Ecosystems a treasure worth protection

VAST LANDSCAPE: The Rakaia River is one of Canterbury's treasures.
VAST LANDSCAPE: The Rakaia River is one of Canterbury's treasures.
HOME: Wrybill breeding on the banks of the fWaimakariri River.
HOME: Wrybill breeding on the banks of the fWaimakariri River.
DONALD COUCH: On the upper reaches of the Rakaia River.
DONALD COUCH: On the upper reaches of the Rakaia River.

Canterbury's braided rivers are home to more than 26 species of native birds, including several threatened breeds. RACHEL YOUNG looks at what Environment Canterbury is doing to protect the unique habitats.

From the air, the term braided rivers is apt.

Below, water channels with varying flows branch and rejoin around "islands".

In the rest of the world, braided rivers occur only in mountainous, glaciated areas, such as Alaska and the Himalayan region, where natural gravel production and gentle gradients help them form.

But it's different in New Zealand, and in Canterbury there are two-thirds of the country's braided rivers.

Environment Canterbury senior biodiversity adviser Frances Schmechel said the unique ecoystems were "absolutely essential" nesting and feeding grounds for 26 species of native birds.

However, predators, humans who need water for power and irrigation, and pests threatened the habitats.

"They are very special ecosystems in Canterbury. If you don't look after them, then nobody will. They are quite unique and they are absolutely essential."

She said Environment Canterbury's Canterbury Water Management Strategy emphasised the importance of braided rivers to the region's biodiversity, economy and social and cultural wellbeing.

The programme offers $1.4 million to local committees to help protect the rivers.

The Braided River Flagship project has been allocated $540,000 over five years for work on the upper Rakaia and Rangitata rivers, with extra funding from bodies including the Department of Conservation and local landowners.

Schmechel said one of the main aims of the project was weed control.

She said the weeds were ruining the natural run of the rivers, which were a vital habitat for several

threatened species, including the wrybill and black-fronted tern.

About $70,000 would be spent annually, as it was vital to eradicate weeds because they affected the rivers' ability to maintain rare species.

Schmechel said gorse, broom and lupin caused major problems because their respective seeds floated downstream, spreading the invasive species.

"For the health of the river and the health of the wetlands, we do whatever actions are required to either protect or enhance the health of the ecosystems."

Controlling weeds went hand in hand with another key aim of the project: to protect and enhance breeding populations for the native braided river animals.

Humans also caused significant problems because activities such as trail-biking ran straight through endangered birds' ground- nesting areas.

Schmechel said well-camouflaged eggs were hard to spot, often resembling riverbed shingle.

ECan planned to manage access to minimise disturbance during the August to February season, when the birds were nesting and breeding, she said.

ECan commissioner and former Ngai Tahu deputy kaiwhakahaere Donald Couch said people often drove across dry riverbeds without thinking about the wildlife.

He said the braided rivers, which were culturally significant for Ngai Tahu, needed to be protected. "It is part of the principal habitat and ecological health.

If the wrybills are doing well and if the gulls are, then the habitat must be good for them."

Couch said several groups, including landowners and volunteers, played an important role in protecting the natural character of braided rivers.

The aim by 2040, according to the Canterbury Water Management Strategy targets, is to have all indigenous braided river-dependent species showing positive trends, an increased habitat area for the various breeds that use the rivers, and the rivers showing the dynamic nature typical of such rivers.

Couch said the project, which was started two years ago, was already making a difference.

THE WRYBILL

The wrybill may be smart enough to pretend to have a broken wing to distract predators from its young.

But even it will be under threat if Canterbury's braided rivers are not looked after.

The small grey bird with the world's only bent bill is one of more than 26 species that live in the strange landscape.

ECan senior biodiversity adviser Frances Schmechel said the bill helped it find food under the shingle in the braided rivers.

At the last count, there were 4200 wrybill nationally, with 98 per cent of those breeding in Canterbury.

The other threats to the survival of the eggs and chicks include roaming dogs, vehicles on the riverbeds and people coming too close, forcing adult wrybills away from their nests, which means the chicks or eggs could die.

THREATS

Weeds

Recreational use, such as trail-biking

Predatory mammals

Introduced predators, including ferrets and hedgehogs

Water abstraction.

BIRD LIFE

Braided rivers are home to the following rare and threatened birds:

Wrybill/ngutu pare

Black-fronted tern/ tarapirohe Black-billed gull/tarapuka.

The Press