9.2 Which diets generate fewer GHG emissions and other environmental impacts?

9.2.1 GHG emissions associated with various diets

A systematic review of studies shows GHG reductions are possible by switching to different diets


Hallström, Carlsson-Kanyama and Börjesson (2015)

 

A comparison of multiple studies shows again that the greatest reductions in GHGs come from vegan or vegetarian diets.

GHG reductions were shown from other diets, such as replacing beef with pork or poultry.

Diets where energy intake is balanced i.e. the amount of energy (calories) consumed is in not in excess of our energy requirements) can also have lower GHG impacts since food not needed is not consumed.

Whilst occasional studies show variations, the trend clearly shows that the lower the meat content the greater the GHG reduction.

Note that none of the studies included in the review take into account the possible carbon sequestering effects of grazing management. The potential that well managed grazing can promote soil carbon sequestration is still an under-researched area, would apply (if borne out by evidence) only to ruminant rearing systems, and is discussed briefly in Chapter 8.

9.2.2 Land use associated with various diets

The picture for land use is similar


Hallström, Carlsson-Kanyama and Börjesson (2015)

Healthy diets (such as the Mediterranean diet, or those based on national dietary guidelines), diets with lower meat content, and meat-free diets also show the potential to reduce land-use requirements. This is important, given increasing pressures on available land to produce food (see Chapter 5 [hyperlink] for more on land-use and biodiversity loss).

9.2.3 GHG emissions of real life diets

Real life non-meat diets have been found to have lower GHGs than various meat-based diets


Scarborough, et al. (2014)

This research was based on real-life diets, from consumer data of over 55,000 people in the United Kingdom. Error bars represent 95% confidence intervals.

Vegan and vegetarian diets were found to have lower GHGs than all meat-based diets.

A vegan diet was found to have 50% of the GHG emissions of a meat-eater’s diet.

A pescetarian diet (fish-based, but no meat) also has lower GHG emissions compared to all types of meat-eater diets. However the difference is not as great between vegetarians, fish eaters and low meat eaters, and the consumption of fish gives rise to a different set of environmental issues concerning fish stocks and marine ecosystems (see Chapter 5).

Other studies have found similar results, with vegetarian and lower-meat diets having lower GHGs. (Soret et al., 2014).

Note that the study does not factor in any possible carbon sequestering effects of grazing management. The potential that well managed grazing can promote soil carbon sequestration is still an under researched area, would apply (if borne out by evidence) only to ruminant rearing systems, and is discussed briefly in Chapter 8.