems to an almost nontransformable state of abandoned coffee plantation, that is highly resilient. The result questions traditional views on agroforestry systems among researchers and prompts more reflection about potential traps induced by passive adaptation processes in perennial cropping systems. (Texte integral)