Many of you seem to be frustrated when I say things like, "Industrial agriculture is extremely productive; thanks to technology and the use of inputs like pesticides, fertilizers, and GMO seeds, we are producing more grain than ever." I'm sorry if you don't like it, but it's really true: these technologies ARE tremendously productive, and what's more, all that productivity means that crops are cheaper than ever. All of us, including the poor, have access to food at lower prices than ever. Nutritional diseases like kwashiorkor and marasmus are basically gone from the US. Environmentally speaking, having tremendously productive fields means that there is less pressure on wild lands.
That doesn't mean that all is well with our food system. There are PLENTY of problems! First and foremost are the many externalities: pollution of our air and water, soil loss, serious depletion of aquifers, etc. Also, all this cheap food hurts farmers. Finally, the food that's cheap isn't quality food, and the mass consumption of foods with little nutritional value (aka "empty calories") is fueling the current boom in obesity.
IMHO the best critic is an informed critic. If you want to call for change, I think you will be most effective if you recognize the good and the bad of the current system instead of being in denial about it. For example, I have seen no credible evidence that GMO technology hurts human health. That could change- I could see a great study tomorrow- but the studies that showed harm have all more or less been shown to be flawed. Again, that doesn't mean you shouldn't criticize GMO's: just go after the real problems such as the monopoly power being brought to bear in seed technologies. That's not ok.
At the same time, the harms of industrial agriculture are clear. We need change to avoid the problems listed above, but we really need to keep up the high productivity on our limited land, since there are people to feed and wild lands that we don't want to bring into cultivation. Local food is tasty: good for gourmets, but it is much, much less productive than allowing Idaho to grow the nation's potatoes. Shipping uses fuel, yes, but a heck of a lot less fuel than trying to grow a potato in Florida.
Organic agriculture is a great start. Clearly the methods we need to take care of our land are incorporated. However, at this point it's about 20 to 25% less productive, at best. We need more research to improve productivity, and we may need some of the fruits of our industrial approach as well.
There are other approaches, and I mostly don't know much about them. Here's someone talking about agroecology, and in class some of you talked about analog forestry. Sounds like these are sustainable, but are they economic? Are they as productive as industry? I don't know! If you want to make the case for these, you need to be aware of the issue and be able to make the case. You need... drum roll please... economics!
Try to keep an open mind about costs AND benefits: that's the best way to generate effective criticism and build leverage for your own push to improve the system.