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the carnivore's catastrophe: how our diets destroy the environment

2023-06-21

“A vegan diet is probably the single biggest way to reduce your impact on planet Earth” ~Joseph Poore, Climate Researcher

Concern about the threat of climate change is at an all-time high across many parts of the world. In Pew Research’s Spring 2022 Global Attributes Survey, climate change ranked as the top concern among citizens of nineteen countries. A median of 75% of respondents across the surveyed countries labeled global climate change as a major threat, with only 5% believing that it poses no threat at all ( , (). Climate Change Remains Top Global Threat Across 19-Country Survey. Pew Research Center's Global Attitudes Project. Retrieved from https://www.pewresearch.org/global/2022/08/31/climate-change-remains-top-global-threat-across-19-country-survey/ ) . Of course, there’s good reason to believe that these fears are warranted. The Sixth Assessment Report of the Intergovernmental Panel on Climate Change displays how the lives of millions of people have already been altered by climate change and how the impacts will only continue to get worse without immediate and drastic change. Even if we contained warming to 1.5° C from pre-industrial temperatures, we could expect to see a four-fold increase in extreme weather events from 2020 to 2100. Further problems include deadly heat stress, rising sea levels, water scarcity, food shortages, among countless other issues ( , (). Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC. ) . 1

As we continue to gain knowledge about the risks of climate change, it’s natural to wonder what we can do about this seemingly gargantuan obstacle. Activist groups have done a great job educating the general-public about solutions relating to renewable energy, sustainable infrastructure, and over-consumption. However, one of the greatest steps we can take starts with the food on our plates. The seemingly inconsequential choices we make in order to feed ourselves on a daily basis have wide-reaching effects on the environment. More specifically, the animal agriculture industry is a major player in the acceleration of climate change and environmental damage. By foregoing meat, dairy, eggs, and other animal products in favor of a plant-based diet, we could take a significant step towards a sustainable future. 2

The Effect of Food Systems

Since everyone on Earth needs food to survive, it’s only natural that an increasing global population will result in an increasing need for food production. The current world population is around 8 billion people, and current estimates suggest we can expect that to rise to about 9.7 billion people by the year 2050 ( , (). World Population Prospects 2022: Summary of Results. United Nations Department of Economic and Social Affairs, Population Division. 52. ) . Although the rate of population growth is starting to slow down, that doesn’t make adjusting to our new population levels any less of a challenge. One issue at hand is a growing demand for crop calories and protein from richer nations. Agricultural and population data ranging from 1961 to 2007 suggests that there’s a consistent relationship between the per capita GDP of a nation and their per capita demand for crop calories and protein. This relationship seems to be especially strong; it’s held up between nations in similar economic standings and across all years in the sample. For instance, data from the year 2000 shows that the per capita demand for crop calories in the wealthiest nations was 256% higher than in the poorest nations. 3 By these metrics, we can expect a roughly 100% increase in global crop calorie demand between 2005 and 2050 ( , & al., , p. 20260 , , & (). Global food demand and the sustainable intensification of agriculture. Proceedings of the National Academy of Sciences, 108(50). 20260–20264. https://doi.org/10.1073/pnas.1116437108 ) .

Along with the issues that we can expect in the future, our global food systems as they exist today are already major contributors to the climate crisis. Using data from a recent database of the greenhouse gas emissions from food from 1990-2015, we can estimate that around 34% of the total anthropogenic GHG emissions on Earth are caused by the global food system ( , & al., , p. 198 , , , , & (). Food systems are responsible for a third of global anthropogenic GHG emissions. Nature Food, 2(3). 198–209. https://doi.org/10.1038/s43016-021-00225-9 ) . These emission levels are putting us at risk of not being able to limit our temperature increased to 1.5° or 2° C, as recommended by the Paris Agreement.

The authors of a 2020 analysis published in the Science journal found that even if we were to see a rapid reduction in fossil fuel emissions, global food system emissions are on a trajectory that would still cause us to hit those limits:

“Our estimate of cumulative business-as-usual food system emissions from 2020 to 2100 is 1356 Gt CO2-we. As such, even if all non–food system GHG emissions were immediately stopped and were net zero from 2020 to 2100, emissions from the food system alone would likely exceed the 1.5°C emissions limit between 2051 and 2063. Further, given our estimate of food system emissions, maintaining a 67% chance of meeting the 2°C target would require keeping cumulative nonfood emissions to <50 Gt CO2-we in total over the next 80 years. This is slightly more than 1 year of current GHG emissions from non–food system activities ( , & al., , p. 2 , , , , , , & (). Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets. Science, 370(6517). 705–708. https://doi.org/10.1126/science.aba7357 ) .”

