Vegan and Vegetarian Diets and Our Climate Emergency: Scientific Updates [2015-2021]

By Jeanne Yacoubou, MS

In this article, The Vegetarian Resource Group highlights several recent (2015 to the present) scientific reports that reveal the relationships between dietary choices and our climate crisis.

Background on Our Climate Crisis and Current State of the Emergency

In November 2019, 11,000 scientists from 153 countries declared a climate emergency in an article published in BioScience. The emergency is driven by fossil fuel burning releasing greenhouse gases (GHG), especially carbon dioxide, that began in the early 1800s with the rise of industry. The burning has accelerated rapidly since then. Life as we know it on a habitable Earth is at stake.

In January 2021, scientists reported new calculations that reveal the underestimation of earlier predictions about the degree of temperature increase already locked in from past and current fossil fuel use.

According to the new research, an increase of 2.3⁰C is guaranteed, but can be delayed if measures are taken now to significantly reduce or eliminate burning of coal, oil, and methane gas.

Note: The Intergovernmental Panel on Climate Change (IPCC) stated in a 2018 report that limiting temperature increase to 1.5⁰C above pre-industrial levels will avert the worst case scenario of extreme weather and sea level rise. The Paris Climate Accord of 2015 is a voluntary agreement among nations to reach this goal.

Emphasizing the gravity and urgency of the matter, 19 scientists wrote in a January 2021 article published in Frontiers in Conservation Science:

“The scale of the threats to the biosphere and all its life forms—including humanity—is in fact so great that it is difficult to grasp for even well-informed experts.”

To better grasp the problem and propose solutions, ecologist William Ripple and several other scientists in January 2021 developed a 6-step plan to reduce or eliminate fossil fuel use. Of interest to vegetarians and vegans, three of the six points are directly related to dietary choice.

• Short-lived pollutant reductions. The authors target methane, the greenhouse gas 84 times more powerful than carbon dioxide. A major source of methane is animal agriculture, especially beef production. (Note: Inaccurate assessment of methane leaks from fracking and from thawing permafrost are not considered in making this statement because these data are only estimates right now. When confirmed, agriculture’s contribution to total methane production would be lessened but still present.) 
• Habitat destruction reductions. Deforestation to make room for livestock grazing or planting livestock feed is a major concern. So, too, is cutting down mangrove forests and peatlands especially for rice paddies and palm oil plantations. Palm oil ingredients are found in hundreds of food and cosmetic products.
• Fewer animal foods and more plants in human diets. Waste food less. Not only an important way to reduce water and land use to produce food, significant reductions in greenhouse gases result.

Scale of Animal Agriculture Impact on Climate Change: Carbon Emissions

How much does animal agriculture contribute to our climate crisis?

The World Resources Institute assembled the latest available data (2016) from credible sources including the International Energy Agency and concluded:

• Total annual world emissions was 49.4 GT CO_2eq. (73% carbon dioxide CO₂, 17% methane CH₄, and 6% nitrous oxide NO₂)
• The top three carbon polluters: China (26%), USA (13%) European Union (8%)
• The breakdown of major emissions by sector: Energy in transportation (16%); Energy for electricity/heating (30%); Energy for manufacturing/construction (12%)
• Agriculture (12%)

Made up of 6% livestock/manure and 6% from soils. Manure is a major source of methane and nitrous oxide (another extremely potent greenhouse gas).  Fertilizer is a major source of nitrous oxide.

• Land use change, forestry 7% (burning 4%)

In a July 2019 report published by the World Resources Institute, the World Bank Group, the United Nations Environment Programme, and the United Nations Development Programme, further information is given about livestock’s contributions to environmental use and greenhouse gas emissions: “Ruminant livestock (cattle, sheep, and goats) use two-thirds of global agricultural land and contribute roughly half of agriculture’s production-related emissions.”

Despite the enormity of the carbon pollution stemming from livestock, the authors do not clearly recommend a switch to a vegan diet as a way to mitigate the impact of livestock on our climate emergency. They mention only “…shifting the diets of high meat consumers toward plant-based foods” and “plant-based beef substitutes.”

In a 2019 special report titled Climate Change and Land, the IPCC mentions “dietary choices” in reference to how climate change can be curbed, but does not specify vegan or vegetarian diets.

From the report: “Balanced diets, featuring plant-based foods, such as those based on coarse grains, legumes, fruits and vegetables, nuts and seeds, and animal-sourced food produced in resilient, sustainable and low-greenhouse gas emission systems, present major opportunities for adaptation and mitigation while generating significant co-benefits in terms of human health.”

Other notable points from this document:

• 70% of freshwater is used for agriculture
• 25-30% of all food is wasted (responsible for 8-10% of all emissions).

Recent Scientific Reports on Carbon Emissions and Animal Agriculture in Relation to Plant-based Diets

The Vegetarian Resource Group looked closely at the environmental consequences of animal agriculture with its 2009 article on the United Nations’ report titled Livestock’s Long Shadow. In that piece, the focus was on water pollution caused by livestock.

Since that time, many researchers have analyzed the carbon emissions associated with raising animals intensively for food. Here are brief summaries of some of their reports.

