Nearly half of New Zealand's greenhouse gas emissions come from agriculture – the main source being methane burped from cattle and sheep.
The Government was currently considering how to treat methane in its proposed Zero Carbon Bill, and whether to bring agriculture into the Emissions Trading Scheme.
A sector survey that formed part of the new report found 64 per cent believed New Zealand agriculture should reduce its greenhouse gas emissions.
But 98 per cent didn't know the greenhouse gas emission rates from their farm, and, when asked to estimate those from the average farm, 97 per cent under-estimated the amount.
Around 42 per cent weren't aware of mitigation strategies other than planting trees.
The report found decisions to take action came down to factors including available time, trust in advice, education level, attitudes toward the environment, and what others were doing.
But modelling suggested that if there was widespread take-up of mitigation options that were currently available – these were largely changes to farm management practices – biological emissions from pasture-based livestock could be pushed down by about 10 per cent.
However, the ability of farmers to do this varied widely – and while some farmers might achieve such reductions without significant negative impacts on profitability, for others, the impact could be large.
The report suggested a reduction of greater than 10 per cent would likely require a combination of on-farm mitigation and land-use change.
One piece of analysis in the report considered the likely adoption of current options if emissions were priced.
This indicated farmers were likely to make changes such as improving productivity per animal, going to once-a-day milking, and planting trees on marginal land if emissions were priced – and the rate of adoption increased with higher prices.
The modelling found that, irrespective of the emission price, if dairy farmers were able to reduce stocking rate and increase productivity per animal, this would be the most adopted option.
But, in reality, there were barriers stopping this.
The report went on to find that farmers' efforts to clean up waterways could also help fight climate change.
A summary of two existing studies indicated that changes already in place by some councils to meet existing Resource Management Act requirements for freshwater management could reduce agricultural greenhouse gas emissions by up to 4 per cent.
And if land-use change to forestry was also considered, up to 800,000ha of trees could be planted as a result of the National Policy Statement on Freshwater Management – the carbon sequestration potential of these trees could be equivalent to about 14 per cent of agricultural emissions.
If successfully commercialised, methane-reducing technologies had further potential to significantly reduce biological emissions from agriculture.
But these were in varying stages of development – and there was only a low confidence that a methane vaccine would be available by the end of the next decade.
Meanwhile, many mitigation options farmers could be using now could be captured in New Zealand's National Inventory, so they could contribute to the country meeting its international climate targets.
Many could be accounted for without requiring any changes, although some might require changes to the National Inventory's data, assumptions, or methodologies.
If new technologies such as methane vaccines are developed, these could also be included in the inventory.
The majority of vegetation found on farms, such as small woodlots and shelterbelts, and which currently didn't meet the requirement for crediting via the New Zealand Emissions Trading Scheme, had the potential to sequester carbon.
Studies of three farms indicated that sequestration by current and planned vegetation had the potential to account for about up to 2.5 per cent of current gross livestock emissions on intensive lowland sheep and dairy farms, and between five and 20 per cent on hill country sheep and beef farms.
MPI's deputy director general policy and trade, Penny Nelson, said BERG saw the need for a good evidence base to support the sector to address some key climate challenges.
"Farmers were asking what practical things they can do to reduce their emissions," she said.
"We needed to improve our shared understanding of the possible innovation and solutions, and the barriers standing in farmers' way."
DairyNZ chief executive Tim Mackle said the findings highlighted the need for good information and tailored advice for farmers.
"There is no single answer to reducing emissions – we'll need a combination of solutions tailored to land and farm types."
Agriculture Minister Damien O'Connor and Climate Change Minister James Shaw welcomed the report.
Shaw said the potential for big emissions reductions offered real hope to farmers and businesses that wanted to combat climate change while maintaining productivity and profitability.
"It also offers real hope to a world that needs to expand food production for a growing global population but also needs to bring down climate pollution at the same time."
More trees the key
Further research, led by from Motu Economic and Public Policy Research, found that achieving a 50 percent reduction in land-sector emissions by 2050 – and beyond those reductions gained through the current ETS - would be possible even with no new horticulture and no new on-farm mitigation technology.
"It would, however, require planting a lot of trees," Motu's Dr Suzi Kerr said.
This modelling suggested that roughly half of the new forest area would come from land currently covered by scrub.
The rest was likely to come from conversions from sheep and beef farming with a small decrease in dairying.
"It would be possible to reach a 2030 target of a 30 per cent reduction in land-sector emissions, but this will be harder to meet because of the speed of change required and the large costs this rapid change would impose," Kerr said.
"Our modelling also shows that if we were able to double the size of Aotearoa's current horticulture sector it would reduce greenhouse gas emissions as much as full implementation of a methane vaccine."
If the horticulture sector could grow rapidly, it would bring large increases in revenue, which were likely to offset any corresponding revenue losses in pastoral agriculture.
The modelling suggested small losses of employment in the dairy and sheep-beef sectors as they expanded less or gradually contracted - but these were more than offset by increases in forestry employment.
"If Aotearoa carries on as it is now, our research showed that there would be around 86,500 people employed full-time in the agricultural sector," Kerr said.
"If we are able to build up horticulture and forestry, this could increase to 136,900 full-time employees.
"These jobs would however sometimes be in different places and require different skills.'
While the ETS remained important in encouraging land use change.
However, Motu reported, even if biological emissions from agriculture were included in the ETS, the emissions price alone would be unlikely to be sufficient to induce efficient land-use change.
"To supplement the changes encouraged by the ETS, landowners will need more information and training," Kerr said.
"There will also need to be support from government and from the horticultural sector as a whole, and probably changes in regulation, to help farmers produce new products and access international markets for these new products."
