The intersection of diet and environmental sustainability has become increasingly apparent. The average consumer may not immediately connect their food choices with global warming, but the reality is that our dietary habits have a significant impact on the planet. A vegetarian diet, with its emphasis on plant-based foods, emerges as a compelling solution for promoting energy efficiency and mitigating the environmental consequences of food production.
The Environmental Impact of Meat Production
The United Nations Food and Agriculture Organization (FAO) has highlighted the substantial contribution of livestock to global warming, estimating that it accounts for 18% of worldwide greenhouse gas emissions. A University of Chicago study further emphasizes this point, revealing that each meat eater contributes 1.5 more tons of greenhouse gases annually compared to a vegan.
The projected doubling of global meat production by 2050 raises serious concerns about the escalating environmental burden. Much of meat's low efficiency stems from grain usage. It takes 13 pounds of grain to produce one pound of beef and three pounds of grain for one pound of chicken. The more meat we eat, the more grain is required to feed the animals that provide that meat-in addition to the extra water and land (often deforested) used to grow that grain, extra energy to harvest it and run the slaughterhouses, and extra chemicals to fertilize it and deter pests.
The digestive systems of ruminant animals, such as cattle, are significant sources of methane, a greenhouse gas with a warming potential 23 times greater than carbon dioxide. While methane has a shorter atmospheric lifespan compared to CO2, its immediate impact on global warming is considerable. Even the study authors were surprised when fish wound up in a virtual tie with red meat, though Dr. Eshel says that not all fish are equal in this regard.
The Vegetarian Advantage: A Lower Environmental Footprint
Research indicates that vegetarian diets are the most energy-efficient, resulting in lower greenhouse gas emissions compared to meat-inclusive diets. In a 2006 study by Drs. Pamela Martin and Gidon Eshel of the University of Chicago, the greenhouse gas effects of a vegan diet were compared to that of the average American (72 percent plant-based, 14 percent meat, 14 percent eggs/dairy), and three similarly constructed diets that replace the 14 percent of meat with red meat-only, fish-only, and poultry-only. The fifth diet was a vegetarian diet (10 percent eggs/dairy). The study looked at the entire lifecycle of these diets, examining the energy it takes to grow, harvest, transport, and prepare them. The vegetarian diet turned out to be the most energy-efficient-and therefore lowest in greenhouse gases-followed by poultry, then the average US diet.
Read also: Is a Vegetarian Elimination Diet Right for You?
Transitioning to plant-based diets (PBDs) has the potential to reduce diet-related land use by 76%, diet-related greenhouse gas emissions by 49%, eutrophication by 49%, and green and blue water use by 21% and 14%, respectively, whilst garnering substantial health co-benefits.
The Rule of 10 and Trophic Levels
The rule of 10 is so named because with every link in the food chain, on average only 10 percent ever makes it to the next step. The currency of energy content in food is the calorie. In 2014, 90 million acres of corn were planted in the United States. On average that year, a single acre of farmland produced a whopping 15 million calories of corn. An acre of potatoes produces roughly 15 million calories also, and rice produces about 11 million calories. Taking corn as the main example, an acre of corn can meet to energy needs of 7,500 people for one day. That acre of farmland, instead of being fed straight to humans, could also be used for animal feed. That same acre would feed 12 hogs that weigh 250 pounds each, and the amount of food that could be eaten from the hogs after processing would add up to nearly two million calories.
Planetary Health Benefits
Plant-based foods have a significantly smaller footprint on the environment than animal-based foods. Even the least sustainable vegetables and cereals cause less environmental harm than the lowest impact meat and dairy products. Innovation and transformation within the food and agricultural sectors are imperative to limiting global warming to 1.5 °C.
Life cycle assessment studies have shown that pork, chicken, and seafood produce less GHG emissions than beef; however, even the lowest impact animal products exceed the average GHG emissions of substitute plant proteins. The adoption of PBDs would substantially reduce agricultural land use. Eshel et al. [17] estimated that Americans could save approximately 34% and 24% of dietary and total land use, respectively, if they replaced all meat with plant-based alternatives. Shifting to PBDs would slow biodiversity loss substantially, thus having a protective effect on global food security. It is estimated that animal product-free diets have the potential to reduce diet-related land use by 3.1 billion hectares (76% reduction), including a 19% reduction in arable land
Approximately 43,000 L of water are required to produce 1 kg of beef, whereas it only takes 1000 L to produce 1 kg of grain. A modelling study found that reducing animal product consumption would reduce global green and blue water use by 21% and 14%, respectively. Animal product-free diets may therefore play a role in water conservation. Animal product-free diets may also improve water quality by reducing eutrophication caused by nitrogenous fertilizer and manure runoff by 49%
Read also: Healthy Vegetarian Eating
Using data from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort involving 443,991 participants, Laine et al. [23] estimated that up to 19-63% of deaths and up to 10-39% of cancers could be prevented in a 20-year risk period by adopting different levels of adherence to the EAT-Lancet reference diet. They also estimated that switching from low adherence to higher adherence could reduce food-associated greenhouse gas emissions by up to 50% and land use up to 62%.
