COP26, the United Nations Climate Change conference held in Glasgow, ended on Saturday the 13th of November. Since then, there has been a lot of stock taking as to what was achieved under the Glasgow Climate Pact. Several gains emerged in the first week of the conference, with the announcement of collective action on deforestation, coal, finance and methane. It is the latter of these, the Global Methane Pledge (GMP), which could provide immediate gains to limiting global warming to 1.5 degrees, as embedded in the Paris Agreement. In this blog article, we explain why cutting methane emissions is an imperative and provide examples of how Scottish Government funded science is helping farmers and food consumers reduce their emissions.
The GMP commits one hundred countries to reduce their methane emissions by at least 30% (based on 2020 levels) by 2030. Although carbon dioxide (CO2) tends to get the headlines, methane is more potent (1 kg methane is equal to 27 kg of CO2 in terms of the warming it causes) and shorter-lived greenhouse gas (half-life of 12 years rather than centuries). The majority of global methane emissions stem from human activities: fossil fuels (35%), landfills and waste (20%), and agriculture (40%). For the latter, ruminant livestock, such as cows and sheep, and slurry storage are responsible for most of the greenhouse gas (GHG) emissions. In Scotland, this is not surprising, given the importance of livestock and grassland for the agriculture sector.
The short lifetime of methane in the atmosphere means that looking at the climate over decades, if methane emissions do not change from year to year, then they do not cause additional global warming. The other side of the same coin is that reducing methane emissions now helps reduce the warming caused by the emission of the other GHGs. The most widely used metric to compare and summarise the effect of GHGs is GWP100, which converts non-CO2 gases to so-called CO2 equivalents via their 100-year global warming potential. Alternative metrics, like GWP* have been proposed to capture the relationship between methane and CO2 in a way that accounts better for the actual temperature change caused by these emissions. While the debate about the GHG metric is an important one and concerns equity between generations and between emitters of different types of GHGs, it is important to remember that all possible emission reductions are needed to reduce the severity of the climate crisis. SEFARI researchers are developing measures to help farmers and wider society reduce their emissions.
Microbiome-driven breeding to mitigate methane emissions from beef cattle
One cost-effective method for farmers to reduce methane emissions from their livestock is to selectively breed animals with lower emissions. SEFARI researchers, in collaboration with the University of Edinburgh and Genus plc, a breeding company, have revealed that the composition of the microbiome in the rumen, the largest of a cow’s four stomachs, is linked to cattle host genetics. The microbiota (i.e. Bacteria, Protozoa and Fungi) in the rumen is a unique symbiotic ecosystem that allows cattle to ferment inedible fibrous plant material, like grass, into nutrients and produce high-quality beef and milk for human consumption. During this conversion, methane is produced by specific microbes (Archaea) as a natural by-product - although how much varies from cow to cow. Sampling the microbiome composition in cattle herds is a cost-effective way to identify lower methane-emitting cattle as well as those with improved characteristics, such as feed conversion efficiency and meat quality, and predict these traits in a large cohort of cattle.
Based on this research, SEFARI scientists are developing a rumen microbiome-driven breeding strategy, which can reduce methane emissions by up to 8% per year or cumulatively up to 50% after 10 years of selection. Improving the feed efficiency of cattle also reduces the carbon footprint of beef and increases the profitability of beef production.
Livestock Health & Methane Emissions
Endemic, production-limiting diseases are a significant constraint on efficient and sustainable livestock production in Scotland and globally. Moreover, disease syndromes (e.g. respiratory, reproductive and neonatal disease) also impact negatively on the carbon footprint of livestock production. Taken together, livestock diseases and syndromes can cause premature death, less meat and milk and introduce more waste in the system.
Work is ongoing across SEFARI to better understand and quantify the impact of livestock health on GHGs, but also to mitigate its impact through the development of new diagnostic tests, novel vaccines and more sustainable disease control strategies. This is something that can be achieved in the relatively short-medium term and is seen as a win-win, as it should not add extra expenses for farmers.
Improving the health of the national flock or herd is also vital to being able to express the full benefits of other longer-term emissions mitigation measures (e.g. breeding and feeding strategies). SEFARI scientists are actively engaged with key players across the livestock sector in Scotland to discuss and agree on the priority ‘climate’ diseases and identify practical intervention strategies that can be implemented on-farm to help us reduce methane (and other associated GHG) emissions.
Healthy and Sustainable Diets
Food consumption and diets were not directly featured in the formal COP26 negotiations around reducing emissions. This contrasts with the perceptions of the media and public, who increasingly see the link between food and climate but often the messages are too simple. The GHG emissions of our food is one factor in a healthy and sustainable diet. In practice, our food choices and diets are more complex and informed by our personal preferences and wider social and economic factors as well environmental ones. Despite national dietary guidelines, our typical diet still contains too many calories, saturated fat, salt and sugar, whilst having insufficient amounts of fibre, fruits, vegetables and fish. Advice for healthier diets proliferates, but many people may not know how to make sense of all these messages, how reliable they are and how to use them. SEFARI scientists have created a way to support consumers in making better nutritional choices. A new tool has been developed, ‘Number Muncher Diets’ creating an individual, healthy and green weekly shopping list using mathematical methods to optimise environmental impact or cost while ensuring dietary recommendations and personal preferences are met.
There is no time to waste on mitigating our GHG emissions and the GMP is a step in the right direction; reducing methane emissions now will help reduce the warming caused by the emission of the other GHGs. However, it is important to know what the best and most cost-effective actions are to undertake. SEFARI researchers have the scientific expertise to help land managers and society by developing mitigation measures to reduce emissions intensities. For example, farmers can breed animals for lower emissions and improve the health of their livestock, while consumers can benefit from a science-informed tool to make healthy food choices which also have a lower environmental footprint.