Seals feast at wind farm buffet 

Traditional windmills are cherished in the Netherlands. Their modern equivalents in Ireland, however, are deemed ugly and intrusive. But beauty is in the eye of the beholder; some of today’s elegant streamlined giants will, no doubt, become ‘listed’ structures in the fullness of time. Meanwhile, nobody wants to live near them.

Locating windmills at sea avoids the NIMBY problem but are marine wind farms as eco-friendly as they seem? Seabed habitats may be damaged when foundations are being laid and electricity cables run ashore. Turbines are lethal to flying seabirds; the tips of the largest blades move at around 250km per hour. Whales and dolphins call to each other and use sound pulses to navigate. Wind-mill noise may upset them. However, research on seals, reported on-line in the July edition of Current Biology, suggests that wind-farms, and undersea pipelines, might actually enhance biodiversity.

Dr Deborah Russell and colleagues at the University of St. Andrew attached GPS tracking units to 96 seals in the North Sea. The devices were glued to the fur on the backs of the seals’ necks. Both grey and common seals were tagged. These ‘mermaids’, the souls of sailors drowned at sea according to Irish folklore, also frequent our coasts.

The tracking units, which last between 25 and 121 days, record the locations at which seals surface from dives. When the movements of the seals were examined, curious patterns emerged. A seal can spend from a few days to a month on a foraging trip at sea, before returning to the coast to haul out and rest. To the scientists’ surprise, some of the tagged animals showed a preference for windmill sites during their ocean sorties.

Eleven common seals visited two particular wind-farms repeatedly. One travelled to the same location on each of 13 trips. Some seals were recorded swimming directly from turbine to turbine, apparently checking out each one before deciding where to hunt. Adult and juvenile seals, of both sexes, visited the structures. An individual lingering at a particular location was assumed to be foraging. Pipelines attracted both grey and common seals. Of 150 common ones tagged in the Netherlands, two followed a section of pipeline for up to ten days at a time. Two others visited pipelines frequently as did one grey and one common marked in Scotland.

When we alter the environment on land, wild creatures avail of new opportunities created. Gulls follow the plough and scavenge on town dumps. Thrushes catch worms on manicured lawns. Swifts and swallows no longer nest on cliffs or in caves but choose buildings instead. Mice, rats and sparrows thrive in our concrete jungles. Marine creatures are equally inventive. Barnacles mussels and limpets attach themselves to piers, mooring buoys and the hulls of boats. Pipelines, cables, and sunken ships, become mini artificial reefs, supporting food chains from molluscs to crustaceans and fish.

Those great opportunists, the seals, seldom miss a trick. They scavenge for discarded fish around Irish ports. Feeding the grey seals was a major attraction at Howth. In the shops on the pier, parents and grandparents bought fish for their freezers while the children got rejects to feed the seals. The fisherman’s great rival, capable of stealing fish from his nets, was helping to boost the fish trade! Then, for reasons unknown, the harbour authorities banned the practice. If seals are visiting wind-farms and pipelines, there must be eco-systems around them, capable of attracting large numbers of fish. The species being targeted include cod and whiting, Russell suspects.

The research examined seal behaviour when the wind-farm mills were already running and not during the highly destructive building phase. Nor can we be certain that undersea installations necessarily increase the numbers of marine animals. It’s possible, though unlikely, that the structures concentrate marine populations already present, making it easier for seals to exploit the fish which visit.