Given that, how do greenhouse gas emissions differ between diets? The authors, Joseph Poore with the University of Oxford and Thomas Nemecek with the Switzerland-based LCA Research Group, found that meat, seafood, eggs, and dairy contribute 56-58% of the world’s emissions despite only providing us with 18% of our calories. As a result of this, they estimate that switching from the current average diet to a plant-based diet would reduce our GHG emissions by about 6.6 billion metric tonnes, or about 49% of our total emissions. In a separate study, a group of researchers from the University of Oxford analyzed a dataset of over 50,000 people with varying diets in the United Kingdom. They found that the even when standardizing the amount of calories consumed, daily dietary emissions caused by meat-eaters were nearly double those of vegans. For all of the diets in between, the amount and types of animal products eaten also had in impact. Emissions were the highest for high meat-eaters, followed by low meat-eaters, fish-eaters, vegetarians, and vegans in that order.

Non-Emission Environmental Impacts

Although greenhouse gases are naturally one of the top concerns relating to the protection of our environment, it’s not the only concern worth investigating. Other issues such as land use, water use, terrestrial acidification, eutrophication 4, and other types of localized pollution also have widely varying impacts from different food sources that will force us to evaluate our dietary choices. One analysis of these issues from 2018 compiled data through a comprehensive meta-analysis of 1530 studies, creating a data set that covers around 38,700 farms in 119 countries and 40 individual food products representing ~90% of global protein and calorie consumption. Poore and Nemecek found that global food production causes 32% of terrestrial acidification, 78% of eutrophication, 43% of non-ice and non-desert land use, and 90-95% of freshwater use when weighted for water-scarcity ( & , , p. 1 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) . Unsurprisingly, the majority of these harmful environmental effects can be attributed to animal agriculture as opposed to entirely plant-based processes. It’s estimated that if the world were to entirely replace all dietary animal products with plant-based alternatives, we could reduce land use by 76%, terrestrial acidification by 50%, eutrophication by 49%, and freshwater use by 19%. These changes would be especially noticeable in the United States where average meat consumption per person is three times higher than the rest of the world ( , p. 5 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) .

Deforestation

Although deforestation for plant-based agriculture tends to be a hotly contested topic, it’s worth looking deeper into the crops that cause these issues along with their intended uses. Poore and Nemecek’s 2018 study found that this problem is controlled by a specific type of agriculture: animal feed. In fact, 67% of the agriculture-related deforestation is either for the growth of plants such as soy or maize which are then used for feeding farmed animals, or is directly used for pasture ( & , , p. 5 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) . For example, data from the University of Oxford’s Food Climate Research Network shows that around 75% of soy is fed to livestock. Only 20% of soy is actually processed for human consumption through oils or foods such as edamame, soy milk, tempeh, and tofu ( , & al., , p. 8 , & (). Soy: food, feed, and land use change .  Food Climate Research Network https://doi.org/10.56661/47e58c32 ) . Furthermore, a separate analysis examined what kinds of food-systems changes would be necessary to meet the demand for food globally if we were to have a world without any amount of deforestation. Out of various scenarios involving different crop yields, feed types, organic processes, and livestock sources, only 18% of western industrial diets and 50% of healthy meat-based diets were found to be feasible. In comparison, 100% of plant-based scenarios were found to meet those criterias
( , & al., , p. 5 , , , , , , , , , & (). Food systems in a zero-deforestation world: Dietary change is more important than intensification for climate targets in 2050. Science of The Total Environment, 735. 139353. https://doi.org/10.1016/j.scitotenv.2020.139353 ) .

Food Waste and Energy Efficiency

One of the questions that arises whenever anyone advocates for a plant-based food system is pretty obvious: how are we going to feed everyone? After all, products such as meat, dairy, eggs, and other animal products have become staples of Western diets. Interestingly, it turns out that it would actually be easier to produce enough food to feed everyone under a plant-based food system compared to the status quo. While much of the debate regarding global hunger centers around how to prevent the large amounts of food that gets wasted, the importance of dietary change is largely overlooked.

