Summary and Conclusions: Environmental Effects of North Sea Oil and Gas Developments

This Royal Society Discussion Meeting has examined the total environmental impact of a whole industry in a single geographical area. Land-based developments related to the exploitation of the North Sea oilfields and their social consequences have been substantial, although neither the worst fears nor the best hopes have been realized. An accommodation has been reached with the fishing industry in the affected area. Offshore platforms are a source of chronic pollution from production water, but in recent years there has been a marked increase in the use of oil-based drilling muds and it is estimated that 20 Mt per year of petroleum hydrocarbons are added to the sea in oil-contaminated drill cuttings. The effect of these additions has been studied in the laboratory, in mesocosms and in field surveys which, together, yield a consistent picture. Within a radius of a few hundred metres of a platform there is impoverishment of the benthic fauna. Close to the platform the production of anoxic conditions through smothering and the activity of sulphide-producing bacteria is probably more significant than the toxic effect of the oil-based muds. Outside this immediate zone of impact, the oil results in organic enrichment and enhanced populations of some of the fauna. The total area affected is, in the context of the North Sea, minuscule. There is no evidence that plankton is materially affected and the success of commercial fisheries dependent upon the plankton crop is more influenced by fishery practices than by any other factor. Seabird populations, about which there was formerly much concern, have not so far been affected by oil pollution in the North Sea. There is wide fluctuation in recruitment success, but populations of species thought most vulnerable to oil pollution are generally increasing. Although marine pollution research has yielded valuable insights into the responses of individuals, populations and communities to perturbation, natural as well as man-made, it is not likely that future problems associated with oil extraction from the sea will be as stimulating to fundamental research. Different problems relating to environmental pollution should now be addressed by marine scientists.