Zero-Carbon Wetlands’ from qualitative and possibilistic perspectives

Understanding how social-nature and ecological-nature functions and their dynamics affect carbon emissions is critical due to the growing anthropogenic impact and its constant denial. According to the Paris Agreement in 2015, several countries and cities aim at becoming zero-carbon areas by 2050. In this context, wetlands and other coastal vegetated systems have been recognized for their major roles in “blue carbon” sequestration and storage. In addition, wetlands such as marshes can be either natural or managed by man for agriculture, aquaculture or other anthropogenic needs. Therefore, it is essential to accurately comprehend wetlands ecological functions for a better understanding of CO2 regulating factors and how they affect carbon budgets in these dynamic and heterogeneous systems. A few quantitative models are already in use for the study of social-ecological system (SES), however qualitative models have demonstrated to be an alternative and novel way for representing the essential long-term dynamics of SES. These models make it possible to qualify the responses of the system as a whole to its many exposed disturbances (human pressures, global change, biological activity, etc.), as well as to predict them. Here, a qualitative rule-based model for La Rochelle city (France) SES in wetlands has been developed to assess carbon neutrality, using the Ecological Discrete-Event Network (EDEN) modeling framework. The most important ecological components (variables) related to carbon emission for wetlands (e.g., phytoplankton, sediments, plants) and social (e.g., transportation, agriculture) domains have been carefully chosen from the literature, field studies, interviews and data analyses. Using these variables and related processes, every possible pathway will be computed to assess whether carbon neutrality is reachable from a chosen initial state by this modeled SES. Moreover, by the hand of EDEN, the recommended and dangerous pathways will be identified. The Eco-Marsh model is the first qualitative and possibilistic model ever, to our knowledge, for assessing carbon neutrality in a social-ecological system as a whole including wetlands. The first results will be presented, and will become part of a larger model which will include additional physicochemical, economical and political domains of La Rochelle region. In a second step, such an integrated model will enable the mechanisms governing these areas to be presented to stakeholders, so that integrated management strategies will be devised to optimise regional carbon functioning.