Farmer testing of popular waterway's health could benefit water quality - and a rare NZ duck.
A group of farmers within the idyllic Pohangina Valley near Palmerston North want to know more about the threats facing its waterways – maybe benefitting another group working in the area to save one of the world's rarest birds.
The Pohangina Catchment Care Group - headed by local farmer MattCarroll, who milks up to 1000 cows alongside running a sheep and beef operation - is conducting monthly water quality tests at key sites in the district. Formed less than a year ago, Carroll says its aim is "gaining knowledge about what we have and identifying its vulnerabilities."
Matt Carroll. Image / Supplied
The Pohangina River runs through the valley and is a popular destination for trout fishing, walkers, swimmers and campers. It's headwaters in the nearby Ruahine Ranges are also home to small numbers of the whio or blue duck, a rare species classified as endangered and found only in parts of New Zealand.
Carroll says while the catchment's environment is relatively healthy and "it's cool to see species like the blue duck, we want to gain more knowledge about the state of the ecosystem, its vulnerabilities and how we can maintain and improve things.
"We want to be a source of encouragement for farm environment planning within the valley as well as maximising biodiversity and minimising pest numbers," he says. "The end goal is to get alongside other groups working in these spaces."
One of the groups is the Ruahine Whio Protectors which, Carroll says, is doing amazing work to maintain the whio populations (the district is estimated to have just 30 breeding pairs). Pests such as stoats are the biggest threat to the birds, but they are also vulnerable to rats, cats, possums and the impact of farming.
Westview farm. Image / Supplied.
According to the Department of Conservation (DOC), the bird was once widespread throughout the country but its populations are now patchy and isolated.
DOC says the bird numbers are only between 2000 and 3000 (around 640 pairs in the North Island and just under 700 in the South Island): "Their population is declining, they have a low reproductive success and there are more males than females."
Carroll says small numbers of blue duck have been seen in the headwaters of the Pohangina, while native fish species, good macroinvertebrate numbers and eels are also present in the area. He believes that is testament to the relative health of the river.
Pohangina Valley East. Image Supplied.
Since its establishment last August, the group has begun monthly water testing at 11 catchment sites - some in the river itself with others along its many tributaries. Carroll says it will take up to three years of data before a true picture of the district's ecological health will emerge.
The testing is self-funded by Pohangina Valley locals but Carroll is hopeful it will eventually attract government funding.
The group has also had input from Massey University freshwater ecology professor Dr Russell Death, who lives in the area. At a recent community workshop, he handed out stream health checklists for landowners to help them assess the health of rivers and streams and which can be used to identify management practices to help improve ecosystem health.
Carroll is the assistant manager for Westview Farming, an equity partnership set up by his parents Shane Carroll and Nicola Shadbolt. The partnership has been farming there since 1987 and today run 4300 ewes, beef cattle and deer as well as a 1000-strong dairy herd.
Carroll says sustainable farming practices have always been a priority for his parents, while he worked for several years as a farm consultant with an emphasis on farm environment planning and sustainable land use.
Because the Pohangina River borders the western edge of the farm (it runs up to the lower reaches of the Ruahine Ranges on its eastern side) and a major tributary, the Matanganui Stream flows through the property, Carroll has always been aware of maintaining the health of these waterways.
Pohangina Valley. Image Supplied.
A 20m riparian strip has been created along the Pohangina River, every year up to 200 poplar and willow trees are planted to control erosion on parts of the farm while a key management practice has been to ensure there is no excessive use of nitrogen fertiliser ("we have always been below accepted industry levels").
Cattle have been excluded from environmentally sensitive areas of the block while Carroll says they are looking at an extensive wetlands development in the near future.
The Pohangina River is itself a tributary of the Manawatu River which it joins at Ashhurst about 15km north-east of Palmerston North from its source in the Ruahine Ranges.
