New Zealand’s native grasslands are dominated by tussocks – grasses that have a clumping growth form, with stems fanning up and outward from a central bunch.
This growth form helps grasses to survive. Much of the plant is protected in a bunch of basal stems, unlike woody plants, which have exposed and vulnerable growing stem tips. Tussocks tolerate fire better than most woody plants.
In the past, farmers burnt off large areas of tussock and tried to replace it with imported grasses, so they could graze more animals. But many people’s attitudes have changed, and grasslands are now valued as important native ecosystems. Tussocks are also popular with gardeners.
New Zealand has around 190 native grass species. Native tussocks belong to three genera: Chionochloa, Poa and Festuca. Most of the 24 species of Chionochloa have a tussock growth form – so do three important Poa species and three Festuca species.
Grasses favour open areas. Very few grow under a closed forest. A few grow on sand dunes or coastal cliffs, but they do not form extensive grasslands.
Most New Zealand grasslands are tussocklands. Before people arrived, there were also some low-growing sward (carpet-like) grasslands – around 2% of the total grassland area. These have been largely replaced by introduced grasses for farming.
The extent of native grasslands has varied in response to the climate, and the frequency and intensity of fire. Over the last 10,000 years (the Holocene period), grasslands formed a mosaic with areas of woody vegetation in many parts of New Zealand. The pattern varied according to altitude, topography, slope, aspect and disturbance (including fire). Grasslands mainly grew in areas that were colder or drier than those which supported shrubland, woodland or forest.
Grasslands reached their greatest extent in the early 1800s, after Māori fires had burned much of the forest in the drier regions, and before Europeans settled in New Zealand and cleared land for farming. At that time, grasslands probably covered about 31% of the mainland (around 83,700 square kilometres).
‘Scientifically speaking, a tussock is not actually a single group of related plants but a growth habit – a particular arrangement of stems and leaves which forms a tuft of vegetation. The stems, or tillers from which the leaves sprout are unusually tightly clustered.’ 1
New Zealand’s grassland ecosystems developed in the absence of grazing mammals. Birds and invertebrates were the main browsers until European settlers brought grazing mammals in the mid-1800s. Scientists still debate the extent to which introduced herbivores have taken the place of native browsing birds such as the now extinct moa.
Grasslands have a rich and diverse invertebrate fauna. As specific groups of life forms evolve over millions of years, this indicates the prolonged presence of grassland habitats at all altitudes in New Zealand’s past. They also supported many reptiles and birds.
Short tussocks (generally less than 50 centimetres tall) mainly grow at lower altitudes. These grasslands are dominated by silver tussock (Poa cita) and hard (fescue) tussock (Festuca novae-zelandiae), often with areas of shrubland or woodland.
In the 1840s, short tussock grasslands made up around 44% of New Zealand’s grasslands. They grew mainly in drier regions – parts of the central and eastern North Island, and particularly the South Island’s plains, interior basins and lower eastern mountain slopes.
These grasslands, which also include areas of the more palatable blue wheatgrass (Elymus solandri), have been greatly modified. They have been grazed, developed for farming, fertilised by aerial topdressing, or sown with imported grasses.
Southern Māori used tussock to make leggings that protected their bare legs from speargrass. They also put tussock in their paraerae (sandals). ‘Patiti (tussock) was a fine thing to put in the paraerae to keep the feet warm and if one was wading it was warmer with patiti round the feet than without it.’ 1
The tall (up to 1.5 metres) tussock grasslands are dominated by Chionochloa – a genus that is largely endemic (found only in New Zealand).
In the 1840s, red and copper tussock (C. rubra) dominated about 23% of the grasslands.
Today, red tussocks grow on the North Island’s volcanic mountains (mostly on conservation land). In the South Island they occur in smaller areas, and only as far south as North Canterbury. They are found mostly below the treeline, on poorly drained soils that are often peaty and acidic.
Copper tussocks (subspecies cuprea) grew in similar, often extensive, areas further south to Stewart Island, particularly on the Southland plains. These tussocklands are now much reduced – the largest areas were developed for farming.
Snow tussock is the name given to several alpine species of Chionochloa. These occur in grasslands where one species is dominant, or share dominance with other species. Snow tussocks naturally dominate the low alpine zone, about 500 metres above the treeline. They made up around 13% of the grasslands in the 1840s, and have complex distribution patterns.
Two snow tussocks share the alpine zone on the North Island main ranges: broad-leaved (C. flavescens) and mid-ribbed (C. pallens) snow tussocks. These also grow with several others in high rainfall regions near the main divide of the Southern Alps.
Curled snow tussock (C. crassiuscula) is widespread at higher altitudes south of Nelson. It often grows alongside megaherbs (large-leaved flowering plants), with the much smaller snow-patch grass (C. oreophila) in nearby snowbanks. Carpet grass (C. australis) is confined to the north-west of the South Island; four species grow in the south-west. Most of these areas are conservation lands.
Narrow-leaved snow tussock (C. rigida) is found in the south-western South Island, but is more widespread east of the main divide, along with slim snow tussock (C. macra). These two are the most common tussocks on the pastoral grazing lands of the South Island high country. C. rigida occurs mostly below 1,250 metres, south of the Rakaia River. C. macra grows at higher altitudes where C. rigida is present, but is more widespread in the north of the South Island.
