geohazards and might trigger mass instabilities. Since natural fluxes of methane from the deep-sea floor are so poorly known, it will be difficult to estimate the further atmospheric and climate effects of active methane extraction and release from gas hydrates. Underwater cables. The laying of underwater telegraph cables came early in our understanding of the deep sea. HMS Cyclops in 1855 was used to determine the depth profile between the UK and Newfoundland for the laying of the first transatlantic cable. The first effort in 1857 failed when the cable-dispensing machinery became disabled and cut the wire, but the cable was finally successfully connected in 1858 [81] . In subsequent years, cables were laid in many parts of the global oceans. It was the recovery of a broken cable from 2180 m between Sardinia and Bona, encrusted with the coral Caryophyllia that demonstrated the viability of life at lower bathyal depths. In the northeastern Atlantic, a maximum spatial extent of submarine cables in the OSPAR northeastern Atlantic area has been estimated to range between 5 and 10 km 2 , although this is most likely an underesftimate as it does not take into account the effects of plough burial [27] . Pipelines offer a similar scenario, although they tend to be physically bigger than cables. We predict minimal impact of underwater cables ( Tables S2 and S3 ). Scientific activity. Since the onset of dedicated deep-sea research, sampling methodologies have evolved continuously and the number of research expeditions investigating the