Offshore Wind Energy and Marine Biodiversity in the North Sea: Life Cycle Impact Assessment for Benthic Communities

Abstract

Large-scale offshore wind energy developments represent a major player in the energy transition but are likely to have (negative or positive) impacts on marine biodiversity. Wind turbine foundations and sour protection often replace soft sediment with hard substrates, creating artificial reefs for sessile dwellers. Offshore wind farm (OWF) furthermore leads to a decrease in (and even a cessation of) bottom trawling, as this activity is prohibited in many OWFs. The long-term cumulative impacts of these changes on marine biodiversity remain largely unknown. This study integrates such impacts into characterization factors for life cycle assessment based on the North Sea and illustrates its application. Our results suggest that there are no net adverse impacts during OWF operation on benthic communities inhabiting the original sand bottom within OWFs. Artificial reefs could lead to a doubling of species richness and a two-order-of-magnitude increase of species abundance. Seabed occupation will also incur in minor biodiversity losses in the soft sediment. Our results were not conclusive concerning the trawling avoidance benefits. The developed characterization factors quantifying biodiversity-related impacts from OWF operation provide a stepping stone toward a better representation of biodiversity in life cycle assessment.

Keywords: artificial reef; characterization factors; marine ecosystems; offshore wind farms; seabed occupation; species abundance; species richness; trawling avoidance.

Figure 1

Overview of studied offshore wind farms (green areas) with turbine foundations (green dots) and sample locations (orange dots). A: the North Sea; B: Belgium; C: the Netherlands; D: Germany; E: Denmark; F: an illustration figure of effect locations (Immediate and Near) and substrate type (Hard and Soft). The maps were drawn using ArcGIS Pro, and the base map is the world topographic map from Esri (http://www.arcgis.com/home/item.html?id=30e5fe3149c34df1ba922e6f5bbf808f).

Figure 2

Species richness evolution from installation to 25 years afterward. The gray shaded area shows the 95% confidence interval.

Figure 3

Species abundance (individuals/m²) evolution from installation to 25 years afterward. The gray shaded area shows the 95% confidence interval. Note that the subplots are not directly comparable because the y-axis limits differ.

Figure 4

Characterization factors and impact assessment results for species richness. AR: artificial reefs, SO: seabed occupation, and TA: trawling avoidance. The average values (red points) are used for CFs and impact assessment results in this study. Note that the average of negative values is applied for TA.

Figure 5

Characterization factors and impact assessment results for species abundance. AR: artificial reefs, SO: seabed occupation, and TA: trawling avoidance. The average values (red points) of CF and impact assessment results are used in this study. Note that the average of negative values is applied for TA.