As part of the global Covering Climate Now initiative, the Herald is dedicating a week of coverage to the issues surrounding the climate crisis. In the fourth of a series of in-depth interviews with leading experts on key policy areas, Herald science reporter Jamie Morton speaks with AgResearch's research director Dr Trevor Stuthridge about farming's climate footprint.
Agriculture has been at the crux of what makes New Zealand's emissions profile a globally-unique one. Can you summarise how agriculture contributes to our greenhouse gas inventory, how that contribution has changed over recent times, and what the barriers to reducing emissions from the sector have been?
New Zealand's relatively small population, limited manufacturing and dominant agricultural sector all contribute to our globally unique emissions make-up, where agriculture contributes close to half our greenhouse gas emissions.
The main source of agricultural emissions is methane produced by ruminant livestock such as cattle, sheep and deer, which makes up almost three-quarters of our agricultural emissions.
Methane is a potent greenhouse gas and a contributor to climate change. Another potent greenhouse gas produced from agriculture is nitrous oxide.
While the research shows emissions of both agricultural methane and nitrous oxide in New Zealand have increased by about 17 per cent since 1990, improvements in modern farming practices have meant the sector has become much more efficient as far as the amount of greenhouse gas produced per unit of agricultural product.
For example, the sheep industry has doubled the amount of lamb it produces while halving the number of ewes.
Agricultural emissions are largely driven by the amount of feed consumed by the animals, which presents significant challenges to bring about reductions in emissions without sacrificing production.
We know that biogenic methane makes up most of the sector's contribution - but what impact does nitrous oxide from soils, and soil carbon, have as well?
Nitrous oxide emissions result from nitrogen being deposited on soils from urine or dung from animals, or the application of nitrogen fertilisers.
The nitrogen is broken down by microbes in the soil and some of this is converted into nitrous oxide.
Nitrous oxide accounts for about 20 per cent of the emissions from livestock farms, but it is a potent gas where it comes to absorbing radiation and trapping heat in the atmosphere.
An increase in organic carbon stored in agricultural soils may be able to offset greenhouse gas emissions while, conversely, losses of soil organic carbon would further add to our emissions.
Organic carbon stocks in New Zealand pastoral soils are already high by international standards.
While changes in soil organic carbon are hard to detect and measure, research is under way to look at management practices that sustain and in some instances could increase soil organic carbon storage.
What have been some of the recent gains the sector has made toward cutting its emissions, and how have these come about?
Productivity gains through improvements on farms, including improved animal genetics, health, nutrition and smarter farm practices, have enabled New Zealand's agriculture sector to remain globally competitive and avoid increases in emissions that would otherwise have occurred.
A recent study by AgResearch (commissioned by DairyNZ) has shown New Zealand is a world leader in the sustainability of its dairy production, with the lowest carbon footprint of 18 dairy-producing countries where a valid comparison could be made.
Research into the sheep and beef sector has helped to build knowledge of the carbon offset potential from native vegetation.
What's your carbon footprint? Try this five-minute FutureFit survey, supported by Auckland Council, to find out.
While the research bodes well, there is broad acceptance there is more work to be done to drive down absolute emissions – as the Climate Change Commission has called for in its draft advice to Government - and more tools are needed to help realise that.
How close are we, currently, to developing methane inhibitors that could effectively give us climate-friendly cattle? And how much do we depend on such technology in making the biogenic methane reductions we've committed to?
The Climate Change Commission has taken a conservative approach around the expected availability of commercial methane inhibitors, which are substances that can be fed or applied to livestock to reduce their methane emissions.
We support that approach given the need to ensure any product is safe and effective for use in New Zealand.
However, our work alongside Fonterra and Royal DSM - a Netherlands-based global health and nutrition company - on a product called Bovaer (otherwise known as 3-NOP) is showing promise.
One formulation for pasture-based farming to date has demonstrated a methane reduction of more than 30 per cent for up to six hours after the additive is fed to cattle.
Given this progress towards a product specific to New Zealand's pasture-based farming, we have suggested the Climate Change Commission factor this into its recommendations to the Government.
Research is also under way into other potential options for inhibitors specific to New Zealand's pasture-based farming.
An effective methane inhibitor or vaccine could provide important tools for farmers to help reduce emissions but will only be part of the solution.
The Climate Change Commission's draft advice found the current biogenic methane target range set under the Zero Carbon Act - a reduction of 24 to 47 per cent by 2050 - couldn't be achieved under status quo measures that would actually only see levels drop by just 12 per cent below 2017 levels. Among other measures, the commission suggested dairy and sheep and beef animal numbers would need to be brought down by around 15 per cent by 2030, compared with an 8 to 10 per cent reduction under current policies. Are these kinds of cuts unavoidable?
Regulations around greenhouse gas emissions and water quality, as well as commercial demand, are likely to require cuts to livestock numbers in some areas.
