Fighting climate change: Food miles vs. food choices

Photo trucks in a rowIf you want to fight global warming with your diet, it is better to change what you eat than where it comes from, according to a recently published article in the peer-reviewed journal Environmental Science and Technology.*

Analysis by Christopher L. Weber and H. Scott Matthews, professors in the Department of Civil and Environmental Engineering at Carnegie Mellon University, found that the vast majority of greenhouse gas (GHG) emissions in the American food system occur during the production of food, not from transportation of the raw materials, inputs, or final product. They estimate that small changes in dietary habits — such as replacing 1/7 of the average person’s red meat and/or dairy consumption with chicken, fish, or eggs, or an all-vegetable diet — can lead to reductions equivalent to those that could be obtained through “maximum localization.”

People’s “foodprints” — the GHG emissions associated with their diet — are receiving attention in climate-change circles because dietary habits are (theoretically) far easier to change than the source of our electricity, how we get around, and so on. In other words, it could be easier for the population to eat less beef than to switch from coal-fired power plants to solar panels or dramatically revamp the built-up landscape so that more people could walk or bike to work.

“All Local” vs. Dietary Shifts

As a thought experiment, the authors examine how an “all local” diet — i.e., a diet that has zero emissions between producer and eater — compares to shifts in diet in terms of GHG emissions. Since that is nearly impossible to achieve, they found that one could achieve equivalent reductions through the following changes:

  • Reduce red meat expenditures by 24% and spend the savings on chicken
  • Reduce red meat expenditures by 21% and spend the savings on a nondairy vegetarian diet
  • Reduce red meat and dairy expenditures by 13% and spend the savings on a nondairy vegetarian diet

The authors also use a automobile comparison to illustrate how changes in diet compare to changes in driving. Using a 25-mile per gallon car as their baseline, they provided the following estimates of mileage reduction through diet shifts:

  • An “all local” diet is equivalent to driving 1,000 fewer miles per year
  • Shifting one day per week’s calories from red meat to chicken/fish/eggs is equivalent to driving 760 fewer miles per year
  • Shifting one day per week’s calories from red meat to a vegetable-based diet is equivalent to driving 1,160 fewer miles per year
  • Giving up red meat and dairy in favor of chicken/fish/eggs is equivalent to driving 5,340 fewer miles per year
  • Switching to a completely vegan diet is equivalent to driving 8,100 fewer miles per year

This is not the first time I’ve seen dietary choices compared to driving choices. The article “Diet, Energy, and Global Warming,” by Gidon Eshel and Pamela A. Martin in Earth Interactions (sub. req’d) compared various diets to various types of cars with similar results.

Get on the life cycle

The authors used a technique called “life cycle analysis” to dissect and examine the food system. Life cycle analysis (LCA) tries to quantify all of the environmental impacts (energy consumption, GHG emission, water pollution, etc.) from production to disposal of a product. An LCA of a glass of wine, for example, could consider production of the bottles, labels, and cork (including all necessary transportation); production and transport of fertilizer and other farm chemicals for the grapes; energy for irrigation; impacts of the actual wine-making process; bottling; climate control for the wine’s fermentation, aging, and transport; and transportation to the wholesaler, retailer, and consumer. (Basic overviews of LCA are available from the American Center for Life Cycle Assessment and the United Nations Environment Programme.)

To create the model, the authors used several collections of economic, transport, and food data from 1997. The age of the data is one of the shortcomings of the study because much has changed since then. The rapid increase in food imports — between 2001 and 2007 the value of food imports rose by 73% — is one of the biggest changes that would affect their calculations. The authors performed additional analysis to include the import increase and found that the longer supply chains increase the average distance traveled by food by about 25%, while increasing the overall GHG emissions associated with transportation by only 5%. The reason for the smaller GHG increase is the frequent use of oceangoing ships in international trade, which are far more efficient than trucks. The recent rapid rise in oil and fertilizer prices could also affect the food system in significant ways.

