Story: Natural environment
Page 1 – Geography and geology
Remote in the Southern Seas
New Zealand lies about 1,600 km from both Australia and Polynesia. Its three main islands are the North and South islands and Stewart Island, or Rakiura, lying due south of the South Island. The South Island (150,437 sq km), often referred to as ‘the mainland’ by its inhabitants, is larger than the North Island (113,729 sq km). Stewart Island is 1,680 sq km.The terms ‘deep south’ for Southland and ‘far north’ for Northland hint at the length of the main islands. The Māori names also signify the country’s long, narrow shape – the North Island is Te Ika a Māui (the fish of Māui, a legendary character), and the South is Te Waka o Māui (the canoe of Māui). The three main islands stretch 1,500 km across latitudes 34° to 47° south.
New Zealand is an archipelago with over 700 offshore islands. Most are small and lie within 50 km of the coast. The islands are the visible surface of an extensive submarine plateau, and enable the country to enjoy a huge exclusive economic zone (fishing grounds).
The Chatham Islands are 800 km east of the South Island. There are also several uninhabited island groups: the Kermadec Islands lie about 1,000 km north-east of Auckland; the Bounty, Snares, Antipodes, Auckland and Campbell subantarctic islands lie south of the mainland.
Topography
The North Island is mainly rolling hill country, much of which is farmed. A series of narrow ranges (Tararua, Ruahine and Kaimanawa) form a roughly north-east belt of higher country that rises up to 1,700 m. Much of the surviving forest cover is found here and in other mountainous areas. In the central North Island, volcanoes that have been active over the past million years jut up thousands of metres near Lake Taupō. This is the country’s largest lake, formed by water filling a volcanic crater. Nearby, Rotorua’s mud pools boil and geysers erupt.Two countries
While the North and South islands are separated by only 20 km of water, they have quite different landscapes. Mountaineer T. H. Scott found this when he moved south. In 1950 he wrote:‘I felt immediately and overwhelmingly that I had come to a quite different country …. Here then was a vast kind of land, whatever its size on the map, giving a sense of great distance where herds of grazing animals might roam, where grain plants might grow and a people wander. This had always been for me the meaning of continents.’ 1
Stewart Island is mainly low rolling hills. Unlike the two main islands, it remains almost entirely covered in native vegetation.
Geological origins
New Zealand is a sliver of the supercontinent Gondwana. The islands are only the visible part of a much larger submerged subcontinent that separated from Australia, on the eastern margin of Gondwana, around 85 million years ago.Since the Cambrian geological period (over 500 million years ago), sea levels and the land have risen and fallen many times. Periods of mountain building have been followed by epochs when mountains eroded away. Huge volcanoes erupted and massive earthquakes and landslides have ravaged the earth. Great glaciers have lain over much of the land, melted away and then returned as the climate has repeatedly cooled and warmed over time spans hard to comprehend.
Earthquakes and volcanoes
Landslide lake
When the climate warmed about 13,000 years ago, the glaciers retreated. In the Monowai Valley in Southland, a glacier that had been propping up the side of a valley melted. A nine-km stretch of mountain range collapsed, generating a massive landslide. Over time large landslide ponds, including Fiordland’s Green Lake, formed in hollows in the rumpled terrain of this landslide. When the next big earthquake occurs on the Alpine Fault in the Southern Alps there will be many catastrophic landslides, cutting road links. It is unlikely they will be as big as the Green Lake landslide, although geologists tell us that you never know.Māori oral traditions refer to earthquakes and tsunamis. In the mid-1400s a tsunami of over 10 m in height is thought to have swept over many Māori coastal settlements. Sometimes known as ‘the shaky isles’, New Zealand undergoes damaging earthquakes every few hundred years. The long gap since the last large earthquake suggests that a major quake of magnitude 8 or more is overdue.
Story: Natural environment
Page 2 – Coasts
About two-thirds of New Zealand’s coastline is hard rocky shore, while soft shores of sand or gravel cover the remainder. Some 80% of it is directly exposed to the sea, with the rest sheltered in harbours and estuaries. The west and southern coasts are more exposed.Currents
Warm, salty, sub-tropical currents bathe the north and west of the country, while cold, less saline, subantarctic currents wash up from the south. Summer water temperatures on the continental shelf range from about 21°C in the north to 14°C in the south. Swimming at northern beaches is much more common than on southern shores.Coastal waters
New Zealand’s coastal waters support hundreds of fish species and many marine invertebrates. Fur seals, sea lions, dolphins and whales also frequent these waters.Who’s eating who?
Shark attacks in New Zealand waters are rare. The many shark species that cruise coastal waters have long had more to fear from humans – much of the ‘fish’ in the popular fish and chips is actually shark. It was a favourite part of the Māori diet, and dried shark eggs were a particular delicacy. In the 1850s on Rangaunu Harbour, Northland, the Te Rarawa people caught 7,000 schooling sharks during two hunts.The estuaries and coastal waters abound in shellfish. Mussels, pāua (abalone), pipi and many other shellfish form an important part of the Māori diet – kai moana (food from the sea). Pāua and scallop shells are often used as decoration in gardens or holiday homes.
