I don't believe that study was regarding climate change but rather the unsustainable nature of modern agriculture. I am a hobby farmer and have done some study into the nature of fertilizer, problem is that our fertilizers destroy the soil and so each year it requires more ferts than the prior year. I believe that the study was referring to this trend.
I agree. The more I read about climate change, the more I realize it's only one part of the anthropocene - so I often end up mixing the two. Anyway, if you do have a source for the diminishing returns of energy use to produce food, please share!