Final transportation accounts for only 4% of emissions

One of the most interesting results is the average amount of transportation required to produce food for an average household. Assuming that 11 pounds of food is required for the average 4-person household per day, they estimate that 4,200 miles of transportation is needed throughout the entire production and supply chain (the “average” household diet was obtained by the authors from the USDA Economic Research Service). The average “direct” distance — the final leg from farm or production facility to the consumer, the segment typically called “food miles” — is 1,020 miles. In terms of GHG, production accounts for 83% of the emissions, while transportation accounts for about 11%. The “direct” segment of transportation causes only 4% of the GHG emissions.

Another interesting result is the clear demonstration that different foods can have dramatically different “foodprints.” The figure below, which I created using some of the data from Figure 1-c of the paper, shows the source of GHG emissions for three food types: chicken/fish/eggs, fruit/vegetables, and red meat (the figure in the paper shows eight food types). The horizontal axis is the annual GHG emission per household from the food group in tons of CO2 equivalent**, with a longer bar corresponding to higher emissions. The colored sub-bars show the contributions from various parts of the food system: black is emissions from the “direct” leg, blue is carbon dioxide emissions, red is nitrous oxide emissions, and so on. The authors calculate that the average household’s diet causes an annual release of 8.1 tons of GHG, so red meat consumption is responsible for almost one-third of the total food-related emissions, whereas chicken/fish/eggs and fruit/vegetables contribute only about 10% each. Note that for each food group, the delivery and transport emissions are relatively small.

Emissions of methane (orange bar) and nitrous oxide (red bar) are the primary reasons that red meat has such a high “foodprint.” Methane is a natural byproduct of digestion in cattle and other ruminants (microorganisms in their gut create methane) and also is formed by decomposing manure. Nitrous oxide is emitted when nitrogen fertilizer breaks down in the soil, during various soil management processes, and when manure decomposes. Since the modern U.S. beef system relies so heavily on intensely fertilized corn and soybean fields for animal feed, the nitrous oxide emissions are relatively high. The far higher GHG emissions from red meat production can also seen in a Belgian study that compared the life-cycle GHG emissions of various animals.

Greenhouse gas emissions from food production and transport

The result in the figure above is for an average household, and therefore the emissions calculation is tied to the quantity of the foods in the diet. To separate the analysis from the average mix of product, the authors also calculated the relative GHG emissions on a per calorie and per kilogram basis. On a per-calorie basis, red meat has about three times the GHG emissions of fruit/vegetable or chicken/fish/eggs, and about twice the GHG emissions of dairy products. On a per-kilogram basis, the ratios are even higher, but that normalization is affected by the high concentration of water in dairy and fruits and vegetables.

Eating local and thinking global

Do the above results mean that locavoreanism has no role to play in fighting climate change? I don’t think so.

First, reducing our GHG emissions will require many discrete actions, not just one or two big shifts. The stabilization wedge concept of Socolow and Pacala is a good example of this thinking. If we were to create a wedge strategy for the food system, reducing the amount of transport would certainly be one of the wedges. Second, rebuilding local food networks can help to create stronger, more self-sufficient communities. Third, teaching people about where their food comes from can be a way of introducing them to concepts about the entire economy (like life cycle analysis). Fourth, much of the innovation in agriculture (or, perhaps “old-ovation,” since much of the new today is drawn from the old ways) is coming from small farms that serve local populations. Think, for example, of Joel Salatin’s operation in Virginia that was profiled in Michael Pollan’s “The Omnivore’s Dilemma.” Salatin is a “grass farmer” and uses his crop of grass to feed cattle and chickens, which then fertilize the land, leading to a high production of animal protein with a relatively low use of industrially derived inputs. Fifth, international trade has many other negative costs, like high levels of air pollution around large ports.

Photo of Alemany Farm in San FranciscoEnergy conservation has never been at the top of my personal “why eat local” list. In my view, there are other more important reasons to choose locally-produced foods: the local produce has better flavor than imports, I can make a connection with the producer, local purchases can preserve nearby farmland, and it is one of the important parts of creating a more resilient food network. Considering these benefits, I see a theme that connects them, something that could be called “food mindfulness.” Practicing food mindfulness, I consider how and where my food was produced, and how those practices affect the big picture (ecosystems) and the smaller picture (my pleasure and health). With the huge number of challenges facing our food system and society, it is possible that food mindfulness is more important than either food miles or food choices.

