I don't think it's time to give up meat yet. Someday, perhaps, but not yet. Perhaps just a reduction. They claim it's healthier, yet the vegetarians I know over time develop weird health issues. I don't think they are getting all the nutrients the human body really needs. But that's not the main reason. It's more about balancing out the quality of life equation. I think we need better substitutes than what currently exists. And this issue isn't the low hanging fruit we should probably tackle first. So lets tackle the bigger greenhouse gas problems first, energy and transportation, and then we can dig deeper into agriculture if needed.
With that said, let me get my rant on.
We should never be satisfied giving up quality of life to solve other problems. We must work hard to solve our problems with minimal or no loss to quality of life. Some contrarians say environmentalists should walk to work, live in huts, and I've even seen going around naked suggested, to "walk the walk" if you will, and minimize their own environmental impact. Arguments about Al Gore's house size or traveling in a jet are along these same lines. Those who don't are incorrectly labeled hypocrits. But it's backward thinking often meant just to dismiss and alienate people voicing environmental concern. Reducing quality of life is not the right answer. Eliminating the negative impacts of those things that give us quality of life is.
At this time, I'm actually less concerned about environmental impact of having livestock, and more concerned about the treatment of livestock. This also is the quality of life concern, just extended to lesser life forms. While I don't think it matters for plants, I do believe that God, if He is up there, would expect us to treat our livestock with a level of respect higher than what currently exists. Their life may not be as important as ours, but it still matters; it's still a variable in the equation.
Someday, I hope we figure out how to grow proteins in food labs, and we can grow a crop of food proteins much like we might a hydroponic crop of wheat. It might not be an exact duplicate, but I could see it being a good subsititute for steak, much better than what substitutes we currently have. This, I think, should perhaps be the end goal for agriculture. Really, it's the end goal for everything. Human progress can be measured by how many things we no longer have to forage from the natural world, but instead can build or grow in a lab. Meanwhile, human morality can be measured by how we treat other life around us, beings that can feel, think, and perhaps even desire a better quality of life for themselves.
In the end, I believe quality of life is all that matters. It's the answer to life. It's the only purpose I can see for life, the universe, and everything. For matter to be satisfied -- even happy -- with the state of it's own existence. Happiness. Acheived by maximizing quality of life. Not just our quality of life. Quality of all life. And not just now, but now and forever into the future.