After Māori burnt areas of forest and woodland in the drier eastern 'rain shadow' region of the South Island, narrow-leaved and slim snow tussocks extended their ranges below the treeline on the drier eastern side of the mountains. Later, these grasslands were much reduced by pastoral farming (grazing and burning) from the 1850s.
After Māori started to burn vegetation on the drier eastern side of the South Island (from around 1300 CE), grasslands expanded. For 500 years they retained much of their native biodiversity. This changed soon after Europeans settled in New Zealand from the 1840s. A wide range of animals and plants were introduced, and farming began on the grasslands.
Canterbury runholder Mary Anne Barker wrote in December 1867 of one of her great pleasures – burning tussock. ‘I am obliged to be careful not to have on any inflammable petticoats, even if it is quite a warm day, as they are very dangerous; the wind will shift suddenly perhaps as I am in the very act of setting a tussock a-blaze, and for half a second I find myself in the middle of the flames.’ 1
Europeans used fire to clear land for farming. Good wool prices in Britain encouraged high stock numbers on the tussocklands of the South Island high country.
Adverse effects were soon obvious. Concern was raised about the combined effects of burning, grazing by introduced mammals, and the spread of aggressive weeds. Comments by botanist-artist John Buchanan in the 1860s, agricultural scientist Alfred Cockayne in 1910 and ecologist-botanist Leonard Cockayne in 1919 showed a disquiet that has continued until today.
For decades, research and conservation efforts focused on native forests, rather than tussock grasslands. Detailed ecological studies of the high-country snow tussocks only really began in the late 1950s. This research confirmed their slow growth and long life. Mature snow tussocks have hundreds of stems, with a range of ages. Each stem takes 10–15 years to mature, after which it may flower and die, and is then usually replaced by one or more new stems. This pattern of rejuvenation means the tussock may potentially live forever, but it also means that scientists cannot tell the age of individual plants.
Tussocks were found to tolerate fire but not grazing mammals, particularly after fire when the new leaves are highly palatable. Concentrated grazing on small burnt patches can kill snow tussocks in just one season, and probably explains their absence in some areas where they would be expected to grow.
Some farmers were slow to apply these findings to farm management, and the destructive effects of farming have continued in many areas. Grazing and burning opens up the plant cover, exposing the soil to weeds and rabbits. Grazing animals eat the more palatable species first, leading to a concentration of unpalatable species. This may encourage more burning by farmers.
Exposed areas of soil are also prone to erosion.
Recent studies have highlighted the ability of snow tussock grasslands in good condition to produce high water yields from their upland catchments.
Studies showed water yields of up to 80% of measured annual rainfall, and 86% for the snow-free six months, on unburnt snow tussockland on the southern Lammerlaw Range. This unburnt grassland was compared with areas with shorter cover – recently burnt tussocks, pasture grassland, blue tussock short grassland and bare soil. These produced much less water, as did exotic pine forest.
Snow tussock areas also have very low water losses through evaporation or transpiration. In some places, fog deposits water directly onto tussock leaves, adding to the water yield. Tussock grassland retains water and releases it gradually, reducing the chance of flash floods downstream.
Many of the remaining tussock grasslands of the South Island high country are on government-owned land leased out to farmers. In the 1990s, the government began a voluntary tenure review process for this leasehold land. Farmers can negotiate freehold ownership of some parts of their runs – usually the more productive areas at lower altitudes. In return, less modified areas – mostly at higher altitudes – are returned to government ownership, to be managed by the Department of Conservation for public benefit, use and enjoyment. These are important for conservation and recreation, and as water catchment areas.
When tenure review began, in the early 1990s, the government of the day predicted that about one million hectares (of a total 2.6 million hectares of leasehold land) would be added to the conservation lands.
Of 347 pastoral leases held in 1992, tenure review had been completed on 121 by June 2017. The Crown had purchased leasehold rights to about 330,000 hectares, while about 370,000 hectares had been converted to freehold
The High Country Accord (a runholders’ association) advocates conservation using private covenants, but other groups believe this is much less satisfactory. Opponents argue that under such covenants, public access is not guaranteed, conservation management is piecemeal, and emergency grazing during droughts could interfere with ecological restoration.
In addition to tenure review, the government has bought some entire high country properties and added them to the existing conservation lands. Four high country conservation parks were set up between 2000 and 2006:
The government also transferred control of the largest high country property, Molesworth Station (180,476 hectares), from Landcorp to the Department of Conservation in 2005. It is to be managed as a reserve, with grazing in certain areas. These larger properties extend over a variety of altitudes, and help protect lands and biodiversity in unbroken stretches from lowlands to the high country.
The government’s high country policy aims to establish some 22 parks and reserves. These will be available for public use, with opportunities for recreation and tourism. They will allow soil, water and nature conservation, and maximise water production for human needs.
Mark, Alan F., and others. ‘Tussock grasslands and associated mountain lands.’ In The natural history of southern New Zealand, edited by John Darby and others. Dunedin: University of Otago Press, 2003.
Stupples, Polly. ‘Fields of gold.’ New Zealand Geographic 66 (November–December 2003): 22–48.
Wardle, Peter. Vegetation of New Zealand. Cambridge: Cambridge University Press, 1991.