Livestock and greenhouse gas emissions: 10 arguments for nuance

The food system is responsible for 20-35% of human-induced greenhouse gas emissions. Agriculture and fisheries contribute about 40% of these food system emissions, while the remainder is split equally between associated land use and land-use changes (30%) and supply chain activities (30%).

Livestock represent the largest source of agricultural emissions, impacting climate and emission budgets. On average, animal-sourced foods have a higher carbon footprint than crops, which is why dietary policies often encourage a shift toward more plant-centric diets.

However, directly comparing individual foods is simplistic and can lead to misguided interventions. Dietary change can involve both benefits and trade-offs. Focusing solely on carbon reduction risks ignoring other critical factors, such as water scarcity, biodiversity loss, ecotoxicity, and social impacts, which may arise from prioritizing low-carbon foods. A more effective approach is to assess overall dietary patterns, considering their broader ecological, nutritional, and societal consequences.

According to the FAO, livestock contribute 12% of global anthropogenic greenhouse gas emissions. Of this, 60% are direct emissions, with the remainder largely attributed to feed and land-use change.

However, global figures should not be used to assess the impact of livestock in specific regions or production systems, as emission intensities vary a lot due to factors like climate and soil conditions, feed digestibility, livestock genetics, and herd management practices. Regional factors, such as a different focus on draft power, fuel availability, and religious significance, also have an influence.

For context, livestock in the EU, North America, and Australia/New Zealand each contribute <1% of global emissions. Emissions for cattle show a particularly large variability, from 5-20 kg CO₂-eq per kg of carcass weight in these regions, to 40-50 kg CO₂-eq in sub-Saharan Africa and South Asia.

However, smallholder farms in the Global South may perform better than assumed, depending on farm-level productivity. About half of smallholder farms in Kenya show milk-related emissions comparable to the European average, though the median emissions are nearly double that figure.

The argument against livestock assumes the status quo, overlooking the sector's potential for improvement. FAO's Pathways report claims that increased efficiency throughout the production chain can both reduce emissions and meet the growing demand for animal protein by 2050. In its COP28 roadmap to mid-century, FAO emphasizes that carbon neutrality for agrifood systems will depend on a halving of methane and nitrous oxide emissions. For animal production systems, this means methane must already decrease by 25% by 2030, while productivity should grow by 1.7% annually until 2050.

Over the past few decades, methane emissions in the US have remained stable, while Europe has made substantial reductions (-31% for 1990-2012). Several regions, including Australia and Northern Ireland, have already set an ambitious net zero goal by 2030. Yet, methane emissions from ruminants may nonetheless increase at the global level, driven by Latin America, Asia, the Near East, and Africa. However, there still remains vast room for improvement, especially in low-efficiency regions. 

Mitigation strategies include feed optimization, smart manure management, soil pH improvement, and better herd management. Improving animal health could be particularly effective but is underutilized due to challenges in quantifying its benefits. In addition, biogas valorization, improved integration with crop agriculture, reusing meat-processing by-products, increasing the consumption of edible offal, and reducing food waste are all viable strategies for improvement.

Filling the gap left by reducing animal-sourced foods requires increasing crop production to meet nutritional needs, which in turn generates its own emissions. Therefore, the potential benefit cannot be viewed as a straightforward elimination of the current 12% of global greenhouse gas emissions from livestock but should also account for the additional emissions from crop production. As a result, the net gains from dietary shifts are a few % points only, much smaller than commonly assumed. FAO's 2023 Pathways report has estimated this to be around 4%, while taking into account population growth.

Other perspectives yield comparable numbers. In the West, the average annual dietary footprint is 1.5-2.0 tons of CO₂-eq., with 2/3 coming from animals. Transitioning to flexitarian, vegetarian, or vegan meals would reduce emissions by 0.2, 0.5, or 0.8 t CO₂-eq, respectively. In a person's total annual carbon footprint of, for instance, 12 t CO₂-eq, this would lead to a reduction of a 1-6%, depending on the degree of dietary restrictiveness. Similarly, from a production standpoint, removing all livestock in the U.S. would result in only a 3% reduction in national emissions due to substitution effects, while raising concerns over nutrient security. Eliminating US dairy would yield a mere 1% reduction.

