NZ farmers need to carry the can for their greenhouse gases - Environment Commissioner

There is no single silver bullet that will cut New Zealand's farming emissions, but a number of measures could help slow the country's contribution to climate warming, the Parliamentary Commissioner for the Environment says.

"Just because there are difficulties does not mean that nothing can be, or should be done," Dr Jan Wright said in releasing the report Climate change and agriculture: understanding the biological greenhouse gases.

The report is in the main explanatory and makes no recommendations in relation to targets to reduce greenhouse gas emissions, or the functioning of the emissions trading scheme (ETS).

It points out New Zealand is in an unusual position, because 43 per cent of its greenhouse gases are caused by methane and 11 per cent by nitrous oxide, the first generated by all livestock, the latter mainly by cows urinating.  

However, Wright warns that if farming does not begin to take responsibility for these gases "other sectors (and taxpayers) will become increasingly 'squeezed'".

Federated Farmers president William Rolleston welcomed the report, saying the best thing farmers could do was what they had been doing over the last two decades - improving their carbon efficiency by 1.2 per cent a year.

The recent Paris agreement on climate change said there needed to be work on avoiding climate change, but that should not undermine food production, he said.

Wright said there had been a number of false starts in dealing with agricultural greenhouse gases, and much controversy over their continuing omission from the Emissions Trading Scheme.

"But the ETS is not the only way forward – there are other things that can be done.

She suggested farms could be made to monitor and report on their biological emissions now . Some larger farms could be brought within the ETS because the compliance costs would be relatively low.

Rolleston said it would be difficult to accurately measure the emissions of animals, and the measurements would only be an approximation.

Wright outlines and evaluates the technological fixes that are being worked on by New Zealand scientists:

* A vaccine that will inhibit methane by 20 per cent is the most promising fix, and she recommends investment into its development be ramped up. Even so success is at least a decade away;

* A methane inhibitor or chemical compound fed to animals. This would be administered as a slow release tablet which kills the methanogens in an animal's stomach;

* Breeding low emission cattle and sheep. Selective breeding could reduce methane emissions from animals by 10-20 per cent without harming production, but it would take time;

* Low emission animal feeds are being developed but do not look very promising, and the impact at a national level would be small.

Farmers could be encouraged to change their management practices - one way might be to reduce stock numbers and still increase profitability. This was proven to be possible in a Waikato case study where a farmer cut cow numbers from 530 to 350 over five years.  

Changes to feeds, fertiliser application, stocking rates, the use of feed pads and forest planting will also help reduce emissions.

Planting trees would help offset emissions. This could be done either by encouraging landowners to allow native forest to regenerate, or grow plantations.

If 1 million hectares of marginal land was left to re-establish in natives, it would capture the equivalent of about 17 per cent of methane and nitrous oxide emissions currently emitted each year for 50 years.

Similarly, pine plantations efficiently soak up emissions. Currently they cover about 1.6 million ha; if a further 1 million ha was planted, they would capture the equivalent of 81 per cent of the methane and nitrous oxide emitted each year.

Rolleston agreed farmers could be given better incentives to plant forests. For example, at present they cannot obtain carbon credits on riparian or shelter belt planting.

Nitrogen fertilisers increase the production of nitrous oxide. One way of reducing the impact is to add an inhibitor to urea, which could be made mandatory, the report said.

But Ravensdown product manager Lloyd Glenny said making any coating or treatment mandatory could be problematic.

"Even though Ravensdown sells a urease inhibitor product the advice we give is that climate and soil conditions may not warrant its use at a given time. Right now as soils become dryer and conditions become warmer, loss of nitrogen to atmosphere (via ammonia) becomes an issue that can be tackled with a coated product like N-Protect.

"However in cold, wet conditions the production benefit of coated urea is unlikely to be worth the 8-10 per cent premium paid compared to uncoated urea."

Wright warned change was inevitable.

"Our farmers have shown time and again their ability to adapt to new challenges. The world will continue to need food. But in the long term the way in which food is grown, and the types of food grown, will have to change if biological emissions are to be reduced."

Climate Change Minister Paula Bennett welcomed the report, saying it was "consistent with the Government's view that mitigation of greenhouse gases from agriculture is difficult and requires a multi-pronged approach".

"Reducing them while growing our economy is a difficult challenge, but one we must solve."

Primary Industries Minister Nathan Guy said he was pleased Wright recognised New Zealand farmers were already amongst the most productive and efficient in the world. 

"Over the past 20 years, they have improved the emissions efficiency of production by approximately 1% per year by improving feed and nutrition, animal genetics, pasture management and animal health."

But Labour spokeswoman Megan Woods said the message from the report was "loud and clear" that immediate action was required to curb agricultural emissions.

"The evidence in today's report means that Government has to come up with more than platitudes; it needs an action plan to address the 'cow in the room'."

"If the Government continues to ignore the biological gases from agriculture they are putting undue pressure on other parts of the economy and are leaving the taxpayer to pick up the tab."

Green co-leader James Shaw said large-scale tree planting and land-use change was needed.

"National isn't doing farmers any favours by telling them no change is needed, while the Government searches for a scientific silver bullet that may never exist." 

The Government should lead a re-think "of how we farm, where we farm and what we farm to try to reduce our emissions".