Urgent clarity must come from policymakers on what exactly will constitute reaching net zero, as differing definitions require starkly different measures for the target to be met, a study led by University of Galway researchers has found.

The paper states that while measuring progress towards net zero is generally straightforward for CO2, assessing progress on other greenhouse gases is less clear.

This lack of clarity on non-CO2 emissions has consequences for farming, as gases such as methane and nitrous oxide represent a larger share of farming’s emissions profile than they do for other sectors of the economy.

While achieving net zero using some of the definitions examined in the study scored well for international fairness, they would reduce milk and beef production in Ireland, as well as having drawbacks for long-term temperature stabilisation.


The GWP100, which is the current international default definition for net zero, was classed in the study as fitting this description.

On the other hand, just looking at CO2 and disregarding other gases would be “inadequate” in taking countries which have large farming sectors - such as Ireland - towards net zero, as it “overlooks major climate forcing emissions” resulting from other gases.

The researchers found that the GWP* method of accounting for emissions is among those which require the “least dramatic changes in agriculture and land use” to meet net zero.

“No definition is ideal across all aspects and trade-offs are involved in selecting one method over another,” the study states.

Notwithstanding the farming sector's emissions reduction target of 25% by 2030 and a 50% economy-wide target over the same time span, the State has pledged to reach net zero emissions by 2050.


The study analysed 3,000 farming and land use scenarios which could play out in Ireland out to 2100, looking at 10 different definitions of what could constitute the achievement of net zero.

The land use scenarios analysed which reached net zero required a drop in livestock production. / Donal O'Leary

Those which achieved net zero across definitions had common actions - larger areas of rewetted peatlands, a more than doubling of the country’s current forestry cover and a “substantially lower” livestock output.

The researchers stated that a “transformation” is needed for farming and the wider land use sector, with a need for “difficult decisions” to be made on whether to prioritise beef or dairy output to meet 2050 climate targets.

With regards to paying farmers for providing eco systems services on their land, the researchers highlighted a need to “better understand the potential economic value of these alternative [land] uses” which could fill the income gap left from less livestock production.

While it was noted that some low-cost measures can be rolled out without hitting farm output, “most” climate mitigation actions will have trade-offs which must be fully considered before implementation.

These measures could have knock-on consequences for farm livelihoods, food security, biodiversity and agri-food exports.

The paper also acknowledged the possibility of carbon leakage resulting from a fall in Ireland’s agri-food production, as less-efficient countries pick up the output slack and increase overall emissions.

The researchers referred to Ireland’s beef and dairy systems as having “amongst the lowest GHG intensity beef and milk production globally”.