“The climate mitigation gap: education and government recommendations miss the most effective individual actions”

1. In 2017, Seth Wynes and Kimberly A Nicholas published an article that quantified the effects of lifestyle choices in terms of tons of carbon dioxide equivalents, tCO_2eq (taking into account methane, nitrous oxide and other chemicals that have substantial global warming potential) produced when people engage in certain activities. They concluded that individuals would contribute the greatest reduction by:

• Having fewer children (58.6 tCO_2eq saved every year per child)*
• Going car-less (2.4 tCO_2eq saved per year)*
• Avoiding flying (1.6 tCO_2eq saved per round transatlantic trip)*
• Buying green energy (1.5 tCO_2eq saved per year)
• Buying a more efficient gasoline-powered car (1.19 tCO_2eq saved per year)
• Buying an electric car (1.15 tCO_2eq saved per year)
• Choosing a plant-based diet (0.8 tCO_2eq per year)*

According to the authors, all of the above actions are considered “high-impact (i.e., low-emissions).” The four which are asterisked are recommended as the most important you can take to lower your personal fossil fuel footprint. Although they do not use the word “vegan” to describe the “plant-based diet,” it appears from the writing that a vegan diet is implied. The VRG has reached out to the authors on this point, but have not yet received a response.

“Calculation of external climate costs for food highlights inadequate pricing of animal products”

2. A report published in December 2020 conducted life cycle assessments of various agricultural products in Germany. The most significant finding was that there is practically no difference between the carbon emissions resulting from organic versus conventional beef production. Organic chicken fared worse than conventionally raised chicken in terms of its contribution to greenhouse gases. Organic and non-organic cow’s milk had similar carbon emission profiles.

By contrast, organic plant foods are responsible for 50% less emissions than plant foods treated with chemical fertilizers and pesticides. All plant production resulted in significantly less carbon emissions than animal foods.

“Substituting beans for beef as a contribution toward US climate change targets”

3. A study published in 2017 compared the environmental costs of beef versus beans. It concluded: “Our results demonstrate that substituting one food for another, beans for beef, could achieve approximately 46 to 74% of the reductions needed to meet the 2020 GHG target for the US. In turn, this shift would free up 42% of US cropland (692,918 km²).”

“The environmental cost of protein food choices”

4. An earlier look at this topic from some of the same researchers in 2015 concluded: “To produce 1 kg of protein from kidney beans required approximately eighteen times less land, ten times less water, nine times less fuel, twelve times less fertilizer and ten times less pesticide in comparison to producing 1 kg of protein from beef. Compared with producing 1 kg of protein from chicken and eggs, beef generated five to six times more waste (manure) to produce 1 kg of protein.”

“Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems”

5. The EAT-Lancet Commission (2019) published an extensive review of the environmental consequences of food choices. Its major conclusions echoed many of the findings noted here from other researchers.

Additionally, this report showed changes in food production practices (such as using feed additives, manure management, better feed conversion ratios) could decrease total greenhouse gas emissions by only 10%. However, dietary changes that increase plant foods could decrease emissions by 80%.

EAT-Lancet also divided up agriculture’s greenhouse gas share in this manner (top three listed here):

• Enteric fermentation by ruminants: 25%
• Manure (direct/indirect): 31%
• Deforestation/desertification 35%

“Which Diet Has the Least Environmental Impact on Our Planet? A Systematic Review of Vegan, Vegetarian and Omnivorous Diets”

6. A 2019 review article from the journal Sustainability compared many studies looking at environmental impacts of vegan, vegetarian, and omnivore diets. Some of the relevant points included:

• “Livestock farming uses 70% of agricultural land overall and a third of arable land. As such, it plays a major role in CO₂ release and biodiversity loss from deforestation.”
• “Many vegans replace animal-based products with processed plant-based meat and dairy substitutes (e.g., seitan burger and soy yoghurt) instead of consuming the unprocessed, plant-based nutritious foods…The vegan diet may not have a lower environmental footprint than the lacto-ovo vegetarian diet. The reason for this is that vegans tend to replace animal-based products in their diet by industrially, highly processed plant-based meats and dairy substitutes.”
• “The reviewed studies indicate the possibility of achieving the same environmental impact as that of the vegan diet, without excluding the meat and dairy food groups, but rather, by reducing them substantially.”

Takeaways on Plant-based Diets, Climate, and Environment

Agriculture (12%) and the burning of forests (4%) to plant feed crops or graze cattle are responsible for approximately 16% of all greenhouse gas emissions. This is comparable to the carbon emissions from the transportation sector.

A July 2019 joint report from several major international organizations stated: “Ruminant livestock (cattle, sheep, and goats) use two-thirds of global agricultural land and contribute roughly half of agriculture’s production-related emissions.”

As a rough estimate using the information of the two paragraphs above: 2/3 x 12% = 8% of all emissions from ruminant production + 4% from burning = 12% out of the total 16% from agricultural emissions is due to ruminant production alone.

There are ways to reduce significantly animal agriculture’s contribution to our climate crisis by switching to a vegan or vegetarian diet. In fact, the EAT-Lancet report in 2019 stated that dietary changes which increase plant foods in human diets could decrease carbon emissions (from the agricultural sector) by 80%.

Unfortunately, major international organizations and mainstream media do not clearly make the recommendation to switch to a vegan or vegetarian diet for climate change mitigation.

Individual actions, including switching to a vegan or vegetarian diet, to curb the negative effects of our climate crisis matter by reducing personal fossil fuel footprints. They also have a bigger impact in that they serve as examples for others to emulate.

However, systemic change – notably the drastic and immediate reduction or elimination of fossil fuel use – is needed to prevent worst case scenarios of extreme weather and sea level rise from happening even more than they already are.

Note from the Editor:

See other environmental articles from The Vegetarian Resource Group at:

https://www.vrg.org/environment/

https://www.vrg.org/links/EnvironmentalInformation.htm