Trophic networks scenarios : assessing cumulative impacts of marine energies and climate change on ecosystem functions and services in the Seine’s Bay

ABSTRACT:

Coastal ecosystems receive increasing anthropogenic pressures, including marine renewable energies and  climate change. These can interact in complex ways, which may lead to cumulative effects like synergetic or dampened effects. Using a holistic approach based on ecological network analysis (ENA)  coupled with a two-dimensional food web model (Ecospace) an ecosystem simulation approach was applied to study the effects of climate change and an offshore wind farm, on ecosystem functions and services. Three ecosystem services were studied: food production from fishing, top predator production for cultural purposes and the potential resistance of the ecosystem inferred from its topology. This study was realized in the extended Seine’s Bay, in the English Channel. Cumulative impacts were not restricted to the wind farm area, i.e., where anthropogenic drivers are concomitant. They varied both in space and among ecosystem properties, displaying that ENA indices can distinguish between different cumulative pathways that modify ecosystem functioning in multiple ways. Moreover, the effects seemed to be tied to the structuring role of climate change, and differed under the 2050 and 2100 conditions. Such changes resulted in stronger loss of ecosystem resilience under the 2100 condition despite the benefits of the reef and reserve effects of the wind farm.

Concerning services, the ability of the Seine’s Bay ecosystem to produce food appeared to be negatively impacted by the effect of climate change. Because of the important economic role of fishing in Normandy, such a change could percolate on the entire social system of the area. The offshore wind farm appeared to increase the supply of services and limit the impact of climate change at the local spatial scale, which could give stakeholders insights into mitigating the effects of climate change. Such ecosystem approach enables for a more integrative view of ecosystem services supply, through the characterization of the entire system functioning.