food Program

Agriculture, Energy & Climate Change

Taking a Bite out of Climate Change

On September 8, 2008 Dr. Rajendra Pachauri, chair of the United Nations Intergovernmental Panel on Climate Change, spoke to 400 people gathered for an event hosted by the animal welfare organization, Compassion in World Farming.    F Pachauri, an Indian economist (and vegetarian) who had just been reelected to a second term as chairman, made one of the most public and bold statements about the connection between our diet and global warming on the world stage: Choosing to eat less meat, Pachauri said, or cutting out meat entirely, is one of the most important personal choices we can make to address climate change.

"In terms of immediacy of action and the feasibility of bringing about reductions in a short period of time, it clearly is the most attractive opportunity," said Pachauri. "Give up meat for one day [a week] initially, and decrease it from there."

To many of us, Pachauri’s specific prescription for addressing change might come as a surprise. When we think about the culprits behind the climate crisis, we tend to think about Big Oil or dirty coal-fired powered plants. We picture cars and industrial skylines, or imagine factories and smokestacks. It’s time we start thinking about another sector of the economy that is increasingly exacerbating the climate crisis. The global food system—including deforestation to make way for crops for cattle and cars—is responsible for an estimated one-third of total greenhouse gas emissions (see below, Main Sources of Emission from Agriculture).

Livestock production alone contributes to 18 percent of the global warming effect—more than the emissions from every single car, train, and plane on the planet.    FThough livestock production only contributes 9 percent of carbon dioxide emissions, the sector is responsible for 37 percent of methane and 65 percent of nitrous oxide, both potent greenhouse gases.    F

Move over Hummer, say hello to the hamburger.

The Food and Climate Change Connection

So how is food—supposedly life-sustaining stuff—one of the key factors in an environmental crisis that threatens the basis of life on earth? A big part of the answer is in the rapid and radical twentieth-century transformation of our food system from sustainably based, locally focused production, to a fossil-fuel addicted industrialized system. Agriculture has changed more in the past two generations than it did in the previous 12,000 years. Unfortunately for us, almost every single aspect of our modern industrial system creates greenhouse gas emissions. And, as Dr. Pachauri says, another big reason is the rapid growth of livestock production. Indeed, to produce 2.2 pounds of beef burns enough energy to light a 100 watt bulb for twenty days, Pachauri noted in his remarks earlier this month.    F

Table 1 : Main Sources of Emission from Agriculture

Main Sources of Emissions

Percent of the Total Global
Warming Effect of Emissions

On the Farm
Fertilizer production and distribution
Methane and nitrous oxide emissions

1.5 to 2%

On the Land
Deforestation and other land use changes


On the Road
Transportation emissions from seed to plate

Specific food-system data unavailable

Additional Sources
Waste and manufacturing

Specific food-system data unavailable

Estimated Total*

33% of the total global warming effect can be attributed to the food system.

*Note: These percentages are a rough estimation of the global warming effect of the food system. Because of the complexity of global warming science as well as the challenge of securing accurate estimations of emissions from these various sectors, this estimation is the best we can hope for. While more research is certainly needed, in the meantime, we must begin to make policy changes to address what we do know: That our food system is a significant contributor to the global warming effect, and that we each can do something about it.

On the Farm

Fertilizers and on-farm fossil fuel use

Industrial farms    Gare fossil-fuel addicted places, from their reliance on fossil fuels for powering machinery to petroleum-based chemicals used to create artificial soil fertility, protect against pests, and stave off weeds. The use of fossil fuels on farms, as well as in the manufacture of fertilizers and agricultural chemicals, contributes to the greenhouse gas emissions generated by the food sector.

