Livestock and climate change

Farmers have a key role to play in the fight against climate change, and we increasingly hear about the need to make significant changes to farming practices to meet the challenge, particularly in the livestock sector. But what is the basis for these claims, and do we as keepers of native breeds need to respond any differently to those who keep continentals?

Around a tenth of UK Green House Gas (GHG) emissions result from farming. But only around a tenth of these emissions are carbon dioxide (CO₂), the main greenhouse gas. Just over half of the emissions from farming are methane (CH₄) with the rest being nitrous oxide (N₂O).

Agriculture is the single biggest source of methane emissions globally, with the livestock sector, primarily cattle, being the biggest emitter at the UK level. However, although emissions have been increasing globally, in the UK they have significantly declined since the end of the 20th century.

The UK-wide figure does hide significant differences across the four constituent countries though. In Northern Ireland, farming accounts for around 26% of the total emissions, whereas in England, Wales and Scotland the proportions stood at 8.4%, 13.8% and 16.3% respectively. This is the result of Northern Ireland being much more skewed towards livestock production than the rest of the UK.

Methane matters for two reasons. Firstly, it is extremely potent and has far greater immediate impact on the climate than CO₂: one molecule of methane has a much greater warming effect than one molecule of CO₂. Secondly, although methane breaks down in the atmosphere much more quickly than CO₂, once emitted it remains in the atmosphere for around a dozen years whereas CO₂ can linger for more than a century.

The standard measure to compare warming effects of different GHGs relative to CO₂ over 100 years is known as GWP100. It calculates the warming caused by one unit of methane as 28 times more potent than one unit of CO₂.

However, to take account of methane’s short atmospheric lifetime, in 2019 the GWP* standard was developed. The aim of this is to reflect the non-cumulative impacts of stable methane emissions by taking account of the way in which methane levels change, not just their potency.

Environmental consequences?

So what are the environmental consequences of the different types of emission?

If methane emissions remain at a relatively consistent level, the amount of methane in the atmosphere will not increase: the methane will break down as fast as it is emitted. With CO₂ though, overall levels will increase as emissions increase. This is because it breaks down so much more slowly.

On the face of it, this would suggest it makes more sense to focus on reducing CO₂ emissions. This may have been true were it not for the potency of methane which has such a significant effect that even a small increase in methane emissions will lead to an immediate increase in atmospheric concentrations and therefore warming. On the other hand, even a small reduction in methane emissions will result in a significant reduction in concentration and therefore have an equivalent cooling effect.

This has a particular relevance for the livestock sector. In the UK, livestock methane emissions are relatively stable, with the level of warming resulting from the sector having been relatively constant for the last decade or so. But these levels still have an adverse effect on the climate. UK livestock may not be having an increasing effect, but they still lead to more warming than would otherwise be the case.

In any event, cutting CO₂ to zero will take many years and the cumulative effect of CO₂ emissions will continue to make matters worse in the meantime. Reducing methane emissions, however has an immediate effect with the benefits becoming apparent in just a few years.

Accordingly, it is impossible to resist the argument that we need to be reducing emissions from livestock.

Is there a difference?

Readers of The Ark will be interested to know whether there is any difference when it comes to emissions between the various breeds. Fortunately, Scotland’s Rural College (SRUC) has done some work on this. The researchers carried out a review of several previous studies comparing the emissions from various different species and breeds. The studies compared Holstein Friesians with Belgian Blues, Charolais with Luings, and Welsh Mountain sheep with Texel amongst many others.

Much of what the researchers found is helpful to those favouring native breeds above their continental counterparts.

Significantly, they began by noting that there were no clear differences between the breeds. The often-heard claims about benefits of continental breeds were without foundation and such differences as there were between the breeds related far more to the animals’ feed intake or the production system used.

They went on to state that methane emissions may be lower per kilogram of beef produced by more productive breeds because they consume a smaller amount of feed. In the same way, an animal that digests its food more quickly will generate fewer emissions as there is less time for processing in the stomach. So, breeds selected for higher production will have reduced greenhouse gas emissions, particularly when expressed relative to production.

Minimising risks

On the other hand, the researchers found that selective breeding could be linked with problems of ill health, increased death rates and reduced fertility, and so overall reductions in greenhouse gas emissions had to depend on minimising these risks – for example by having an appropriate breed for the environment or management system.

Interestingly, the researchers found evidence of significant genetic variation in greenhouse gas emissions within all breeds.

The livestock sector as a whole clearly needs to engage with the climate challenge and this does include the keepers of native breeds. We increasingly hear arguments that favour the removal of meat from our diets “for the sake of the environment” but native breed keepers are in a strong position to counter that view by demonstrating that farming with native livestock can offer a sustainable solution. High levels of animal health and welfare, a natural forage-based diet and the low food miles involved in good quality local food production all have a part to play in sustainability and can all be delivered by our traditional native breeds.

April 2022