Although plant-based diets come with lower emissions, some vegetarians may have a larger impact than some omnivores, as certain plant-based products have high footprints, especially out-of-season items, whereas meat substitutes (1-6 kg CO₂-eq/kg) are comparable to poultry (2-6 kg/kg), or pork (3-10 kg/kg). In vitro meat, still largely unavailable, has an estimated footprint of around 3-25 kg/kg, which may even be 4-25x higher than median beef if reliance on chemicals and media is also factored in.

Moreover, and importantly, such dietary transitions to plant-based eating are only meaningful if sustained. Up to 70-80% of vegans and vegetarians quickly revert to consuming animal-sourced foods, with a third returning to such diets within three months of making the change.

Livestock serve as convenient scapegoats, although a shift to plant-based diets would only save a small amount of carbon. Matters of diet thus seem to be elbowing other topics out of the climate change discourse, which leads to misguided and thus less effective policies. 

The claim that livestock produce more emissions than transportation is incorrect. Its direct emissions (7% of the global emissions, on a CO₂-eq basis), and even its total emissions (12%), are lower than the direct emissions of the transportation sector (14%). Living car-free can save 1.0-5.3 t CO₂-eq per person per year, which is greater than one's annual savings via plant-based eating (<0.8 t CO₂-eq).

Global tourism accounts for 8% of GHG emissions. A single roundtrip flight can produce 0.7-2.8 t CO₂-eq per person, potentially offsetting a year of veganism or decades of a flexitarian diet. But even this number is overshadowed by emissions from private jets (up to 7,500 t CO₂ per year) and superyachts (4,500 t CO₂ per year), highlighting the contradiction between the virtue-signalling of elites and their carbon-intensive lifestyles. The wealthiest 1% contribute to half of the emissions from commercial aviation, with some billionaires' personal consumption emissions reaching 8,000 t CO₂ per year.

Digitalization and data centres also carry a substantial carbon cost. The use of email alone can result in 0.1-0.6 t CO₂-eq per person per year, and ICT is projected to account for over 14% of the global emission budget by 2040, with smartphones surpassing the emissions from desktops and laptops. By 2030, communication technologies could represent 23% of the emission budget.

Other aspects of modern lifestyles, such as the excessive purchase of consumer goods, also contribute to global emissions but are usually ignored in discussions. The fashion industry alone generates 10% of the global GHG budget, whereas pet food accounts for 1-3% of global GHG emissions. Yet, issues like pets, fashion, travel, and smartphones receive far less attention than dietary changes.

Dietary policies aimed at reducing greenhouse gas emissions must prioritize health alongside environmental goals. Climate change mitigation strategies should ensure that dietary shifts are carefully assessed to prevent exacerbating nutrient deficiencies, as low-carbon diets tend to lower the intake of essential micronutrients, such as calcium, iron, zinc, and vitamin B12. Moreover, policies like carbon pricing or meat taxes would raise food costs, further undermining nutrient security. 

Using environmental metrics like CO₂-eq/kg to compare very different foods is misleading, as it overlooks their nutritional value. The quality of protein and the presence of essential micronutrients should always be taken into account, knowing that animal-sourced foods are crucial sources of these nutrients. Despite their lower carbon impact per kilogram of product, ultra-processed foods offer little nutrition, lead to substantial dietary emissions, and cause health problems.

Poor diets contribute to obesity and cardiometabolic diseases, which themselves have high carbon footprints. In fact, the pharmaceutical industry’s carbon footprint exceeds that of the automotive industry. Besides bringing carbon costs linked to disease, obesity also leads to a 20% increase in carbon emissions due to higher food intake, greater metabolic demands, and increased mobility costs.

