Habitat disturbance
Habitat disturbance
Habitat disturbance refers to changes in conditions that interfere with the normal functioning of a biological system. Offshore wind and grid infrastructure can cause habitat disturbance in various ways, for instance by introducing hard artificial substrates or by disturbing the seabed when laying subsea cables.
Lifecycle phase
Impact
Biodiversity receptor
Measure for wind turbine
Measure for grid
Avoidance or minimisation
Status offshore
Planning
Displacement
Benthos
Siting away from areas designated as SPAs and MPAs. In other areas, micro-site in a way to avoid habitats valuable for threatened species (e.g. spawning, nursery and feeding grounds) and biogenic reefs.
Avoidance
Implemented
Planning
Displacement
Benthos
—
Siting of offshore converter station away from areas with sand waves present to reduce the need for dredging prior to installation
Avoidance
Implemented
Planning
Displacement
Benthos
—
Siting of offshore converter station in a way to minimise the number and length of interarray cabling.
Avoidance
Implemented
Planning
Displacement
Benthos
—
Siting of offshore converter station and micro-siting of cables in a way to avoid valuable habitats
Avoidance
Implemented
Planning
Displacement
Benthos
Micro-siting of cables to avoid dense aggregations of reef building organisms and valuable spawning areas.
Avoidance
Implemented
Planning
Displacement
Benthos
Micro-siting of cables (micro-rerouting) to avoid silty deposits and peat to avoid the risk of turbidity and replacement with sand
Avoidance
Implemented
Planning
Displacement
Benthos
—
Define exclusion zones for anchoring based on baseline information on the distribution of sensitive species and habitats.
Avoidance
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
Timing: Avoid sensitive spawning times for substrate spawning species (e.g. Atlantic herring, sandeels, dogfish). Avoid times of of seasonal migration of specific fish and shelfish species.
Avoidance
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
Using Horizontal Directional Drilling method when doing underground cable laying to avoid damage in intertidal and landfall areas where habitats may be more sensitive (e.g. chalk cliffs, saltmarsh)
Avoidance
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
When seabed allows, using narrow blade conventional plough to allow/aid recovery of the seabed after cable burial
Minimisation
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
Using frend mattress in soft sediments when laying cables close to turbine foundations if cables can't be completely covered
Minimisation
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
In hard substrate areas, back fill the material after cable laying. In case the same material cannot be used (e.g. in rocky seabed, use sustainable nature-based materials to cover cables).
Minimisation
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
In case of existance of species sensitive to suspended sediment, use technique of cable burial resulting in lowest release of sediment. This is particularly important in the cases with sediment with various degrees and types of pollution.
Minimisation
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
To promote recovery of the seabed, back fill the displaced material that was a result of cable burial activities to reduce the potential for remobilisation of sediments and enable recovery of benthic organisms.
Minimisation
Implemented
Construction
Avoidance, displacement and injury
Fish, marine mammals, sea turtles and benthos
—
In soft seabeds, use jet ploughing to reduce benthic distrubance.
Minimisation
Implemented
End of life
Injury
Benthos
Lifetime extension
Avoidance
Implemented
End of life
Injury
Benthos
Cutting monopiles below seabed: leaving part of monopile behind, which will be covered once seabed is resettled
—
Minimisation
Concept
End of life
Injury
Benthos
Topping: monopile is cut 2 meters above seabed and scour protection is left in situ
—
Minimisation
Concept
End of life
Injury
Benthos
Leaving scour protection behind
—
Minimisation
Concept
End of life
Injury
Benthos
—
'Bury and forget': to avoid seabed disturbance during decommissioning, subsea cables are left behind (buried at an appropriate depth)
Avoidance
Implemented
End of life
Avoidance, displacement, and injury
Fish, marine mammals, sea turtles and benthos
Timing: Avoid sensitive spawning times for substrate spawning species (e.g. Atlantic herring, sandeels, dogfish). Avoid times of of seasonal migration of specific fish and shelfish species.
Avoidance
Implemented
End of life
Avoidance, displacement, and injury
Fish, marine mammals, sea turtles and benthos
—
In case of existance of species sensitive to suspended sediment, use technique of cable removal resulting in lowest release of sediment. This is particularly important in the cases with sediment with various degrees and types of pollution.
Minimisation
Implemented
End of life
Avoidance, displacement, and injury
Fish, marine mammals, sea turtles and benthos
—
To promote recovery of the seabed , back fill the displaced material that was a result of cable removal activities to reduce the potential for remobilisation of sediments and enable recovery of benthic organisms.
Minimisation
Implemented
End of life
Avoidance, displacement, and injury
Fish, marine mammals, sea turtles and benthos
—
In hard substrate areas, back fill the material after cable removal. In case the same material cannot be used (e.g. in rocky seabed, use sustainable nature-based materials to cover cables).
Minimisation
Implemented
