Eating less meat: can going vegetarian help save the planet?

Meat and dairy are responsible for 60% of agriculture’s greenhouse gas (GHG) emissions and 14.5% of global emissions. Eliminating meat and dairy consumption could cut global farmland use by more than 75%. This is important as the loss of wild areas due to agriculture is the leading cause of the mass extinction of wildlife.

Greenhouse gas emissions per kilogram for different food groups. Chart by Carbon Brief using Highcharts. Adapted from Dr Hannah Ritchie/Our World in Data (2020) Data source: Poore & Nemecek (2018). 

As the graph above shows, animal-based foods often have a substantially bigger carbon footprint. Ruminant animals such as cows and sheep produce a lot of methane during their digestion. Cows also require more feed and land than other meats since they take significantly longer to grow and reproduce. What's more, carbon dioxide and nitrous oxide, both greenhouse gasses, are released during the manufacture of fertilisers that are used by farmers. Dark chocolate has a surprisingly large footprint, which can be attributed to land-use change in order to produce cocoa.

Scientists have also warned that some dietary changes will be required to meet the objective of a ‘global temperature rise below 2°C.' They contend that high-income countries should take responsibility for the majority of these changes and that government and corporate action is essential.

In his recent documentary, David Attenborough proposes switching to a primarily plant-based diet to save the natural world. He suggests that farmland currently used to raise animals should be repurposed for crop cultivation, as this would be significantly more efficient.

Should I switch to a vegan or vegetarian diet?

A study investigating the environmental impact of omnivorous, vegetarian and vegan diets found that an omnivorous diet generated significantly worse carbon, water and ecological footprints. This was attributable to the consumption of meat, fish and other animal-based foods.

Figure 1 taken from: https://www.nature.com/articles/s41598-017-06466-8 

Environmental footprints: Daily carbon (a), water (b), and ecological (c) impacts expressed as average of 7-d food records (grams of CO2 equivalent/d, litres of H2O/d, and square meters of land/d, respectively). Values are means ± standard deviation of fifty-one independent measurements for each diet group. Different letters indicate significantly different values (P < 0.001) as calculated by one-way ANOVA with post hoc Tukey HSD test among the three diet groups. O, omnivores; VG, ovo-lacto-vegetarians; V, vegans.

However, they did notice that when compared to a vegetarian diet, veganism was not associated with significantly lower environmental footprints. This could be owing to the replacement of animal-based products with industrially highly processed plant-based meat and dairy, such as seitan burgers and soy yogurt. Whilst vegan and vegetarian diets have a lesser environmental impact, it seems that the extent of this impact is dependent on what animal-based products are replaced with, implying that individual dietary habits must be considered.  

A study analysing the dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK found that an average 2,000 kcal high meat diet had 2.5 times as many GHG emissions than an average 2,000 kcal vegan diet. High meat-eating men had the highest dietary GHG emissions and vegan women had the lowest. They stated that the majority of UK adults would be categorised as ‘high meat consumers’ (more than or equal to 100 grams per day) and concluded that a healthy, sustainable diet should include the recommendation to reduce the consumption of animal-based foods.

A similar investigation into the environmental impacts of different diets also claimed that the ‘vegan diet is the optimal diet for the environment’ as ‘its production results in the lowest levels of GHG emissions’. They also pointed out that the meat substitutes used by vegans and vegetarians can have vastly different environmental impacts, with some even triggering a negative trend. Substituting cheese for chicken, for example, could result in increased GHG emissions. Food miles are particularly important because a plant-based diet that demands products from all over the world could have the same carbon footprint as a moderate meat eater. Therefore, consuming locally produced products should be the preferable alternative. Notably, the study also found that by significantly reducing meat and dairy intake in one’s diet, it may be possible to have the same environmental impact as a vegan diet.

To summarise: 

• A vegan diet is arguably the most effective way to reduce your environmental footprint
• However, cutting down on meat and dairy products can still make a significant difference

If the most harmful half of meat and dairy production were replaced by plant-based food, we would still witness around two-thirds of the benefits of eliminating meat and dairy production altogether.