Interdependencies among hydro-saline dynamics, economic activities, ecological processes, and biodiversity in a deltaic social-ecological system: insights from the Rhône delta (southern France)

Deltas are complex social-ecological systems (SESs) that involve many economic activities that interconnect closely with ecological processes and biodiversity. Sustainable management of such intricate SESs requires developing an integrated and understandable representation of their main human and ecological entities, processes, and interactions. We developed a formal representation of the Ile de Camargue (center of the Rhône delta), in which hydro-saline dynamics, water management, economic activities (e.g., agriculture, hunting, fishing, tourism), and natural environments (i.e., habitats for biodiversity) interact. The conceptual model was based on four submodels that provided complementary representations of i) water governance, ii) agriculture, and iii) bird and iv) fish communities. The conceptual model highlights the strong relationships (i.e., causal chains, feedback loops, interactions, side effects, and trade-offs) among the multiple entities of this deltaic SES. It provides information about the region and describes deltas as a SES to support decision-making. One major feedback loop in the delta concerned relationships among regulations, rice fields, and use of marshes as a habitat for birds: strengthening pesticide regulations to improve water quality and bird habitats caused the area of rice cultivation to decrease which degraded habitat conditions for birds. Directly related to pesticide use, the most common trade-off is to decide whether water management should prioritize water quality or quantity in the delta’s Vaccarès lagoon, and opinion differs among stakeholders. The conceptual model could be used as a starting point to develop computer-based integrated assessment and modeling to explore dynamics of and resilience to climate change in the Ile de Camargue.