When assessing animal production systems, the value of co-products should not be overlooked. Life cycle analyses usually do not fairly distribute emissions from services and by-products of the animal industry, overstating the impact of foods. These relate to non-edible (e.g., hides, wool, bone, manure) and edible parts of the carcass (e.g., offal, which hold a large part of the nutritional value). In lamb, for instance, co-products account for 1/4 of total edible product by weight, 1/5 of total protein, 1/3 of total fat, and almost half of the total iron content, while the liver contains more vitamin A, B9, and B12 than the carcass and other co-products combined.

If these factors were to be properly factored in, carbon footprints of animal source foods would decrease. Yet, proper allocation methods are required to account for the various uses and markets of co-products, which can be complex.

When assessing the climate impact of livestock, it is essential to not only consider emissions but also the potential for carbon sequestration. Grass and grazers co-evolved over millions of years, with grazing ecosystems serving as massive carbon sinks. Grasslands, which now cover nearly half of the planet's land surface, may even have contributed to global cooling at some point, up until the extinction of the megafauna which disrupted the carbon cycles. 

The sequestration process in grasslands is influenced by a variety of factors, including photosynthesis, soil biology, and grazer-ecosystem interactions. Properly managed grazing systems can increase soil carbon, improve fertility, and boost forage biomass. Conversely, poor grazing practices can result in soil degradation and carbon depletion. The success of carbon sequestration, therefore, hinges on the management strategies employed, which must be tailored to each region and ecosystem.

Despite concerns about land requirements, there is still a very large potential for sequestration on degraded or underutilized lands that are not suitable for efficient crop production. When restored through regenerative practices, these lands can become major carbon sinks. Increased land demands can also be mitigated by higher stocking densities needed for adaptive rotational grazing.

Critics contend that carbon sequestration in soils will eventually plateau as mineral binding sites reach saturation. However, recent research challenges this notion, suggesting that there may be no upper limit to the accumulation of mineral-associated organic carbon under certain conditions. Some regenerative ranchers have achieved remarkable increases in soil carbon, offsetting emissions.

Another criticism is that grass-fed cattle produce more methane, which is often seen as a disadvantage compared to grain-fed cattle. While this is partially true, it overlooks the trade-offs involved in grain feeding, such as higher fossil fuel consumption and longer-term carbon emissions. Furthermore, many grain-finished cattle spend a considerable portion of their lives on grass, allowing for the integration of regenerative practices into their management.

While rewilding scenarios are theoretically associated with potential carbon savings, they tend to overlook important factors such as the carbon sequestration role of grasslands. Moreover, rewilding does not come without its own emissions, either through the digestive processes of wild grazers or from the decomposition of plant matter. Wild animals, such as moose in Norway, can also reduce forest carbon sequestration through browsing. Replacing livestock with wild animals may therefore not offer as much of a reduction in greenhouse gas emissions as expected. 

Importantly, livestock emissions are classified as 'anthropogenic' without considering the historical context of natural herbivore populations. In many ecosystems, especially in temperate regions of Europe, the presence of wild herbivores in the past was likely higher than generally assumed. As a result, current emissions from domestic livestock should not be viewed as entirely human-driven, as these animals are replacing the wild herbivores that once roamed these landscapes. This raises the question how much of the estimated 12% of global livestock emissions are truly anthropogenic?

In places like Spain, for instance, a baseline of natural herbivore populations should be factored into assessments of livestock emissions. When this baseline is considered, the carbon footprint of transhumant lamb meat, raised under more traditional grazing systems, can be lower than that of intensive lamb production.

Deforestation, exacerbated by livestock expansion, is a major contributor to climate change. While protecting forests is vital, large-scale afforestation of grasslands is not the universal solution that some claim it to be. This approach is particularly problematic for open ecosystems like grasslands, which depend on grazing, and which cover vast areas of the planet.