However, time will tell what technology becomes available, what gains farmers and industries can make and how that will affect stock numbers.
Farmers have demonstrated over time they can produce more from fewer animals and whatever stock reductions occur, it will be critical that researchers like ourselves provide the right advice and tools to support the transition.
This includes how best to diversify land use on farms and still allow farmers to remain profitable.
An important point we made to the Climate Change Commission is that greenhouse gas emissions from agriculture are driven not by stock numbers, but by the total amount of feed eaten by the animals.
This is because feed intake is the main driver of methane emissions from animals such as cows, sheep and deer.
There is good evidence, for example, that reductions in emissions can be achieved on some dairy farms without significantly decreasing production.
The good news in the advice was that New Zealand could indeed achieve what the commission recommended - a 16 per cent drop by 2035 - provided its suggested technology and behaviour changes were made. Along with adjusting stocking rates, it prescribed supplementary feed and nitrogen inputs for emissions efficiency, and breeding low emissions sheep into the national flocks. Are all of these gains achievable?
Based on the record of innovation from Kiwi farmers over the past decades, supported by good science, there is every reason to think that the sector will adjust and adapt to meet the targets required of it.
Providing new technologies and tools is going to be critical and we are already seeing some of these become available to farmers.
Our world-leading research to breed low methane emitting sheep, through the support of government and farmers, is an example of what can be achieved with the right investment of time and money.
Once rolled out to the national sheep flock, we think there is the potential for a methane reduction of up to about 1 per cent every year, which will be significant as it accrues over time.
Crucially we see this change happening without any sacrifice in the health of the animals or the quality of the products that come from them.
This experience in breeding low methane sheep is now being shared with other researchers with a view to achieving something similar with cattle.
A major change facing the agriculture sector is the introduction of emissions pricing. How will this work, how does the scheme differ from the Emissions Trading Scheme, and is the sector equipped for it?
New Zealand has an Emissions Trading Scheme that puts a price on greenhouse gas emissions, with the purpose of creating a financial incentive for businesses to reduce their emissions.
To date, agricultural greenhouse gases have been excluded from this scheme, but the Government has decided that from 2025 – once the necessary tools and systems for measuring and reducing emissions are in place - it will put a price on agricultural emissions.
Government officials are working with the sector and iwi, through the He Waka Eke Noa – Primary Sector Climate Action Partnership, to determine what the farm level pricing mechanism could look like.
The government has committed that if agricultural emissions are to be part of a scheme with financial obligations linked to emissions, then farmers would only pay for 5 per cent of their emissions initially.
A crucial issue here is that farmers will need access to the right tools so they can benchmark and monitor their emissions at the farm level and plan to reduce their emissions accordingly.
Climate scientists like Victoria University's Professor Dave Frame have argued that we're using the wrong measure to account for agricultural greenhouse gases relative to their global warming potential - that being GWP100 - and that this unfairly put methane, particularly, in the same "basket" as carbon dioxide. AgResearch made this point, too, in its submission to the commission's advice. Why is this important?
Greenhouse gases can be measured in different ways and with different weighting given to gases depending on how long-lived they are.
Using the right metrics and achieving clear and accurate reporting of emissions is vital to get buy-in from all involved in the agriculture sector, and for New Zealand as an export nation to be seen as transparent to consumers about the impact of its food production.
The Climate Change Commission has used a measurement known as GWP100, which is the agreed metric for reporting under the Kyoto Protocol and the Paris Agreement, which converts methane emissions to carbon dioxide equivalents.
At AgResearch, we suggested to the Commission that it could also consider the use of a recently proposed new metric, known as GWP*, which accounts for the surface temperature effects of gases with different lifetimes.
This would give a stronger warming effect than GWP100 when methane emissions are rising and a smaller effect when methane emissions are stable or falling, reflecting the actual physical effects on surface temperatures.
We have suggested a discussion across science, government and industry on the use of different metrics is a good way forward.
We've also heard much about genetically modified (High Metabolisable Energy) ryegrass. What's this, how far has AgResearch come in field trials, and what benefits could this deliver in a climate change context?
AgResearch scientists with the support of the government and industry have used genetic modification to develop a form of ryegrass that grows faster and has more energy available to the animal that feeds on it.
Research to date in the lab and in field trials in the United States also suggests there will be reduced methane emissions from animals feeding on this High Metabolisable Energy (HME) ryegrass.
The field trials in the US have been under way since 2018 and in a future phase will involve feeding the best form of this HME ryegrass to animals to test its effectiveness.
The field trials are taking place in the US because current regulations in NZ do not permit genetically modified organisms to be released without approval.
The HME ryegrass does offer one potential tool to help farmers reduce their emissions.
In AgResearch's recent submission to the Climate Change Commission, we make the point that it would be timely to revisit a national conversation about use of genetic modification and related technologies in New Zealand, given the potential to help in reducing agricultural emissions in New Zealand.