You want to know a little secret? The most environmentally friendly way to eat is completely unattainable these days.
If we were all nomadic hunter-gatherers, we would be constantly on the move, allowing species to regenerate in the areas we left behind. Our diets would be varied and seasonal, and, since wild foods are much higher in vitamins and minerals than their domesticated counterparts, we would be well nourished. We wouldn't need exercise because movement would be worked into our days. We would have an intricate knowledge of the plants and animals in our environment. We would have more free time than anyone who works a typical 9 to 5 office job has now. We would be eating and moving the way our bodies evolved to. The downsides? There would be times when food was scarce. Things were generally less cushy and convenient back then; make a mistake, and you could end up dead. And, of course, things like hygiene were not always up to modern standards.
We and the environment would be better off if we were all hunter-gatherers. But, the thing is, there are just too many humans now, and not enough undeveloped, open spaces. It would be impossible for any large number of people to return to our ancestral lifestyle. And I find it hard to believe that many people would want to, given the comfort and safety of our lives today. Modernity has brought with it many great things, but it has a great deal of problems as well, both for our health and the health of our planet.
The good news is that there are many good ways of farming, as well. Agriculture can be seen as a form of symbiosis between humans and other organisms; we provide, say, lettuce, with protection from predators and enhanced reproduction (by planting them all over the place), and, in return, they provide us with food. This is an ancient, species-level pact of reciprocation between us and the animals and plants we cultivate. Our gardens and farms, when well managed, can also provide habitat for pollinators, like bees and butterflies, and birds, contributing to the ecosystem rather than taking away from it.
To be a sustainable eater, you can grow your own food, and/or make wise consumer choices. For those of you who don't have the room or time to garden, or for those of you who grow some of your food and buy the rest, these two guidelines will help you make the sustainable choice:
+ Buy Local - If food doesn't have to travel as far, it doesn't use as much fossil fuel for transportation, and it is in line with your area's seasons. Local foods also retain more of their nutrients because they're still fresh by the time they reach your table (instead of sitting for days in a truck, and then in a grocery store).
+ Buy Small - Small farms are generally using better farming practices these days. That's not to say that big organic companies (like, say, Earthbound Farm) are bad, but they use a system of farming called monoculture. Monoculture means that they plant the same species in large swaths. This leads to increased susceptibility to pests, which leads to the application of more pesticides (organic companies simply use organic pesticides, which are not nearly as harmful). This also depletes the soil because crops aren't being rotated. Small farms typically use polyculture (many different species planted together), which reduces the need for pesticides. They use compost and manure to return nutrients to the soil. They rotate crops. They use ground covers to prevent weeds, or pull them by hand. They integrate animals into their produce production, allowing the chickens to eat pests, and the cows to fertilize the fields. They don't require petroleum-based, water-polluting herbicides, pesticides, or fertilizers. Buying from small farms supports people in your local community who are doing good things, rather than supporting big corporations who rely on fossil fuels to ship their goods--organic or not--all over the country.
The best place to buy small and local is at the farmer's market, or though a local CSA (community supported agriculture) program that ships local produce to your door. Many grocery stores, like Whole Foods, also mark which goods are local and in season.
So, if we can't be hunter-gatherers, then at least we can support good farming practices that are healthy for us and for the Earth. Grow what you can, buy local, and buy small.