Other resources



The full citation of the paper discussed above is “Food-Miles and the Relative Climate Impacts of Food Choices in the United States,” Christopher L. Weber and H. Scott Matthews, Environmental Science and Technology, 42 (10), 3508–3513, 2008. DOI: 10.1021/es702969f

* Subscription required, available in libraries of most academic institutions with a science program. If you really want the article, the authors might be able send you a copy, as they often retain limited rights to distribute their own articles.

** The term “CO2 equivalent” is used to express the climate changing power of a mixture of greenhouse gases in terms of the equivalent amount of CO2 that would cause the same effect. Methane (CH4), for example, is 25 times more potent than CO2, so one ton of methane would can be expressed as 25 tons of CO2 equivalent. Another food related greenhouse gas is nitrous oxide (N2O), with a relative potency of about 298 times that of CO2. (The methane and nitrous oxide climate factors are from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.)

    Photo of trucks from PhillipC’s flickr collection, subject to a Creative Commons License.  Photo of the Alemany Farm in San Francisco by the author.

    25 Responsesto “Fighting climate change: Food miles vs. food choices”

    1. Cascadia Girl says:

      Good food for thought! I would  be curious to know whether how the animal was raised impacted the emmissions levels (e.g. factory farm vs organic, pasture raised/finished)

    2. Charlotte says:

      My thoughts exactly — lumping all “red meat” under the same banner seems odd to me. For example, the antelope I killed last fall is red meat, but it has a very different carbon footprint than a feedlot steer or even a grass fed lamb.

    3. Michael says:

      I agree – it seems they didn’t take into account how many locavores patronize local producers whose production practices are much more sustainable than larger operations. I fail to see how fish (for example), many of which must include endangered populations, destructive fishing practices, and/or highly-polluting aquaculture practices, would be a good alternative to red meat. Perhaps switching half of one’s industrial beef consumption to unsustainably farmed salmon would be technically better in terms of food miles, but it isn’t exactly a great solution. Thanks for a great post.

    4. Debs says:

      The point about there being many reasons to eat local beyond the carbon footprint is a good one.  And I agree with Cascadia, Charlotte and Michael that not all red meat leaves the same kind of footprint.  I buy a lot of local, pastured meat and I think that actually has a positive impact (not just on my health and taste buds).  Specifically, it helps small producers who raise animals on pasture survive and thrive in an economy that favors the industrial scale producers.  Buying grass-fed red meat may end up reducing pollution from industrial scale producers if it contributes to the pendulum swinging a little more in favor of sustainably produced food.  I buy this meat, you stay in business, other people are encouraged to buy from you, etc.


    5. Unfortunately that research is slanted because they’re looking at modern factory farming raising of the animals, e.g., hog barns, beef feed lots, etc which are highly grain intensive.
      The best thing to do is eat locally produced pastured meat, be it chicken or red meat along with a good balance of also locally produced veggies and fruit. This minimizes the production and transportation.
      If they were to look at pastured animals they would find that the production costs are far lower than what they are showing.

    6. Anastasia says:

      The study didn’t say “local doesn’t matter”, it said “eat less red meat”.
      Too many people continually miss the point that meat and dairy are bad for the environment – no matter how the animals are raised. We can agree that a pound of pastured beef has less environmental impact than a pound of feedlot beef, due to concentration of wastes and the issues associated with growing feed. However, pastured and CAFO animals alike release methane. There’s actually some evidence that the high-fiber diets of pastured animals cause the bacteria in their rumens to emit more greenhouse gases than those in animals fed high protein diets. Nitrous oxide is also released by animals in both types of systems. Specifically, the hooves of pastured animals release nitrous oxide when they tread on soils that contain their own urine.
      I’m not saying that people shouldn’t enjoy beef or pork (local or otherwise) in moderation, but we’re doing the whole planet a disservice by pretending that we’re helping the environment by eating meat.