Grasslands play a crucial role in carbon sequestration, storing carbon in deeper soil layers than forests, making them reliable long-term sinks. In some contexts, permanent grasslands can even sequester carbon more efficiently than forests. Moreover, the benefits of trees take decades to materialize, and the short-term effects can sometimes result in a net carbon loss. 

Moreover, uncontrolled afforestation can lead to unintended consequences such as biodiversity loss, ecosystem degradation, and an increased risk of wildfires—especially in fire-prone, semi-arid areas. The environmental costs of such projects can be severe, as seen in New Zealand, where carbon credit systems have led to the replacement of sheep farming with monoculture pine forests, damaging biodiversity. Trees can even create a net warming effect through changes in albedo and increased aerosol scattering, sometimes outweighing the carbon storage benefits. 

Agroforestry and silvopastoral systems offer a middle ground, where trees and livestock coexist. These systems, such as the Dehesa agroforestry in Spain enhance carbon sequestration, with some farms achieving negative carbon footprints. In Ireland, hedgerows have been found to have higher carbon density than woodlands, further demonstrating the potential of integrated systems. Similarly, in New Zealand, woody vegetation on sheep and beef farms has offset significant portions of agricultural emissions. However, much of this vegetation does not qualify as forest, meaning farmers are not always credited for their carbon sequestration efforts, despite the environmental benefits.

Methane is a potent greenhouse gas emitted by ruminants. Unlike CO₂, a long-lived stock pollutant that can persist in the atmosphere for centuries, methane is a short-lived flow pollutant with a lifespan of about a decade, breaking down relatively quickly through interactions with hydroxyl radicals. Moreover, while fossil methane comes from carbon sources that are millions of years old, methane from ruminants is part of a biological carbon cycle, meaning it does not introduce new carbon into the atmosphere—provided herd sizes remain stable.

This fundamental difference means methane behaves differently from CO₂ in terms of its warming potential. Indiscriminate use of the conventional Global Warming Potential (GWP100) framework to compare methane and CO₂ leads to misleading conclusions, exaggerating methane's impact. Stabilizing herd sizes—or better yet, achieving a sustained reduction in methane emissions—can significantly reduce methane's contribution to global warming. Research using the GWP metric suggests that even a modest annual reduction of around 0.3% could prevent additional warming, with further reductions potentially contributing to a cooling effect.

To address these differences more accurately, scientists have developed the GWP* metric. When evaluated with GWP*, the warming impact of beef and sheep meat is substantially lower than previously estimated. For example, research from New Zealand found that sheep meat is effectively climate neutral when assessed with GWP*, and beef is moving in the same direction.

Despite notable methane reductions in regions like the EU and New Zealand, global emissions remain a challenge. However, the rise in methane levels since 2007 and their acceleration after 2014 may not primarily be linked to livestock. The global cattle population's most substantial growth occurred between 2000 and 2006, a period when methane levels remained stable. This challenges the assumption that livestock growth is the dominant driver behind rising methane concentrations.

Instead, other factors could be at play, including landfills and fossil fuel activities. Methane leaks from Turkmenistan's gas fields caused more global warming in 2022 than the UK's total carbon emissions, whereas flooded rice paddies, wetlands, and salt marshes may account for up to 50% of global methane emissions, a contribution often overlooked. Compounding this issue is the weakening of methane sinks, particularly atmospheric hydroxyl radicals. Blaming cows and sheep thus not only oversimplifies the complex global methane dynamics but also diverts attention from more effective solutions.

Lastly, simplistic comparisons between meat types based on methane emissions per kilogram risk distorting the bigger picture. While ruminants produce higher emissions per kilogram of meat (10–150 kg CO₂-eq/kg) compared to pork (3–10) or poultry (2–6), such comparisons ignore critical factors like land-use changes, feed efficiency, nitrogen pollution, and nutritional value. In fact, partially shifting global livestock production from monogastric animals to ruminants could potentially lower overall greenhouse gas emissions by reducing land-use pressures and mitigating feed-food competition.