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 (the supercontinent of 190 million years ago).
When sea levels were lower, around 45 million years ago, the land that we know as New Zealand was part of a mini-continent that included New Caledonia. But once sea levels rose, New Zealand became cut off and some of its flora evolved in relative isolation over millions of years. The origins of many other species are more recent. Since New Zealand became isolated, many plants from Australia and the tropical Pacific have arrived after drifting on the ocean, being blown by the winds or carried by birds.
In the 700 years since human arrival, 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 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 three layers are the 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 the South Island and Stewart Island, but only in the lowlands.
In the South Island, most native forests that escaped the settlers’ fires are found 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 within 200 or 300 years 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 occur in the North Island mountain regions.
In both islands the altitude limit of trees, known as the bush line, is an important feature. Near the bush line, trees become smaller, forming a subalpine ‘goblin forest’. The central North Island’s bush line is around 1,450 metres; at the bottom of Stewart Island it appears 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 some 700 years ago 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 this commodity second only to food. 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 bush line, when alpine fell-fields bloom even while remnants of snow linger in the 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 alpines 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 bush line 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 also 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 river banks, 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. They threaten to change the landscape in parts of the South Island high country.