Modelling impacts of offshore wind farms on trophic web: the Courseulles-sur-Mer case study, an example of cumulated impacts
Résumé
The French government is planning the construction of three offshore wind farms in Normandy. These offshore wind farms will integrate into an ecosystem already subject to a growing number of anthropogenic disturbances such as transportation, fishing, and sediment dredging. The possible effects of this cocktail of stressors on ecosystem functioning are still unknown, but they could impact their resilience, making them susceptible to changes from one stable state to another. Understanding the behaviour of these complex systems is essential in order to anticipate potential state changes, and to implement conservation actions in a sustainable manner.
Currently, there are no global and integrated studies on the effects of construction and exploitation of offshore wind farms. Moreover, approaches are generally focused on the conservation of some species or groups of species. Here, we develop a holistic and integrated view of ecosystem through the use of complementary trophic webs modeling tools (quantitative and qualitative models). In fact, trophic models such as Ecopath are based on the quantification of flows between the ecosystem components (ecological processes). This approach allows modelling the ecosystem complexity from phytoplankton to top predators. Moreover, interactions with the ecosystem and human activities are then be added through qualitative models. Theses models allow to introduce unquantified actions of various actors.
Results of these two complementary models contribute to a better knowledge of the impacts of the offshore wind farms on ecosystems and cumulated impacts. They also allow to define recommendations for environmental managers and industry in terms of monitoring the effects of Marine Renewable Energy, not only locally, but also on other sites, national and European levels. Finally, this combined approach could contribute to a better social acceptability of Marine Renewable Energy projects allowing a holistic vision of all pressures on ecosystems.