The Heart of the High Country

Department of Conservation botanist Nick Head shakes his head in dismay as he explains that some people see the vast, open landscapes of the Mackenzie Basin as a “wasteland”.

By Helen Bain 

 

To Head, the Mackenzie Basin is the most distinctive and largest inter-montane basin in New Zealand, a landscape found nowhere else in the world, and habitat for
a rich and unique biodiversity.

“These landscapes are our natural heritage and how we sell ourselves to the world. We lament what happened to the Canterbury Plains; we say ‘how did that happen?’ but it
is happening in the Mackenzie today.”

Head says that while the landscape has undergone many changes, much of its natural character remains. The Mackenzie Basin was once covered in a mosaic of forest,
scrub and tussock, but the arrival of Maori about 900 years ago had a profound impact, with fire destroying most of the scrub and forest. By the time of European arrival in the
1840s, the Mackenzie Basin was largely covered by great expanses of tussock grassland, not too different from what you can see today – minus the hydro canals and power pylons, of course.

There are 68 rare and threatened plant species known to live in the Mackenzie Basin – as well as its distinctive red tussock, the basin floor is home to some of the rarest plants in New Zealand, many specifically adapted to survive in this harsh environment.

Head says you won’t find anything anywhere else like the collection of kettlehole tarns – small wetlands created by glacial moraines – that exist in the Mackenzie Basin,
which support hundreds of native species. As well as unique plants, you will also find distinctive species of weta, moths, beetles and grasshoppers in these places.

Chris Woolmore is manager of DOC’s Project River Recovery, a programme working to protect the Upper Waitaki River and Lakes Takapo, Pukaki and Ohau. He says the region’s braided rivers are among its most special features.

High rainfall in the Southern Alps erodes the greywacke and soft sedimentary rocks, and when this material flows from the mountains and reaches the plains it spreads out,
creating rivers with many braids that divide, rejoin and divide again.

These riverbeds are nesting grounds for some of New Zealand’s rarest birds. Rarest of them all is the black stilt (pictured above) – only about 180 remain in the wild and they are critically endangered.

The Black Stilt Recovery Programme is trying to “shortcircuit” the predator cycle by taking the eggs from the wild, incubating them and raising the chicks in a captive rearing
centre at Twizel before releasing them back into the wild as juveniles.

Without such intervention the stilts’ nests in the gravels of the riverbeds are easy prey for feral cats, hedgehogs, stoats and ferrets, and in the late 1970s the wild population
fell as low as 23 adults. But truly heroic recovery efforts have been very successful – in the last 10 years the population in the wild has doubled, and it is hoped that eventually pest control will be enough protection so that the stilts can nest safely ouside the wire mesh of the breeding facility.

Predator-proof fences around their wild breeding environment are not an option in the dynamic environment of braided riverbeds – pest control here requires an
intensive programme of poisoning and trapping.

Four-wheel-drive vehicles are a growing problem: they can easily crush black stilts’ grey-and-black speckled eggs and tiny grey chicks, which are highly camouflaged
in the river gravel.

Other rare riverbed species are also threatened. Wrybills (which number just 3000-6000 nationally) use their unique “bent sideways” bills to retrieve insects from under
the riverbed stones. Black-fronted terns, also nationally endangered, with a national population of about 10,000, also rely on the riverbeds, as do banded dotterels, which
appear to have undergone major population decline recently.

Woolmore says hydro dams have had a big impact on the braided riverbeds’ wildlife and ecosystems: damming the rivers for hydro lakes created an extra 22,000 hectares
of water – but lost 7400ha of braided riverbeds.

As river flows are diverted in hydro canals, braided riverbeds are “de-watered”. Managed lake levels for hydrogeneration, and measures such as stopbanks and planting
of willows to protect farms, roads and settlements, also mean there are few floods, on which the naturally dynamic processes of braided riverbeds rely.

Invasion by weeds is another problem. Introduced weeds such as lupins colonise riverbeds and displace native plants and bird habitats, and change the way braided
riverbeds operate, trapping sediment and stabilising the once-shifting gravels. DOC monitors weeds and remove small infestations before they become big ones, but don’t
have the resources to tackle the problem everywhere, Woolmore says.

On land, Pete Williams, based at DOC in Twizel, has been fighting a similar battle against the spread of wilding pines for the last four years in the Mackenzie Basin.
Originally planted to control erosion, these pines have been dispersed across the landscape by their wind-blown seed – at first the red and brown of the tussock is dotted
with dark green specks, which steadily grow till they form a dense blanket that completely covers the landscape, blocking out all light and preventing anything else from growing.

Williams and his team use powered saws known as scrub bars to cut the pines down before they are 4-5 years old, when they bear cones. “After that you lose the battle.”
The wilding pine warriors are also experimenting with chemical sprays – trialling “different brews” – to see what nails the pines most effectively, and “skid-hopping” –
jumping down from the skid of a helicopter to cut down isolated pines, before flying on to the next, which is the only way you can cover the huge expanses of land.

Exterminating wilding pines costs millions – funding comes from DOC, Environment Canterbury and landowners – but Williams believe the battle can be won, as long as
sufficient resources are available for them to hold the line against the spreading dark green menace.

Another kind of green – bright grassy green – is also spreading through the reds and browns of the Mackenzie landscape. Driving through the main highway you can see
huge irrigators pumping water on to the naturally dry land to feed the enormous thirst of ever-expanding dairy farms. One irrigator ran parallel to a long, straight stretch of road
– checking the odometer I noted that it was nearly two kilometres long.

Forest & Bird resource management planner Anna Cameron says there are currently 110 applications to Environment Canterbury to irrigate the Mackenzie
Basin, which would irrigate more than 18,000ha and take more than 90 million cubic metres of water each year. If granted, the Mackenzie Basin of the future will bear little
resemblance to the iconic landscapes we all think of when we think of New Zealand.

Stopping to photograph a vista of tussock flats with a craggy mountain range behind, I chat with a German couple, among many tourists in campervans exploring
this wilderness, who have stopped to also photograph the scenery.

“Is beautiful, ja?” the man suggests, and I readily agree, wondering whether he and his fellow travellers will be so impressed if they if they return to find this magnificence replaced by dairy farms.