Research report

Mitigating agricultural greenhouse gas emissions: strategies for meeting New Zealand’s goals

11 Sep 2018

New Zealand is in a position to lead the world in dealing with greenhouse gas (GHG) emissions from agriculture; this is based on our acknowledged expertise in agricultural and climate science, and our commitment and responsibility to act. The New Zealand agricultural sector is already world-leading in terms of the high-value, high-quality products it generates, and it supports a thriving economy. But emissions from this sector also dominate New Zealand’s total emissions profile, and reducing them is important to meet both our international targets and our own goals as a nation.

We face some unique challenges. In contrast to the power and transport sectors, agriculture has fewer options to make large emissions reductions quickly and costeffectively. Obligating farmers to reduce their emissions should not impose a disproportionate burden on them relative to their international competitors, nor relative to other sectors within New Zealand. There are no zero-emission strategies for biological GHGs, yet there are many reasons to act aggressively to reduce their emissions. This goes beyond arguments of short-lived versus long-lived gases; there are also strong market and reputational reasons for driving down agricultural emissions while making farms more efficient and sustainable.

Methane and nitrous oxide are the main GHG emissions occurring on farms. Methane, derived mainly from enteric fermentation in ruminant livestock, is a short-lived gas, but one that has contributed most to the sector’s increasing emissions since 1990. Although methane does not accumulate in the atmosphere like CO2 does, it has potent effects on near-term warming, and this potency increases with increasing rates of methane emissions over time. While noting that methane emissions from agriculture cannot, and need not be, reduced to zero, reducing global methane emissions quickly will impact the peak warming temperature and the rate at which CO2 emissions need to be reduced. The metrics used to account for the different gases are important, particularly if biological GHGs are to be included in the ETS or similar mechanism at any level, as different metrics have implications for carbon, nitrous oxide and methane budgets.

Strategies exist now that can help reduce biological GHGs, but currently, individual strategies are only expected to have modest effects on total emissions reduction, and there are trade-offs between possible options that will require careful consideration at an individual farm situation.

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