Penguin paradise
Penguins – the birds that want to be fish – abound in New Zealand’s waters. The most common is the little blue penguin or kororā, found from Northland to Stewart Island. With slate-blue plumage and a bright white belly the little blues are the world’s smallest penguins, just under 25 cm tall, and weighing a little over 1 kg. They breed underground in burrows or natural hollows. In coastal towns such as Ōamaru in North Otago, Oban on Stewart Island, and even in the capital Wellington, their nests are sometimes found under houses.Ocean deep
The deep waters beyond the continental shelf are not well understood. Huge areas of deep water, much of it barren of fish, extend over a muddy seafloor. These are underwater deserts. But even in the deep oceans there are oases – in the form of higher land known as seamounts or rises. Marine life flourishes on and around these subterranean mountain ranges and peaks, which occasionally rear up from the muddy plains. They are rich fishing grounds and a haven for marine life.Story: Natural environment
Page 3 – Climate
New Zealand is roughly midway between Antarctica and the tropics, lying between 34° and 47° latitude south. This spans the ‘roaring forties’, which can bring high winds and stormy seas to much of the country. The northern outlying islands are subtropical, while those in the south are subantarctic. Between these extremes, New Zealand’s climate is cool to temperate, but can vary widely, even within one day. The saying ‘raining at seven, fine by eleven’ often rings true for the weather forecasters.The weather pattern
At New Zealand’s location, warm moist air from the tropics meets cold dry air from Antarctica. The two don’t mix: they twist around and bump into each other. These swirling air masses sweep over New Zealand from the west.
Large volumes of stable, dry, descending air are known as high-pressure systems, often termed ‘highs’, which bring settled weather. Eastward-travelling highs cross the country every six to seven days. Between the highs are areas of unstable, ascending air known as low-pressure systems, or ‘lows’.Within the air systems there are often cold fronts – the boundary between a cold and warm air mass. These fronts produce one of the most common weather sequences. As the front approaches from the west, north-westerly winds strengthen and cloud increases. It then rains for several hours as the front passes over, with a subsequent change to cold showery south-westerly winds.
The weather consists largely of this endless procession of highs and lows sweeping over the country.
The seasons
New Zealand’s seasons roughly follow this pattern:- Spring arrives in September and October, as the days lengthen and the yellow kōwhai blooms mark the end of colder weather. Springtime is often windy, as variable weather sweeps over the country. Average temperature: 12.1°C.
- Summer is cool to mild in the south, and mild to warm in the north. Although Christmas Day is officially in summer, the weather is often still unpredictable. As the days shorten in January and February, there are long fine spells. Average temperature: 16.6°C.
- Autumn is the most settled time. In the far north an extended ‘Indian summer’ is a very real prospect. Average temperature: 13.3°C.
- Winter is cold, especially in the South Island and inland areas. Southerly blasts coat the mountains on both islands with snow. Average temperature: 8.3°C.
Wind
The wind comes to New Zealand mainly from the west. In New Zealand's southern latitudes there is no other land apart from the tip of South America. Nothing gets in the way of these ‘brave west winds’, as mariners call them; they finally hit New Zealand after travelling 10,000 km.An ill wind
A paradoxical wind, the nor’wester dumps metres of rain on the West Coast, then rises over the Southern Alps and descends on the Canterbury Plains in hot, dry gusts. When Canterbury’s dust-laden nor’wester blows, suicide rates go up and people get headaches or become grouchy. At gale force, it does serious damage to farms and buildings. Known to Māori as parera, it is one of several ‘bitter’ seasonal winds, including France’s mistral, California’s Santa Ana, and the Chinook of western Canada. And yet in winter Canterbury’s ‘mad dog’ is tamed, bringing welcome mild weather.One of the most readily recognisable regional winds is Canterbury’s nor’wester – a hot, dry wind. And the whole country knows the southerly, which blasts up from Antarctica.
Rainfall
The distribution of New Zealand’s ample rainfall is greatly affected by the mountains. The general rule is that east is drier, west is wetter. The mean annual rainfall varies from 300 mm in Central Otago to over 6,000 mm at Milford Sound, on the south-west coast. The highest recorded annual rainfall was over 18,000 mm, measured at Cropp River (Hokitika catchment) on the West Coast. However, most areas receive 600–1,500 mm, and large areas of both islands receive over 2,500 mm a year.Sunshine
As New Zealand lies just west of the International Date Line, Chatham Islanders are the first people to see the sun rise each day. The sun beams down on Blenheim and Nelson (in the South Island), and Whakatāne (in the North Island), where average annual sunshine hours exceed 2,350. The Bay of Plenty and Napier also bask in the sun. Many retired people move to the sunnier northern and eastern areas. But the New Zealand sun is especially harsh, and Auckland has the highest rate of melanoma (skin cancer) in the world.Much of the country gets at least 2,000 sunshine hours a year, and even rainy Westland, which tourists dub ‘Wetland’, has 1,800 hours. Annual sunshine hours drop to around 1,700 a year in Southland and coastal Otago.
