Unfortunately there is no way really support world populations need without certain amount of farms, especially the ones where animals don't have very good lives. By what I have heard the way western world eats anyways world can only support 1.5 billion people and even by the way most Asian cultures eat it can only support about 9 billion which we are going to hit rather soon in current rate. There is a lot that would have to be done in order to change this and I don't think there is very many people who will be willing to give up on certain food products.

Though there is a lot of good things that have happened in past few years like people leaning more and more towards more gas efficient cars or even hybrids or fully electronic ones as well as discovery of bio-plastic which has far less of an impact on environment than regular plastic. So I could say that we are on right track, but lots of work needs to be done.

What comes to buying locally produced stuff as well as using products packed in things that are more environmental friendly, it's usually difficult to do so. First of if you live in big city it might be hard to find any produce that is locally produced as farms are usually far from the cities and then in another hand small communities don't have wide variety of products to choose from that would be local. Also Locally produced things are generally far more expensive which do not appeal to most people especially if they live close to poverty. And things packed in glass or metal are easy to identify but bio-plastic is usually the one that causes problems even if you want to buy items packed in it.

I think aiming for recycling is the best thing people can currently do to effect on environment as well as try to move away from fossil fuels. Using wind, water or Nuclear energy is far better option than coal and way safer too.

I know I went a bit off the title of the thread, but I do think these are the things that are way easier to tackle rather than the specific diet you're having and have greater impact as well. Of course, what been said doesn't hurt either.