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The Bible is full of references to domesticated animals. Camels, goats, sheep, asses abound; the good shepherd tends his flocks; and so forth. In the book of Genesis, Cain, the tiller of the soil, and Abel, the livestock producer, bring their respective offerings to God. But God rejects Cain's vegetables, and Cain then slays his brother Abel.

Islamic and Jewish dietary laws both prescribe ritualistic forms of animal slaughter to sanctify meat consumption. Sacrificing a rooster before Yom Kippur is a traditional Jewish practice. Muslims sacrifice an animal before undertaking the Hajj, the pilgrimage to Mecca -- recalling that Abraham sacrificed a ram after an angel's last-second reversal of God's command that he sacrifice his son Isaac.

That all three Abrahamic religions emphasize animal husbandry is hardly surprising, given their origins in the Middle East where pastoralism was a dominant way of life, and where many domesticated breeds originated. It does, however, raise the question of whether scriptural references to animals still resonate in a modern world where few people have regular contact with livestock.

Eastern religions have a more nuanced view of eating animals. The Buddha rejected animal sacrifice, but some Buddhists, as well as Hindus and Sikhs, do eat meat. In some Hindu temples, animals are sacrificed to the goddess Kali. Of the world's major religions, only followers of Jainism follow strict vegetarian diets, practicing non-violence by avoiding harm to animals.

Linking diet and environment

Not harming animals also motivates many Westerners to become vegetarians. Increasingly, however, people are adopting vegetarian diets for other reasons, such as limiting damage to the planet.

Today's vegetarians -- while still concerned about how animals are raised and slaughtered -- are also raising issues such as the collateral damage to non-target species caused by industrial fishing, the huge amounts of land and water used to grow animal feed crops such as corn and soybeans, the pollution and pollinator deaths caused by pesticides and fertilizers applied to these same feed crops, indiscriminate use of antibiotics for livestock growth promotion, and the large emissions of greenhouse gases associated with livestock production.

Corporate agriculture has been able to downplay these issues, perhaps because food is so closely linked to human survival. The agribusiness lobby is politically astute, well networked, and active worldwide.

Yet there are critical voices, even within the agricultural community. The Food and Agriculture Organization of the United Nations (FAO) created a stir in 2006 when it released Livestock's Long Shadow. This report examines environmental aspects of livestock production, including its contribution to climate change.

The report's authors explain that livestock breathe out huge amounts of carbon dioxide (CO2), but their respiration is not a net source of CO2: it is "part of a rapidly cycling biological system, where the plant matter consumed was itself created through the conversion of atmospheric CO2 into organic compounds."

However, cows also breathe out methane -- a powerful greenhouse gas -- that is produced in their rumens by anaerobic bacteria. Fossil fuels are burned to manufacture fertilizers used to grow animal feeds, run tractors and transport livestock. Greenhouse gases are released when soil microbes break down manure and fertilizer compounds. CO2 is released when forests are cleared to create pastures, and when pastures are overgrazed and soil organic matter degrades.

The FAO study quantifies all these pathways of greenhouse gas emissions associated with livestock production. It concludes that raising livestock accounts for 18 per cent of greenhouse gases emitted by human-caused activities, and for nearly 80 per cent of all emissions associated with food production. This suggests that if large numbers of people switch to a vegetarian diet it would significantly advance the global effort to combat climate change. A vegan diet (free of all animal products) would be better still.

The case against eating meat

This point is hammered home in an attention-grabbing documentary film called Cowspiracy. The film notes that organizing against the livestock industry can be dangerous, with over 1,000 activists killed in Brazil during the past 20 years. It claims that even in North America, major environmental organizations such as Greenpeace and the Sierra Club are silent on the environmental impacts of eating meat, owing to the power of the cattle industry.

The film is not without its flaws. It greatly overstates the proportion of greenhouse gases arising from livestock production, incorrectly including cattle respiration in the total. And it ignores the multiple benefits derived from domesticated animals -- transportation, plowing, clothing (e.g., wool and leather), fuel and fertilizer (manure), and so forth.

The film also suggests that lands freed up from livestock production would revert to forests. But grazing by domesticated animals such as cattle, goats and sheep occurs largely in grasslands. In Africa, Asia and Europe, where early humans domesticated these species from their original wild relatives, native grassland species and livestock have co-existed for millennia. Livestock were introduced more recently to Australia and the Americas, and impacts on native herbivores such as bison, guanacos and kangaroos have been more severe. Nonetheless, well-managed grasslands on all continents can support both livestock production and diverse populations of native plants, birds and insects.

Many traditional cultures still exist in which the bonds between people, domesticated animals, and wild animals remain strong. Hunting and fishing remain important to rural Canadians, both Aboriginal and non-Aboriginal.

But Cowspiracy is clearly resonating among younger activists. It is said that if you want to create a new generation of environmentalists, make the link to what people are eating. According to a blog in the New Internationalist, teenagers are forcing their parents to watch the film, and whole families are turning vegan as a result. And a 2003 article in the American Journal of Clinical Nutrition reviews a number of research studies that have linked low meat intake with greater longevity.

With hundreds of cookbooks available, going vegan is one way to make a positive connection between food and the environment. But there are many other options: community-supported agriculture, farmers' markets, buying organic foods, community gardening, minimizing food waste, composting and creating backyard pollinator habitat.

Food for thought, at any rate.

Ole Hendrickson is a retired forest ecologist and a founding member of the Ottawa River Institute, a non-profit charitable organization based in the Ottawa Valley.

Photo: B. K./flickr

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