Unst may be the Treasure Island of Robert Louis Stevenson, but it is certainly a treasure trove for the naturalist. This is partly due to the island’s varied geology, which produces a variety of landscapes and habitats, and partly due to geographical location.

Unst is often described as a geologist’s paradise and even for the less scientific visitor there is much of interest. Geologically Unst can be divided into western and eastern halves. Schists and gneisses create the spectacular scenery in the west of the island. These rocks are impermeable to water, which leads to the formation of the water logged peat and blanket bog landscape. Thin, well-drained soils however overlie the eastern portion of the island where serpentine and gabbroic rocks, which were once part of an ancient ocean seafloor, are most common. This creates herb-rich heathland or ‘sedge lawns’ which is particularly impressive at the Keen of Hamar as described below.

Further information on the geology of Unst, including the economic influence and examples of the rock types, can be found at Unst Heritage Centre.

Birds are the most obvious wildlife to be seen by the visitor to Unst. Hermaness National Nature Reserve (NNR) includes one of Shetland’s largest seabird colonies, with 15 breeding species. The Gannet (known in Shetland as Solan) and the Fulmar (Maalie) are two of the most obvious species on the cliffs (known locally as the banks), while on a good day there may be thousands of Puffins (Tammie Nories) on the clifftops.

The interior of Hermaness is blanket bog, an internationally rare habitat, where the visitor runs the gauntlet of the nesting Great Skua (Bonxie or Skui), an internationally rare bird, although common in Shetland. Another special breeding bird of the blanket bogs is the Red-throated Diver (Rain Goose), a shy bird specially protected by law, but which can be commonly seen on lochs or on the sea. Unst’s hills also hold many breeding waders, including a large proportion of Britain’s Whimbrel (Peerie Whaup).

Unst’s position means that it has played host to many rare birds. Although fewer than 50 species breed more than 300 species have been recorded, many rare vagrants from far corners of the globe: Collared Flycatcher from eastern Europe, Serin from southern Europe, Sykes’s Warbler from central Asia, Pallas’s Grasshopper Warbler from Siberia or Swainson’s Thrush from North America.

There are no native land mammals in Shetland as they have all been introduced by man. Even the Otter (Dratsie) was probably brought by humans for its pelt. With luck, Otters can be seen almost anywhere around Unst, including in the voes and bays around the main settlements at Uyeasound, Baltasound and Haroldswick.

Both species of seal, Grey Seal (Haaf Fish) and Common Seal (Tang Fish) may also be seen, with the latter most often seen inshore but the former species usually commoner off Hermaness. Whales and dolphins may occasionally be seen in summer, usually off the north coast - try Hermaness or Lamba Ness but remember it is really just a matter of luck.

Butterflies are usually fairly uncommon. The Large White may breed for several years at a time, but may be rare in other years, while Red Admiral and Painted Lady are just about annual. Other species are all rare. Moths attracted many visitors in the early 20th century as Shetland has several unusually dark varieties. One, the Exile, is found nowhere else in Britain and Hermaness was the most famous locality.

Migrant moths also occur. The Convolvulus Hawkmoth, Britain’s largest moth, is recorded almost annually in August or September, while one of the most remarkable natural events of recent years was the arrival of literally millions of Silver Y moths in August 1996.

Unst has a wealth of flowers, partly due to the variety of underlying rocks and partly due to the relatively low grazing levels in several areas, although species are still being lost as crofting becomes less diversified. In early summer, the wetter hills look almost white with Cotton Grass, which is replaced later in the summer by the golden-yellow of Bog Asphodel and, in a good summer, the pinks and purples of three species of heather. Several species of orchids are quite common - Heath Spotted Orchids on the hills, Northern Marsh Orchid around the crofts and Frog Orchids on close-cropped serpentine grassland.

The botanical highlight of any visit to Unst is the Keen of Hamar NNR. This apparently barren ‘moonscape’ is the place where, in the 19th century, the teenage botanist Thomas Edmondston discovered the endemic Shetland Mouse-eared Chickweed - more commonly referred to as Edmondston’s Chickweed. Several other rare plants grow on the Keen, including Norwegian Sandwort, Northern Rock-cress and Stone Bramble.

Thanks to Mike Pennington, Micky Maher (Shetland Ranger Service), Danny Laurier and Anne Meller for the above.