The changing character of the high country, from north to south, is reflected in the enormous diversity of the native plants and animals that have evolved to cope with its varying and harsh conditions.
Generally, the high country has a dry climate, and is often hot and windswept as predominant northwesterlies cause rain to fall on the Southern Alps, creating a rainshadow over the eastern grasslands.
Because much of the land lies above 700 metres it is also frequently cold. From daylight to nightfall the temperature can drop from baking hot to freezing. In winter, snow covers the mountains and many lakes freeze, while sheltered slopes and valley floors experience hoarfrosts.
Before European settlement, vegetation in the high country was predominantely tussock - ranging from red tussock in wetter areas to waist-high snowgrass on the mountainsides. Herbaceous and small shrubby plants, including hebes, heaths and many smaller species grew among the tussocks.. Higher up, herbfields and cushion plants predominated. Some of the prostrate shrubs can be 200-300 years old, and the prostrate Raoulia daisy, or “vegetable sheep,” many times older.
Repeated burning of tussock to stimulate young growth for extensive farming has reduced fertility and increased soil erosion. Fire has removed the protection of many of the remaining beech forests on the mountainsides.
The insect life of the high country is extraordinary, including alpine butterflies, day-flying moths – even alpine weta that survive freezing conditions with a natural “anti-freeze” in their blood. The high country has a large variety of skinks and geckos, often found only in small local areas.
A range of birds, some endangered or threatened, live in the high country, or migrate there to breed. These include native falcons, riverbed-nesting birds such as the wrybill, oystercatcher, dotterel, black stilt and black-fronted tern, mountain birds such as kea and rock wren, and high country wetland birds such as crested grebe, scaup, shoveler, grey duck, grey teal, paradise shelduck, Australasian bittern, Australian coot and marsh crake.