Submarine cables have a long history in telecommunication services and are increasingly important for transmission of electric power. Most telecommunication cables are located in the southern parts of Region II, Region III and in a transatlantic corridor in Region V Figure 9.8. Almost all power cables are located in Regions II and III. Submarine cables are usually buried, but in areas of exposed bedrock they are laid directly on the seabed and may be covered by a protective structure. The development of offshore power generation and transnational energy networks will require new power cables and the need for new communication links is likely to remain high in some areas.
Placement and removal of power cables causes temporary local disturbance of the seabed. There are also a range of permanent environmental effects. These include the settling of non-indigenous hard-substrate species on unburied cables or protective structures. During operation, electromagnetic fields from power cables may affect the behaviour and migration of fish and marine mammals that use electric fields or the Earth’s magnetic field for orientation. Heat from power cables may affect bottom-dwelling species and biogeochemical processes. These effects need further study.
So far, no common programmes or measures for the placement of subsea cables have been developed either by OSPAR or by other organisations, but some OSPAR countries subject the placement and operation of cables to licensing procedures.
Mitigation measures should be used, such as the choice of cable type, appropriate selection of burial or surface laying and scheduling placement according to the sensitivity of local habitats. OSPAR should develop guidelines to help OSPAR countries assess the environmental effects of cables. Research is needed on the effects of heat emission and electromagnetic fields and the impact of burial and removal operations on marine organisms.
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