Retail-to-consumer food loss in the United States tends to hover around 30% for vegetables and 40% for meat due to factors like spoilage and supply chain issues. Reducing these losses, such as by investing in better ways to keep food fresh for longer, is certainly important if we want to reduce hunger and increase our sustainability. However, solely looking at this number would ignore the more nuanced concept of “opportunity food loss”. Animal food sources require more resources to create than plant food sources, meaning that there are many opportunities to replace foods with more efficient alternatives. A study from Shepon et al. in 2018 demonstrated just how important these differences can be:

“We find that the opportunity food losses at the consumer level range from 40% for eggs to 96% for beef (the most and least efficient animal food categories). Put differently, nutritionally comparable plant-based diets optimized to nutritionally replace eggs and beef produce twofold and 20-fold more protein per acre than the eggs and beef they replace
( , & al., , p. 3805 , , & (). The opportunity cost of animal based diets exceeds all food losses. Proceedings of the National Academy of Sciences, 115(15). 3804–3809. https://doi.org/10.1073/pnas.1713820115 ) .”

Simply put, even when producing eggs, which are the among the most nutritionally efficient animal products, there’s a 40% loss in potential nutrients. In the worst cases, as with beef, choosing to produce the animal-based product over plant-based alternatives is functionally equivalent to throwing away 96% of our protein supply! More practically speaking, if we were to replace all animal-based products in the United States (based on the average American diet), we would be able to feed an additional 350 million people ( , p. 3806 , , & (). The opportunity cost of animal based diets exceeds all food losses. Proceedings of the National Academy of Sciences, 115(15). 3804–3809. https://doi.org/10.1073/pnas.1713820115 ) . To bring that to a smaller scale, just two Americans choosing to switch to a fully plant-based diet would free up enough resources for an extra person to be completely fed without using any extra resources.

Are There Any Alternatives?

Even if one is to believe that animal agriculture is currently unsustainable, it could still be possible that it could eventually become sustainable some time in the future. Or alternatively, one could argue that the types of foods people are eating aren’t even the biggest environmental problems to be found in our global food systems. Therefore, it’s important to consider the various alternative approaches that we could take towards fixing these systems.

One natural concern is that it doesn’t seem to make sense to lump all the animal-based products and all the plant-based products into two distinct piles when there are countless foods in each group. After all, there are varying levels of emissions based on the individual products that consumers choose to buy within each group. Maybe if we could just focus on producing animal products in a more sustainable way, then the gap in environmental effects between the two groups could close. Regrettably, this approach doesn’t seem to be especially effective.

The trends that we see of animal products having higher impacts than plant products tend to be very consistent. For example, if we specifically look at the animal products that have the lowest impacts in the animal product category, they still tend to have higher emissions, eutrophication, acidification, and land-use than average vegetable proteins. There are a few reasons for this. First, producing animal products requires an excess of protein in their feed compared to the protein we get back as an output. Therefore, the emissions from those animal proteins add up to be larger than the amount of the feed itself. This is shown in the statistics regarding soy feed for livestock that I mentioned earlier. Second, animals naturally create additional emissions due to their biological processes. The most well known example of this is the methane that gets released during the digestive processes of cows. Third, more emissions are added from the processing of live animals, particularly from when they’re processed through slaughterhouses 5. Finally, animal products tend to spoil faster, meaning that more energy needs to go into preventing waste
( & , , pp. 4-5 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) .

Beyond the differences between food products, there are also differences in emissions between individual producers. Across all types of foods, a large amount of emissions can be attributed to relatively high-impact producers. On average 56% of the environmental impacts will come from the top 25% of producers with the highest impacts ( , p. 2 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) . Although there are mechanisms that could help to address this, there are of course several significant barriers. Primarily, the actions that would be best for reducing emissions for each producer are vastly different based on geographic conditions and economic feasibility. Since there are so many sources of emissions and other environmental impacts, it wouldn’t make sense to just focus on a few of them on a global scale ( , p. 3 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) . There’s also the obvious issue that consumers could easily continue purchasing from the highest impact farms. Despite efforts to label and certify sustainable palm oil sources, there was found to be virtually no demand for the certified products in important markets such as China and India. The case of organic foods demonstrates how consumers aren’t necessarily willing to pay a higher price for their food in order to buy a more sustainable product. This results in food producers having little incentive to increase their sustainability ( , p. 4 & (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216 ) .

