A key feature of Berneray is its machair. The machair is a coastal plain made up of windblown shell sand. Traditional crofting practice, which involves summer agriculture using seaweed together with dung from winter grazing animals as natural fertiliser, has, over time, bound together and stabilised the land. The machair is ploughed in rotation, giving a patchwork of crops and fallow of different ages which supports a wide range of flowers. Berneray has a particularly fine machair, a result of careful husbandry by the island's crofters, helped by the absence of rabbits.