    7. joeblueskies says:

      Holey-Moley, this is the most educated bunch of consumers I have ever seen around this red meat and pastured husbandry issue.  You guys get the difference between grass farming and CAFOs.  Most studies lump it all into one pile (of course, that may be because 3 companies pack over 80% of the beef raised in America).  One thing I would love to see is a good study relating to the amount of carbon sequestered in the ground in a good intensive rotational grazing regime.  Grass plants grow down in proportion to the amount they grow up, and shed root growth in proportion to the amount they lose when grazed.  That is a significant amount of carbon going into the soil.  There is a lot of talk these days of cow burps – no one ever mentions the balancing effect of what healthy pasture does for carbon sequestration.  Just sayin’

    8. Parke says:

      Interesting article, and part of a great line of research in recent years about food choices and the environment.  But each of these articles has a punchline, for press consumption, that is far from the most interesting part.  Usually the punchline supposes a pretend competition.  Which saves the environment more, switching to a hybrid or eating local?  Eating local or eating less meat?  Eating less meat or turning down the thermostat?
      Who put these choices in a horse race against each other?
      Some choices in life really are in a competition.  Choose to live near public transportation or in an automobile suburb?  Eat meat 10 times a week, or 2 times a weak?  Let’s put those choices in a horse race against each other.
      When we’re discussing eating local and choosing foods that are more environmentally sound, let’s be dogmatic about neither an eager about both.

    9. Jen Hendrickson says:

      Anastasia you don’t get it. Mass producing veggies is bad for the environment. It creates huge monocultures and destroys the habitat of billions of plants and animals. Plant matter does not have as much or complete food value. Harvesting plants kills animals who get caught in the harvesting machinery. Vegetarianism is not without a huge price to the environment.

      Meat grown on a small scale is highly sustainable and not bad for the environment. The livestock turn what is indigestible pasture materials into quality food for us to eat.

      The issue is not vegan vs meat. The issue is big vs little. Cities are unsustainable and that is the real issue.

    10. wb says:

      Interesting data.  I see one skew – the lifecycle of poultry and vegetables is usually only a few months.  The lifecycle for beef is 18 months from birth to slaughter, probably 2 to 3 times as long as for poultry or vegetables, so naturally the emissions would be 2.5 times as much.

      Oddly enough, this data will defend my choices in buying local food.  I can tell global warming skeptics that I am doing it for taste and freshness and to support small farms, not as a carbon footprint reduction measure.

    11. Matt says:

      To the CMU profs’ credit, their conclusion acknowledges that there are lots of reasons people choose to eat local other than that of trying to reduce their GHG footprint, including other environmental reasons. Their argument is only that *if* reducing your GHG footprint is your goal, eating local won’t make much difference, contrary to the oft-heard refrain that reducing food miles is a good way to do that.  As Marc nicely explains, they offer several ways of modifying one’s diet — that is, the average American’s diet — to make a dent in one’s GHG footprint equivalent to shifting to an all local diet. That some of these shifts might have other, non-GHG-related environmental downsides (e.g., farmed fish), is beside the point (as far as their argument goes), as is the fact that there are other ways that one could also make the same dent or a bigger one (by eating grass-fed meat, buying local organic rather than local non-organic, or whatever).  Those are important things to think about, of course, but they aren’t in the sights of the study under discussion, contrary to what most of the above comments seem to think.
      And nice discussion, Marc. Much better than the one by Dubner over at the Times Freakonomics blog, which, as with some of the comments here, takes Weber and Matthews to have proven far more than they claim too — only Dubner concludes that the whole eat local movement has been proven to be bogus.

    12. katherine says:

      Definitely a great post and fruitful discussion! Two years ago, when we (at Bon Appetit Management Company, where I work) started compiling LCA research for our Low Carbon Diet Calculator (, we were also surprised with the findings that food production has a greater GHGe impact than transportation.  After sharing this information with our chefs and managers (who are all about local), they raised great questions, just like those posted here, about the carbon impact of local grass-fed beef, for example. As with many food/environment issues, there isn’t one easy answer but I think having these discussions and developing ‘best-possible’ operational changes are steps in the right direction.

