Grassholm

Grassholm, known in Welsh as Ynys Gwales, lies some 13 kilometres off the south-western tip of Pembrokeshire, a small, uninhabited island of just 26 acres rising to 42 metres, formed largely from keratophyre rock with a band of basalt along its north-western coast.

Despite its remoteness and modest size, Grassholm is one of the single most important seabird islands anywhere in the world.

Wildlife

The island hosts the world’s third-largest colony of northern gannets, with around 39,000 breeding pairs crowded onto its slopes each summer, a colony so large it supports roughly 10 percent of the entire global gannet population on this one small outcrop of rock. Seen from a boat in the breeding season, Grassholm’s white-covered slopes and the dense clouds of birds wheeling above them make it one of the most spectacular wildlife sights in British waters.

The RSPB has owned Grassholm since 1947, making it one of the charity’s oldest reserves, and it holds National Nature Reserve status in recognition of its outstanding ornithological importance. Landing on the island is prohibited to protect the breeding colony from disturbance, and visitors instead view it from boat trips departing the Pembrokeshire coast. In recent years, conservationists have documented a troubling side effect of marine plastic pollution: as much as 80 percent of gannet nests on Grassholm have been found to contain plastic waste, birds having mistaken floating debris for natural nesting material, an ongoing concern that has been monitored on the island for well over a decade.

Wildlife and area

In medieval Welsh literature, Grassholm has long been identified with Gwales, the legendary island of the Mabinogi tales associated with the mythological figure Brân the Blessed, adding a layer of folklore to an island already extraordinary for its wildlife. Grassholm’s waters support Grey Seal and Chough along the wider Pembrokeshire coast, and the island lies within reach of the other great Pembrokeshire seabird islands, Skomer and Skokholm Island, both renowned for their own enormous Manx shearwaters colonies.