An excellent article by a scientist who started out defending organic food but after some research discovered some interesting history and facts. She includes some thoughts on what "natural" means. Some selective quotes below:
"I thought organic farming was based on evidence, but it wasn’t. It wasn’t designed by studying what would be best for the environment. On the contrary, to my surprise I found it’s roots were actually in biodynamic agriculture – a method that emphasizes spiritual and mystical perspectives on farming. What? How could I have missed such a point for a decade? The picture I was beginning to piece together was that being ‘organic’ was based on the idea that modern farming – industrial agriculture – was bad, and the old ways of farming were better. That whatever natural was, that was better."
"I began to question if there even was a ‘natural way to farm’? If natural was defined by, say, the exclusion of human activities, then surely there was nothing natural to farming. On the other hand, if we accepted humans as a part of nature, and our continued innovations as part of *our nature*, then all farming was natural. Saying that more traditional farming practices would be inherently better than those using more advanced technology wasn’t a concept that could be settled by a romantic appeal to nature. Only careful definitions of ‘better’, followed by observations, testing, and evaluation of evidence could tell us something about that."
The entire article is at: http://www.geneticliteracyproject.org/2015/05/22/natural-illusions-biologists-failed-attempt-to-defend-organic-food/