FWIW, this was also discussed on the animal rights blog yesterday afternoon: http://animalrights.change.org/blog/view/worldwatch_livestock_account_for_51_greenhouse_gases_meat_and_dairy_must_be_replaced

I think it's worth pointing out, as mentioned in that post, that the authors don't just make the recommendation and move along; a large portion of the article is devoted to exploring just how this transition would and could work and what the multiple benefits would be.

And the figure really isn't that hard to swallow when you consider all the figures the researchers provide and the fact that we're breeding and using (and of course, ultimately killing) no small number of animals; we're talking about several tens of billions of land animals each year alone (i.e., not even counting all the billions of aquatic animals as well).

I'd also like to head off some expected adverse reactions to the proposal of meat and dairy analogs as a solution here. I think we all know that processed foods are not and should not be the ultimate goal as a primary food source, but using these foods as a transition away from animal-based foods can be helpful for a number of people. I wrote about this over at the AR post as well: http://animalrights.change.org/blog/view/worldwatch_livestock_account_for_51_greenhouse_gases_meat_and_dairy_must_be_replaced

As a vegan with a degree in environmental policy, I feel that I am an unlikely candidate to say that I find these numbers HIGHLY questionable, and I would advise all animal advocates and environmentalists to be cautious when spouting off this new sketchy figure.

There is absolutely no doubt that switching to a vegan diet is the simpliest and most direct way to save the earth via food choices, BUT this report pitts it as a false choice between taking drastic steps in industrial and residential power sectors OR switching to vegetarian/vegan diets. We need both, equally quickly and with an equal force.

This does seem high, but I also know people are addicted to their meat.  It's not that hard to give up meat.  I didn't say totally, but cutting back is easy, I've done it.  People, if you have children I'd think you'd want to do what you can to make sure they have a world to live on when they grow up!  ...or maybe you just don't care...  

As my Grandfather used to say, "there are lies, Damn lies, and statistics."  Without the raw data I could make the case that butterfly farts can cure cancer... I suspect much the same principal is at work here, especially when you figure in the fact that EVERY living organism that breathes oxygen and gives off C02 is now a "polluter".

Cows' breathing?  I'm no scientician, but isn't that part of the carbon cycle, and therefore shouldn't be included in one of these analyses.

I wonder how true this study is.  Either way, meat-eating needs to be severely reduced.

Seth and Ross, let's hear your objections. If you are two different people it's funny that you both brought up respiration. Even funnier that that's the first topic the authors explain in detail - you know, if you'd, like, read the report. So what's your objection to their explanation of this?

I could believe that number, but I do find it highly suspenct that "they advocate entirely replacing the meat and dairy industries with plant-based substitutes such as soy milk and seitan burgers."

Vast fields of soy and wheat wouldn't improve a damn thing... Anyone seriously looking at this issue should know that.

I would venture a guess that these high numbers would be easy to find at a corporate feed lot. There's mounting evidence that the cow is not the problem, but rather the diets humans are forcing on the cows.

http://www.gourmet.com/foodpolitics/2009/09/the-conscientious-carnivore

Nature didn't design cows to eat grains.  A cow's rumen should be an alkaline environment.  When fed grains, the rumen becomes acidic as the grains ferment.  That's why the cattle industry is one of the largest antacid purchasers in the country.  It's that very same process in the cow's rumen that causes all the obnoxious gas.

Plus, the process of growing corn fro cows is less environmentally sound than allowing cows to eat grass.

http://simplesteps.org/food/eating-well/top-10-reasons-eat-grass-fed-meat#pagination-top

It's not the cows.  It's the modern farming techniques.  We need to shift back to crop and animal rotation, multiple crops planted strategically both time wise and location wise, and away from mono culture agriculture where pesticides and drugs are used to "fix" all the problems the techniques are creating.

Let's also not forget one of the biggest contributors to these problems in the U.S. - food industry subsidies.  If the subsidies went away, many of these problems would cure themselves by allowing the market demand to dictate which food products would be grown.  Right now, organic produce is yielding nice profits for farmers around the world.

Unfortunately, I just reviewed the report in detail and it is full of errors and damages the credibility of food and climate researchers.

1. The authors are right that the FAO does not include livestock breathing emissions in GHG emissions. But when the authors add livestock breathing emissions back into total emissions, they don’t add human breathing emissions back in. So when they conclude that livestock emissions are 51% of anthropogenic emissions, they are conveniently neglecting another major source, thereby incorrectly inflating the proportion that comes from livestock.  

2. Next the authors tackle land use. They acknowledge that the FAO counts emissions from converting land from forest to livestock use, but say the estimate is too low because it doesn’t count emissions from all the pre-existing land used to support livestock, which could instead be used to grow climate-friendly biofuels. That’s like saying we should count my bathroom floor as a GHG emitter, because I’m not currently growing biofuels on it.

3. The authors insist that we have to look at livestock methane emissions on a shorter timeframe than the FAO does, which is arguable. But even if you agree, they do not recalibrate methane emissions from non-livestock sources as they do for livestock, saying it requires “further work.” So, just as they did with livestock breathing emissions, they inflate livestock methane emissons but conveniently neglect to inflate non-livestock methane emissions. Then of course the percent of emissions from livestock looks astronomical.

There are other problems too; for my whole analysis see my blog post at http://eatinganimals.wordpress.com/2009/10/30/climate-chicanery/

We can prove anything to continue our sinful activity.