      I find it really interesting how complex locavorism has become and how parallel it seems with “nutritionism,” if you will. At one point, all fat was bad but now there are good fats and bad fats. Similarly, eating local was best for the environment but now specific local foods have different impacts. Just as we’ve been counting calories, now we can calculate food miles. Although I believe that ultimately the more information we have the better, I also appreciate (and think it’s important to emphasize) Marc’s suggestion of “practicing food mindfulness.” Sounds simple and instinctive enough but that’s surprisingly not the case. As a registered dietitian, I’m constantly taken aback by how much mindless eating takes place in general. When it comes to healthful eating and nutrition, being mindful of what you eat is half the battle. There’s no question in my mind that practicing food mindfulness would also benefit our environment and local communities.

    13. SpEdLaw2 says:

      I just voted for your blog for Bloggers Choice Awards.
      Would you please return the favor at:

    14. joeblueskies says:

      Matt – the authors of the study may have had one thing “in their sights”, but they made some pretty major data aggregations to form their crosshairs.  My particular “beef” is about the aggregation that I see so often in these types of articles and studies – all beef is one thing.  And that is patently false, whether you are looking at it from a standpoint of nutrition, economics, community development, environmental impact, etc.  I think this has been a thoughtful and considered discussion – no need to slam us for taking the ball and running with it.

      And I love Katherine raising the nutritional aspects.  Food mindfulness would be a lot easier if there was better information out there about nutrition, instead of the crap that comes out of the anti-fat “nutrition experts” noise machine.  So much of what passes as nutrition advice is really just cleverly disguised propaganda from the food processing industry.  Personally, I am a big fan of Sally Fallon and the Weston Price tradition, so if you know that data you know where I am coming from.  The “food mindfulness” approach is also Oprah’s latest gig.  From a recent post in her b log, discussing a book by auther Kathy Freston -
      Conscious eater. That struck a nerve. I had recently come to the conclusion that after spending weeks reading and rereading A New Earth and being on line with Eckhart Tolle that bringing a higher level of awareness to my eating was the solution I’d been avoiding. My idea of a conscious eater, however, was not quite the same as Kathy’s.

      I thought it meant not allowing yourself to eat emotionally and filling the void of anxiety with food, as I’ve struggled with for years. I thought it meant taking your time, making healthy choices and chewing slowly—being conscious of every bite and not scarfing down a meal and then thinking about the next one.

      That is one level of consciousness. But what she talks about in her book is a higher level. She speaks of “spiritual integrity.” How can you say you’re trying to spiritually evolve, without even a thought about what happens to the animals whose lives are sacrificed in the name of gluttony?
      Gluttony? Why not health?  or greed?  A meat eater automatically becomes a glutton?  I have a very strong reaction to this statement.  Of course, the conflation of food and mindfulness is a clear allusion to the Buddha’s Noble 8-fold Path.  But even his Vinaya, or monastic rules, 30 of which referred to eating practices, made no mention of meat-eating as a practice to be avoided.  I think the notion of food mindfulness is a great thing.  Please don’t assume it means demonize meat eaters.

    15. Ian Lewis says:

      JoeBlueSkies, great comment. I am also a huge fan of the Weston A Price Foundation and they had a series of articles on this very topic in their journal, Wise Traditions, a few months back.

    16. Great points JoeBlueSkies and Jen H. While I am not nearly as educated on this matter as some, from what I have read, I have no doubt that pasture-raised meat is an extremely sustainable practice that has minimal environmental impact at most.

      And, to be honest, it bothers me when vegetarians get up on their high horse about meat. Unless you are a vegetarian only eating local and organic veg, please don’t try to tell me that your way of eating has any less of an impact on the environment than my choice to eat almost strictly pastured meat in moderation, 80%+ of which I get from within 60 miles of my house.

