"...Environmental assessments of the livestock sector are all too frequently stated in simplistic terms making use of a myopic selection of metrics, and overlooking underlying heterogeneity and complexities…" - Manzano et al.
In mid-April 2023 several peer-reviewed papers were published in the Oxford University Press’ Animal Frontiers journal. This was put together following the October 2022 International Summit on the Societal Role of Meat. This special edition of Animal Frontiers was published by guest editors and authors, among the nearly 1,000 signatories of the Dublin Declaration warning that livestock systems are too precious to society to become the "victim of simplification and reductionism."
After gaining an understanding in Part 4, which introduced the importance of livestock’s role in ecosystems including agroecology and circularity, the next article concludes the environmental investigation by looking into the industry comparatives commonly used such as greenhouse gas emissions, water use, and land use. How we measure things is important and simple, common metrics have been misleading without looking at the fuller picture.
Key topics that will be reviewed in this article include:
- An explanation of how greenhouse gasses are measured and compared, including the differences and challenges in comparing methane to carbon dioxide;
- Factoring nutrition and co-product benefits to comparing environmental impacts; and
- Measuring water usage vs. water competition and balancing the unique benefits of livestock to land use and biodiversity
Complexities Related to Accounting for Biogenic Methane’s Impact on Climate
- Developing balanced metrics to evaluate the environmental, social, and economic impacts of agriculture has been a major challenge for the scientific community to enable feasible policy action to balance natural capital with food security.
- In ruminant agriculture, the primary greenhouse gas (GHG) emissions are not carbon dioxide, but rather methane and nitrous oxide. Yet the way these are equated to carbon dioxide is overly simplified.
- Carbon footprint impact assessments typically adopt a global warming potential (GWP) for a 100-year time horizon. It is typically reported that methane as a GHG is 28 times more potent than carbon dioxide. More recently this number was adjusted to 27.2 for biogenic/non-fossil origin sources of methane. IPCC (2021) breaks this down further suggesting the GWP (20-year timeframe) is 80.8 times more potent while GWP over 500 years is 7.3 times more potent. The decimal place precision suggests an accuracy of understanding of atmospheric dynamics, which is not a reality currently.?
Greenhouse Carbon Dioxide Equivalents, Inherent Weaknesses, and Novel Solutions
- One of the complexities in converting methane to a carbon dioxide equivalent (CO2-eq) is differences in their decomposition or removal (sink) from the atmosphere.
- Methane decomposes mostly to carbon dioxide and water in the atmosphere within a few years. This usually happens through a reaction with hydroxyl radicals, nicknamed the detergent of the atmosphere as they also clean up other damaging build-ups, such as reactions with carbon monoxide and or volatile organic compounds.
- Meanwhile, carbon dioxide is highly inert and reacts minimally in the atmosphere. It requires terrestrial and aquatic sinks to be removed – mostly through photosynthesis or dissolution in oceans (increasing acidification). Since both photosynthesis and ocean capture cycles are in equilibrium, additional carbon dioxide injections end up in the atmosphere without the prospect of dissolution within human-relevant timescales.
- Climate change models are prone to uncertainties. The processes and timelines behind hydroxyl radical sinks are quite variable and still poorly represented and under scientific debate. There is an urgent need to address this, so the understanding of methane budgets can be improved and compared more accurately to GHGs that are long-lived.
- With a history of CO2-eq criticisms, numerous attempts have been made to offer alternatives to GWP. Global Temperature Change Potential (GTPx) offered a much lower factor for methane at 6 times carbon dioxide, now included in IPCC reports.?A recent metric GWP* handles methane more like a flowing gas rather than a stockpile gas. So, a gas like carbon dioxide is added to the stockpile, while methane as a short-lived gas would be treated as an addition or subtraction from the flow. A 2022 study using cumulative GWP* showed how a 7% drop in methane production from 2020 to 2040 would stop further methane-related increases in global temperatures – analogous to the impact of net-zero carbon dioxide emissions. Reducing these emissions by 5% annually would neutralize warming since 1980.
- But GWP* is not always “livestock friendly”, if emissions were to rise by 1.5% annually, the GWP* method predicts a 40% greater climate impact than the GWP (100-year) method.
