It's just occurred to me that in medicine, we have clinical trials that consider the effect of a drug on the whole system - a whole human body. If you get a brain tumour from a kidney treatment, they'll notice.
But for food/farming, that's not the case. We never do trials on the whole system - the natural environment. It's only ever local - effects on yield in one field. And maybe that's why modern food systems cause problems, for the climate, human health etc.