Australia

Australia spans nearly 7.7 million square kilometres and an entire continent, from the wet tropical forests of Cape York and the Daintree to the cool temperate rainforests of Tasmania. The land is geologically old, low, and flat — the Great Dividing Range along the east coast is the major topographic feature, with Mount Kosciuszko at 2,228 metres marking the highest point on the mainland. The lowest natural point, Lake Eyre (Kati Thanda) at fifteen metres below sea level, sits in the arid centre.

Climate is exceptionally varied for a single political unit. About seventy per cent of the continent is arid or semi-arid — the Simpson, Great Sandy, Great Victoria, and Tanami deserts, the Nullarbor Plain — but the coasts diverge sharply. Cape York and the Top End carry tropical savanna and monsoon forest; the eastern seaboard runs from subtropical Brisbane south through wet sclerophyll forest to Mediterranean and temperate Victoria and Tasmania; the southwest corner around Perth holds a Mediterranean climate distinct from anywhere else on the continent.

The flora is unusually distinctive because Australia separated from Gondwana early and drifted in isolation. About 85 per cent of vascular plant species are endemic. Three families dominate. Myrtaceae provides the Eucalyptus, Corymbia, Melaleuca, Leptospermum, and Callistemon that define most of the country's forest and woodland. Fabaceae contributes some 1,000 species of Acacia (wattles) — more than the rest of the world combined. Proteaceae — Banksia, Grevillea, Hakea, Telopea — radiates spectacularly in the Mediterranean Southwest, a recognised biodiversity hotspot with more than 8,000 vascular plant species and roughly 50 per cent endemism. The wet tropical northeast holds Australia's small but botanically extraordinary rainforest belt, and Tasmania carries Gondwanan relicts including Nothofagus (southern beech), Dicksonia antarctica (soft tree-fern), and Athrotaxis pencil pines.

The discovery of Wollemia nobilis — the Wollemi pine, found alive in 1994 in a single canyon less than 200 km from Sydney — counts as one of the great botanical events of the late twentieth century. The Royal Botanic Gardens at Sydney (1816) and Melbourne (1846) hold many of the original collections used to describe this flora.