- As a final consideration, natural baselines are key to the climate change discussion. Farmed livestock emissions are considered anthropogenic, yet this ignores how ruminant management integrates into grazing ecosystems, predating animal husbandry by millions of years.
- Re-wilding and abandoning livestock systems without adequate herbivore populations would reduce habitat for some species like ground-nesting birds. It will also lead to other scenarios such as increased wildfires or termite abundances – both with the capacity to generate large quantities of carbon dioxide or methane, respectively.
- There are also regional differences – methane seems to be lower in tropical-grass areas with extremely low inputs. Similarly, nitrous oxide emissions are lower in extensively managed grassland than in intensively managed systems.
Factoring in Nutrition and Co-product Benefits
- Evaluating and comparing food or agriculture products is a contentious area. The life Cycle Assessment (LCA) method is a systems analysis. Currently, this is commonly undertaken with a mass or volume denominator with the impact category (like CO2-eq) as the numerator.
- To help refine and include the ‘function’ of that food, nutritional LCAs (nLCA) have been developed over the last decade. One current drawback of such a method is that it can be easily manipulated to favour one product over another, whether plant or animal source. This is done by singling out specific nutrients (e.g., fiber or vitamin C vs. vitamin B12 or digestible amino acid balanced protein).
- Protein is a critical macronutrient, particularly when comparing animal-based foods. It is important to consider the bioavailability of Indispensable Amino Acids (IAA) of the protein sources being evaluated. Digestible IAA Score (DIAAS) provides a value to the total digestibility of the IAA and these scores can be over 100% for some animal-based foods or around 45% for some plant-based foods (e.g., cereals such as wheat). Without such accounting, the analysis is largely inconclusive, yet such methods rarely achieve recognition due to a lack of interdisciplinary collaboration between the fields of environmental and nutrition/health sciences.
- Another such method uses nutrient density scores (NDS) which provide for a comparison of a wider range of nutrients. Such methods still can be manipulated, especially in the plant vs animal-based debates, by choosing which nutrients to include in the analysis.
- Subjectively weighted trade-off between environmental impacts and human nutrition adds to the complexity. Curious claims that sweets score higher than red meat or eggs as a result of sugars and syrups with a low CO2-eq footprint being compared to high nutritional value foods with a higher CO2-eq footprint.
- Animal-based foods are susceptible to poor policy since such comparisons also ignore the non-anthropogenic nature of part of such GHG emissions or the positive land use aspects of grazing livestock.
- In addition to nutritional value, the way LCAs are often interpreted neglect to equitably allocate potions of the emissions profile to non-edible co-products and services associated with production (e.g., hides, wool, fats, organs, milk, bone, serum, manure, draught power, pet food, pharma, etc.)
- Moreover, livestock is known to provide other important benefits, such as social status, access to capital, opportunities to fund education and health services, or elements necessary to female emancipation, which interact with each other in complex ways.
Balancing Impacts Related to Land Use, Water Wastage, and Biodiversity
- When assessing the impacts of ruminant livestock, it remains important to consider this is typically about lands not suitable for human food production and feed supplies that are generally byproducts from the food industry.
- One way of categorizing this upcycling of industrial byproducts and non-productive land is through the Net Protein Contribution (NPC) of a food system. Due to less feed-food competition from monogastric livestock, ruminants upcycle 3-4-fold more NPC to the human diet than pork or poultry.
- Further, ruminant livestock play a vital role in subsistence farming in the developing world, through a provision of financial and climate resilience.
- On water use, grazing livestock are also questionably attributed to large water footprints. Footprinting includes all water sources regardless of their depletion of natural capital. (These sources are often referred to as green, blue, and grey water).
- Green water is particularly contentious as it measures rainfall over grazing lands, where little will be removed from grazing livestock directly. Rather the majority will infiltrate the ground to recharge underground stocks of flow to feed streams – both being sources for the “blue” water that food-producing or industrial activities and water supplies compete with.
- A paradox can happen in mountainous regions with strong water flow, shallow soils, and negligible potential for crop production, local livestock will be attributed with a very high-water footprint.?
- However, livestock can be intensive consumers of water in hyper-arid areas or where livestock production requires the use of channeled or irrigated water, competing directly with other uses.