    17. Matt says:

      Joeblueskies -

      I wasn’t slamming people personally, only pointing out that their arguments against Weber and Matthews’ argument miss the mark. Given how eager some are to dismiss us locavores, we need to be careful about what exactly is at issue and what our case is. Combating climate change by reducing food miles is one of the reasons commonly given to people for why they should eat local, and W&M do a pretty convincing job of showing that that’s actually a pretty lousy reason. The average person who wants to reduce GHG emissions by altering their diet can do more by eating less red meat, and here it’s perfectly legitimate to treat all red meat as the same because the red meat in the vast majority of the diets of the people hearing the food miles-GHG claim is industrial red meat. Yes, W&M leave out that tiny fraction of people who eat grass-fed meat shipped long distances. For them, getting their grass-fed beef closer to home might make a significant dent in their overall GHG footprint (assuming grass-fed makes a big difference with respect to GHG output). But why is it a problem that they didn’t single out this group of people, given how few they are?
      The lesson I take from W&M’s study is that we would do well to avoid trying to motivate people to eat local by claiming that they’ll be helping the climate by reducing miles traveled by their food. (It’s still possible, of course, that eating local may bring with it positive, climate-related benefits, but W&M’s argument entails that most of these will not be due specifically to the reduction in food miles.) We should just concede that the focus on food miles is mistaken, or make clear that it is a proxy for a whole set of other concerns that are mostly only indirectly related to climate change.  If we don’t, we set ourselves up for the easy “refutation” of the sort Dubner gives on the Times’ Freakonomics blog.
      - Matt

    18. helen says:

      cool discussion!  something to ponder:
      - It’s a bit tough to tell from Marc’s graph (beautiful work, by the way!), but it looks to me like replacing a meal of standard grain-fed beef with either fish or veg gives you a ~70% reduction in GHGe (~2.5 vs ~0.8).
      - by moving to grass-fed, you reduce methane and and nitrous oxide emissions by 40%, according to a Swedish study cited in the Worldwatch Institute’s latest State of the World report (chapter 5, p. 65.  You can download the chapter for free at their website.  It’s a good read).  Cattle find grass easier to digest than grain-based feed they didn’t evolve to eat, funnily enough, so they produce less gas digesting it.  Methane and nitrous oxide are ~60% of the total emissions, so 40% of 60% gives an overall reduction of ~25%.
      - by moving to grass-fed, I’m pretty sure you also remove all the CO2 emissions from production, for a further reduction of ~20%.  Check my logic:  There’s no chemical fertiliser production emissions because you don’t dump NPK on pasture; there’s no diesel tractor to plough, sow, weed/pesticide, harvest feed crops; there’s no feed processing emissions.  Should anything else be factored in?
      - Grass-fed, by co-incidence, also often means local if you’re in the US (not necessarily here in Australia);  if it is, then you can take out your transport costs as well – another ~15% by the looks.
      So, by switching to grass-fed, locally-grown red meat, you drop ~60% of your GHG emissions, based on available figures.  If you add in the observation that pasture actually sinks carbon, which Joe already pointed out, it’s not hard to believe you’d start to get quite competitive with the 70% for going the veg or chicken/fish/egg options.
      … which then of course just prompts the question:  well, what if we were talking about organic (in the holistic, not agribusiness sense) veg/chicken/fish/eggs?
      so – fwiw, I think the main point we can take away is:  almost anything is better for the climate than factory-farmed red meat :-).
      also for ref:  I’m veggie, so no conflict of interest here!