Buying From Local Sources

Another common approach among the environmentally conscious is to prioritize buying their food from local sources. Despite that, transportation only plays a small role in emissions compared to production stages. Looking at a study of U.S. commodity flow and energy use statistics, we can see that clearly:

“We find that although food is transported long distances in general (1640 km delivery and 6760 km life-cycle supply chain on average) the GHG emissions associated with food are dominated by the production phase, contributing 83% of the average U.S. household’s 8.1 t CO2e/yr footprint for food consumption. Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%
( & , , p. 3508 & (). Food-miles and the relative climate impacts of food choices in the United States. Environmental Science & Technology, 42(10). 3508–3513. https://doi.org/10.1021/es702969f ) ”

The authors continue by creating a comparison between shifting the foods that one eats and shifting the sources of one’s food to local sources. They find that if an average American were to shift just 11-19% of their calories away from red meat and dairy, they would achieve the same greenhouse gas emissions reductions as someone who switched to a diet composed entirely of locally sourced food ( , p. 3512 & (). Food-miles and the relative climate impacts of food choices in the United States. Environmental Science & Technology, 42(10). 3508–3513. https://doi.org/10.1021/es702969f ) . While this does show that there is a benefit to buying from local sources, buying local is by no means a suitable alternative to changing our diets. 6

Moving Forward

Despite the clear environment detriments, the idea of switching from the high-meat American diet to a plant-based one can seem daunting. However, it can be a critical step in aligning your values with your lifestyle. If you’re worried about the potentially catastrophic effects of climate change or even if you just consider yourself to be environmentally conscious, I would encourage you to critically reflect on the impacts that your everyday dietary decisions have on the world. The Academy of Nutrition and Dietetics has come to the conclusion that vegan diets can be nutritionally adequate for all people at all stages of life, including pregnant people, infants, the elderly, and even athletes. Since animal products aren’t necessary in order to be healthy, our choice to pollute the environment through our diets is nothing more than a choice to prioritize our taste preferences and convenience over the future of our planet.

I’ll leave you with a motivating anecdote from Joseph Poore, a climate researcher that I’ve mentioned many times throughout this post. In an interview with the Guardian, he said the following about his research into this topic:

“The reason I started this project was to understand if there were sustainable animal producers out there. But I have stopped consuming animal products over the last four years of this project. These impacts are not necessary to sustain our current way of life. The question is how much can we reduce them and the answer is a lot.” ( , (). Avoiding meat and dairy is ‘single biggest way’ to reduce your impact on Earth. Retrieved from https://www.theguardian.com/environment/2018/may/31/avoiding-meat-and-dairy-is-single-biggest-way-to-reduce-your-impact-on-earth )

Resources for Plant-Based Diets

  • Vegan Health: A great resource for scientific recommendations relating to concerns about plant-based diets.
  • 7 Beginner Tips for Going Vegan: A video giving practical tips about how to gradually transition to a plant-based diet.
  • Vegan Cheat Sheet: A massive collection of studies, books, documentaries, cookbooks, charities, and everything else related to veganism/plant-based diets.
  • Happy Cow: A map of restaurants with plant-based options in any location.
  • Veganuary: A non-profit that guides people through a one-month vegan challenge. I can’t personally vouch for the eating guides, but I’ve heard great things about them from other people.
  • Vegan Bootcamp: A similar challenge involving education about nutrition, recipes, and ethics.
  • Good Food Institute: A charity that puts donations towards research and development of alternative proteins such as plant-based and cultivated meat. They have a great overview of how alternative proteins can make a positive impact on the world.