With one-third of the world’s cereal harvest and 90 percent of the world’s soy harvest being raised for animal feed, the energy required to grow those crops is a major factor in these on-farm emissions.    FIn the United States and Canada, half of all synthetic fertilizer is used for feed crops.    FIn the UK, the total is nearly 70 percent.    F

A major reason that beef, in particular, has such a large environmental impact is because, of all livestock, cattle are among the worst converters of grain to meat. Whereas in nature, cattle, which are ruminants, convert inedible-to-humans grasses into high-grade proteins, under industrial production, grainfed cattle only provide about one pound of beef for every 10 to 16 pounds of feed they consume.*

Because industrialized agriculture also relies on huge amounts of water for irrigation, these farms will be much more vulnerable as climate change increases extreme droughts. Globally, 70 percent of the world’s available freshwater is being diverted to irrigation-intensive agriculture.    F

*Note: "Conversion ratios" are hotly contested. In Frances Moore Lappe’s book, Diet for a Small Planet, she estimated that the conversion ratio for US-feedlot cattle is sixteen pounds of grain and soy to produce one pound of beef. In The End of Food, journalist Paul Roberts argues that these conversion ratios don’t account for the 60 percent of a cow’s weight that is bone, organ, and hide—inedible stuff. The real conversion ratio for beef, Roberts argues, should be even lower. He estimates that it takes "a full 20 pounds of grain to make a single pound of beef."    F   F 

The impact of livestock

The other reason that livestock production has such a substantial impact on climate change is that livestock are among the main sources of the world’s methane emissions. (Rice cultivation is another, accounting for one-tenth of all agricultural emissions, according to the Stern Report).    F Ruminant livestock, including cattle, buffalo, sheep, and goats, are the main agricultural sources of methane. Ruminants digest through microbial, or "enteric" fermentation, which produces methane that is released by the animals through belching and, to a lesser degree, via flatulence. While this process enables ruminants to digest fibrous grasses that humans can’t convert into digestible form, it also contributes to livestock’s impact on climate change. Enteric fermentation accounts for one-quarter of the total emissions from the livestock sector. (Land use changes, such as deforestation and desertification caused by over-pasturing livestock or growing feed crops, account for another 35.4%, while manure accounts for 30.5%).    F

Industrial livestock production also generates greenhouse gasses due to the manner in which animal waste is managed. In sustainable agricultural systems, there's no such thing as waste: manure is part of a holistic cycle and serves as fertilizer. But in concentrated animal feeding operations (CAFOs), animal waste is not cycled through the farm since there’s simply too much of it. Instead, waste is stored in huge pits euphemistically called "manure lagoons." Without sufficient oxygenation, waste stored in this manner ends up emitting methane and nitrous oxide. The US scores at the top of the world for methane emissions from manure, and pigs are at the top in terms of methane emissions, responsible for half of the globe’s total.    F

The sheer number of animals being raised for meat on the planet is another reason that livestock production accounts for nearly one-fifth of all global greenhouse gas emissions. In 1965, 10 billion livestock animals were slaughtered each year; today that number is 55 billion.    F

On the Land

The bulk of the pressure on land around the globe, from precious wetlands in Indonesia to rainforests in Brazil, comes from the agricultural sector.    F These rainforests and wetlands play a vital role in climate stability because they sequester carbon, absorbing and storing carbon dioxide from the atmosphere in the soils and plants. With their destruction, carbon is released back into the atmosphere and the carbon cycle that keeps our climate in balance comes further unhinged. Because these lands play such a vital role as carbon sinks, it’s no surprise that their destruction is partly responsible for the emissions from land use changes that add up to nearly 18 percent of the total global warming effect.

The biggest driver behind these "land use changes," as the climate change folks call them, is the expansion of pasture for cattle, feed crops for livestock, and oil palm for processed foods and biofuels.    F Most of these land use changes are concentrated in just a handful of countries. Brazil is the heart of rainforest destruction, mainly to meet demand for livestock grazing and feed. Malaysia and Indonesia are the world’s main producers of palm oil; here, plantations are leading to rapid rainforest and wetland habitat destruction. Malaysia produced 43 percent and Indonesia 44 percent of the world’s total palm oil last year.    FWhile the exact amount of land that has been converted into oil palm plantations is hard to determine, we know that demand for palm oil has soared in the last two decades, especially due to growing demand for edible vegetable oils from the world’s top two importing countries, India and China, according to an assessment by the USDA’s Foreign Agricultural Service.    F

The erosion and deterioration of soils on industrial farms also releases greenhouse gases into the atmosphere. By destroying the natural soil fertility and disturbing the soil through tillage, industrial farming also adds to the deterioration of soil and its carbon emissions.    F 

On the Road: The Food Miles Question

And what about the distance food travels to get to our plates? Despite all the attention to food miles, emissions from food transport are not the biggest component of the sector’s impact on climate change.