- The consensus among researchers points to water scarcity measurements being much more effective at impact determination than footprinting.
- Uses of land for ruminant production can have strong positive impacts on biodiversity, including increasing the carbon stocks in the soil, mimicking the behavior of the wild herbivores that have shaped most of the planet’s ecosystems in the last 12-15 million years.?
- Carbon carrying capacity of grasslands will reach an equilibrium and would have the most positive impact on land already depleted from intensive cultivation.
- In high-carbon, well-structured, and more oxygenated soils such as grasslands, microbes assimilate nutrients into biomass more effectively and nutrients are therefore retained in the soil. The increased water-holding capacity of high-carbon soils, typical of grazed grasslands also has practical implications for reducing flood risks, a vital service.
- When considering the value of livestock products against their environmental impact, a holistic assessment is needed using metrics and avoiding tunnel vision. Besides factoring in nutrition and co-product benefits, other natural capital, and societal assets that result from well-managed farm enterprises need to be acknowledged, even if no empirical metric can currently fully account for their true value. Examples include biodiversity, soil health, land stewardship, and rural community support; especially in a time of extreme variability due to climate, social unrest, and economic crises.?
Author's takeaways: The last four topics covered the core nutritional and environmental elements. Both topics are polarizing and highly debated on their own. Taken together, it is safe to say finding a clear answer to settle the debate on both for most of the population is a fool’s errand.
For those open to animal agriculture the science on these topics seems clear:
- The nutritional functions of meat consumption cannot be fully replaced by plant-based solutions. Current alternatives are highly processed substitutes that fall short of the mark on digestible amino acids and other key nutrients for human thriving.
- Livestock animals consume industrial food byproducts and utilize land not suitable for human food production creating high-quality, nutrient-dense human food. Replacing this with substitutes would require more cropping. While animals also use feed from cropland and utilize resources that could be put to other uses, a balanced approach is required. I believe there is a solution that optimizes the huge benefit of livestock utilizing byproducts and poor land with some degree of resource competition, such as the finishing phase of cattle production.
- The holistic approach to properly account for the benefits of well-managed grasslands should not be understated. This is a significant carbon sink opportunity while soil health, water holding capacity, erosion prevention, wildfire control, biodiversity, and other environmental benefits are clear. These benefits cannot be replaced by monoculture or more plant-based raw material cropping production.
As policymakers read headlines and briefing papers from people and organizations that want the meat industry eliminated, it is important to maintain food freedom and choice.
As more research on livestock’s impact is developed it is clear there are real benefits to the environment. GHG emissions remain an issue for all human activity.?One side argues for removing all human impact on the environment and demands net-zero while rejecting nuclear energy or other currently available technologies to replace fossil fuels. Another side points to erroneous climate catastrophizing over decades and suggests we should focus on adaptation technology rather than increase the price of carbon and doom billions of citizens to poverty or worse.?
We may learn soon that global warming may not be as critical of an issue as other environmental problems, like biodiversity, soil health and food security. Energy security is already a major issue among most of the world, especially under inflationary times.
The last four articles have helped me understand the issues around nutrition and environmental impact more clearly. For me the path forward for the industry is to commit to doing better each year by focusing on production methods that optimize for nutrition and soil health. I believe soil health is a catch all for improving carbon sequestering, water holding capacity, nutrient density, biodiversity, and drought and wildfire risk mitigation.
-???????Grass left to rot instead of being eaten by a ruminant will release about the same about of methane.
-???????I just listened to a podcast from Jake Muise, CEO of Maui Nui Venison. As a meathead I found aspects of this conversation interesting. The discussion around micronutrient density of these grazing animals to conventinal beef makes me wonder how much we can boost the nutrient density of farmed livestock through more widespread use of solid
Part 6 will turn attention to the economics of raising livestock and the need to grow this industry to meet global population requirements -?“Affordability of meat for global consumers and the need to sustain investment capacity for livestock farmers" Ederer et al. 2023.
Literature focus of Part 5:
Manazno et al. 2023 Challenges for the balanced attribution of livestock’s environmental impacts: the art of conveying simple messages around complex realities, Animal Frontiers 13(2):35-44.?https://doi.org/10.1093/af/vfac096
