New Zealand is a green land – most of its many native trees and shrubs are evergreen. The lush forests, often referred to as ‘native bush’ or simply ‘the bush’, have an almost tropical feel. Huge kauri and tall trees known as podocarps tower over a multitude of ferns and creepers, evoking a primeval scene. Kauri and podocarps have links back to the ancestral forests of Gondwana (a supercontinent that broke away from an even larger one some 190 million years ago).
The land we now know as New Zealand was once part of a mini-continent that included New Caledonia. But as sea levels rose, New Zealand became cut off and its flora evolved in relative isolation over millions of years. The origins of many other species are more recent. After New Zealand became isolated, many plants arrived from Australia and the tropical Pacific by drifting on the ocean, being blown by the wind or carried by birds.
In the 750 years since humans arrived, over 75% of New Zealand’s forest cover has been burnt or chopped down. Fire, axe and plough converted forest into pasture. New Zealand, once a giant forest, was transformed into innumerable farms. Still, large areas of native bush remain, mainly in the high country.
Much of the North Island bush is conifer-broadleaf forest, which thrives in lowlands and on good soils. Rimu, mataī, miro, kāmahi and tawa are common trees. A typical North Island forest has five layers. The forest giants form a canopy over a layer of smaller trees, through which emergent trees appear. Below these are shrubs and, finally, ground plants. Many varieties of fern spread over the forest floor, while tree ferns rise above it. Among the tree ferns is the ponga. Its fronds, with their shimmering underside, are a national emblem – the silver fern. Conifer-broadleaf forests are also found in lowlands in the South Island and Stewart Island.
In the South Island, most native forests that escaped the settlers’ fires are in the high country, on poorer soils. They are generally more open, simpler in structure, and dominated by the beech species – red, hard, black and silver beech. There are also occasional enclaves of conifer-broadleaf within these forests, often on valley floors, and larger pure stands in coastal areas. Half of the South Island forests, mainly those in the eastern lowlands, were destroyed by fire in the first two or three centuries of Māori settlement, and replaced by tussock grasslands. Possums, deer, goats and other European-introduced animals have wreaked havoc on the native bush, which did not evolve with browsing mammals. Beech forests also grow in North Island mountain regions.
In both islands the altitude limit of trees, known as the bushline, is an important feature. Near the bushline, trees become smaller, forming a subalpine ‘goblin forest’. The central North Island’s bushline is around 1,450 metres; in the southern Stewart Island it is as low as 500 metres.
People and the bush
The bush is more than just forest: the dense green wilderness and its trees, shrubs and ferns, are embedded in the national psyche. The bush is where people go to walk or tramp, to fish and to hunt – a refuge from the pressures of modern life. Cabbage trees clattering in the wind, the yellow blooms of kōwhai and the scarlet brushes of pōhutukawa are New Zealand touchstones.
Common as cabbage
The hardy Cordyline australis, found throughout New Zealand, was known to Māori as tī kōuka. They used its leaves, stems and roots for food, clothing and medicine. Its common name, the cabbage tree, was coined by early European settlers who also saw it as a source of food, using the inner parts of its sword-like leaves and the stem as a cooked or raw vegetable. Contemporary estimates roughly match human and cabbage tree populations – there are some 4 million of each.
Mighty forest trees – tōtara, mataī and kauri – were widely used by Māori for canoes and houses. On arrival, Polynesians found the fibre of flax superior to anything they had known in the Pacific. In a culture without metal and a land without mammals for hides and clothing, they rated flax second only to food as a resource. They extended their mat- and basket-weaving skills to binding ropes for fishing lines and nets, and producing fabric for sails, shelter and clothing.
New Zealand has some 600 alpine plant species, 93% of them found nowhere else. Spring is the time to be above the bushline, when alpine fell-fields bloom although remnants of snow linger in south-facing gullies. The further south you go, the more persistent the snows. The bloom of alpine flowers begins in the north and moves down the country like a wave. In the southern part of Stewart Island, where alpine plants grow at sea level, the main flowering can be as late as January.
With striking white petals and yellow centres, the Celmisia species (mountain daisies) are a familiar upland flower. In early summer the 50-odd alpine species form white specks across the tussock lands, while giant buttercups add a splash of yellow.
A sharp impression
When early botanical explorers ventured above the bushline they found many new species. Among the novel plants William Colenso encountered on his first journey to the Ruahine Range was the speargrass or Spaniard. It was especially memorable if you sat in the wrong place. ‘A large stout species of the ever-to-be-remembered genus Aciphylla was, for us, alas! far too plentiful’. 1
Swamps and wetlands
Swamps were considered wastelands by European settlers, who drained and ploughed them into farmland. Wetland areas have been reduced by about 85% in the last 150 years, from nearly 700,000 hectares to about 100,000. While several thousand wetlands remain, most are small. Coastal wetlands are very productive, providing habitat, breeding areas, and food for shellfish, crustaceans, inshore fish and birds. Wetlands are home to 20% of New Zealand's indigenous birds.
Much of New Zealand’s land area is farmed. It is estimated that 25,000 exotic plant species have been introduced – mainly for gardening and farming. Ryegrass and clover are ubiquitous on farm paddocks across the country.
Willows line creeks and riverbanks, and Lombardy poplars, macrocarpa and eucalypts are common windbreaks. Broom, gorse, blackberry and many other introduced species have become troublesome weeds, while others such as pine are now part of the landscape.
The radiata pine (Pinus radiata) is used for huge forestry plantations. In 2001 there were 1.6 million hectares of the species. Together with the many introduced grasses and crops, they cover almost half of New Zealand. In some places, pine trees, regarded as weeds, are referred to as ‘wilding pines’, as they have been sown by the wind. These are changing the landscape in parts of the South Island high country.