Horizons Region dairy farmers encouraged to reduce emissions by new local DairyNZ climate change ambassador Keith Riley

Dannevirke dairy farmer Keith Riley is the DairyNZ climate change ambassador for the Horizons Region. Photo / Supplied

Dairy farmers need to urgently reduce the greenhouse gas their operations emit because global markets expect it, Keith Riley says.

He owns a 178ha dairy farm near Dannevirke and has volunteered to be the DairyNZ climate change ambassador for the Horizons Region. The ambassadors are part of DairyNZ's Dairy Action for Climate Change initiative, launched last year.

Riley farms in the Tararua District, which will be his primary focus.

It's been designated a "sensitive catchment" by Horizons Regional Council, because its high rainfall and heavy soils mean it contributes a lot of unwanted nutrients to water.

The global community and markets have expectations of New Zealand agriculture, Riley says. With 95 per cent of dairy product exported, it's important for farmers to meet those expectations.

"I believe that time is of the essence, and manageable change is possible now. Delay will only cause more disruption."

There's been talk of compulsory capping of cow numbers, and there's a lot of fear and misinformation about, he says.

But there are also some attractive options.

Reducing greenhouse gas emissions will be easiest for people with the most intensive farming systems - high stocking rates, lots of food imported, lots of milk solids produced and lots of fertiliser used.

Reducing any of these will mean less gas is emitted, and less nutrient enters waterways.

What's needed is just enough stock to eat the grass produced. If that balance is found there will be less work for the farmer and per-cow production can increase.

"I think it will be a popular option, when we understand it," Riley said.

The average dairy farm emits 11 tonnes of greenhouse gas per hectare per year, according to DairyNZ figures. Of that, 60 per cent is methane, mainly from cows belching, and 25 per cent is nitrous oxide, mainly from urine interacting with soil microbes.

Methane is 30 times more potent than carbon dioxide at causing climate change, and nitrous oxide is 300 times more potent. However, carbon dioxide lasts thousands of years in our atmosphere, whereas methane is destroyed in 12 years and nitrous oxide in 114 years.

Agriculture produces about half of New Zealand's greenhouse gas emissions, and dairy farming produces half of that half - 22.5 per cent of New Zealand's total emissions.

New Zealand has committed to reducing its emissions to 30 per cent below 2005 levels by 2030 - a challenging target.

• DairyNZ is holding eight half-day workshops on climate change for dairy farmers. The closest to Whanganui is in Palmerston North on June 22. It's at the Manawatu Golf Club from 10am to 2.30pm, with lunch provided. Register online at www.dairynz.co.nz/roadshow.