A friend recently told me that she has stopped eating
meat because it contributes to global warming. That seems a bit far-fetched to
me so I’m wondering if you can set the record straight by connecting the dots
between environment and diet.
Surprisingly, what we choose to eat has one of the biggest impacts on the
environment, including the climate, of any human activity.
A 2006 Italian study published in the
European Journal of Clinical Nutrition
evaluated the environmental impact of various dietary patterns combined with
different food production systems. Researchers examining the impact of a typical
week’s eating showed that plant- based diets are better for the environment than
those based on meat. An organic vegan diet had the smallest environmental impact
and all non-vegetarian diets required significantly greater amounts of
environmental resources, such as land and water. But the most damaging food was
beef, with up to 100 calories of grain required to produce four calories of
More recent Japanese research assessed
the effects of beef production (including the effects of producing and
transporting feed) on global warming, water acidification and eutrophication,
and energy consumption – in other words, the total environmental load on a
portion of beef. Published in
Animal Science Journal
in August, 2007, research by the National Institute of Livestock and Grassland
Science found that producing a kilogram of beef leads to the emission of
greenhouse gases with a warming potential equivalent to 36.4 kilograms of carbon
dioxide – more than driving for three hours while leaving all the lights on back
home. They also found that a kilo of beef releases the equivalent of 340 grams
of sulphur dioxide and 59 grams of phosphate, and consumes 169 megajoules of
The calculations, which are based on standard industrial
methods of meat production in Japan, did not include the impact of managing farm
infrastructure and transporting the meat, so the total environmental load is
even higher when they are factored in. Since global beef consumption is rising
dramatically, meeting this demand will no doubt require that animals be reared
more intensively and cheaply with factory farming, creating further pollution,
water and land usage problems.
By feeding grain and vegetables directly
to people, rather than to livestock,
we can increase the amount of food available.
The environmental load is so high, in fact, that in a 2005 study, University
of Chicago researchers suggested that going vegan would reduce one’s
environmental footprint by more than if they switched to a hybrid vehicle. Gidon
Eshel and Pamela Martin told a meeting of the American Geophysical Union that
they studied the amount of fossil fuel needed to cultivate and process various
foods, including running agricultural machinery, providing food for livestock
and irrigating crops. They found that the typical American diet, about 28
percent of which comes from animal sources, generates the equivalent of nearly
1.5 tonnes more carbon dioxide per person per year than a vegan diet with the
same number of calories. By comparison, the difference in annual emissions
between driving a regular car and a hybrid car is just over 1 tonne.
In fact, farmed animals produce more greenhouse gas emissions (18 percent)
than the world’s entire transportation system (13.5 percent,) according to the
Food and Agriculture Organization of the United Nations (FAO.) Most of the
greenhouse gas emissions from cattle are in the form of methane released from
the animals’ digestive systems. According to a 2003 report issued by the EU’s
Environment and Agriculture Informal Ministerial Councils, along with nitrous
oxide, methane is the real threat to global warming from agriculture. Methane
has 23 times the global warming impact of carbon dioxide and a single cow can
produce as much as 500 liters of methane per day.
Cattle manure contains other problematic pollutants like nitrous oxide (which
is considered to be almost 300 times as damaging to the climate as carbon
dioxide) and ammonia (which contributes to acid rain.) In a 2006 report
Livestock’s Long Shadow – Environmental Issues and Options, the FAO pointed out
that farming animals also generates greenhouse gas emissions through the
manufacture of fertilizers to grow feed crops, industrial feed production and
the transportation of both live animals and their carcasses across the globe.
Rearing animals for food causes a variety of other environmental issues
besides contributing to global warming. Much of the world is running out of
fresh water. In an alert issued last March, the FAO estimated that by 2025 there
will be 1.8 billion people living with absolute water scarcity and two thirds of
the world’s population could be living under water-stressed conditions.
Scientists agree that farming accounts for around 70 percent of all fresh
water withdrawn from lakes, waterways and aquifers and that meat production,
especially the feeding of cattle, is a particularly water-intensive process. The
FAO says that livestock production accounts for over eight percent of global
human water consumption. Depending on a variety of factors, a kilogram of beef
is estimated to require upwards of 13,000 liters of water, compared to the 1,000
to 2,000 liters required to produce a kilo of wheat.
Livestock production also contributes to water pollution, with manure,
antibiotics and hormones entering the water cycle alongside chemicals from
tanneries, fertilizers and the pesticides used to spray feed crops. In a 2005
report entitled Facts About Pollution from Livestock Farms, the Natural
Resources Defense Council noted that in the Gulf of Mexico, pollutants in animal
waste have contributed to a “dead zone” where there is not enough oxygen to
support aquatic life. During the summer of 2004, this dead zone extended over
5,800 square miles.
According to the Center for Sustainability and the Global Environment at the
University of Wisconsin, 40 percent of the earth’s entire land surface is used
for agriculture, and 70 percent of all agricultural land is used for farming
animals. Much of this is grazing land that would otherwise host a natural
habitat such as rainforest. Livestock production is reportedly responsible for
70 percent of the deforestation of the Amazon rainforest. Aside from
contributing to the loss of biodiversity, deforestation increases greenhouse gas
emissions by releasing carbon previously stored in the trees.
One third of the land suitable for growing crops globally is
used to produce animal feed.
Farmland that could grow grain and other human food crops is also a casualty
of the livestock industry. According to the FAO, one third of the land suitable
for growing crops globally is used to produce animal feed.