Bibliography

Atske (2022)
(). Climate Change Remains Top Global Threat Across 19-Country Survey. Pew Research Center's Global Attitudes Project. Retrieved from https://www.pewresearch.org/global/2022/08/31/climate-change-remains-top-global-threat-across-19-country-survey/
Carrington (2018)
(). Avoiding meat and dairy is ‘single biggest way’ to reduce your impact on Earth. Retrieved from https://www.theguardian.com/environment/2018/may/31/avoiding-meat-and-dairy-is-single-biggest-way-to-reduce-your-impact-on-earth
Clark, Domingo, Colgan, Thakrar, Tilman, Lynch, Azevedo & Hill (2020)
, , , , , , & (). Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets. Science, 370(6517). 705–708. https://doi.org/10.1126/science.aba7357
Crippa, Solazzo, Guizzardi, Monforti-Ferrario, Tubiello & Leip (2021)
, , , , & (). Food systems are responsible for a third of global anthropogenic GHG emissions. Nature Food, 2(3). 198–209. https://doi.org/10.1038/s43016-021-00225-9
Fraanje, Garnett & Breewood (2020)
, & (). Soy: food, feed, and land use change .  Food Climate Research Network https://doi.org/10.56661/47e58c32
IPCC (2022)
(). Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC.
Poore & Nemecek (2018)
& (). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392). 987–992. https://doi.org/10.1126/science.aaq0216
Shepon, Eshel, Noor & Milo (2018)
, , & (). The opportunity cost of animal based diets exceeds all food losses. Proceedings of the National Academy of Sciences, 115(15). 3804–3809. https://doi.org/10.1073/pnas.1713820115
Theurl, Lauk, Kalt, Mayer, Kaltenegger, Morais, Teixeira, Domingos, Winiwarter, Erb & Haberl (2020)
, , , , , , , , , & (). Food systems in a zero-deforestation world: Dietary change is more important than intensification for climate targets in 2050. Science of The Total Environment, 735. 139353. https://doi.org/10.1016/j.scitotenv.2020.139353
Tilman, Balzer, Hill & Befort (2011)
, , & (). Global food demand and the sustainable intensification of agriculture. Proceedings of the National Academy of Sciences, 108(50). 20260–20264. https://doi.org/10.1073/pnas.1116437108
UNDES (2022)
(). World Population Prospects 2022: Summary of Results. United Nations Department of Economic and Social Affairs, Population Division. 52.
Weber & Matthews (2008)
& (). Food-miles and the relative climate impacts of food choices in the United States. Environmental Science & Technology, 42(10). 3508–3513. https://doi.org/10.1021/es702969f

  1. For a good summary on these issues, see the Frequently Asked Questions section on the IPCC 6th Report Working Group II contribution website. I specifically referred to Question 3 (“How will climate change affect the lives of today’s children tomorrow, if no immediate action is taken”) for the four-fold extreme event increase figure. ↩︎

  2. There’s an important discussion to be had about the efficacy of various governmental polices regarding animal agriculture, but those aren’t the focus of this post. Similarly, issues of how difficult/healthy/expensive it is to switch to a plant-based diet won’t be covered aside from some external references at the end. ↩︎

  3. In this study, the authors looked at the top 100 largest nations and grouped them in seven groups based on average per capita GDP. The “richest nations” for this figure were those in the Group A and the “poorest nations” were those in Groups F and G. ↩︎

  4. Eutrophication is a process which results from a heavy increase of nutrients into estuaries and coastal waters. This results in ocean acidification, which can kill fish and other sea life ( , (). Retrieved from https://oceanservice.noaa.gov/facts/eutrophication.html ) . ↩︎

  5. Slaughterhouses also create significant harm to surrounding environments and the health of residents that live nearby. In a study of slaughterhouses in India, nearby residents reported increased infections from flies and mosquitos, horrible odors, drinking water contamination, and even drain clogs containing visible blood. Additionally, those who were closer to the slaughterhouses reported severe headaches, heavy coughs, loss of appetite, and various diseases
    ( , & al., , , & (). Environmental and health impacts from slaughter houses located on the city outskirts: a case study. Journal of Environmental Protection, 05(06). 566–575. https://doi.org/10.4236/jep.2014.56058 ) . ↩︎

  6. As an interesting side note, an entirely locally-sourced diet might not even be the best way to reduce transportation emissions. The role of seasons can occasionally cause imported foods to create lower amounts of GHG emissions depending on the climates of the importer and exporter locations. One small case was a study of lettuce farming, where it was found that importing lettuce from Spain into the UK during the winter caused lower amounts of emissions than just growing lettuce in the UK. This was primarily due to the energy that was needed to preserve the growing conditions in the UK’s harsher climate outweighing the cost of refrigerated transport ( , & al., , p. 382 , , , , & (). The role of seasonality in lettuce consumption: a case study of environmental and social aspects. The International Journal of Life Cycle Assessment, 14(5). 381–391. https://doi.org/10.1007/s11367-009-0091-7 ) . ↩︎