    19. joeblueskies says:

      Matt – I actually don’t consider climate change issues to be a major selling point for eating local.  The issue is so complex, and at this juncture, the data are scarce.  Unravelling that knot can take a while.  Not that people shouldn’t mindfully consider making lifestyle changes in light of climate change issues.  But in terms of selling points, there are better ones for being a locavore.
      My personal favorite has to do with sustainable community development.  You keep the food dollars in the community, you give family farmers a fighting chance for survival, you keep farmland intact, you keep rural traditions and cultures intact, you support future food security against the worst Mad Max Peak Oil scenario.  Where I live, there are a lot of small family dairies.  Many of them are supported by one or even two off-farm incomes to keep them going, because they have no alternative at the moment to selling to the one large regional buyer available to them, who absolutely hammers them on price.  So they are effectively volunteering to work themselves to death to produce dairy products for us, running a farm at break even, because they love farming, they love their farms, they love their animals, they love their life.  Its crazy.  Their children often do not want to inherit the family business. funny.
      Another great reason is  personal health.  Local small farm grown produce, grass fed animals, pastured poultry and eggs – They are much much more likely to relatively pesticide-free, antibiotic and hormone free, and more nutrient rich.  Organic produce in particular is typically more mineral and nutrient rich than conventional.  It stands to reason, since the soils are so much healthier.  The studies are beginning to emerge, but I will let people do their own research – no links here.  Plus you have to start with a whole food and turn it into a meal.  Anytime you can eliminate the secret guest at the dinner table – the food processor – you are miles ahead.
      I think another good one is pleasure.  For a city dweller, there is nothing better than walking through the farmers market on a Saturday or a Sunday morning, really taking your time, having breakfast and a coffee nearby, checking out the flowers, smelling all the fresh fruit, and later a great meal with your purchase.  Or buying a few flats of berries and spending the afternoon putting them up, making jam, what have you.  Or driving past the farm where you know some of your food is produced, and feeling a sense of connection to that place.
      There are other good ones – environmental management, worker quality of life, sense of place, seasonal awareness, food security writ large, others.  Not sure that climate change is a good starting point, necessarily.  It is a great way to get people thinking about the issue, though, which may be why local food and climate consciousness are probably the two hottest issues on college campuses right now.  When they get linked together, quite an educational hotbed is created, as the unsustainability of our entire society becomes clearly illustrated.

    20. Matt says:

      Joe – I’m in complete agreement with you about all those reasons for eating local, and I think most people who end up as locavores don’t think about it in terms of greenhouse gas reduction any more than you do. Which is why it’s unfortunate that the “hook” used to get people thinking about eating local is climate change. If the claim “reduce your carbon footprint, eat local” weren’t so widespread, Weber and Matthews wouldn’t have had an article to write. Now that they have, and thereby made it easy for globavores to rebut this common reason for being a locavore, we have all the more reason to stress the things you mention. (It’s unfortunate that their numbers worked out as they did, as it’s hard to see what equally effective “hook” we might come up with, what with climate change so prominent in the media.)
      Helen – your numbers look good as far as I can tell for grass-fed, so, assuming they are, W&M could add to their list of pro-climate ways to alter your diet that of switching from industrial meat to grass-fed. Of course, for the average person eating average industrial meat, this isn’t likely to be as feasible a switch as some of the others (availability and cost), and probably couldn’t be done at the same scale, at least in the short term, but mathematically it looks good.
      - Matt

    21. joeblueskies says:

      One response to Helen – grass-fed in temperate parts of the world typically require some degree of hay-making.  You have to run a tractor around to 1) cut, 2) rake, and 3) bale, then 4) pick up bales and put in storage.  You also have to take animals to slaughter, and to market, and you use energy to cool and/or freeze them.  So you can’t take energy out of the equation altogether.
      on another track, some farmers around here (mid-appalachian area) are experimenting with traditional free-range hog raising, where the pigs are allowed to forage in oak forests for some of the year.  They fatten on acorns – reduces grain requirements by as much as 20-25%.  Something to look out for.

    22. some farmers around here (mid-appalachian area) are experimenting with traditional free-range hog raising, where the pigs are allowed to forage in oak forests for some of the year. They fatten on acorns – reduces grain requirements by as much as 20-25%.
      Uh, grain is not a requirement. We have a herd of about 40 sows plus boars and around 200 growing pigs but we don’t grain feed or use commercial hog feed either. They are completely out on pasture. In the winter they get hay. We get waste whey and cheese trim from a small organic cheese maker in the next town over – they have to get rid of the material and it is great for the pigs. It is a myth that pigs need grain – one of many myths. We do occasionally get left over boiled barley from a local pub and the occasional small amount of expired bread but those are just treats for training when you have 200 pigs. Virtually all of their diet is pasture/hay and whey which produces a superior pork.

