A recent study published in Elementa: Science of the Anthropocene seeks to determine which diets are most efficient for our environment. The study, titled Carrying Capacity of U.S. Agricultural Land: Ten Diet Scenarios, aims, more specifically, to examine the “carrying capacity” of ten distinct diets.
The authors argue that the best way to examine a given diet’s environmental efficiency is to examine its “carrying capacity”- defined as, “persons fed per unit land area.”
The ten diets assessed were the following:
- The “Baseline” diet (the current American food consumption pattern).
- The “Positive Control” diet (same as above but with fewer calories from added fats and sweeteners).
- The “100% Healthy Omnivorous” diet (scenario in which all Americans exactly follow the current USDA dietary guidelines).
- The “80% Healthy Omnivorous” diet (Americans substitute 20% of the USDA dietary guidelines for more eggs and dairy products, in place of meat).
- The “60% Healthy Omnivorous” diet (substitute 40%).
- The “40% Healthy Omnivorous” diet.
- The “20% Healthy Omnivorous” diet.
- The “Ovolacto Vegetarian” diet (no meat, includes eggs and dairy).
- The “Lacto Vegetarian” diet (no meat, no eggs, includes dairy).
- The “Vegan” diet (no meat, no eggs, no dairy).
Below, one can see the types of foods and their quantities that are ingested in each of the ten diets outlined above:
According to the results of the study, it seems that reducing meat intake does have a positive correlation with increased carrying capacity:
More specifically, it appears that the “Lacto Vegetarian” diet had the highest carrying capacity. Interestingly, the “Vegan” diet has a carrying capacity that is somewhere in between the 40% and 60% “Healthy Omnivorous” diets. From this, one can conclude that, contrary to claims perpetually made by vegans, their diet is:
- Not necessarily better for the environment than certain diets which incorporate various degrees of meat consumption.
- Worse than vegetarian diets which include some animal products, namely dairy.
However, there are a couple of caveats to this study which would make it far from conclusive.
Firstly, there is the methodology of the paper, which assumes that the United States is a closed system- i.e. one in which no food importation occurs from abroad. The paper states that this was done in order to, “conduct a complete accounting of all land needed to meet total food needs and thus, calculate carrying capacity.”
This problem alone renders the study quite problematic, as the trading of foodstuffs between nations could greatly alter results on a global basis. If the USA’s land, for example, were better suited to cropland, while another country’s land was better suited to grazing, then trade between the two countries could result in a completely different conclusion in terms of U.S. (and global) environmental impacts of various diets.
Secondly, there is the issue of variations of food sources within each diet. As the study itself notes, “for example, diets containing meat could vary in terms of the proportion of servings from beef, pork, and poultry.”
This point is vital, as there is already some evidence that the production of different types of meats have very different impacts on carbon emissions:
It is important to state that measuring carbon emissions of various different meats is clearly not the same as analyzing the carrying capacity of U.S. agricultural land. But the point I wish to make is merely that the specific type of meat being produced could considerably skew the ranking of the environmental impacts of these ten diets.
All in all, due to the aforementioned limitations of this study, it would be difficult to draw any sweeping conclusions, although there will certainly be a temptation to infer that the cultivation of meat is categorically harmful. More research is clearly needed at this time for us to understand the profoundly complex relationship between diet and environment.