The reserve is situated near the southern tip of The Ayres, an area of unique heathland and sand dune. Cronk y Bing has one of the widest strips of yellow dune on the Island. In the past sand has been extracted from the back dunes, forming a flatter area behind the leading dunes upon which coastal grassland, grazed by rabbits, has developed.

Marram grass (bent) dominates with a range of other plants including pyramidal orchid, sea bindweed, restharrow, common stork's-bill, bugloss, harebell, sheep's-bit, wild carrot, common cornsalad, burnet rose and wild mignonette. Sea holly and saltwort are found on the shore. The Lhen Trench is a largely canalised river draining part of the Ballaugh Curragh. The trench has a range of additional species including water mint, hemlock water dropwort, marsh woundwort, cudweed, angelica, marsh bedstraw and figwort.

The adjacent shoreline is a favoured breeding ground for the little tern. Other breeding birds include oystercatcher, ringed plover and meadow pipit. During the autumn divers, grebes, sea duck, skuas, a variety of gulls and waders are often seen. Off the coast seals, basking sharks and diving gannets may also be seen. The coastal footpath (Raad Ny Foillan) runs along the shore section of the reserve.

Habitats are and dunes and shingle foreshore, waterside at the mouth of the Lhen Trench. Notable species include Isle of Man cabbage and pyramidal orchid, oysterplant, dune fescue and the little tern.