...without... ...petrochemical insecticides... Organic (CNHO) chemicals aren't in the slightest dependent on petroleum, it is only a passing quirk of the earl

...without... ...petrochemical insecticides... Organic (CNHO) chemicals aren't in the slightest dependent on petroleum, it is only a passing quirk of the early 21st-century economy that oil and natural gas byproducts are the most common chemical feedstocks. CNHO atoms are everywhere on earth, and they're not going anywhere (mass doesn't leave the earth, for the most part). Basic organic chemistry building-blocks, e.g. ethylene, are not much more difficult to obtain from biological matter (e.g. ethanol) than from oil/gas. Organic chemistry -- insecticides, plastics, pharma, what have you -- isn't going anywhere, and this is all a silly misunderstanding from confused Malthusians. ...aquifers... ...artificial irrigation... There's no theoretical limit to artificial irrigation (well there is, but it's ludicrous). In refutation: nuclear or solar powered ocean desalination plants, with aqueducts, large pipes, or underground canals piping freshwater inland -- thousands of miles if need be. Elementary, existing technology, and I think not too far from economic feasibility even today. Desalination is already economic (if not directly competitive with natural freshwater sources, when they are available) -- lots of it in the Middle East, Southeast Asia. Aqueducts are ancient technology. ...phosphorus fertilizers... Nothing stopping us from recycling phosphorus -- it's not like we're flinging it off the earth into space. The whole earth is a closed cycle for chemicals -- water, CNOH, trace minerals, all of them sustainable. Since the issue is framed as "maximum theoretical", well, in the limit we can ion-exchange phosphorus out of the seas -- the ultimate repository for "used" phosphorus. (Although in the nearer term there's more simple resolutions, like preventing runoff waste, recovery from sewers/rivers, mining new types of phosphorus minerals, etc.) But the green revolution is totally unsustainable. Ignorance is totally unsustainable. Please conserve.