While total emissions from transportation contribute to 13.1 percent of the global warming effect, this includes emissions from toting around all kinds of things—from people to pork chops.    FTransport emissions specifically from food are just a sliver of these emissions.

Nonetheless, reducing food miles can still make a meaningful dent in our foods' emissions toll. Consider the fossil fuels wasted carting fresh tomatoes to New Jersey, a state with ample farmland that exports tons of tomatoes every year. Researchers at Rutgers University estimated that meeting the New Jersey demand for just one year’s supply of out-of-state tomatoes used up enough fossil fuel to drive an 18-wheeler around the world 249 times.

Food miles matter because so much of our food transport is unnecessary. Local food is also a better choice because it is fresher and therefore healthier for us. Buying local also supports our local economies. Purchasing local foods means supporting small-scale businesses and protecting green space in our communities.

Of course, direct trade with small-scale farmers in far away places can be a critical way to support economic development in other parts of the world. But most of the global food trade isn’t benefiting small-scale farmers — it’s benefiting the biggest grain traders at the cost of the climate.    FAnd most of this global food trade is completely unnecessary, or redundant. Consider, for example, the fish caught off the coast of Maine, flash frozen, shipped to China for processing into filets, and shipped back to our mega-markets in the United States. Or, consider the business of beef. In 2007, the US exported 1.431 billion pounds of beef and veal (5.4 percent of our total beef production)    Fand imported 3.052 billion pounds of the same, measured by commercial carcass weight.    FThis cross-continent transport of food makes economic sense only because the true costs of such transport, including the big bill for its contribution to climate change, are not counted on the balance sheets of food corporations.

The main reason for sticking with the locavores is that the local food being celebrated is often a pseudonym for sustainably raised foods—and those foods will be the ones produced without fertilizers, grown without destroying precious wetlands or rainforests, and with animals raised on pasture rather than in confinement.

Other Sources of Emissions

Because the food system is connected to so many aspects of our lives, it’s hard to get an exact tally of total emissions. Here are some other places where the food system’s emissions crop up.

  • Waste: Another four percent of global greenhouse gas emissions comes from waste, including food waste. Where does all our uneaten food end up and the tons of food ready for harvest that never even makes it to our plates? Landfills. And landfills are a key source of methane as food and other refuse decay.
  • Manufacturing: An additional 10 percent of global emissions stems from manufacturing and construction, which includes construction for the food industry.

How Can Farming Help Address the Climate Crisis?

In nature, plants transform the sun’s energy into food that provides a foundation for life. Humans are fueled by this transformation either directly (we eat the food) or indirectly (we eat the animals that have fed on this energy). It’s a clever cycle: it’s inherently abundant. But the industrialization of agriculture, picking up pace in the past generation, has flipped the natural abundance of farming on its head. Instead of producing energy, industrial agriculture consumes it, through the addiction to fossil fuel-powered machinery and petroleum-based agrochemicals. Industrial farms are often considered highly efficient, but only because these wasted inputs and devastating outputs—including the impact on the climate—are not accounted for. (See Table 3 : The Core Differences between Climate-Crisis Agriculture and Climate-Friendly Farming).

Unlike industrial farms, small-scale organic    G and sustainable farms rely on people power, not heavy machinery, and depend on nature, not manmade chemicals for soil fertility and pest management. As a result, small-scale sustainable farms have been found to emit between one-half and two-thirds less carbon dioxide for every acre of production.    F

New research is documenting that organic farms can emit as little as half the carbon dioxide generated by industrial farms. Organic farms also use much less fossil-fuel energy than their conventional counterparts—in many cases as much as one-third less, and studies are also showing that organic farming can sequester carbon, providing a potentially powerful tool to help us address climate change. In fact, 10,000 medium-sized organic farms can store as much carbon in the soil as we would save if we took one million cars off the road.

Yes, the very source of energy—the food consumers eat—has become one of the planet’s most significant contributors to climate instability, but it need not be. There is another way.