A nice cold beer
In Central Otago they are used to the chill, but in July 1991 many hardy locals were tested. When a high-pressure system brought clear skies and intense frosts, the temperature dropped to -15°C for days on end. For the first time in at least 100 years the Shotover River froze over. Power lines snapped, weighed down by sausages of ice. Sheep’s coats froze to the ground, water pipes burst and diesel fuel in engines turned to sludge. But perhaps the direst challenge was when the beer inside pubs froze.Temperature
Northland’s reputation as the ‘winterless north’ is well earned. By contrast, in parts of the deep south the winter chill approaches that of regions at similar latitudes such as Europe. Average coastal temperatures range from about 15°C in Northland to about 10°C in Southland. January and February are the warmest months, and July is the coldest.The highest recorded temperature of 42.4°C occurred in the South Island simultaneously at Rangiora (Canterbury) and Jordan (Marlborough) on 7 February 1973. And on 3 July 1995 the mercury dropped to a record -21.6°C at Ophir, Central Otago
Story: Natural environment
Page 4 – The bush and its plants
Ancient forests
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.Conifer-broadleaf forest
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.
Beech forest
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.Alpine fields
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’. 1Swamps 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.Introduced plants
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.
Story: Natural environment
Page 5 – Fauna
Dominating the recent history of New Zealand’s fauna – birds, reptiles and insects – is the damage caused by humans and the predators they brought with them.Native birds
Before people arrived, New Zealand was a land of birds. Night and day the forests were alive with rustlings, calls, booms, whistles and hoots. There were over 120 species of geese, ducks, rails, moa, parrots, owls, wrens and other perching birds. Around 70 of these were found only in New Zealand. Almost a quarter were nocturnal, and many were giants. The huge, flightless, foliage-browsing moa occupied niches usually the reserve of mammals, while the tiny wren scampered about on the ground like a mouse.
Gone for good
The moa, a huge bird that was once common in New Zealand, has become a national symbol of extinction, much like the dodo. This folk song explains how it died out:‘No moa, no moa
In old Ao-tea-roa
Can’t get ’em
They’ve et ’em
They’re gone and there ain’t no moa’. 1
Introduced predators
Many bird species became extinct after the arrival of Polynesians, who brought the kiore (Pacific rat) and the kurī (dog) from Polynesia. Flightless and ground-nesting birds proved easy pickings for Polynesians, who simply walked up to moa and clubbed them. While humans are the most likely cause of the larger birds’ extinction, the kiore is the prime suspect in the disappearance of smaller birds and invertebrates.
By the 1900s Europeans had introduced other rat species, ferrets, weasels, stoats, cats, pigs and dogs, which further extinguished New Zealand’s birds and other animals.A remarkable coincidence
Scientists Trevor Worthy and Richard Holdaway have clarified why so many of New Zealand’s bird species have disappeared over the past 700 years. Theories about climate or habitat variations, disease, and even the belief that some species were somehow genetically inferior don’t explain a remarkable coincidence. When humans arrived, extinctions occurred: ‘the simple, inescapable fact is that the New Zealand avifauna [birdlife] has been decimated by introduced mammalian predators, including people.’ 2Birds under threat
Some species managed to survive on offshore islands. Visionary conservationists recognised this and relocated threatened bird populations to these ‘arks’. In the 21st century offshore islands are a major focus of conservation – introduced predators have been exterminated and birdlife has flourished again.However, around 30 species are listed as endangered. The kiwi is also under threat. A curious bird, it cannot fly, has loose, hair-like feathers, long whiskers and is largely nocturnal. Many New Zealanders have never seen one. Māori refer to it as ‘te manuhuna a Tānemahuta’ – the hidden bird of Tāne, god of the forest. In some areas kiwi still whistle their high-pitched calls after dark.
Wētā, peripatus and other creatures
There were also other native species, many of which survive today. When humans arrived there were only three terrestrial mammal species – all were bats, and one is now extinct.Other unique fauna include the wētā. These resemble rather terrifying large grasshoppers, but are harmless. New Zealand’s most famous reptile, the tuatara, grows to about 24 cm long, is rather slow-moving, and lives for up to 60 years.
Only birds and dogs
In his 1770 account of New Zealand, Joseph Banks noted (using his own spelling) the scarcity of four-legged creatures:‘It appears not improbable that there realy are no other species of Quadrupeds in the countrey; for the natives, whose cheif luxury of Dress consists in the skins and hair of Dogs and the skins of divers birds, and who wear for ornaments the bones and beaks of birds and teeth of Dogs, would probably have made use of some part of any other animal they were acquainted with: a circumstance which tho we carefully sought after, we never saw the least signs of.’ 3
The ngākeoke or peripatus is another living fossil – its relatives have been around for hundreds of millions of years. An odd creature, it resembles a worm with legs, and hunts down its prey in the leaf litter by spitting on them. Also on the bush floor are giant carnivorous land snails known as Powelliphanta and Paryphanta.
Comments
Post a Comment