Also (and this should be obvious) our own ability to harness primary production is confined to a small number of species; backing these into an adaptive corner

Also (and this should be obvious) our own ability to harness primary production is confined to a small number of species; backing these into an adaptive corner could play havoc with our large heterotrophic society, where calorie production from the CHON cycle has very little slack relative to our ability to keep adapting at pace (i.e. R&D doesn't like starvation)