Feeding cattle takes up so much land because they are inefficient converters
of feed to meat. Thomas White, a professor in the Department of Economics and
Global Studies at Assumption College in Worcester, Massachusetts, described just
how inefficient in his paper “Diet and the Distribution of Environmental Impact”
published in 2000 in Ecological Economics. He says that cattle require
approximately seven kilos of grain in order to generate one kilo of beef and
pigs require four kilos of grain for one kilo of pork.
When cattle are allowed to overgraze, the result is soil erosion,
desertification and deforestation. The FAO says that 20 percent of the world’s
grazing land has been designated as degraded due to the rearing of animals for
Many people who give up meat end up eating more fish, which is a healthy
source of essential fatty acids (although some fatty fish retain pollutants,
making their health benefits questionable). However, eating fish isn’t without
its environmental problems. Over-fishing is threatening the existence of many
fish species, a trend that we’ve been tracking for many years here in
Natural Life. Fishing practices like bottom trawling cause untold damage to
non-target species and destroy the fragile ecosystem of the seabed. It’s been
called “underwater strip mining.”
The aquaculture industry has experienced huge growth. However, fish farming
can pollute rivers and streams, while harming wild fish. Plus, feeding farmed
fish can be problematic, intensifying pressure on the ocean stocks. The
Worldwatch Institute says, for example, that it takes five tonnes of wild-caught
fish to feed each tonne of farmed salmon.
Then there is the need to fuel the fishing fleets. A paper entitled “Fuelling
Global Fishing Fleets” published in the journal Ambio calculates that
fisheries account for about 1.2 percent of global oil consumption and directly
emit over 130 million tonnes of carbon dioxide into the atmosphere.
What About Organics?
Generally, small, mixed farms and those operated in a sustainable manner,
such as organically or biodynamically, are more environmentally friendly than
large-scale factory farms. But the research as to whether or not
organically-raised meat generates lower levels of greenhouse gas emissions is
uneven. A 2003 Swedish study that was recently cited in the New Scientist,
suggested that organic beef, raised on grass rather than concentrated feed,
emits 40 percent less greenhouse gases and consumes 85 percent less energy than
non-organic beef. But a 2000 Swedish study from the Department of Applied
Environmental Sciences at Goteborg University compared organic and conventional
dairy production and found a much less dramatic difference. Life Cycle
Assessment of Milk Production concluded that the organic system
generated slightly fewer greenhouse gas emissions than the conventional. Carbon
dioxide and nitrous oxide levels were lower, largely due to the absence of
energy intensive nitrate fertilizers, but methane emissions were higher in the
organic system due to the cattle’s higher intake of roughage fodder.
A French study published in Ecosystems and Environment in 2005
compared organic and conventional pork production. It found that per kilogram of
pig, climate change emissions were highest for the organic system, but on a
per-hectare basis, the lowest emissions were found in the organic system.
There is also a large body of literature focusing on other farming techniques
that either require lower energy inputs or that lead to fewer emissions of
greenhouse gas emissions. They include harnessing the methane and other animal
wastes for biomass energy. One report cited in the New Scientist in
2003 described research from Belgium that indicated switching animals from
regular feed to a diet laced with fish oil could cut the amount of methane they
emit by nearly half. But then there is the fishery problem….
One prominent ecologist, who says that raising cattle is the most damaging
aspect of agriculture, believes that eating lower on the food chain is becoming
increasingly important. Dr. Robert Goodland, who was the Environmental Advisor
to the World Bank for 25 years and now advises the UN World Summit on
Sustainable Development, has concluded that diet does, indeed, matter because a
diet containing meat requires up to three times as many resources as a
vegetarian diet. He has advocated a food conversion efficiency tax. The least
efficient converters (pork, beef) would be highly taxed; more efficient
converters (poultry, eggs, dairy) would be moderately taxed. Most efficient
converters (ocean fish) would be taxed lowest and grain for human consumption
would not be taxed at all.
Dr. David Fraser of the University of British Columbia’s Animal Welfare
Program agrees that economics may be the answer: Higher prices for meat products
might allow for better treatment of animals and the environment.
Nevertheless, it does appear to be a good practice for the health of people
and the ecosystem to feed grain and vegetables directly to people, rather than
to livestock. But even vegetarians can decrease their impact on global warming
by eating organic, seasonal, locally-grown produce wherever possible.
The Pros and Cons of Grass-Fed Beef by Gene Sager in Natural Life
Magazine, November/December 2008
Dilemma: A Natural History of Four Meals by Michael Pollan (Penguin, 2007)
Food Rules: An
Eater's Manual by Michael Pollan (Penguin, 2009)
Miracle: A Year of Food Life by Barbara Kingsolver (Harper Perennial, 2008)
Eating to Save the Earth by Linda Riebel and Ken Jacobsen (Celestial Arts,
Six Arguments for a Greener Diet by Michael Jacobson (CSPI, 2006)
The Vegan Sourcebook by Joanne Stepaniak (McGraw-Hill, 2000)
Vegetarian Society - UK www.vegsoc.org
University of Surrey’s Centre for Environmental Strategy Food Climate
Research Network www.fcrn.org.uk
Food and Agriculture Organization (FAO)
Marine Conservation Society
Wendy Priesnitz is the Editor of Natural Life Magazine and a journalist with over 35 years of
experience. She has also authored twelve books. Visit her