Heathland is favoured where climatic conditions are typically hard and dry, particularly in summer, and soils acidic, of low fertility, and often sandy and very free-draining; a mire may occur where drainage is poor, but usually is only small in extent. Heaths are dominated by low shrubs, 20 centimetres (7.9 in) to 2 metres (7 feet) tall.
Heath vegetation can be extremely plant-species rich, and heathlands of Australia are home to some 3,700 endemic or typical species in addition to numerous less restricted species. The fynbos heathlands of South Africa are second only to tropical rainforests in plant biodiversity with over 7,000 species. In marked contrast, the tiny pockets of heathland in Europe are extremely depauperate with a flora consisting primarily of heather (Calluna vulgaris), heath (Erica species) and gorse (Ulex species).
The bird fauna of heathlands are usually cosmopolitan species of the region. In the depauperate heathlands of Europe, bird species tend to be more characteristic of the community and include Montagu's harrier, and the tree pipit. In Australia the heathland avian fauna is dominated by nectar-feeding birds such as honey-eaters and lorikeets although numerous other birds from emus to eagles are also common in Australian heathlands. Australian heathlands are also home to the world's only nectar-feeding terrestrial mammal: the honey possum. The bird fauna of the South African fynbos includes sunbirds, warblers and siskins. Heathlands are also an excellent habitat for insects including ants, moths, butterflies and wasps with many species being restricted entirely to it. One such example of an organism restricted to heathland is the silver-studded blue butterfly, Plebejus argus.