Sraheens is dominated by black bog-rush and purple moor-grass - the two species that together set the colour of the western bogs, slate-dark in winter, washed with bronze and green in summer. Mixed through them you find ling heather, cross-leaved heath, carnation sedge, common cottongrass with its white tufts shivering in the wind, and bog asphodel turning the ground yellow in July. And then, at your feet, glistening like beads of mercury, the round-leaved sundew. A carnivorous plant the size of a coin, the sundew's red tentacles hold sticky droplets that trap midges, lacewings, and even small dragonflies, which the plant then slowly digests. It is one of nature's quiet adaptations to a soil so nutrient-poor that the plants have learned to hunt.

Blanket bogs like Sraheens form only where it rains constantly and drains slowly, which describes Achill almost perfectly. The peat builds up at roughly a millimetre a year - which means the deepest layers down at the base of Sraheens Lough were laid down when the first Christian monks were arriving on the offshore islands. Every pollen grain, every bog oak stump, every fragment of charcoal from an ancient fire is preserved in the anaerobic peat, unchanged by time. Walk across this ground and you are walking on a slow archive.

The townland of Sraheens sits in the barony of Burrishoole, the historic Achill Parish, and borders four other townlands - Cashel and Dooega to the west, Derreen to the south, Salia to the north. To the east a rocky ridge breaks the bog, and the Sraheens River runs off the slopes toward Achill Sound, about three kilometres away. The village of Dooega lies the same distance west. None of these places are big. The whole human population of Sraheens itself is well under a hundred, scattered along the few roads that thread between the wetter sections. The bog is the dominant resident.

Sraheens Bog is classified by Ireland's National Parks and Wildlife Service as a Natural Heritage Area - a national-level protection for sites of conservation importance. The reason is simple: intact lowland blanket bog is one of the rarest habitats in Europe, and Ireland has more of it than most of the continent combined. The threats are equally simple: overgrazing by sheep, mechanical peat extraction, drainage, and the slow drift of climate change altering rainfall patterns. So far, Sraheens has held. The sundews still catch their midges; the bog asphodel still bloom; the cottongrass still shivers in late June. The work of staying intact is most of what bogs do.