HUMANS IN THE HIGH COUNTRY
Photo copyright: Antonia Steeg
Before human settlement, natural tussock grasslands covered a very limited area – roughly 5% of New Zealand. Most of this grassland was above the tree line where tall tussocks (Chionochloa spp.) predominated. At lower altitudes more than 85% of the country, including the South Island, was forested.
On the drier eastern side of the Main Divide of the South Island, most of the forests were dominated by either beeches (Nothofagus spp.) or native conifers such as totara or matai. Patches of tussock grasslands occurred within the forests. Red tussock (Chinochloa rubra) grew where poor drainage inhibited tree growth. Short tussocks (principally Festuca or Poa spp.) grew initially where landslides, windthrow or lightning strike had temporarily cleared the forest.
In drier seasons in low rainfall areas, such as Central Otago, fire caused by lightning strike seems to have periodically destroyed large areas of forest or scrub. Grasslands colonised these burnt out areas, but over centuries forests regenerated, so long as fires did not recur.
Between 600 and 750 years ago, much of the forest in the drier eastern areas of New Zealand and in the central high country was removed by fires. These were lit by Polynesians in the course of their travels or to hunt birds of the forest, especially the moa.
Most of the forests failed to recover because of repeated fires and the naturally slow regeneration of beech forest. Most of area burnt became occupied by bracken, shrubs and tussock grasses.
In the area we now call the high country, tall tussock grasslands (Chionochloa spp.) became widespread downslope from their natural environment in the high mountain zone. Short tussocks (Festuca, Poa spp.) and other grasses moved upslope from riverbeds and other disturbed sites. Red tussock (Chionochloa rubra) spread widely at lower altitudes from its niche in wetter soils within the forests.
Were it not for the recurrent lighting of fires by humans over the last 750 years, recovery of scrub or forest would have occurred everywhere except for the driest parts of Central Otago.
Early European settlers over-grazed the high country, leading to the widespread degradation of existing vegetation. Photo copyright: Antonia Steeg
At the time of European settlement a mosaic of indigenous tall and short tussock grassland and shrubland (Dracophyllum, Discaria, Coprosma) was already established in the high country.
As they explored during 1850s, the Europeans brought sheep and some cattle onto burnt ground. In the 1860s they added deer, goats, hares and rabbits. Grazing pressure soon exceeded whatever effect birds, rats and invertebrates might have had before them.
Sheep numbers increased by more than 200% from 1861-71, reaching numbers that were far greater than the land could sustain. By 1890, sheep numbers on unimproved grasslands were declining, and continued to fall for 70 years in most areas.
Where tall tussocks were repeatedly burned and grazed they gave way to short tussocks and other plants. In drier areas, short tussocks were replaced by exotic grasses and weeds.
By 1900, under the impact of over-grazing, burning and rabbits, grasslands had been depleted to near-desert in North Otago, Central Otago, and drier parts of the Mackenzie Basin and Marlborough. Scabweeds (Raoulia spp.) became widespread in these areas.
During this period populations of deer, goats, Canada geese, pigs and tahr all grew rapidly, destroying vegetation, causing soil erosion and competing for livestock for feed in large parts of the high country.
As pastoral production declined, successive Governments tried to correct the problems, without understanding the ecological and other reasons for the land degradation.
In these stunning shots, photographer Antonia Steeg captures the action as sheep dogs attempt to move Hereford cows across a riverbed to new pasture