Yesterday's Grist magazine featured an article on the effects of global warming on the nutritional content of our food. Is the GES right? Are fossil fuels good for continued survival and health of hairless monkeys?
Grist concedes that there is something to the science -- CO2 fertilization does yield growth in plants. However, as they say, "there's a catch." High levels of CO2 may yield faster-growing plants, but they also yield less nutritious plants, much to the detriment of the critters who feed on said greenery (including the aforementioned hairless monkey, i.e. us).
Monocultures decrease nutritional value of plants as well, as the nutrients in the soil are depleted and not replenished via crop rotations. Increased use of chemical fertilizers and engineered high-yield crops also decreases the nutritional value of plants. The World Bank has termed the resulting nutritional deficiencies (most frequently felt in "developing" nations) "hidden hunger." Wealthy nations like those in the G8 can compensate for these nutritional shortcomings by supplementing crops, animals, and people with missing nutrients. Less wealthy nations may not be able to keep up. There's more in the article. It's quite interesting.
It also mentions that higher levels of CO2 increase production of non-nutritious elements in plants -- compounds that serve as the plants' natural defenses. Tomatoes might be bigger, but they'll also be meaner. Who needs nuclear radiation when you have CO2?
Also, it seems that it will be increasingly difficult to be a healthy vegetarian in a world with higher levels of CO2. Even if you grow your own organic produce, there's no way to keep your plants from interacting with a CO2-laden environment. Granted, organic produce will still be healthier than non-organic, bioengineered, factory-farmed produce, but nevertheless, the "veg block" should be pissed. And so should we all if yet another way of life becomes closed to us.