An Even More Inconvenient Truth? (Part 3)

For the first three months of 2007, the focus of my columns is a new phenomenon: the recognition by scientists, and increasingly by the public, that dietary choice has an immense impact on global warming and the environment. In other words, it’s not just big ticket items like buying a hybrid car, or replacing our car with a bike that will impact future generations of life on earth. We can make a difference at our next meal or snack.

European environmentalists observe that “people generally and openly display extreme reluctance to change their eating habits”. We may be willing to use funny looking light bulbs that cost a little more. Some might donate a few dollars to an environmental group. But change to a plant-based diet? Sorry. Even though we’d cut our risk of colon cancer, heart disease and diabetes, reduce our weight, and favourably affect global warming, when it comes to changing our own menu, our eyes glaze over and we quickly change the subject.

A change in our eating habits and dietary trends can play an immense role in the arrest and reversal of major current environmental problems. (1) Considering the impact of single foods, environmentalists recognize that beef has the greatest negative impact on the environment. The other high impacting foods are cheese, fish and milk.
Using a variety of analytic perspectives researchers conclude that:

1) 3 to 4 percent of the overall impact is due the impact of animal waste on the ecosystem. This is comparable to the impact of pesticides and chemical fertilizers [39].
In Canada, animal wastes have caused specific and immediate problems, such as the May 2000 water contamination and deaths in Walkerton Ontario that were eventually linked with a dairy farmer’s manure. Also,  there are the incidences of gastroenteritis, hemolytic uremic syndrome, and kidney failure in children living in the vicinity of “Feedlot Alley” nearBrooks,Alberta and whose environment is contaminated by manure from slaughterhouse bound cattle. (http://cat.inist.fr/?aModele=afficheN&cpsidt=2232573)

2) 5 to 13 % of the impact is due to land consumption. According to EU Commission data, Europecan grow enough vegetable proteins to feed all its inhabitants, but not all its farm animals. Only 20% of the proteins which are fed to animals originates in Europe. The missing amount is imported from other countries, including developing ones, playing an important role in the further impoverishment of these countries and in the exploitation of their environmental resources [41].  The increase in the use of land for animal husbandry purposes is linked to deforestation and to the modification of the management of rainforests [42].
Every year 17 million hectares of rainforests are destroyed, and the trend is increasing: the Institute for Space Research (INPE) of the Brazilian government has documented a 40% growth of deforestation from 2002 to 2003. Even though not all the land is used for rearing cattle, most of it is: in the Amazon 88% of the land cleared from rainforests has been used for grazing; in Costa Rica and Panama the amount is about 70% [43], while the influence of wood production in the deforestation process is relatively lesser [44].
In semi-arid areas like Africa, land is increasingly used for extensive farming of products which are not used to feed the local human population but are exported to developed countries as cattle feed, or for cattle grazing. This use of land is an important factor responsible for  the desertification process. The UN estimate that at
present 70% of drylands and about 25% of the total land area of the world  is undergoing desertification [45].

3) 15 to 18% of the impact is due to damage to respiration from inorganic chemical compounds, while 20 to 26% is due to consumption of fossil fuels. Both these processes are due to production and transport of foodstuffs; they represent energy management and its related pollution. Their combined overall impact is 35 to 44 % of the total impact. If animals are considered as \”food production machines\”, these machines turn out to be extremely polluting, to have a very high consumption and to be very inefficient. When vegetables are transformed into animal proteins, most of the proteins and energy contained in the vegetables are wasted; the vegetables consumed as feed are used by the animals for their metabolic processes, as well as to build non-edible tissue like bones, cartilage, offal, and faeces [40]. A large amount of energy is also employed in production of animal feed and the upkeep of animal husbandry facilities, from stables to slaughterhouses. If we only take into account fossil fuel consumption, production of one calorie from beef needs 40 calories of fuel; one calorie from milk needs 14 fuel calories, while one calorie from grains can be obtained from 2,2 calories of fossil fuels [11, 12].
4) Water consumption represents by itself the most dramatic impact: it counts for 41-46 % of the overall impact.
Animal farming and agriculture are responsible for 70% of freshwater consumption on the planet, while only 22% of water is used by industry  and 8% is used for domestic purposes [39]. This is the reason why, during the yearly \”Water Week\” which took place in Stockholm in August 2004, the foremost specialists in water resources explicitly linked the issue of water shortage with eating habits and explained that the planet\’s freshwater reserves will no longer be sufficient to feed our descendants with the present Western diet: \”Cattle feed on grains; even those which are left to graze need much more water than is necessary to grow cereals.

Nevertheless, consumers in the developed countries, and even in developing ones, are asking for more meat. It will be almost impossible to feed coming generations on the same diet which we now have in Western Europeand in North America.\” The executive director of the Stockholm International Water Institute added that the rich countries will be able to buy their way out of the dilemma by importing \”virtual water\”, that is, food (cattle feed or meat) from other countries, even from water-poor ones.
The concerns of the water experts can be more easily understood if we consider that most of the water consumed from agriculture is used to irrigate cereals or oleaginous seeds (soy, sunflower, cotton, linseed
etc.) which are, in turn,  used as:  food and protein integrators in cattle feed; to keep agricultural productivity high in order to feed cattle and to keep their intestines active; to quench their thirst; to clean stables, milking halls, slaughterhouses and so on [46, 47].

The above considerations seem to support  the opportunity of educating people living in developed countries to \”change their attitude with regard to consumption and to individual behaviour\”, as stated in the 1st objective of the \”EU programme in favour of the environment and of a sustainable development\”. A shift in eating
habits towards the increase of the direct consumption of plant foods seems to be a desirable objective in this perspective. Owing to their lighter impact, confirmed also by our study, vegetarian and vegan diets could play an important role in preserving environmental resources and in reducing hunger and malnutrition in poorer nations [48, 49].


  1. Baroni L, Cenci L, Tettamanti M, Berati M. Evaluating the environmental impact of various dietary patterns combined with different food production systems. European Journal of Clinical Nutrition.Oct 11 2006.
  2. http://cat.inist.fr/?aModele=afficheN&cpsidt=2232573 
  1. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=220841
  1. Reijnders L, Soret S. Quantification of the environmental impact of different dietary protein choices. Am J Clin Nutr. 2003 Sep;78(3 Suppl):664S-668S.
  1. Pimentel D, Pimentel M. Sustainability of meat-based and plant-based diets and the environment. Am J Clin Nutr. 2003 Sep;78(3 Suppl):660S-663S.
  1. Leitzmann C. Nutrition ecology: the contribution of vegetarian diets. Am J Clin Nutr. 2003 Sep;78(3 Suppl):657S-659S.


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