A liveable Earth? Look up "nine planetary boundaries". The "biogeochemical boundary" especially pertains to the nitrogen and phosphorus cycles, both necessary to plants. Nitrogen- and phosphorus-supplying fertilizer is energy intensive to produce and toxic in wide-area run-off. Some crops live in a symbiotic relationship with nitrogen-fixing bacteria, so scientists are actively researching ways of engineering that abiility into other crops -- which would greatly reduce the need for producing fixed nitrogen for fertilizer, which, in turn, would greatly reduce the need for the high fossil-fuel-consuming method of generating fixed nitrogen for fertilizer, thus helping out on the global warming front. It's not all about cost.