Human Health Benefits
Unhealthy diets now represent the largest burden of disease globally, presenting a greater risk to morbidity, disability, and mortality than unsafe sex, alcohol, drug, and tobacco use combined. Adopting plant-based food systems may allow countries to reduce their environmental footprints and tackle their obesity and diet-related non-communicable disease burdens simultaneously.
The consumption of diets high in fruits, vegetables, legumes, whole grains, nuts, fish, and unsaturated vegetable oils, and low in animal products, refined grains, and added sugars are associated with a lower risk of all-cause mortality.
An extensive body of population studies and clinical trials supports the implementation of PBDs for the prevention of obesity and obesity-related diseases. Observational data from the Adventist Health Study-2 (AHS-2) involving 41,387 participants, showed that body mass index (BMI) was positively correlated with the amount of animal-based foods consumed, such that non-vegetarians had the highest BMI, followed by semi-vegetarians, pescatarians, vegetarians, and vegans
Large cohort studies show that the prevalence and incidence of T2D are significantly lower among those following PBDs. T2D prevalence in the AHS-2 cohort followed a similar trend as BMI with the lowest prevalence occurring in vegans (2.9%) and the highest in non-vegetarians (7.6%) [43]. Pescatarians (4.8%), semi-vegetarians (6.1%), and vegetarians (3.2%) had intermediate T2D prevalence.
Read also: Is a Chicken-Inclusive Vegetarian Diet Right for You?
Mitigating the Impact of Meat Consumption
Even small changes in dietary habits can have a positive ripple effect. "The difference between eating the average American diet and the poultry diet is about 0.9 ton of emissions, so even just switching your meat intake to poultry makes a big difference," says Eshel.
If you eat meat, consider curbing your meat consumption-and looking for certified organic meat and organic, grass-fed beef to help mitigate some of the planetary problems associated with meat.
Land Use and Deforestation
Around 43% of the planet’s ice-free terrestrial landmass is occupied by farmland (including croplands and pasturelands). Approximately 83% of this farmland is used to produce meat, eggs, farmed fish, and dairy, yet they only provide 18% and 37% of our calories and protein, respectively. The adoption of PBDs would substantially reduce agricultural land use.
Considering the amount of land required to produce animal products, it is unsurprising that they are accountable for 67% of the deforestation caused by agriculture. The destruction of ecosystems for croplands and pasturelands is the single largest factor causing species to be threatened with extinction. Shifting to PBDs would slow biodiversity loss substantially, thus having a protective effect on global food security.
Water Conservation and Quality
In total, 70% of all global freshwater withdrawals are used for the irrigation of crops, of which 24% are fed to livestock. A modelling study found that reducing animal product consumption would reduce global green and blue water use by 21% and 14%, respectively. PBDs may therefore play a role in water conservation. Animal product-free diets may also improve water quality by reducing eutrophication caused by nitrogenous fertilizer and manure runoff by 49%.
Empirical Evidence from the UK
Diet-related environmental impacts vary substantially by diet groups within this cohort of UK adults which includes a large sample of vegans, vegetarians and fish-eaters. For measures of GHG emissions, land use, water use, eutrophication and biodiversity, the level of impact is strongly associated with the amount of animal-based products that are consumed. Point estimates for vegan diets were associated with less than half of the impact of high-meat-eater (>100 g d−1) diets for all indicators, and 95% uncertainty intervals were below 50% for all outcomes except water use and biodiversity.
Reducing Agricultural Land Use
Research suggests that if everyone shifted to a plant-based diet, we would reduce global land use for agriculture by 75%. This large reduction of agricultural land use would be possible thanks to a reduction in land used for grazing and a smaller need for land to grow crops. The research also shows that cutting out beef and dairy (by substituting chicken, eggs, fish, or plant-based food) has a much larger impact than eliminating chicken or fish.
The Role of Cereals
Less than half - only 48% - of the world’s cereals are eaten by humans. 41% is used for animal feed and 11% for biofuels. Livestock waste a lot of energy and protein, but do produce more nutrient-dense protein sources.
Global Recommendations and Policies
The UK has a legal commitment to a 78% reduction in GHG emissions by 2035 compared to 199017 and of halting biodiversity loss by 203018. The UK Committee on Climate Change has stated that if the government is to achieve its ambitious targets for carbon reductions, then rapid progress must be made across all sectors including implementing measures to encourage consumers to shift diets19. Shifts in diets towards plant-based consumption was also emphasized in the 2021 National Food Strategy, which called for a 30% reduction in meat consumption.
There are many population-level interventions that could be implemented to support transitions towards lower meat diets. The UK Health Alliance on Climate Change recommends that sustainable diets should be supported by mandatory environmental labelling on foods, regulation of promotions and taxation of high-carbon foods.
Addressing Barriers to Plant-Based Diets
Meat appreciation, health concerns, convenience, and expense are prominent barriers to PBDs.
tags: #vegetarian #diet #energy #efficiency