    23. Thanks to all of the commenters for the great discussion, for any compliments on my post, and for saving me some work by answering questions posed by other commenters (seemingly before I even get the e-mail telling me that there was a new comment).

      I’ll address a few of the items that could use a little bit more clarification.

      Michael, in comment 3, makes a great point about food miles vs. sustainability. Salmon that spawn in California rivers or the Dungeness crabs that live off the coast are a good example of seafoods that have low “food miles” for Californians but that could be wiped out in a hurry if restrictions were removed.

      Walter, in comment 5, wrote “Unfortunately that research is slanted because they’re looking at modern factory farming raising of the animals, e.g., hog barns, beef feed lots, etc which are highly grain intensive.” That’s true, the researchers were analyzing data from the screwed up, “low prices at any cost” food system from 1997 — a time that is probably even a bit bleaker than today’s system. Organic and local sales were probably almost unmeasurable in that year, the words “grass fed beef” or “pastured pork” were nearly unknown concepts. And so the study provides a snapshot of the food system in America.

      After we have a “baseline” analysis, it’s time to start finding improvements, analyzing the performance of alternative agriculture systems, and try new concepts. For example, it would be interesting to compare industrial corn-fed beef with pastured beef on a per calorie basis (including the entire life-cycle, of course). A look at the carbon implications of converting a petroleum and natural gas drenched Iowa corn field into pasture for beef, pork or poultry would also be interesting. And then it would be interesting to see how the overall system performs relative to the 1997 system.

      I haven’t seen any statements by the authors about why they wrote this paper, but I’m guessing that it wasn’t just to get a few headlines. They probably chose an analysis of the food system because it provides a good case study for the LCA techniques that they are developing (which will be used to analyze parts of the global trade network). The work was funded by a fellowship from the EPA and a grant from the National Science Foundation.

    24. Rodney North says:

      This is a great and overdue conversation, and personally I think its exciting to see a friendly jostling of ideas that lay out _complementary_ ways to be more mindful about what we eat: Try to eat local (for a variety of reasons) AND try to cut back on meat, especially red meat AND for what beef/pork you eat look for grass-fed sources, etc. etc.

      Further, we can add yet another “wedge” to our strategies for shrinking the carbon footprint of our diets – that of choosing organic over conventionally grown foods (just as Cascadia Girl hinted at.)

      Last year an arm of the UN released a meta-study that concluded that whereas conventional agriculture contributed as much to global warming as did all forms of transportation combined ORGANIC agriculture (as a whole) actually helps to sequester carbon.

      You can read it & download at:
      At Equal Exchange this mattered to us a great deal. We trade with small-scale coffee, tea, & cocoa farmers around the world – crops for which local is not an option (excluding a tiny amount of coffee from Puerto Rico, & Hawai’i is just as far away as Central America).

      We had long known a great many reason to ‘go organic’, and so 95% of our imports are just that, but the push for “buy local” sometimes meant we were losing out to “local” roasters, even when the roaster was only offering conventional coffee.  With this UN study we can now see that this was a case where a simple, well-meaning idea actually sometimes lead to the opposite of the desired result. 

      But we also accept that this is the predictable ’2 steps forward, 1 step back’ phenomenom that society necessarily has to go through as our understanding continues to grow bit by bit.

    25. Mike Licht says:

      I have not read the Weber and Matthews paper, but I have yet to see an analysis of the USA farm-to-retail food chain that breaks out the energy cost of the “cold chain,” refrigeration at all stages — producer storage, distributor storage, wholesale and retail storage — and the intervening “reefer” transport between stages. One could even add in home refrigeration costs.
      I am not widely travelled, but I know of no other contemporary society so highly dependent on artificial refrigeration of foodstuffs. Surely this contributes to GHG as well as energy and food costs.