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Ecosystem services model

Ecosystem services are supplied through interactions between ecosystem functioning, which is a result of the complex interactions between the biophysical structures and processes of the system, and socio-economic processes, which define the demand for ecosystem services. The ecosystem services model developed in SUMES is a quantitative model that explicitly represents the key structures and processes for the supply of ecosystem services in the Belgian Continental Shelf, and that incorporates the socio-economic demand for ecosystem services.

The model allows to quantify impacts of marine human activities on 11 ecosystem services: 5 provisioning (fisheries production, mussel aquaculture production, surface for navigation, wind energy production, sand production), 3 regulating (carbon sequestration, nutrient mediation, nursery and habitat maintenance) and 3 cultural (wildlife watching, recreational fishing, aesthetic value). The ecosystem services were carefully selected based on literature and stakeholders’ perceptions and knowledge of the system. For now, ecosystem services which are restricted to the coastal zone are not included in the model.

The model combines equations derived from existing models and literature with newly developed equations using diverse techniques such as statistics and food web modelling.

Results are presented in biophysical (e.g. fish biomass, nitrate removal) and, when relevant, also in economic terms (€). The ecosystem services model can be used to evaluate development scenarios and support in the development of more multifunctional design.

The ecosystem services model is applied to the showcase and to the advanced case. The main impact pathways of the OWF on ecosystem services are via the introduction of new benthic habitat (turbine foundations and scour protection layer), changes in hydrodynamic currents, and exclusion of other socio-economic activities (e.g. fishing, shipping and sand extraction). These initial effects on their turn lead to changes in the benthic and pelagic components of the marine ecosystem via filter feeding, biomass production, biodeposition and organic enrichment and fining of the sediment, ultimately impacting on nutrient and carbon cycling and food web structures and flows. Moreover, emergent parts of the turbines may also lead to changes in the ecosystem and its socio-economic benefits by collisions with birds and visual (horizon) disturbance. According to the ecosystem services model, all of the ecosystem services (except for aquaculture production) are affected to some extent by the introduction of OWF. The mussel farming in the multi-use case causes additional impacts via the introduction of ropes which are quickly colonized by large biomasses of filter feeders (i.e. mussels), and via harvesting of the filter feeder biomass. These result in direct impacts on ecosystem services via changes in nutrient and carbon cycling, removal of biomass from the system and alterations in the food web flows and structures (similar to the hard substrate introduced with the wind turbines). But the multi-use of space may also indirectly impact on ecosystem services via interactions (e.g. resource competition between mussels in the farm and mussels on the turbines may lead to lower productivity of mussels on the turbines, resulting in lower biodeposition and a relatively smaller impact on nutrient cycling than without the presence of the mussel farm).


Cause-effect chains from human activity over changes in ecosystem structures and processes to impacts on ecosystem services for offshore wind energy production and mussel farming