Acre for acre, monocultures of soy, wheat, corn, canola, coffee, etc. are more damaging to topsoil which leads to erosion and desertification, more dependent on the use pesticides/herbicides/fertilizers, and likely to be GMO.

Of course, CAFO cattle, industrial poultry farming, and other such operations create vast lagoons of excrement, breed antibiotic resistant bacteria, and are recipients of much of the the aforementioned monocultures of soy, wheat, corn, etc with all of their incumbent negative effects.

I think that your friend needs to be educated as to why those third world problems of hunger exist in the first place.

I see bigger problems than ordering steak. For example, Monsanto can patent a seed, insert a terminator gene (effectively rendering the seed useless for future plantings), require the use of roundup brand herbicide, sue a farmer whose crops are polluted with their GMO, receive subsidies from the American taxpayer, cheat the farmer who is going broke trying to grow enough of the subsidized crop to make a living, and then sell this "food" via global markets thereby depressing the prices and wages of third world farmers, putting them out of business, making them dependent on our food "aid", and thus promoting starvation and malnutrition in spite of the most "productive" food system in history.

I see the eco-conscious choice as growing, hunting, harvesting some of your own food, supporting local food economies, favoring fair-trade goods, and eliminating all of the commodity crops from your own diet as much as possible. In my mind, paleo is very eco-conscious because I don't eat corn, soy, wheat, processed foods, etc. and am therefore voting with my food dollars each time I go to the store, farmer's market, etc.

If I have to occasionally consume beef or pork that was grain-fed I don't worry myself to death because eating Paleo is also reducing the chances that I will be a burden to our health-care system in the future. But, that's another topic!

it's a good question, and i'm glad people keep thinking about it. i know it's it's hard to know what to search for exactly on this topic. here are some other threads that may be of interest:

http://paleohacks.com/questions/560/how-environmentally-responsible-green-and-sustainable-is-the-paleo-diet#axzz1NxW3shtu

http://paleohacks.com/questions/28391/former-vegetarians-ethical-meat-abstainers-gone-paleo/28398#28398

http://paleohacks.com/questions/27001/is-the-sustainability-argument-misguided#axzz1NxW3shtu

This question in various forms does seem to be cropping up more frequently these days... and I think that is a good thing. It means the whole idea of paleo is starting to be taken on board by people who are interested in more than just their own health. I very strongly believe that the food 'industry' is the single most important industry there is and we won't get any where near sorting out the problems of sustainability, overpopulation and equality in any area until we get to grips with food production. I think the whole idea of huge industrial companies making a profit - and only being interested in making a profit - out of food is at the root of many of the world's ills but I also think that the paleo mindset is going to be the way things get changed. When we realise that we cannot remove ourselves as individuals from what our bodies have evolved for then we might start realising that we can only go so far in other areas of our lives too. Science and technology have progressed so far now that we are starting to lose our instincts but I'm not in favour of regression or re-enactment. We can't go back but we can go forward in a new more enlightened way and I think science and technology, starting with the research into nutrition and evolutionary psychology, will bring us full circle. We have worked ourselves and the planet to the limit and now we need to start healing ourselves and the planet. At the height of the Industrial Revolution we believed we were far above animals and then Darwin came along and proved that we weren't. Progress is exponential, think of the rise in computer power since 1950. We had a massive change in diet 10,000 years ago and we've only just returned to the average height and lifespan we had before then. Another huge dietary change occurred about 30 years ago when food became industrialised and we added seed oils and HFCS to our diet in massive quantities. Once again we are embarking on a nutrition experiment. It won't take 10,000 years for a response this time and the results of the current experiment are plain to see with the obesity epidemic and diseases of civilisation increasing. I am optimistic that there will be a sea change in attitude towards food production; that the public will not continue to accept people dying of starvation in half the world and dying of obesity in the other half. At the moment too many 'eco-warriers' don't get it but the increase in these type of questions on this site proves that the message is starting to get through. There is definitely room out there for a paleo politics forum - somewhere where we can discuss how we can use modern technology and research to help us live in a way that fulfills not only our biological heritage but also our psychological and emotional evolutionary heritage too, and that is achievable for a stable world population. People often talk about feeding the ever increasing world population but I don't think it will be ever increasing. It is already starting to decrease in many developed countries and the more the developing countries become better fed, the more technology they get, the less their populations will grow. We have the potential for a virtuous circle. Feed and educate the existing population properly and it will peak and then start to fall. Well-fed, educated and empowered people do not have more and more children they have less. This goes for the developed countries too. At the moment it is the people at the bottom of the social hierarchy who have the most children.
I know this question from Oak0y recently got lots of downvotes but many of the responses were very valid and on just this point. http://paleohacks.com/questions/40787/can-we-accept-veganism-as-healthy-transition-till-we-find-friedndly-ways-to-farm#axzz1NxZrnvnq

The best summary of the environmental argument against grains and for local, pastured meat is Lierre Keith's The Vegetarian Myth. I also think Richard Manning's writings are key here. He points out that pre-contact bison population in the plains states were probably roughly equivalent to the population of cows in the U.S. today. He supports expanding non-cross-bred bison populations in large refuges and culling them for meat when populations allow. Food, and hunted food in carefully restored ecosystems in particular, is going to be a lot more sustainable and better for the environment than ecotourism and grain agriculture.

I personally am not too awful worried about it, I do what is needed to take care of me and mine.

There is a continuous group of new paleos out there - not too familiar with the site's locations - I can only say that I too, find the question worthy of multiple repititions - since there is a lot of eco-concerned citizens - as there ought to be - she beat me to the question - so happy to have heard and visited the sites that address the question! Particularly impressed with the answer Melissa gave -- I'm still not convinced, as a former buddhist that the animal sacrifice is a "good" thing, but looking at my miraculously altered health - I'm not complaining, but "thanking" the animals that feed me! I can't afford "grass-fed" in NYC and on disability! When I did my first 30 -didn't make it through because of the expense - had to turn to regular meat! - That said I supplement with fish oil --- it's a great question!!!