Approaching Coll by steamer from the east, the island appears to be one of the most inhospitable environments imaginable. There seems to be more bare rock than vegetation and even the wildest imagination could not guess that the island was in any way fertile. Yet Coll does contain some fine herb-rich pastures scattered along the northern shores and covering extensive areas in the south-west.

Farming in Coll, as in Tiree, Colonsay and large sections of the Outer Hebrides, depends to a great extent upon domestic livestock making full use of the natural vegetation, in turn, depends upon sand derived from seashells forming the interesting landform known as 'machair'. Countless millions of marine molluscs have, over the centuries, died on our western seaboard. Their shells, pounded by the relentless action of the Atlantic swell, form the superb beaches. Picked up by the equally relentless wind, the grains of sand have formed dunes and machair plains.

Each year there is a windborne top dressing of sand, rich in calcium, which maintains flowery grasslands supporting red and white clovers, wild carrot, kidney vetch, lesser meadowrue and many other herbs. A few unexpected plants such as the bloody crane'sbill and mossy saxifrage, more often associated with cliff ledges than sand dunes, appear dotted over the machair or clinging precariously to eroding dunes.

Pools and marshy hollows affected by this input of marine lime produce lush fen and marshland communities of plants, including some distinctive orchids, such as the brick-red Hebridean variety of the early marsh orchid. The blown sands provide feeding and breeding grounds for small birds and waders. Wheatears nest in rabbit holes, skylarks soar over the machair plains, ring plovers and oyster catchers trill and bubble by the shore. In the duneslacks, dunlin, redshank and snipe breed.

The transfer of nutrients in the form of marine animal material from sea to land has, inevitably, resulted in the colonisation and establishment of distinctive species of plants and insects. One such example is a handsome little moth known as the Belted Beauty. In Scotland this insect is largely confined to the Hebrides with main centres of population concentrated on the machair. The grey and white males, with attractively striped wings, fly during April to visit the curiously unmothlike females, which are wingless and spend their time crawling over stones or pieces of driftwood on which they lay their eggs. Once hatched, the looper caterpillars crawl out over the machair feeding on a wide range of plants, eventually burying themselves in the sand to pupate, the moths emerging the next Spring. How did this little flightless insect manage to disperse itself throughout the Hebrides? The females seem to be attracted to pieces of wood thrown up by the sea. Perhaps, in former times, they crawled onto wooden boats hauled up on the beaches and in this way were transported to new breeding grounds on other islands.