You claim that “ as GMOs move from lab into the real world, they end up being very disappointing” and then go on to admit that there have been significant gains for Indian cotton farmers among others. The near universal adoption of Bt technology for cotton, corn and soybeans by economically savvy farmers for decades surely attests to its advantage. They will ditch RoundupReady and Bt as soon as the sums don’t add up.

Could it be that GMOs have not delivered “ a widespread quantum leap in the yield of important food crops” because it is precisely for those crops that GMO applications have been most vigorously and successfully blocked? Despite billions of human GMO consumers suffering no discernible health effects over decades the EU for one blocks their use in food.

Perhaps European farmers’ incomes depend less on yield than on protectionist policies and generous subsidies. The world’s subsistence are perhaps less fussy because their incomes do depend on yield.

The arms races between pests and their victims has been going on since both appeared billions of years ago. Why would you expect pests not to become resistant to the natural pesticide expressed by the Bt bacillus for millions of years just because humans have given plants the ability to produce it by genetic manipulation?

Herbicide resistance to Roundup appears to have developed by natural selection, just as short-stemmed dandelions evolved in response to the unnatural attack from lawn-mowers, and not by horizontal gene transfer as predicted by the anti-GMO lobby.

Following Marie Antoinette’s logic that the poor, lacking bread, should eat cake you advise them to “ simply grow more diverse crops” to avoid vitamin B deficiency. How is not eating a GMO product preventing them from doing just that? The really poor can’t afford vegetables. They eat cheap bulk grains and pulses.

The question “What is trulylimiting yield to food crops in different locations and different farming systems?” manifests the lack of systems thinking you ascribe to the GMO proponents. It isn’t yield that is the issue, it is poverty. The poor usually live in dense urban environments and cannot grow their own vegetables. They will continue to eat rice and suffer nutritional deficits until they escape poverty. Improving the nutritional quality of the food they can afford is system thinking. Mulching is utopia.