Farmers need clarity on actions for net zero

Lack of consensus on how to account for powerful greenhouse gases from agriculture is impeding policy development for net zero climate targets to ensure a just transition for farmers, the authors of a new scientific study have said.

Many countries have signed up to net zero climate targets by 2050 – less than 26 years from now – which means no longer adding to the total amount of greenhouse gases in the atmosphere in a bid to limit global temperature rise to 1.5°C.

Can we achieve net zero?

What this means for one of the main contributing emissions, carbon dioxide (CO2), is very clear, the study led by researchers at University of Galway notes.

However, the team say their findings raise concerns over significant gaps in how countries should tackle powerful greenhouse gases which are intrinsically linked with farming – nitrous oxide (N2O), often considered a forgotten greenhouse gas, and methane.

In the study, published in Nature Communications, Earth & Environment, the researchers analysed 3,000 scenarios of agricultural activities and land uses in Ireland out to the year 2100, using 10 definitions of net zero while also accounting for future emissions reductions via farm management and new technology.

In order to meet targets using any of the definitions of net zero, the analysis found:

–      Transformation of Ireland’s agriculture and land sector is required, involving ambitious tree planting and wetland restoration.

–      The increased biodiversity is needed alongside technical abatement measures such as low emission slurry spreading and anaerobic digestion of manures.

–      Land use scenarios that achieved net zero had larger areas of rewetted peat soils, more than double the current area of forestry, and substantially lower meat and/or milk outputs relative to 2021.

–      Maintaining milk production close to 2021 levels would require a reduction of up to 97% in suckler-beef output.

–      Net zero definitions requiring the least dramatic changes in agriculture and land use include those focussed only on carbon dioxide – meaning no targets for nitrous oxide and methane – or those based on an alternative accounting approach (“GWP*”) that attributes a “cooling” effect to a reduction in methane emissions.

–      Net zero definitions requiring the most dramatic transformations – eg the largest reductions in milk and beef output – were those based on the long-term offset of cumulative emissions between 2050 and 2100 and those based on Irish methane emissions being capped based on a per-capita “fair share” of “allowable” global methane emissions.

Colm Duffy, Research Fellow at University of Galway and co-lead author, said: “Our study shows just how much the national interpretation of net zero could shape Ireland’s future landscape, with implications for the environment, the economy and rural communities. Choices that may seem difficult now will only become more difficult with delay – clarity is urgently needed to plan a just transition.”

David Styles, Associate Professor at University of Galway and study coordinator, said: “For carbon dioxide, net zero represents a clear, absolute target that is invaluable for strategic decision making. Including nitrous oxide and methane emissions from agriculture in national climate targets is crucial, but lacks consensus and involves contentious value judgements. Some targets may be perceived as unfair to Ireland, given that they either don’t take into account the distinct warming effect of methane through time, or they disregard Ireland’s outsize contribution to global milk and beef production. Other targets may be perceived as unfair by other countries because they allow Ireland to maintain disproportionately high emissions of methane (and nitrous oxide).”

George Bishop, Postdoctoral Researcher at University of Galway and co-lead author, concluded: “Actions like planting forests take time to deliver benefits. Delaying decisions due to fuzzy net zero goals makes the challenge harder, but also risks missing out on economic opportunities that can support a just transition. A clear vision for a net zero agriculture and land sector is desperately needed to inform strategic decision making by farmers and other stakeholders. This vision must be founded upon a robust and internationally-defendable definition of net zero.”

The question of net zero and how to define strategic policy to achieve the targets has profound implications and the “what, where, and how” of future sustainable food production, peatland management and tree planting – actions that farmers will be expected to deliver.

The issue is acute for Ireland, where more than 40% of greenhouse gas emissions originate from farming and land use, largely in the form of methane and nitrous oxide.

The researchers also noted that policy on net zero should not just be about 2050. Some definitions consider the long-term warming impact out to the year 2100, which is vital to ensure that achieving net zero can be sustained beyond mid-century.

Link to blog post summarising article: https://go.nature.com/3URPOww

Link to main article: https://www.nature.com/articles/s43247-024-01275-0

Why is defining net zero so complicated? 

Ambiguity persists regarding appropriate 2050 targets for agricultural emissions of methane and nitrous oxide because:

(i)            global scenarios for climate stabilisation in line with the Paris Agreement imply non-zero net emissions of these gases in 2050;

(ii)           different metrics can be used to compare the warming effects of these gases with carbon dioxide over various time horizons;

(iii)          downscaling global emissions targets to individual countries involves value judgements around factors such as feasibility and fairness in relation to historic emissions;

(iv)          the Paris Agreement on climate stabilisation states that climate action should not threaten food production.  

Reaching net zero emissions means different things depending on how you count them. The researchers explored several ways to define it for Ireland:

·      Carbon Only: Just balance out carbon dioxide (CO₂) emissions – the most easily achievable option, but ignores the warming effect of other greenhouse gases.

·      GWP100: The standard approach. Balances ALL greenhouse gases, but disregards the different timescales of warming linked with different gases.

·      GWP*: A newer method. Accounts for how long different gases stay in the atmosphere to improve estimates of warming effect through time, and recognises the distinct non-zero emission target for methane. However, problematic for attribution of warming effects. 

·      Methane Targets: Sets a specific limit for methane emissions based on downscaling of global methane emissions compatible with climate stabilisation (important since Ireland has lots from livestock). How the limit is set impacts fairness between countries.

The Fairness Factor:

·      Grandparenting: Countries use recent global emissions levels as a baseline against which to target equal % reductions across countries (allows historical polluters to keep emitting relatively more).

·      Population-Based: The target global emission level is shared across countries based on number of inhabitants (everyone is attributed an equal “share” of “allowable” global methane emissions). 

·      Protein-Based: The target global emission level is shared across countries based on how much animal-based protein (meat, dairy) a country produces.

 About University of Galway 

Established in 1845, University of Galway is one of the top 2% of universities in the world. We are a bilingual university, comprised of four colleges, 18 schools and five research institutes, with more than 19,000 students, including around 3,000 international students. We have been accredited with an Athena SWAN Institutional Bronze Award, and 11 out of our 18 schools hold individual Athena SWAN Awards. We have more than 2,500 staff, and research collaborations with 4,675 international institutions in 137 countries. We have 133,000 alumni and 98% of graduates are in employment or further study within six months.

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