An Overview of Food System Sources of Greenhouse Gases

Carbon dioxide

Carbon dioxide is emitted by burning fossil fuels to power farm machinery, produce agricultural chemicals, and transport food. In addition, carbon dioxide is released when forests and wetlands are cleared for crop production, particularly for animal feed, pasture, or oil palm production. Finally, trapped carbon in soils is also released through soil erosion and deterioration on industrial farms.


Agricultural methane is released primarily by ruminants such as cattle, and during rice production. It has 23 times the greenhouse effect of carbon dioxide over 100 years.

Nitrous oxide*

Nitrous oxide is released mainly from the use of man-made fertilizer, especially the overuse of nitrogen on crops grown for animal feed. It has 296 times the greenhouse effect of carbon dioxide over 100 years, or 275 over 20 years.

*A note about methane and nitrous oxide: In the US, the food system accounts for an estimated 17 percent of all fossil fuel use, but accounts for a much larger percentage of the country’s methane and nitrous oxide emissions. Widespread overuse of artificial nitrogen fertilizer, for instance, much of which is wasted in leaching and runoff, contributes to three-quarters of total US nitrous oxide emissions. And globally, agriculture is responsible for nearly two-thirds of methane emissions. While methane and nitrous oxide make up much smaller portions of total greenhouse gas emissions, these gases are still important factors in the climate crisis, in part because they each have stronger global warming effects than carbon dioxide and also because they constitute an increasing portion of total emissions.

Table 3 : The Core Differences Between Climate-Crisis Agriculture and Climate-Friendly Farming

Climate-Crisis Agriculture

Climate-Friendly Farming



Ignores Place

Values Place

Emits Carbon

Stores Carbon

Dependent on Chemicals

Depends on Nature for Fertility and Pest Management

Disrupts Natural Cycles

Protects Nature’s Cycles

Squanders Energy

Produces Energy

Fossil-Fuel Powered

People and Animal Powered

Wastes Water

Retains and Conserves Water

What You Can Do

  • Eat and Drink with the Environment in Mind
    Many of the resources at Sustainable Table can help you make climate-friendly food choices every day. Here are some of the principles of low-carbon dining, with links to more information.
    • Eat less meat and dairy: Go cold turkey, or just trim your consumption. Try cutting out meat just one day of the week. Check out Meatless Monday for more inspiration.
    • Choose organic and sustainably raised foods: Visit Eat Well Guide to find sustainable food throghout the US.
    • Eat local: Lower your food mile odometer, and always try to find local sustainable food. Get inspired with these ideas and by the original locavores.
    • Eat whole foods: Cut back on processed foods—visit In the Kitchen for recipes and cooking ideas. Check out your "carbon foodprint" at Bon Appetit’s Low-Carbon Diet Calculator.
    • Take back the tap: Kick the bottled water habit. Visit Food & Water Watch for more information about the environmental impact of bottled water, the benefits of tap water, and how you can add your voice to those of people across the country demanding better regulation of our precious public resource—water.
  • Get Involved on a Broader Scale
    Go beyond your plate to get involved with exciting campaigns that are making the food and climate connection. Here are three recommendations.
  • Get Informed
    • Read the Environmental Working Group's Meat Eater's Guide to Climate Change and Health to learn more about the issue and to find tips for reducing your diet's impact on the planet.
    • Visit Take a Bite out of Climate Change to find more resources and sign up to stay informed.
    • Learn more about the meat and climate change connection. Read the definitive study from the United Nations: Livestock’s Long Shadow.
    • Check out the manifesto on Food and Climate Change from Vandana Shiva and her colleagues at the International Commission on the Future of Food. The Manifesto summarizes the connections between industrial agriculture and climate change and offers a compelling call to action from the perspective of farmers in the global south.
    • Read Soil not Oil by Vandana Shiva from South End Press: Shiva connects the dots between the world’s most pressing crises: food insecurity, oil dependence and climate change.

This article was adapted from Diet for a Hot Planet, a book about food and climate change by Anna Lappé. Visit the Take a Bite Out of Climate Change website to learn more, or contact the author at [email protected].